Solar Water Heating - Heschong Mahone Group

Solar Water Heating 

2013 California Building Energy Efficiency Standards 

California Statewide IOU Codes & Standards Team, 

Nate Dewart, Energy Solutions 

DRAFT March 16, 2011 

CONTENTS 

1. Purpose......................................................................................................................... 2 

2. Overview ....................................................................................................................... 3 

3. Methodology ................................................................................................................. 9 

4. Analysis and Results ................................................................................................. 17 

5. Recommended Language for the Standards Document, ACM Manuals, and the 

Reference Appendices .............................................................................................. 20 

6. Bibliography and Other Research ............................................................................ 24 

7. Appendices ................................................................................................................. 26

Measure Information Template Page 2 

1. Purpose 

Through Codes and Standards Enhancement (CASE) Studies, the California Investor Owned Utilities 

(IOUs) provide standards and code-setting bodies with the technical and cost-effectiveness 

information required to make informed judgments on proposed regulations for promising energy 

efficiency design practices and technologies. 

The IOUs and their consultants began evaluating potential code change proposals in the fall 2009. 

Throughout 2010, the CASE Team evaluated energy savings and costs associated with each code 

change proposal. The Team engaged industry stakeholders to solicit feedback on the code change 

proposals, energy savings analyses, and cost estimates. This Draft CASE Report presents a code 

change proposal for solar hot water systems for residential low-rise, single-family buildings and 

introduces a new proposal for commercial buildings, specifically restaurants. 

The measure proposes to increase the existing solar fraction requirement for single family residential 

buildings with electric water heating, and to add a new solar fraction requirement for restaurants with 

both electric and natural gas water heat and above a certain square footage. 

Another purpose of this code change proposal is to address several limitations of the language, format 

and representation of the existing code. While natural gas is preferred over electric for water heating 

from a resource consumption perspective, the current documentation of the solar fraction requirement 

for residential buildings using Package C [§151f, TABLE 151-B] (particularly in cases of natural gas 

non-availability) provides inconsistent guidance and should be clarified. 

The final purpose of this code change proposal is to address the current limitations of how solar water 

heating is calculated for both prescriptive and performance compliance. The current method for 

calculating solar fraction is the software program F-chart, which is based on monthly solar radiation 

values and is a separate calculator instead of being integrated into any existing building performance 

software programs. This measure proposes the use of an hourly model of solar radiation to increase 

precision and to align with the California Energy Commission’s (CEC) Time-Dependent Valuation 

(TDV) of energy calculations. The measure also proposes integration of solar modeling into the 

Alternative Calculation Method (ACM) while changing it from an “optional capability” to a “minimal 

capability,” thereby simplifying and making consistent the solar inputs for the compliance analyst. 

This could make solar thermal a more broadly applied measure, while also improving enforcement 

and error checking. In addition to addressing this integration of F-Chart, the measure proposes a 

reduction in the water heating energy budget for restaurants, a differentiation of restaurant occupancy 

types, and introducing hot water demand load profiles for each into the ACM, while integrating these 

load profiles into the F-Chart tool. 

The contents of this report, including cost and savings analyses and proposed code language, were 

developed taking feedback from industry and the California Energy Commission (CEC) into account. 

This is a Draft version of the CASE Report. A final version will be released in summer/fall 2011. 

2013 California Building Energy Efficiency Standards March 2011


2. Overview 

Complete the following table, providing responses for each category of information. 

a. Measure Solar Water Heating – Residential and Specialty Commercial 

Title 

b. 

Descriptio This proposed measure increases the required minimum fraction of water heat to be 

n provided by solar water heating systems for individual dwelling units (i.e. single-family 

housing) with electric storage water heaters. The solar fraction required is climate-zone 

dependent. In addition to changing the requirements, this code change proposal 

addresses several limitations of the language, format and representation of the existing 

code in the standards document and the compliance manual, e.g. placing the requirement 

in a more central location in the standard and compliance manual, and clarifying 

language that seems to be remnant from previous code cycles. 

The proposed measure also introduces a required minimum fraction of water heating 

provided by solar water heating systems for restaurants with natural gas storage water 

heaters and conditioned and unconditioned floor area of at least 12,500 sq. feet. The 

solar fraction required is climate-zone dependent. 

The proposed measure introduces a required minimum fraction of water heat to be 

provided by solar water heating systems for restaurants with electric storage water 

heaters and conditioned and unconditioned floor area of at least 1,500 sq. feet. The solar 

fraction required is climate-zone dependent. 

For the ACM Manuals and F-Chart tool, this proposal introduces an hourly energy 

savings model for solar water heating systems and makes it a requirement for 

compliance software. For the ACM Manual only, the proposal introduces a reduction in 

the water heating energy budget for restaurants with natural gas storage heaters and 

conditioned and unconditioned floor area of at least 12,500 sq. feet, and with electric 

storage heaters and conditioned and unconditioned floor area of at least 1,500 sq. feet. 

The proposal introduces a differentiation of restaurant occupancy types, with new 

definitions of “quick-service” and “full-service” restaurants. Finally, the proposal also 

introduces and integrates these hot water demand load profiles for each into the ACM. 



c. Type of 

Change 

Prescriptive Requirement - This proposed measure would increase the prescriptive 

required fraction of water heating provided by solar water heating for single-family 

housing with electric resistance water heating systems from the existing 25% to a 

climate-zone dependent percentage. 

For the non-residential Base Code, the proposed measure would introduce a required 

fraction of water heating provided by solar water heating for restaurants with natural-gas 

water heating and at least 12,500 sq. ft of conditioned and unconditioned floor area. 

For the non-residential Base Code, the proposed measure would introduce a required 

fraction of water heating provided by solar water heating for restaurants with electric 

storage water heating and at least 1,500 sq. ft. of conditioned and unconditioned floor 

area. 

Modeling - This measure would modify the calculation procedures and assumptions used 

in making performance calculations, by introducing an hourly model into the Alternative 

Calculation Method (ACM) Manual to more accurately reflect solar radiation and match 

the hourly Time Dependent Valuation of electricity used by the CEC in Title 24 

development and compliance. This measure also moves "Solar Water Heating" 

capabilities which are currently in "1.2 Optional Model Capabilities" of the ACM Manual 

and places them into "1.1. Minimum Modeling Capabilities." 

