Combining a Heat Pump with Photovoltaics: How to Raise Your Self-Consumption
, By NeueEnergie24, 9 min reading time
Photovoltaics can supply part of a heat pump's electricity. We explain the limits in winter, control via SG Ready, buffer tanks, battery storage and using surplus power for hot water.
Summary: A photovoltaic system can supply part of the electricity for a heat pump and thereby increase your self-consumption. It does not cover the full heating demand: according to the Verbraucherzentrale (the German consumer advice organisation), solar yield in winter is not enough for completely running a heat pump. The combination makes the most sense when the heat pump runs specifically at times when solar power is available, for example for hot water, a buffer tank or cooling in summer. This article explains the basics, control via interfaces such as SG Ready, and which components help.
What the combination can and cannot do
The Verbraucherzentrale puts it soberly: a photovoltaic system can supply part of a heat pump's electricity and thus reduces heating costs, but in winter the solar yield is not enough for completely running the heat pump. From November to February in particular, a photovoltaic system produces little electricity, regardless of the size of a battery storage unit. You should therefore set realistic expectations: the combination improves self-consumption and the utilisation of your system, but it does not replace drawing power from the grid in the cold season.
When solar power suits the heat pump
- Hot water: Hot water is needed all year round, including in summer when a lot of solar power is generated. When there is a surplus, the hot water temperature can be raised temporarily by a few degrees.
- Shoulder seasons: In spring and autumn, the system covers a larger share on sunny days.
- Cooling in summer: According to the German Heat Pump Association (Bundesverband Wärmepumpe, BWP), the demand for cooling often matches the photovoltaic yield well, provided the unit can cool.
Control: SG Ready and energy management
For the heat pump to use solar power in a targeted way, it needs a signal from the energy management system or the inverter. The BWP describes the SG Ready interface for this purpose. It identifies heat pumps that can be addressed via a defined interface for load management, and according to the BWP it can also be used to achieve the highest possible self-consumption in combination with photovoltaics. For heating heat pumps under interface specification 1.1, there are three operating states:
| State | Meaning according to the BWP |
|---|---|
| 1 | Power consumption is limited, in the extreme case to 0 kW (grid-supportive operation) |
| 2 | Normal operation |
| 3 | Boosted operation for heating and/or hot water; surplus energy is stored as heat in buffer or hot water tanks |
According to the Verbraucherzentrale, an energy management system is usually connected to the inverter and controls the flow of electricity between the photovoltaic system, heating, household and grid. The installer must make sure the components are compatible. Whether your heat pump supports SG Ready and how the signal is provided can be found in the manufacturer's technical documentation.
Avoiding frequent cycling
The BWP points out that the heat pump should not be switched on and off too often, because too many start-stop cycles put additional strain on the system. Surplus control should therefore work with minimum run times and threshold values.
Storage as a buffer: heat and electricity
When there is a surplus, a buffer tank can be charged more heavily. According to the BWP, heating cycles can be brought forward and the thermal mass of the building can be used, so that heat is produced when plenty of solar power is available. The Verbraucherzentrale notes that buffer tanks are not always necessary and cause losses; with inverter-driven units, the heating pipe system can already be sufficient as storage. In addition, a battery storage unit can take up electricity for the evening. For a typical single-family house (in general, without reference to a heat pump), the Verbraucherzentrale cites an increase in the self-sufficiency rate through a battery storage unit from about 25 to 30 percent to up to roughly 70 percent. A heat pump changes the consumption profile and should be taken into account when sizing the system. As a rule of thumb, the Verbraucherzentrale gives 1.5 kilowatt-hours of storage capacity per 1,000 kilowatt-hours of annual consumption; oversized storage units age faster and bring hardly any additional self-consumption. In our Battery storage category you will find systems for various applications.
Surplus power directly into heat: My-PV
Besides the heat pump itself, surplus solar power can also be used directly for hot water. According to the manufacturer, the My-PV AC ELWA 2 is a hot water heating device for grid-connected photovoltaic systems, continuously controlled from 0 to 3.5 kW, which uses surplus photovoltaic energy for water heating; it can be installed in hot water and buffer tanks. According to the manufacturer, the My-PV AC THOR 9s is a photovoltaic power manager, continuously controlled from 0 to 9 kW, for hot water, electric heat sources and optionally the heating, which can also be combined with a heat pump. Which solution suits your home depends on system size, storage and your heating; we will gladly advise you.
