Last Updated 1 year by Lukas
In this article I’d like to share my experience of owning a Passive House. I’ll also describe what I would have done differently if I had known what I know now. Together we will explore what are reasonable expectations of a Passive House. How to avoid the pitfalls I’ve fallen into, and how to get the most enjoyment and benefit from your new Passive House. As in the previous article, which described systems I had personal experience of, we will now go system by system and evaluate them. This article is based on almost three years of using, learning and fine-tuning the Passive House.
- System parameters
- Solar System 7 kWp, 11,5 kWh LiFePo4 battery, storage into water. As decribed here.
- Recuperation unit, heat pump, water monitoring. As described here.
- Passive house in ‘A’ energy category
- Two people living inside the house
- 5000 litres underground water tank for rain water
- Installed water saver devices which limit flow of water (shower, bath, sinks)
- Evaluation for year 2022 (After fine-tuning of systems)
- Living space 100 square meters
- Outside water temperature 10 degrees
- Internal temperature setup – day 22 degrees / night 21 degrees (0,5 degree hysteresis)
- 425 litres water tank setup (heating with heat pump) – cold days 37 degrees / sunny days 27 degrees (3 degree hysteresis). Maximal temperature is 75 degrees
- 65 litres water heater setup – heating up to 60 degrees
- Theoretical house storage capabilities (how much energy it can capture):
- LiFePo4 battery 11,5 kWh
- 65 litres of water (heating outside water by 50 degrees (from 10 to 60)) – 3,8 kWh
- 425 litres water tank (maximum is 75 – 24 = 51 degrees) – 25,4 kWh
- In total – 11,5 + 3,8 + 25,4 = 40,7 kWh (In theory, in reality we can expect something around 30 kWh)
Historical data of solar system production
On the picture below we can see the production of the 7 kWp solar system installed on the house. It’s clearly visible that during the months 11. , 12., 1., 2. the minimum energy is produced. During these months the house is mainly dependent on the external electricity grid.
Historical data of power consumption
The figure below shows the consumption of the Passive House from the grid. We can see that the highest consumption is associated with months when the production of the solar system is minimal. The total energy consumed from the external grid is approximately 2 700 kWh (2.7 MWh).
Historical data of power export into grid
On the picture below we can see how much the solar system was able to produce above the house’s needs and ability to consume the produced energy from the sun. In total, about 1.5 MWh was exported to the grid (for free at the time). Fortunately, since 2023 it’s possible to sell electricity to one company and buy from another at the same time. This means you can buy at a fixed price and sell at a spot price.
Historical data of water consumption
Here we can see the water consumption in the Passive House with installed water savers. The total consumption in 2022 is about 78 000 litres (78 cubic metres). The house has a 5000 litre underground water tank for rainwater. This is used exclusively for irrigation to save drinking water from outside.
How does it translate into real money?
- 2022
- Electricity bill 2022 – 2,7 MWh – CZK 14 000,-
- Water bill 2022 – 78 m3 – CZK 8 600,-
- Total 2022 – 14 000 + 8 600 = CZK 22 600,-
- Per month 2022 – 22 600 / 12 = CZK 1 900,-
- 2023 estimation (dramatic price change)
- Electricity bill 2023 (As per estimation from distributor) – 3,5 MWh – estimated total CZK 30 000,-
- Water bill 2023 – estimation 80m3 – estimated total CZK 10 500,-
- Estimated total 2023 – 10 500 + 30 000 = CZK 40 500,-
- Per month 2023 – 40 500 / 12 = CZK 3 375,-
According to current estimates for 2023 and dramatic price increases for electricity and water. It seems like 77% increase compared to the previous year. In order to compensate from a long-term point of view, in the next section we will propose several changes to the current configuration of the house systems.
Proposed changes for 2023
- Increase solar system from 7 kWp into 10 kWp (or if possible into maximum of inverter 14 kWp)
- To decrease electricity consumption
- Change currently used car into plugin hybrid car with at least 50-60 km range on elecriticty
- To decrease payment for gas
- To increase capacity for self-consumption of electricity produced by solar system
- Start selling electricity from solar system for spot price to make extra money to pay for elecricity bill
- To decrease price of electricity