The proposal measure also introduces a reduction in the water heating energy budget in 

the performance approach for restaurants. 

The proposal introduces a differentiation of restaurant occupancy types, with new 

definitions of “quick-service” and “full-service” restaurants. Finally, the proposal also 

introduces hot water demand load profiles for each into the ACM, while integrating these 

load profiles into the F-Chart tool. 

Other - The change would modify the language and visual representation of the solar 

fraction requirement in the standard, compliance manual and compliance form 



d. Energy 

Benefits 

The proposed measure results in energy savings and demand reduction beyond 2008 Title 

24 Code. 

All yearly energy savings are multiplied against the 2013 TDV (Time Dependent 

Valuation) values to determine the monetary value of the energy savings over the entire 

measure life cycle. The TDV values weight peak savings more heavily than off-peak 

savings to account for the real cost of energy to society. For residential non-envelope 

measures, the TDV period of analysis is 30 years at a 3% discount rate. For nonresidential 

non-envelope measures, the TDV period of analysis is 15 years at a 3% discount rate. 

Residential: Single Family – Electric Storage Water Heating (Climate Zone Average) 

Electricity 

Savings 

(kwh/yr) 

Demand 

Savings 

(kw) 

Natural Gas 

Savings 

(Therms/yr) 

TDV 

Electricity 

Cost Savings 

TDV 

Gas Cost 

Savings 

Per Prototype 

Building 

3,302 .41 N/A $12,330 N/A 

Savings per 

square foot 

1.22 .00015 N/A $4.57 N/A 

Commercial: Restaurant - Electric Storage Water Heating 1 

Electricity 

Savings 

(kwh/yr) 

Demand 

Savings 

(kw) 

Natural Gas 

Savings 

(Therms/yr) 

Per Prototype 

Building 

Savings per 

square foot 

TDV 

Electricity 

Cost Savings 

TDV 

Gas Cost 

Savings 

TBD TBD N/A TBD N/A 

TBD TBD N/A TBD N/A 

e. Non- 

Energy 

Benefits 

Commercial: Restaurant - Natural Gas Water Heating 2 

Electricity 

Savings 

(kwh/yr) 

Demand 

Savings (W) 

Natural Gas 

Savings 

(Therms/yr) 

Per Prototype 

Building 

Savings per 

square foot 

TDV 

Electricity 

Cost Savings 

TDV 

Gas Cost 

Savings 

(532) (.07) 2,945 ($1,179) $42,602 

(.04) (.0057) .24 (.09) $3.41 

We found little evidence to suggest there are substantive non-energy benefits. Increased 

property value may be likely, however, further research is needed. 

1 These are rough estimates calculated by scaling upwards in size the modeling of the 80 sq. ft. collector, 80 gallons per day to 200 sq. ft collector, 250 

gallons per day. Complete numbers will follow with additional modeling results from TESS. 

2 The natural gas water heating system saves a significant amount of natural gas, but uses a small amount of electricity, for the collector and heat 

exchange pumps, hence the negative electricity cost savings values. 



f. Environmental Impact 

Section to be completed 

Emissions Factors 

Per Unit Measure 

NOX SOX CO PM10 CO2 

Per Prototype 

Building 

Material Increase (I), Decrease (D), or No Change (NC): (All units are lbs/year) 

Mercury Lead Copper Steel Plastic Others 

(Indentify) 

Per Unit Measure 

Per Prototype 

Building 

Water Consumption: 

Per Unit Measure 1 

Per Prototype Building 2 

On-Site (Not at the Powerplant) Water Savings 

(or Increase) 

(Gallons/Year) 

Water Quality Impacts: 

Comment on the potential increase (I), decrease (D), or no change (NC) in contamination compared to 

the basecase assumption, including but not limited to: mineralization (calcium, boron, and salts), algae 

or bacterial buildup, and corrosives as a result of PH change. 

Mineralization 

(calcium, boron, and 

salts) 

Algae or Bacterial 

Buildup 

Corrosives as a 

Result of PH 

Change 

Others 

Impact (I, D, or NC) 

Comment on reasons 

for your impact 

assessment 



g. 

Technology 

Measures 

Measure Availability: 

Over the past several decades, availability of solar water heating systems increased 

worldwide. Between 2000 and 2009, the number of solar thermal collector companies 

more than tripled, and sales nearly doubled (EIA 20011). Solar Rating and 

Certification Corporation (SRCC) currently rates 48 different solar water heating 

systems. 

In California, system and contractor availability is strong, with manufacturers generally 

supplying the systems to the contractors. California Solar Initiative Thermal Program 

(CSI Thermal), as of February 1 st , 2011, listed 25 different contractors across 9 of the 

16 climate zones having installed tanks with electric backup from 11 different 

manufacturers in residential single family buildings. For natural gas, in the same data 

set, there have been 7 different contractors across 6 Climate Zones, having installed 

natural gas tank systems from 11 different manufacturers in multi-family and 

commercial buildings. 

Useful Life, Persistence, and Maintenance: 

Compared to standard storage water heaters, solar water heating systems with utility 

back up are more complex, with many components and varying life expectancies. With 

proper installation and maintenance, however, systems are expected to maintain 

persistent savings over time. The table below summarizes the useful life of each 

component (Stakeholder Interviews 2010/2011): 

Life Expectancy / 

Component 

Frequency (years) 

Collector 20 

Auxiliary and Auxiliary / Solar 

Combined Tank 10 

Solar Tank 15 

Motor and Pump 10 

Controller 20 

Heat Transfer Fluid 3 

h. 

Performance 

Verification 

of the 

Proposed 

Measure 

No additional performance verification such as diagnostic testing or acceptance tests 

will required for compliance with this measure. 



i. Cost Effectiveness 

We began our cost-effectiveness analysis by examining all 16 climate zones, given the climate 

sensitivity of the measure. We first performed this analysis for residential solar systems with electric 

back up and commercial solar systems with natural gas back up. Then, for the commercial solar 

systems with electric back up, we modeled the three least-cost effective climate zones from these other 

two analyses. The numbers provided in this table are the averages from the climate zones of the 

respective number of climate zones modeled. Nonresidential envelope measures are evaluated over a 

30 year period of analysis and all other nonresidential measures are evaluated over 15 year period of 

analysis. 

