*4.3. Primary Energy Consumption*

The annual index of primary energy consumption for space heating and domestic hot water for the considered low energy solar house is equal to 25.77 kWh/m2. The annual index for domestic hot water accounts for 4.11 kWh/m2. These are really very small values, far below the existing and future (since 2021) limits for such indices required by the present regulations. The primary energy consumption is based on renewable energy sources: solar, solar thermal collectors and ground, ground source heat pump; on waste heat, i.e., recovery of heat from the ventilation system and on conventional electrical energy taken from the grid. In Poland, more than 90% of electricity is produced in power plants fired by coal (hard and brown). Thus, taking electricity from the grid means using primary energy based on fossil fuels. The calculated value of annual CO2 emissions is equal to 596.8 kg per year. To estimate that value the official Polish energy mix with referred emissions for fossil fuel used was taken into account [27].
