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Who can use the form and what is required
The form is intended exclusively for detached houses with direct electric heating (underfloor or ceiling heating, radiant panels, convectors).
Specific building parameters must be entered into the form; you will therefore need to have an Energy Performance Certificate (EPC) drawn up in accordance with Decree No. 264/2020 Coll. PLEASE NOTE – the form is intended solely for a single-zone model of a detached house. The certificate may specify any type of heating or domestic hot water system; these details are not decisive for the calculation form. The output from this calculation will then be provided to the energy specialist, who will use it to adjust the technical systems in the PENB.
To keep the form as simple as possible, it does not include all possible variants of technical systems, and some variables are set as fixed values (such as system efficiency). The resulting values should therefore be regarded as indicative, albeit with a relatively high degree of accuracy.
The form cannot be used for blocks of flats (due to a different method of calculating hot water demand and a different reduction in PEzNZ consumption for the reference building) nor, due to the revised methodology, for certificates drawn up in accordance with Decree No. 78/2013 Coll.
What is Primary Energy from Non-Renewable Sources (PEzNZ)?
PEzNZ consumption is calculated by multiplying the energy consumption for individual systems (heating, domestic hot water, lighting, etc.) by a coefficient (conversion factor) depending on the source from which the energy is or will be produced (i.e. the energy carrier).
The table below sets out the currently valid conversion factors and how they influence the assessment of buildings:
| Energy carrier |
Conversion factor
PEzNZ |
Energy consumption
for heating |
Consumption
PEzNZ |
| Natural gas |
1.0 |
5.0 MWh/year |
5.0 MWh/year |
| Solid fossil fuels (lignite/bituminous coal) |
1.0 |
6.5 MWh/year |
6.5 MWh/year |
| Heating oil |
1.2 |
5.0 MWh/year |
6.0 MWh/year |
| Electricity |
2.1 |
4.0 MWh/year |
8.4 MWh/year |
| Logs, wood chips |
0.1 |
7.0 MWh/year |
0.7 MWh/year |
In practice, this means that a house with electric heating, which has the lowest energy consumption thanks to the high efficiency and controllability of the heating system, appears to be the least efficient when compared with other systems (including coal or heating oil). And it is precisely the figures in the last column that are decisive for assessing a building’s energy performance.
In order to install electric heating in a building, it is essential to reduce the high PEzNZ consumption, which has been artificially inflated by a coefficient. This can be achieved through a suitable combination of various measures:
- reducing the energy required for heating – for example, by improving the building envelope or installing ventilation with heat recovery
- installing supplementary systems utilising Renewable Energy Sources (RES) – for example, a heat pump for domestic hot water, or a (multi)split reversible air-conditioning system, which can also be used for heating (= A/A heat pump)
- Installing a supplementary source utilising an energy carrier with a more favourable conversion factor. Typically, wood-burning stoves, which have a conversion factor of 0.1
- By installing a small domestic photovoltaic power plant (PV), as the electricity generated has a negative conversion factor and the energy produced by the PV system is deducted from consumption
The calculation form allows you to test various combinations of the above options and find a solution that should lead to compliance with the legislation requirements for PEzNZ consumption whilst also being acceptable to the investor.
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