A B C E F g 

Additional Costs 1 PV of Additional 3 

– 

Maintenance Costs 

Current Measure Costs 

(Savings) (Relative to 

(Relative to Basecase) 

Basecase) 

($) 

(PV$) 

Measure Name 

Measure 

Life 

(Years) 

Per Proto Building 

Per Proto 

Building 

PV of 4 

Energy 

Cost 

Savings – 

Per Proto 

Building 

(PV$) 

LCC Savings Per 

Prototype Building 

($) 

(c+e)-f 

Based on Current Costs 

Residential 

Electric 

Commercial 

Electric 

Commercial – 

Natural Gas 

30 $5,705 $4,111 $12,330 $1,833 

15 TBD TBD TBD TBD 

15 $20,058 $19,271 $41,423 $15,224 

j. Analysis 

Tools 

k. 

Relationship 

to Other 

Measures 

Our team hired a consultant, Thermal Energy System Specialists (TESS), to provide 

hourly energy usage numbers in order to align with hourly TDV, and therefore provide 

a more precise assessment of energy costs. The software used is called TRNSYS, 

(Transient Energy System Simulation Tool) from which F-Chart is based. While a 

more fully integrated TRNSYS modeling tool would be ideal for compliance purposes, 

we believe an integration of F-Chart into compliance software is sufficient. 

This section will describe relationship to the proposed water heating measure, if any. 



3. Methodology 

For the three separate components of this measure, we used the same basic methodology, with slight 

variations. The sections below describe the factors for selecting the base case systems and the 

proposed standards case systems, and data that informed the cost-effectiveness calculation. 

3.1 Single Family Residential Buildings 

As mentioned above, in this code change proposal for the residential sector, we examined individual 

dwelling unit buildings exclusively. A separate proposal in this code cycle addressed residential 

multi-family buildings. 

Base Case System Selection: 

While the current code contains a prescriptive requirement for a 25% solar fraction for homes with 

electric storage water heating, market research suggests that many single family homes with electric 

water heater are not being built with solar hot water systems. For example, the Residential Appliance 

Saturday Survey (RASS) 2009 database (KEMA 2010) indicates in a statewide survey covering all 

the investor owned utility service area, there were no homes built after 2001 with a solar water heater 

and electric backup. For the base case we therefore selected a standard electric storage water heater 

with an 80-gallon tank and a .9 energy factor, instead of a solar system w/ electric backup with a 25% 

solar fraction. This represents an extremely conservative approach for a cost-effectiveness analysis, 

because our analysis assumes the full cost of the solar hot water system, despite the fact that a 25% 

solar fraction is already the minimum prescriptive requirement. 

Proposed Standards Case System Selection: 

With a wide range of systems in the marketplace, we initially selected four system types to model 

costs and energy savings. We modeled these systems across all 16 climate zones due to the variation 

in TDV and the climate-dependent energy consumption of solar water heating systems. As more field 

data became available, we focused our analysis on the most commonly installed system, an active 

indirect system w/ glycol freeze protection. This system was modeled with an 80 sq. ft flat plate 

collector and one 120 gallon tank with electric backup and a .6 energy factor. This size of system was 

based on estimates that this would provide the optimal solar fraction. It should be noted that a 1.5 to 

2.0 gallon / sq. ft. ratio is needed to prevent the system from overheating (DOE 2010, Stakeholder 

Meeting 2010/2011). 

Calculation of Costs: 

The three main costs of both systems are the energy costs, installation costs, and maintenance and 

replacement costs over the 30-year period of analysis for residential buildings. 

The base case energy costs were calculated by the following equation: 

Equation 1: Energy Costs=∑ (Hourly energy delivered to load (TESS 2011) / Energy Factor * TDV (CEC 

2011 v3)) 

The proposed standards system energy costs were calculated using a similar approach: 



Equation 2: Energy Costs=∑ (Hourly energy consumption (TESS 2011) * TDV (CEC 2011 v3)) 

The inputs for calculating the hourly energy use and their sources are as follows: 

Prototype building size: 2,700 (Residential ACM manual) 

Gallons Per Day: 56.5 (Residential ACM Manual) 

Hourly Draw Schedule (Residential ACM Manual) 

Inlet Water Temperatures: (NREL algorithm) 

Outlet Water temperature: (Residential ACM manual) 

Installation and replacement for the base case were sourced from RSMeans (2010) for California. 

Using this methodology the installation costs for the Base Case system total $1,495. See Table 1 for 

the replacement costs. There was assumed to be no maintenance. 

Table 1 Maintenance and Replacement Costs: Base Case System 

Auxiliary Tank 

(80 gal) 

Material + 

Warranty 

Cost Per 

Unit ($) 

Labor 

Rate ($) 

Labor 

Time 

Labor 

Cost ($) 

Total Cost 

Overhead & 

Profit ($) 

Replacements / 

Maintenance 

per building 

life 

PV 

Replacements 

/ Maintenance 

per building 

life ($) 

$1,081 $34.88 5.0 $174 $1,495 1 $1,112 

Installation, maintenance and replacements costs for the proposed Standards case system were derived 

from a variety of sources. For installation costs, we first determined the total costs for electric back up 

tank systems with 74 to 80 sq. ft. collectors from the California Solar Initiative - Thermal public 

database (2011).To determine a weighted state average, given the different material and labor rates in 

different parts of the state, we first multiplied these installation costs by the estimated percentages of 

the totals costs that equal labor and materials (25%, 75% respectively) for residential systems as 

determined by the Itron (2009). We then multiplied these labor and material costs by a respective 

normalizing conversion factor for each city based on population using data from the American 

Community Survey 2006 – 2008 (Census 2010) and cost data from RSMeans data (2010). See 

Appendix A. 

Using this methodology, the installation costs for the Proposed Case system are $7,200. See Table 3 

for the maintenance and replacement costs, derived from Stakeholder Interviews (2010/2011) and 

Stakeholder Meetings (2010/2011), and weighted for California rates as well using RSMeans data 

(2010). 



