Guidebook for Energy Efficiency in Municipalities

Hot water production
T4
Supplying hot water in municipal facilities can be an expensive process. For example,
supplying just 100 litres of hot water per day can cost €180 each year. In many cases,
heat loss from tanks and pipes is greater than the amount of useful heat delivered. While
providing hot water is an obvious task in healthcare and catering facilities, it is also
significant in offices when the purchase and operating costs of the many boiling water
units and hot water services throughout the building are considered.
Opportunities for savings
The key issues to consider in ensuring that costs and energy consumption for hot water
preparation are as low as possible are:
minimising hot water consumption;
maintaining properly the system;
choosing the right equipment, based on:
o the energy source - gas and solar are preferable concerning cost and greenhouse
intensity,
o the consumption patterns - how much will be used (taking into account efficient
water use), and what will be the peak requirements,
o the performance of the equipment, taking both standby losses and hot water use
into account.
Rationalize hot water consumption
Water-efficient shower and tap fittings can cut hot water requirements by up to half. For
new buildings and refurbishments, they also offer the opportunity to install smaller
diameter pipes, which are cheaper and hold less water (so less hot water is wasted by
cooling between uses). When purchasing water-using equipment such as dishwashers or
washing machines, select the models that use the least hot water. Many household
products now carry water rating labels which can help choosing the most efficient model.
In facilities such as swimming pools or recreation centres, where multiple showers are
likely to be in use, AAA-rated water-efficient showerheads can reduce the risk of running
out of hot water, as well as save hot water overall. In many cases, hot water may not be
needed at all or the thermostat of the system can be set to a lower temperature to reduce
heat losses. However, the storage temperature for hot water systems should normally be
set above 50°C to limit the risk of legionella infection.
Carry out maintenance
Maintenance tips include:
fix dripping taps;
check yearly the pressure/temperature valves fitted to mains pressure hot water units,
as these can leak large quantities of hot water without this being noticed; if more than
a bucket of water is released over 24 hours, the valve should be repaired or replaced;
drain off sediment from the bottom of HWS tanks regularly; in gas units, sediment can
significantly reduce heating efficiency;
replace sacrificial anodes in glass-lined steel HWS tanks at recommended intervals to
prolong tank life.