Solar energy and a heat pump work together in two ways. Photovoltaic (PV) panels on the roof generate the electricity the heat pump uses; solar thermal collectors transfer the sun's heat directly into the hot water tank. You can install both, or just one of them. Because a heat pump already takes most of its heat from the outdoor air, combining it with solar means a large share of the building's heating and hot water demand comes from renewable sources.
This article explains how each arrangement is set up, at which hours it pays to use the electricity the panels generate, and how AD indoor units connect to solar collectors.
A heat pump already uses renewable heat
An air-source heat pump delivers several times as much heat as the electricity it uses. The difference comes from the outdoor air, and the heat in that air is, in the end, the heat of an atmosphere warmed by the sun. The European Union's renewable energy legislation counts this heat taken from the air as a renewable source under the name aerothermal energy.
A simple example: a unit with a COP of 4 delivers 4 kWh of heat from 1 kWh of electricity, and 3 kWh of that comes from the air. If the remaining 1 kWh is generated by the sun as well, all of the heat entering the building during that hour is renewable. We explain how the unit takes heat from the air in our article on what a heat pump is and how it works.
With photovoltaic panels: electricity from the sun
This is the most common arrangement, and it needs no special equipment on the heat pump side. The panels and their inverter are connected to the building's electrical installation, and the heat pump draws its power from that installation like any other appliance. To size the panels, you first need to know the heat pump's annual electricity consumption.
Let us work through an example. Our assumptions: the building's annual demand for heating and hot water is 12,000 kWh, the heat pump's seasonal efficiency (SCOP) is 3.5, and 1 kWp of panels generates 1,400 kWh of electricity a year in the region. The heat pump then uses about 3,430 kWh of electricity a year, and on paper about 2.5 kWp of panels is enough to cover it. That, however, is an annual total; the real question is whether generation and consumption fall in the same hours.
When choosing the panel capacity, it also helps to know how much power the unit draws at any moment. According to our technical table, the maximum power input of the Poyraz 12 is 3.7 kW and that of the Poyraz 16 is 4.7 kW; most of the time the unit runs at part load, below these values. The closer the panels' output around midday comes to these figures, the larger the share of the heat pump's electricity that comes straight from the roof.
We look in detail at what drives consumption and how the calculation is set up in our article on heat pump electricity consumption.
Timing: when to use what the sun produces
Panels generate most in summer and around midday. Heating demand peaks in winter, in the morning and evening. This mismatch is handled in two ways: net metering with the grid, to the extent local regulations allow it, and increasing self-consumption, that is, running the heat pump more during sunny hours. The second needs somewhere in the system to store heat.
- Heat the hot water at midday: heating the domestic hot water tank during sunny hours is the easiest gain. The tank keeps the water for the evening.
- Use the tank and the floor as storage: a buffer tank or an underfloor heating screed carries heat stored during the day into the evening. Raising the indoor set point by about one degree around midday does the same job.
- Summer cooling matches by itself: the hot afternoons when cooling demand peaks coincide with the hours when the panels generate most.
- Monitor consumption: the touch panel of the HİDRA and HİDREM indoor units shows energy consumption by day, month and year. Comparing these figures with the panels' output shows which hours are working for you.
The difference between seasons also has to be taken into account. In a building where heating dominates, the panels' summer surplus usually goes to the grid, and in winter the shortfall is drawn from the grid. On the Mediterranean and Aegean coast, where cooling outweighs heating, the balance is different: most of the load already falls in the sunny months. The Vaha series, which we designed for these regions, suits this pattern well because its cooling is tuned for long, hot summers.
The heat pump does not depend on the sun. On a cloudy winter day the electricity comes from the grid and comfort stays the same; the sun only decides how much of that day's electricity came from the roof.
Solar collectors and an indoor unit with tank
Solar collectors (flat-plate or evacuated-tube) turn sunlight directly into heat and carry that heat to a tank with a circulation pump. You can think of them as a pumped, controlled version of the solar water heaters often seen on roofs in Türkiye. Used together with a heat pump, the collector heats the tank and the heat pump only makes up whatever is missing.
AD indoor units are ready for this connection:
- The HİDRA indoor unit with tank connects the collector circuit to its built-in 80–140 litre tank through a second Grundfos circulation pump inside the unit. When the sun is enough, hot water comes from the collector; when it is not, the heat pump takes over. No separate solar tank and no pipework of its own are needed.
- The HİDREM indoor unit with direct-expansion cooling uses the same tank body and second pump. In summer, while it cools through air-conditioner indoor units, it also transfers the heat drawn from the rooms into the tank, so summer hot water comes both from the collector and from the heat of cooling.
- The HİD / HİT wall-mounted indoor unit has no tank; hot water is prepared in an external cylinder, and the collector line is again connected through the second Grundfos pump in the unit.
Collectors are most useful in summer. In the winter months their output drops and most of the load falls to the heat pump. It is best, therefore, to think of the collector as a helper that takes much of the hot water load off the heat pump throughout the summer.
Panels or collectors?
- Collector: produces heat only, but delivers a lot of heat per square metre. It works well where hot water is the main need and on buildings with small roofs. Heat produced in summer is wasted if it cannot be used.
- PV panel: produces electricity, which can be used for heating, cooling, hot water and every other appliance in the house. Used with a heat pump, each kWh the panel generates becomes as many kWh of heat as the unit's COP.
An example: assume a panel efficiency of 20% and a heat pump COP of 3. The heat obtained is then about 60% of the solar energy falling on the panel. That is in the same range as the typical efficiencies collectors reach when producing hot water, and the panel's electricity is useful for other things in every season of the year.
In practice the decision depends on the roof and the need. If roof space is limited and hot water demand is high, the collector comes first; if the house will also be cooled in summer and has other electricity use, panels do. Where there is room, both can be installed: the indoor units with tank take care of the collector, the electrical installation takes care of the panels.
For a cleaner world
How we heat our homes also decides the air our children will breathe. When a heat pump with no flue gas is combined with the sun on the roof, the building generates part of its own energy and burns nothing to keep warm. Large changes start with small, well-calculated decisions like this. You can read about the climate impact of heat pumps in our article on the environmental impact of heat pumps, and about our approach on our sustainability page.
For your project
Include the existing or planned panel capacity, the collector area and your type of heating system (underfloor heating, radiators, fan coils) in your quote request, and we will choose the outdoor and indoor units accordingly. The series and indoor units are on our heat pump products page, and the quote form is on our contact page.