It is recognised that the amount of energy used to heat water can be a significant contributor to the cost of running a home. With this in mind, it can be useful to identify the amount of energy used in running a terminal fitting for the consumer as part of the general water label information.
To calculate, consistently, the energy used to heat water, average supply and delivery temperatures along with average use patterns have to be established. The basic calculation is based on first principle physics:-
Energy [kWh] = Mass [kg] x spec. Heat-coefficient of water [kWh (kg x K)] x Delta T [T]
This basic calculation coupled with average use times can easily be used to calculate expected annual energy consumption.
Average use times to be used for the following products are:-
Basin (& bidet) taps: 1 minute per event, 5 events per person per day
Kitchen taps: 1 minute per event, 7 events per person per day
Showers (handsets & mixer controls): 7 minutes per event, 1 event per person per day
Electric Shower Flow Rate Calculation Sheet
For basin & bidet taps and showers the average outlet temperature is always regarded as 38°C while for kitchen taps the average outlet temperature is regarded at 45°C. In all cases the average seasonally adjusted inlet temperature is regarded as 15°C.
Core assumptions have been taken directly from the European Commission study into taps and showers task 3 report: users. For reference purposes this document can be found via the following link:- http://susproc.jrc.ec.europa.eu/taps_and_showers/docs/Task3_2ndTWG_v2.4.pdf
For Baths, the same core calculation can be used to help users understand, in energy terms the cost of filling the bath for each bathing event.
The energy icon can be added to the base of the Water Label to depict to the consumer the expected annual energy cost of using the product. It is required that all basin taps, kitchen taps, showers (handsets and mixer controls) and baths shall carry the energy icon.
Energy Calculator for Showers
Energy Calculator for Basin Taps
Energy Calculator for Kitchen Taps