Energy performance classes A-G

Decree No. 264/2020 Coll. on the Energy Performance of Buildings places buildings in seven classes: A - extremely efficient, B - very efficient, C - efficient, D - less efficient, E - inefficient, F - very inefficient and G - extremely inefficient. The classes are part of the energy performance certificate.

How the class is set

The class is not based on a fixed number of kWh per square metre. Instead, the building is compared with a reference building: a calculated model of the same type, shape, size, orientation and use, but with reference properties for its structures and technical systems. For non-renewable primary energy, the figure used in listings, the upper limit of class A is 0.8 times the reference value, B 1.2 times, C 1.6 times, D 2.3 times, E 3 times and F 3.7 times. Anything above that is class G.

The energy source matters too. The decree gives each energy carrier a primary energy factor, for example 2.1 for electricity, 1.0 for natural gas, 0.1 for logs and pellets and 0 for ambient energy, such as the heat a heat pump draws from its surroundings. For the same delivered energy, electric heating therefore scores worse on primary energy than gas, and the same house can get a different class with a different heating system.

Other indicators in the certificate

The certificate also gives classes for total delivered energy, for partial delivered energy (heating and cooling, hot water and humidity control, lighting and mechanical ventilation) and for the average heat transfer coefficient of the building envelope, which reflects the quality of walls, roof and windows. It helps judge how much insulation would help. The graphic part also shows the share of each energy source in delivered energy.

How to read it

The values in the calculation are theoretical and assume typical use, not the actual behaviour of the occupants. Two buildings in the same class can therefore use different amounts of energy, and real costs also depend on how the home is used and heated. The class is useful for comparing listings; for estimating costs, compare it with actual energy bills. A G in a listing can also mean that the agent never received a certificate, see class G.