Table 2 Maintenance and Replacement Costs: Standards Case System 

Collector 

(80 sq. ft.) 

Solar & 

Auxiliary 

Combined 

Tank (120 gal) 

Motor & 

Pump 

Material + 

Warranty 

Cost Per 

Unit ($) 

Labor Rate 

($) 

Labor 

Time 

Labor 

Cost 

($) 

Total 

Cost 

Overhead 

& Profit 

($) 

Replacements/ 

Maintenance 

per building 

life 

PV 

Replacements/ 

Maintenance 

per building 

life ($) 

$1,500 $34.88 13 $453 $2,419 1 $1,339 

$1,081 $34.88 6 $204 $1,544 3 $2,513 

$422 $34.88 2 $61 $572 3 $743 

Controller $175 $34.88 3 $87 $338 1 $187 

Heat Transfer 

Fluid Check 

- $34.88 1 $17 $17 20 $92 

Heat Transfer 

Fluid Check 

& Replace 

$106 $34.88 2 $70 $175 9 $1,039 

Total $5,913 

The cost-effectiveness of the proposed Standards case system was determined by calculating the 

difference between life-cycle costs (energy costs + installation costs + NPV (maintenance & 

replacement)). See Appendix A for a screenshot of the spreadsheet. 

The final component of the methodology was the calculation of the solar fraction. The solar fraction 

was calculated using Equation 3, as derived from SRCC (2011) 

Equation 3: Solar Fraction = 1 – Energy Factor (EF) / Solar Energy Factor (SEF) 

Where: EF = 0.9 for a standard electric auxiliary tank and 0.6 for a natural gas tank. 

Solar Energy Factor = Qdel / (Qaux + Qpar) 

Where: 

QDEL = Energy delivered to the hot water load (TESS 2011) 

QAUX = Daily amount of energy used by the auxiliary water heater or backup element with a solar 

system operating, kJ/day (Btu/day) (TESS 2011) 

QPAR = Parasitic energy: Daily amounts of AC electrical energy used to power pumps, controllers, 

shutters, trackers, or any other item needed to operate the SDHW system, kJ/day (Btu/day). (TESS 

2011) 



3.2 Non-Residential Buildings 

In determining the potential applications for solar water heating systems in the commercial sector, we 

first examined the non-residential (non-hotel/motel) 3 building types with the greatest hot water 

demand. The ACM Manual formula for calculating hot water demand (btu/hr/sq ft.) indicates that 

restaurants surpass others by an order of magnitude, and so we selected this occupancy type. We also 

analyzed electric and natural gas water heating separately, given their differences in efficiencies and 

utility costs. 

It is important to note that while the building prototype is specified in the Residential ACM, with both 

gallons per day of hot water and sq. footage defined, the Non-Residential ACM applies a different 

approach: it specifies btu/h of hot water per person by occupancy type and the number of people per 

1,000 sq. ft. Multiplying these values together provides the standard recovery load, in btu/h/sq.ft. 

Since prototype building square footage by occupancy is not specified, however, we therefore had to 

develop our own value for analysis. Instead of researching and defining the prototype size, we instead 

used the approach of determining square footage thresholds. These thresholds were determined by the 

results of the LCC analysis. To calculate energy use and costs, instead of using the Residential ACM 

standard recovery load and hourly profiles, we utilized the gallons per day metric, and ASHRAE 

hourly profiles for hot water demand used by the California Solar Thermal Initiative. Once we 

determined the threshold of gallons per day for cost-effectiveness, we plugged this value into the 

ACM formula for Standard Recovery Load btu/h/sq. ft. to determine the resulting square footage. 

Base Case System Selection: 

The base case for restaurants with a standard electric storage water heater is an 80-gallon tank found 

in a small restaurant or coffee shop (Food Service Technology Center 2010). The tank was estimated 

to have a .9 energy factor (SRCC 2011). For restaurants with a natural gas storage water heater, the 

base case is a 400,000 btu/hr rated, 100 gallon tank (Wallace & Fisher 2007). The tank was estimated 

to have a .6 energy factor (SRCC 2011). 

Proposed Standards Case System Selection: 

For restaurants with electric water heating we modeled costs and energy savings of the most 

commonly installed system according to CSI Thermal (2011) and California Center for Sustainable 

Energy – Solar Hot Water Pilot Program (CCSE) database (2010), which was an active indirect, flatplate 

collector system w/ glycol freeze protection. 4 For sizing the system, we first used the same 

specifications as the residential system given the comparable hot water demand. However, this sizing 

of 80 Sq. ft. and a 120 gallon tank proved to be cost-ineffective. We therefore determined that a 

larger, two-tank system was needed (a 300 gallon solar tank, and an 80 gallon electric storage back 

up) and sized the collector to be 200 sq. ft. 

3 A separate CASE report in this code cycle is addressing non-residential hotel and motel buildings. 

4 The database included both new and retrofit installations, and while there was a cost differential between types, this differences was deemed statistically 

insignificant using T-Test methods at 95% confidence interval. 



Using the results from the residential modeling, we chose to model these systems across the 3 least 

cost-effective climate zones. Cost-effectiveness in these climate zones can be assumed to demonstrate 

cost-effectiveness across all climate zones. 

For restaurants with natural gas heating, the proposed Standards case system to be a two-tank system 

(120 gallon solar tank, and a 100 gallon natural gas storage tank) and again active indirect flat-plate 

collector system w/ glycol freeze protection. This solar system is the most common in the CSI- 

Thermal database (2010). 5 

Calculation of Costs: 

The three main costs of both systems are the energy costs, installation costs, and the post-installation 

costs (maintenance and replacement) of the 15-year useful building life. 

Energy Costs: 

The base case energy costs were calculated by the following equation: 6 

Equation 4: Energy Costs=∑ (Hourly energy delivered to load (TESS 2011) / Energy Factor * TDV (CEC 

2011 v3)) 

The proposed standards system energy costs were calculated using a similar approach: 

Equation 5: Energy Costs=∑ (Hourly energy consumption (TESS 2011) * TDV (CEC 2011 v3)) 

Where: 

Hourly Energy Consumption - Electric = Collector Pump + PV Controller + Electric Auxiliary (TESS 2011) 

Hourly Energy Consumption - Natural Gas = Collector Pump + Heat Exchanger Pump + Natural Gas Auxiliary 

(TESS 2011) 

The inputs for calculating the hourly energy use and their sources are as follows: 

Prototype building size: 

Given that there are no prototypes for building square footage by type specified in the nonresidential 

ACM, as mentioned above, we tested for square footage thresholds and the 

corresponding gallons per day using the non-residential ACM Manual Table N-2 to show costeffectiveness. 

