Bluetti EP 600 Energy Storage System in a modern terrace house with underground garage and two floors of living space in central Graubünden at 600 meters above sea level.

The approximately 32 m² solar panels with an output of 5.8 kWp are used exclusively to supply power to the heat pump, the circulation pump for the underfloor heating, and the trace heating for the hot water pipe via the Bluetti EP600 inverter with the two B500 power storage units (total 10 kW).

The pure concrete construction with 20 cm external insulation on the walls and 30–40 cm insulation on the ceiling above the upper floor has a very good, low overall U-value. This makes the concrete construction an optimal mass storage unit. The advantage of this is that the house reacts slowly to temperature fluctuations. In summer, the apartments remain cool, and in winter they stay consistently warm for several days, regardless of whether the weather is sunny or cloudy with cold outside temperatures. This also applies in the event of a heating failure due to power outages or technical problems.

The photovoltaic system is located on the west-facing, 30° sloped roof surface of the annex on the roof terrace.

Components used

• Photovoltaics: Sunskin Roof Lap solar modules from Swiss Pearl. Total area 32 m² and maximum output of 5.8 kWp.
• Inverter and power storage: Bluetti EP600 ESS 6 kVA / 6 kW PV batteries: Bluetti B500 2 units for 10 kWh power storage
• Heat pump: Mitsubishi Ecodan PUZ air-to-water heat pump. Max. heating output 11.2 kW. 600 L hot water tank with 3 kW electric heating element for weekly, short-term heating of hot water to 63° (legionella switch). 750 L heating water buffer tank.
• Heat/heating surface: Underfloor heating, total 340 m², distributed across four apartments on two floors. 12 meters of trace heating for the hot water riser.

Conclusion after one year (2025) of operation

Photovoltaic production: 6,900 kWh. Purchase of 4,800 kWh of electrical energy from the power company (70% low tariff). Own consumption of electricity from photovoltaics: 4,600 kWh. 2,300 kWh were fed into the grid with a credit from the power company.

Due to the westward orientation of the solar panels and the favorable location of the terrace house in a virtually fog-free area on a southwest-facing slope, the astonishing yield of around 6,900 kWh of solar power is achieved.

Thanks to the two Bluetti B500 power storage units with a total storage capacity of 10 kWh, a high level of self-consumption of solar power was achieved.