Energy class C and D is normal for water heaters
The energy efficiency value of a water heater emerges through calculation and measurement:
Supplied electrical energy to water heater - Loss = Energy in the form of hot water
Energy efficiency = Energy in the form of hot water / electrical energy consumed
The definition of PEF - Primary Energy Factor is the following:
A conversion factor; is a coefficient that reflects the estimated, average calculated
40 percentage EU generated efficiency of electricity production, referred to in Directive 2012/27 / EU of the European Parliament and of the Council (1); value of conversion coefficient is PEF = 2.5.
The directive does not take into consideration that the Scandinavian countries use clean green energy in the form of hydropower; and therefore has a lower PEF than 2.5. Our influence in this context is very small compared to the rest of Europe.
Primary Energy Factor is used to calculate the maximum energy efficiency using the following formula:
100% available energy - Loss of production = 40% of consumption (100% / 2.5 = 40%)
The theoretical best result a water heater can achieve is therefore 40%.
40 % is the theoretical maximum efficiency attainable for electrically heated water heaters.
Reference to EU directive: Directive 2009/125/EC no 814/2013