To calculate the corresponding square footages, we used assumptions from the 

ACM Manual, as indicated in the following formulas: 

5 Given the constraint of available roof space, we limited the maximum system size to 6 collectors. 

6 The methodology for calculating the hourly energy delivered to the load and the hourly energy consumption for the commercial system w/ electric 

backup were approximations of savings based the numbers of the one tank, 80 Sq. ft. collector system. These values were multiplied by the ratio of 

new gallons per day / old gallons per day, 250/ 80 given that the collector size was increasing at approximately the same ratio. The pump and 

controller electricity consumption were held constant. 



Equation 6: Sq. ft. = Gallons / day * 1 / Gallons/ day /sq. ft 

Where: 

Equation 7: Gallons / day / sq. ft = (Standard Recovery Load / day/ 1,000 sq. ft) * 1/ (total degrees raised* 

btu/degree per gallon) 

Where: 

Equation 8 : Standard Recovery Load / day/ 1,000 sq .ft. = (∑ (people/sq. ft. & btu/h/person (ACM, Table N2- 

5))* occupancy load profile for year(ACM, Table N2-5)) /(days in a year) 

Gallons Per Day: 

1. Electric Water Heating: 250 gallons per day (estimate) 

2. Natural Gas Water Heating: 2,000 gallons per day (Karas and Fisher 2007). 

Hourly Draw Schedule / Occupancy Load Profile 

1. Electric Water Heating: ASHRAE, from CSI Thermal, Food Service B (2011a) 

2. Natural Gas Water Heating: ASHRAE, from CSI Thermal, Food Service A. (2011a) 

Inlet Water Temperatures: (NREL algorithm) 

Outlet Water temperature: (Karas and Fisher 2007) 

Installation & Post-Installation costs 

Installation, maintenance and replacement costs for the base case and for proposed standard case 

system for both electric water heating and natural gas were sourced from CSI Thermal and CCSE 

(2010), RSMeans (2010), Census (2010) and Stakeholder Meetings (2010). One key additional 

modification to the methodology for the system w/ natural gas backup, was that since there was a 

smaller sample of these exact sized systems in the CSI Thermal and CCSE, we examined three 

different methods for estimating costs (see Appendix B) All three were quite close in this range of 

collector sq. ft. with CSI Thermal (2010) and Stakeholder Meeting (2010) being congruent, so we 

used these at $150/sq. ft (See Appendix B). 

The installation costs for the Base Case electric storage water heater is $1,600.The installation costs 

for the Base Case natural gas storage water heater is $12,941.The installation costs for the Proposed 

Standards Case solar system with electric storage back up is $29,000. The installation cost for the 

Proposed Standards Case natural gas storage water heater is $35,714. Table 3, 4, 5, and 6 summarize 

the maintenance and replacement costs for these systems. 

Table 3: Maintenance and Replacement Costs: Base Case System Commercial Electric Storage 

Total 

PV 

Replacements/ 

Material + 

Cost 

Replacements/ 

Maintenance 

Warranty 

O&P 

Maintenance 

per building 

Cost Per Labor Labor Labor (Per 

per building 

life 

Unit Rate Time Cost unit) 

life ($) 


$1,082 $53.41 5 $267 $1,610 1 $1,526 

(80 Gal) 



Table 4: Maintenance and Replacement Costs: Proposed Standards System Commercial Solar 

System w/ Electric Storage Back up 

Total 

PV 

Replacements/ 

Material + 

Cost 

Replacements/ 

Maintenance 

Warranty 

O&P 

Maintenance 

per building 


per building 

life 


life ($) 


(80 gal) 

$1,082 $53.41 5 $267 $1,610 1 $1,526 

Motor & Pump $422 $53.41 2 $93 $612 1 $455 

Controller $175 $53.41 3 $134 $395 0 - 

Heat Transfer 

Fluid Check 

0 $53.41 1 $27 $27 10 $141 

Heat Transfer 

Fluid Replace 

$106 $53.41 2 $107 $212 5 $820 

Total $2,940 

Table 5: Maintenance and Replacement Costs: Base Case System Commercial Natural Gas 

Storage 

Total 

PV 

Replacements 

Material + 

Cost 

Replacements 

/ Maintenance 

Warranty 

O&P 

/ Maintenance 

per building 


per building 

life 


life ($) 


(100 Gal, 400 

GPH) 

$10,000 $53.41 20 $1,068 $12,941 1 $9,629 

Table 6 : Maintenance and Replacement Costs: Proposed Standards System Commercial 

Natural Gas Storage 

Total 

PV 

Replacements 

Material + 

Cost 

Replacements 

/ Maintenance 

Warranty 

O&P 

/ Maintenance 

per building 

Cost Per Labor Labor Labor (per 

per building 

life 


life ($) 


(100 Gal, 400 

GPH) $10,000 $53.41 20 $1,068 $12,941 1 $9,629 

Heat Transfer 

Fluid Check 0 $53.41 1 $27 $27 10 $427 

Heat Transfer 

Fluid Replace $106 $53.41 2 $107 $212 5 $122 

Total $13,810 



Table 7: Prototype Size 

Occupancy Type 

(Residential, Retail, 

Office, etc) 

Prototype 1 Residential Low Rise - 

Individual Dwelling Unit 

Prototype 2 Commercial – 

Restaurant, electric water 

heater 

Prototype 3 Commercial – 

Restaurant, natural gas 

water heater 

Area 

(Square Feet) 

2,700 Sq. Ft. 2 

1,500 Sq. Ft 1 

12,500 Sq. Ft. 1 

Number of 

Stories 



4. Analysis and Results 

Our analysis resulted in several conclusions. First, installing and utilizing solar water heating with an 

electric storage backup water heater in residential, individual unit dwellings saves a significant 

amount of energy in all 16 climate zones. Moreover, the most common system, an active indirect 

system with glycol freeze protection is cost-effective. 