A summer day as a thought model
In the morning the system runs at low load, and at midday the photovoltaic system reaches its peak output. If the hot water tank is now charged to a slightly higher set temperature, the house uses electricity that would otherwise flow into the grid. In the evening the household draws on the stored heat and, where applicable, on the battery storage unit. In winter the picture is different: the heat pump runs mainly on grid electricity, and the solar yield contributes only a small share. How large the share is in your house depends on system size, roof, consumption and control. Before making a decision, therefore, have a specialist company or energy consultant carry out a planning assessment.
Measuring and monitoring
Whether the coordination is worthwhile can be seen from measured values. According to the Verbraucherzentrale, a heat meter shows the heat delivered in kilowatt-hours. The seasonal performance factor (Jahresarbeitszahl) is calculated from the heat delivered divided by the electricity consumed over a year. Together with the electricity drawn from the grid and the solar yield, you can check how much solar power is actually converted into heat. You should discuss a conspicuously low seasonal performance factor with the specialist company.
Typical operating strategies
- Charge hot water at midday: Hot water is preferably produced during the sunny hours and the tank is deliberately heated up in the process.
- Raise the buffer: When there is a surplus, the buffer tank is temporarily charged more heavily, and in the evening the house draws on the stored heat.
- Bring heating cycles forward: Heat is produced when plenty of solar power is available and stored in the building mass.
- Use the weather forecast: The BWP mentions integrating weather forecasts as a further option.
What always matters is that comfort and operational safety take priority and that the heat pump does not cycle more often than necessary.
Sizing the system correctly
For photovoltaics and heat pumps, the rule is: clarify the heat demand first, then plan the system. How to size the heat pump is explained in our article Air-to-water heat pumps: selection and sizing. On the photovoltaic side, module area, inverter and storage must be matched to one another. You will find modules under Solar modules, suitable inverters under Inverters and the heat pumps under Heat pumps.
Tax classification (Germany)
Regarding VAT in Germany: according to the German VAT Application Decree (Umsatzsteuer-Anwendungserlass, section 12.18), electricity consumers for newly generated electricity, for example charging infrastructure or a heat pump, are not among the essential components of a photovoltaic system. The zero rate under section 12(3) of the German VAT Act (§ 12 Abs. 3 UStG) therefore applies to the photovoltaic system and its essential components, not to the heat pump. You can read more in our article 0 percent VAT on photovoltaics. This is not tax advice.
Checklist
- Consider the annual electricity consumption of the household and the heat pump separately.
- Check whether the heat pump supports SG Ready or another interface for surplus control.
- Check the energy management system and inverter for compatibility.
- Have the buffer tank and hot water tank sized for surplus charging.
- Do not oversize the storage unit.
- Coordinate the metering concept and tariff with the grid operator.
Frequently asked questions
Can I run my heat pump entirely on solar power?
No, not all year round. The Verbraucherzentrale states that the solar yield in winter is not enough for completely running a heat pump. However, part of the electricity can come from your own system.
What does SG Ready mean?
SG Ready identifies heat pumps that can be addressed via a defined interface with three operating states for load management, for example for more self-consumption with photovoltaics.
Is a balcony power plant enough for the heat pump?
A plug-in solar device is limited to 800 VA of inverter output and 2,000 Wp of module output, and covers only a very small part of a heat pump's electricity demand. It can nevertheless make sense as a contribution to the household base load.
Do I also need a battery storage unit?
Not necessarily. A buffer tank on the heat side can also absorb surplus. Whether a battery storage unit is added depends on your consumption profile.
Sources
- Verbraucherzentrale (German consumer advice organisation): Wärmepumpe: Alles, was Sie wissen müssen (as of 14 April 2026)
- Verbraucherzentrale: Technik und Ausstattung einer Wärmepumpenanlage (as of 5 January 2026)
- Verbraucherzentrale: Lohnen sich Batteriespeicher für Photovoltaik-Anlagen? (as of 2 July 2026)
- Bundesverband Wärmepumpe (German Heat Pump Association): SG Ready-Label and Wie lässt sich die Wärmepumpe sinnvoll auf PV-Überschuss abstimmen? (as of 6 July 2026)
- Bundesfinanzministerium (German Federal Ministry of Finance): Umsatzsteuer-Anwendungserlass Abschnitt 12.18
- Bundesnetzagentur (German Federal Network Agency): Balkon-Solaranlagen
Are you planning photovoltaics, storage or water heating with surplus power? We will gladly advise you by email: kontakt@energie24.shop.
As of October 2026, not legal or tax advice. This article refers to the situation in Germany.