Research collaboration with Oxford Uni on Energy Labels
We conducted controlled experiments involving a market leading electric hot water tank against an instantaneous gas combi boiler using representative draw cycle tests. Hot water tanks outperform combis on efficiency by a significant margin (87% as opposed to 73% in this particular example. This is due to the fact that most hot water draw events are short in duration. In a combi boiler, the gas burners have to be fired up and all of the internal heat transfer equipment warmed up before useful heat can be delivered. Once the draw event is over, all of the heat which has been invested in getting the system up to operating mode is lost through the flue and casing of the appliance. For frequent and short draw events, this is very wasteful. Interestingly, these findings are consistent with work undertaken by Sustainable Homes who measured real world efficiencies of gas combi boilers and gas system boilers operating in tandem with hot water tanks. They found that system gas boilers with a tank outperformed gas combi boilers since the tank allowed for much lower cycling losses along with the installation of smaller and more efficient gas heating systems.
Given the backdrop in our energy system, where electric carbon intensity is now regularly sitting below the carbon intensity values for gas, these findings add further to the calls for the electrification of heat. Mixergy are working to assist in these efforts by developing highly efficient hot water tanks which make intelligent use of electricity whilst enhancing the performance of a system gas boiler or heat pump.
Read the full paper article here