Table 8 summarizes the energy savings, energy cost savings, incremental cost and the life-cycle cost 

savings for the Standards Case for residential buildings with electric resistance water heating, as well 

as the corresponding solar fraction achieved by the solar system. 

Table 8 Proposed Standards Case Results: Residential Solar w/ Electric Storage back up 

Climate Zone 

Annual Energy 

Savings (kWh) 

30 Year TDV 

Energy Cost 

Savings ($) 

Incremental 

Measure Cost 

(installation and PV 

maintenance and 

replacement) ($) 

Life 

Cycle 

Cost 

Savings 

($) Solar Fraction 

1 2,923 $11,393 $9,633 $1,825 0.64 

2 3,303 $12,535 $9,633 $2,173 0.77 

3 3,316 $12,648 $9,633 $2,286 0.77 

4 3,342 $12,751 $9,633 $2,388 0.79 

5 3,594 $13,648 $9,633 $3,285 0.84 

6 3,426 $12,558 $9,633 $2,193 0.84 

7 3,450 $13,159 $9,633 $2,797 0.86 

8 3,367 $12,383 $9,633 $2,018 0.84 

9 3,325 $12,146 $9,633 $1,781 0.84 

10 3,348 $12,118 $9,633 $1,753 0.85 

11 3,169 $12,019 $9,633 $1,656 0.77 

12 3,153 $12,025 $9,633 $1,663 0.75 

13 2,982 $11,331 $9,633 $969 0.75 

14 3,549 $12,735 $9,633 $2,370 0.87 

15 3,052 $10,913 $9,633 $548 0.89 

16 3,531 $12,924 $9,633 $2,559 0.75 

The second conclusion is that installing and utilizing solar water heating with a 200 sq. foot flat-plate 

collector with an electric storage backup water heater in commercial restaurants with 250 gallons per 

day hot water demand, is cost-effective over the base case, an electric storage water heater. 7 Table 9 

summarizes the energy, energy cost savings and the life-cycle cost savings for the Standards Case for 

restaurants with electric storage water heating, as well as the corresponding solar fraction achieved by 

the solar system. 

7 Pending TESS results, whether they confirm estimates. 



Table 9 Proposed Standards Case Results: Commercial Solar w/ Electric Gas Storage back up 

Incremental 

Measure Cost 

Climate Zone 

Annual Energy 

Savings (kWh) 

30 Year TDV 

Energy Cost 

Savings ($) 

(installation and 

PV maintenance 

and replacement) 

Life Cycle 

Cost 

Savings ($) Solar Fraction 

1 TBD TBD TBD TBD TBD 
















Third, installing and utilizing solar water heating with a natural gas backup water heater in restaurants 

12,500 sq. ft. or larger is cost-effective over the base case, a natural gas storage water heater. Table 

10 summarizes the energy, energy cost savings and the life-cycle cost savings for the Standards Case 

for restaurants with natural gas water heating, as well as the corresponding solar fraction achieved by 

the solar system using Equation 10. 

Table 10 Proposed Standards Case Results: Commercial Solar w/ Electric Gas Storage back up 

Incremental 

Measure Cost 

(installation 

and PV 

Climate Zone 

Annual Energy 

Savings (Therms) 

15 Year TDV 

Energy Cost 

Savings ($) 

maintenance 

and 

replacement) 

Life Cycle Cost 

Savings ($) 

Solar 

Fraction 

1 2,847 $41,038 $26,199 $887 0.34 

2 3,001 $43,105 $26,199 $4,689 0.37 

3 2,949 $42,407 $26,199 $3,909 0.36 

4 2,994 $43,030 $26,199 $5,140 0.38 

5 3,027 $43,756 $26,199 $5,867 0.38 

6 2,891 $42,081 $26,199 $4,590 0.37 

7 2,884 $42,353 $26,199 $5,266 0.38 

8 2,885 $41,935 $26,199 $4,907 0.38 

9 2,890 $41,986 $26,199 $5,270 0.39 

10 2,912 $42,348 $26,199 $5,664 0.39 

11 2,975 $42,688 $26,199 $5,230 0.38 

12 2,957 $42,364 $26,199 $4,383 0.37 



13 2,831 $40,560 $26,199 $3,554 0.38 

14 3,094 $45,012 $26,199 $8,344 0.40 

15 2,744 $39,895 $26,199 $5,717 0.42 

16 3,246 $47,078 $26,199 $7,362 0.37 

Statewide Energy Savings and Peak Demand Savings[Placeholder] 



5. Recommended Language for the Standards Document, 

ACM Manuals, and the Reference Appendices 

Part 6 

RESIDENTIAL STANDARDS: 

Subchapter 8 

● Section 151 

● Revise & Add: language to read as follows: 

● “Domestic Water-heating systems. Water heating systems shall meet the 

requirements of either A, B, C or D and meet the requirements of E and F or 

shall meet the requirements of Section 151(b)1. 

● D. For systems serving individual dwelling units using Package C, an electricresistance 

water heater may be installed as the main water heating source, only 

if the water heater is located within the building envelope and the minimum 

percent of the energy for water heating is provided by a passive or active solar 

system as specified in Table 151-B COMPONENT Package C 

● Table 151-B COMPONENT Package C 

● Remove: Footnote 7 from table and below text: “Electric-resistance water heating may 

be installed as the main water heating source in Package C only if the water heater is 

located within the building envelope and a minimum of 25 percent of the energy for 

water heating is provided by a passive or active solar system. 

● Adjust Climate Zones (see below) 

● Add to “Water Heating” section, an additional sub-row and include “If electricresistance, 

Solar Fraction = (See below),” and remove “or section 151 (b)1” 

Climate 

Zone 

Water 

Heating 

1 2 3 4 5 6 7 8 & 9 10 11 12 13 14 15 16 

System shall meet Section 151(f)8 or Section 151(b)1 7 

If electricresistance, 


Fraction = .65 .77 .77 .79 .84 .84 .86 .84 .85 .77 .75 .76 .81 .89 .75 

RESIDENTIAL MANUAL: 

● 5.1.3 Water Heater Types: 

o Add: Solar Water Heater w/ electric backup 

Solar Water Heater w/ natural gas backup 



● 1-18-1 Package C 

o “Electric resistance water heating may also be used with Package C if the water heater is 

located within the building envelope and the minimum percent of the energy for water 

heating is provided by a passive or active solar system as specified in Table 151-B 

COMPONENT Package C 

● Table 151-B COMPONENT Package C 

o Remove: Footnote 7 from table and below text: “Electric-resistance water heating may 

be installed as the main water heating source in Package C only if the water heater is 

located within the building envelope and a minimum of 25 percent of the energy for 

water heating is provided by a passive or active solar system.” 

o Adjust Climate Zones (see below) 

o Add to “Water Heating” section, an additional sub-row and include “If electricresistance, 

Solar Fraction = (See below),” and remove “or section 151 (b)1” 

Climate 

Zone 

Water 

Heating 

1 2 3 4 5 6 7 8 & 9 10 11 12 13 14 15 16 

System shall meet Section 151(f)8 or Section 151(b)1 7 

If electricresistance, 


Fraction = .64 .77 .77 .79 .84 .84 .86 .84 .85 .77 .75 .75 .81 .89 .75 

● 5-1.5. pg. 5-5 

o Revise: “So Solar water heating is also required if electric resistance water heater is 

installed (using prescriptive package C).” 

COMPLIANCE FORMS 

● CF-1R – Certificate of Compliance - Residential New Construction (page 4 of 5) Water 

Heating: 

o Add: electric storage water heating with solar fraction requirement and reference to 

Solar Water Heating and CF-SR (Solar Water Heating Calculation). 

● CF-6R-MECH-01 – Domestic Hot Water (DHW) (page 1 of 2): 

o Add: electric storage water heating with solar fraction requirement 

● CF-6R-MECH-02 - Solar Domestic Hot Water Systems (SDHW) (page 1 of 1): 

o Revise: “Net Solar Fraction” 

NON-RESIDENTIAL STANDARDS: 

Section 145 



o 

Add: (a) Nonresidential Occupancies. Buildings with building category designated as 

“restaurant” or area category as “dining”and a total square footage (conditioned floor 

area & non-conditioned floor area) of 12,500, may install a natural gas water heater if 

the water heater is located within the building envelope and the minimum percent of 

the energy for water heating is provided by a passive or active solar system as specified 

in Table__: 

Climate 

Zone 


Fraction 

Table __ 

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 

.34 .37 .36 .38 .38 .37 .38 .38 .39 .39 .39 .37 .38 .4 .42 .37 

Climate 

Zone 


Fraction 

Table __ 

Buildings with building category designated as “restaurant” or area category as 

“dining”and a total square footage (conditioned floor area & non-conditioned floor 

area) of 1,500, may install an electric storage water heater if the water heater is located 

within the building envelope and the minimum percent of the energy for water heating 

is provided by a passive or active solar system as specified in Table __. 

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 

A service water heating system installed in this building type and all nonresidential 

buildings complies with this section if it also complies with the applicable 

requirements of Sections (111,113 and 123). 

NON-RESIDENTIAL COMPLIANCE MANUAL: 

● Section 4.7 

o Modify: All of the requirements for service hot water are mandatory measures, except 

for restaurants and dining facilities that must comply with §145(a), and high-rise 

residential, hotels and motels that must comply with the l Residential Standards 

§151(f)8. These requirements are described in the Residential Compliance Manual. 

Section 4.7.1. 

o Insert: Natural Gas Storage Restaurants or Dining 

§145(a) 



area) of 12,500, may install a natural gas water heater if the water heater is located 



Climate 

Zone 


Fraction 

Table __ 



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 

.34 .37 .36 .38 .38 .37 .38 .38 .39 .39 .39 .37 .38 .4 .42 .37 

Climate 

Zone 


Fraction 

Table __ 

Electric Storage Restaurants or Dining 

§145(a) 



area) of 1,500, may install an electric storage water heater if the water heater is located 



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 

o Modify: A service water-heating system is considered to comply with the prescriptive 

requirements when all mandatory requirements are met for occupancies, other than 

restaurants, dining facilities and high-rise residential and residential. Buildings that 

have both occupancies other than high-rise residential shall meet the service water 

heating requirements that apply to each occupancy. 

COMPLIANCE FORMS 

 

MECH-2C 

o Add: a space for “Building Area (ft 2 )” and a space for “Restaurant (Building Category) 

or Dining (Area Category) (see LTG-1C) and space “for solar fraction.” 



6. Bibliography and Other Research 

California Solar Thermal Initiative. 2011. https://www.csithermal.com/public_export/. January 10, 

2011. 

California Solar Thermal Initiative. 2011a. “CSI-Thermal Multifamily/Commercial; SRCC OG-100 

Incentive Calculator Guide” https://www.csithermal.com/media/docs/CSI-Thermal_SRCC_OG- 

100_Incentive_Calculator_Guide.pdf 

[Census] U.S. Census Bureau. 2010. American Community Survey 2006 – 2008. 

http://www.census.gov/acs/www/. U.S. Census Bureau. December 2010. 

[FSTC] Food Service Technology Center. 2010. Personal Communication. October 20, 2010. 

Itron. 2009. Solar Water Heating Pilot Program: Interim Evaluation Report. Prepared by Itron for the 

California Center for Sustainable Energy. January 16, 2009. Vancouver, Wash. 

Itron. 2006. California Commercial End-Use Survey (CEUS). Prepared for California Energy 

Commission. March 2006. http://www.energy.ca.gov/2006publications/CEC-400-2006-005/CEC- 

400-2006-005.PDF 

KEMA. 2010. California Residential Appliance Saturation Study (RASS) 2009. Prepared for 

California Energy Commission. 

Karas, Angelo and Don Fisher. 2007. Energy Efficiency Potential of Gas-Fired Water Heating 

Systems in a Quick Service Restaurant: An Emerging Technology Field Monitoring Study. October 

2007. FSTC Report 5011.07.19. San Ramon, Calif. Food Service Technology Center. 

Wallace, Charles and Don Fisher. 2007a. Energy Efficiency Potential of Gas-Fired Commercial Hot 

Water Heating Systems in Restaurants: An Emerging Technology Field Monitoring Study. April 2007. 

FSTC Report 5011.07.04. San Ramon, Calif. Food Service Technology Center. 

[DOE] U.S. Department of Energy. “Sizing a Solar Water Heating System” 

http://www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=12880 

Washington, D.C.: U.S. Department of Energy 

[EIA] U.S. Energy Information Administration. 2011. “Solar Thermal Data and Information Release 

Date: January 2011” 

http://www.eia.doe.gov/cneaf/solar.renewables/page/solarthermal/solarthermal.html 

Washington, D.C.: U.S. Department of Energy 

RSMeans. 2010. Costworks. 2010 4 th Quarter Data. http://www.meanscostworks.com/ 

[CCSE] California Center for Sustainable Energy. 2010. Project Report. Solar Hot Water Pilot 

Program. 2010. Excel. August 12, 2010. 



[SRCC] Solar Rating Certification Corporation. 2011. http://www.solar-rating.org/ratings/ratings.htm. 

Stakeholder Interviews. 2010/2011. Personal Communication. 

Stakeholder Meetings. 2010/2011. “Solar Topics: Title 24: California Statewide Utility Codes and 

Standards Program. Hosted by Energy Solutions & Heschong Mahone Group, Inc. on behalf of 

Pacific Gas and Electric Co., Southern California Edison and Sempra Energy. November 2 nd , 2010 

and January 11, 2011. 

[TESS]. Thermal Energy System Specialists. 2011. Excel spreadsheet. 


7. Appendices 

APPENDIX A 

Population Weighting for Plumbing Labor and Materials 

Plumbing 

Labor 

Metro Region Population (millions) Location Weighted State/City 

American 

Factor Loc. Ratio 

Community Survey, (*US Factor 

Census 2007-2009) Rate) RS (Pop. 

Means Location 

Factor) 

Location 

Factor 

(*US 

Rate) 

Plumbing 

Material 

Weighted 

Loc. 

Factor 

State/City 

Ratio 

Alhambra 0.086 96.3 8.2818 1.0955498 93.4 8.0324 1.066880948 

Anaheim 0.334 112.9 37.7086 0.9344681 100.1 33.4334 0.995471334 

Bakersfield 0.318 94.2 29.9556 1.1199729 100.1 31.8318 0.995471334 

Berkeley 0.108 123.2 13.3056 0.8563429 93.4 10.0872 1.066880948 

Eureka 0.027 102.4 2.7648 1.0302876 93.3 2.5191 1.068024443 

Fresno 0.472 107.8 50.8816 0.9786776 100.2 47.2944 0.99447785 

Inglewood 0.116 96.3 11.1708 1.0955498 93.4 10.8344 1.066880948 

Long beach 0.463 96.3 44.5869 1.0955498 93.4 43.2442 1.066880948 

los angeles 3.75 112.9 423.375 0.9344681 100.2 375.75 0.99447785 

marysville 

modesto 0.204 107.8 21.9912 0.9786776 100.1 20.4204 0.995471334 

Mojave 

Oakland 0.362 136.1 49.2682 0.775176 100.2 36.2724 0.99447785 

Oxnard 0.176 112.9 19.8704 0.9344681 100.1 17.6176 0.995471334 

palm springs 0.039 96.3 3.7557 1.0955498 93.3 3.6387 1.068024443 

palo alto 0.063 122.3 7.7049 0.8626447 93.4 5.8842 1.066880948 

pasadena 0.138 96.3 13.2894 1.0955498 93.4 12.8892 1.066880948 

Redding 0.091 98.7 8.9817 1.0689103 100.1 9.1091 0.995471334 

richmond 0.099 119.7 11.8503 0.8813822 93.4 9.2466 1.066880948 

riverside 0.302 112.9 34.0958 0.9344681 100.1 30.2302 0.995471334 

sacramento 0.447 110.8 49.5276 0.9521792 100.1 44.7447 0.995471334 

Salinas 0.144 108.2 15.5808 0.9750596 93.4 13.4496 1.066880948 

san bernardino 0.208 96.4 20.0512 1.0944134 93.3 19.4064 1.068024443 

san diego 1.25 113.3 141.625 0.931169 100.2 125.25 0.99447785 

san francisco 0.798 165.1 131.7498 0.6390154 100.2 79.9596 0.99447785 

san jose 0.905 138.5 125.3425 0.7617433 100.1 90.5905 0.995471334 

san luis obispo 0.048 96.4 4.6272 1.0944134 93.4 4.4832 1.066880948 

san mateo 0.093 137.1 12.7503 0.7695219 93.4 8.6862 1.066880948 

san rafael 0.054 132.9 7.1766 0.7938409 93.4 5.0436 1.066880948 

santa ana 0.328 96.3 31.5864 1.0955498 93.3 30.6024 1.068024443 

santa barbara 0.086 112.9 9.7094 0.9344681 100.1 8.6086 0.995471334 

santa cruz 0.055 108.2 5.951 0.9750596 100.1 5.5055 0.995471334 

santa rosa 0.153 132.1 20.2113 0.7986484 93.3 14.2749 1.068024443 

stockton 0.286 98.8 28.2568 1.0678284 100.1 28.6286 0.995471334 

susanville


vallejo 0.114 112 12.768 0.9419772 100.1 11.4114 0.995471334 

van nyus 

TOTAL 12.117 1409.752 1198.9805 

Population (millions) 

California 36 

23.883 105.50145 99.64668 



APPENDIX B 

Installation Cost Curves for Commercial and Multi-Family Solar Hot Water Systems 

$90,000 

$80,000 

$70,000 

$60,000 

Stakeholder Input: $150/ft2 

collector area 

RS Mean: $12,000 per 4x 

(3'x7') collector = 84ft2 

Pilot Program and CSI Thermal 

Project Installed Costs* 

y = 150.44x ‐ 111.13 

R 2 = 0.6723 

System Cost ($) 

$50,000 

$40,000 

$30,000 

$20,000 

$10,000 

$‐ 

Collector Area (ft 2 ) 

0 50 100 150 200 250 300 350 400 450 500

Solar Water Heating - Heschong Mahone Group

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?