A part of the heat pump electricity can be covered with your own solar electricity – but not the largest part. The reason is the season: the heat pump needs the most in winter, when the roof delivers the least. Over the year, the own system therefore covers a noticeable, but limited share of the heating electricity; the lion's share of the solar benefit is in the summer half of the year, for hot water and via control and battery. Anyone who takes «heating with the sun» literally will be disappointed – those who understand the coverage rate correctly plan more satisfactorily. (As of: July 2026)
Key points in brief
- The coverage rate states what proportion of the heat pump electricity comes from your own PV system – and on an annual average, this proportion is smaller than advertising suggests.
- The opposing curve is to blame: a lot of heating demand in the low-light winter, a lot of sun in the heating-free summer.
- Hot water is the most grateful part – it accrues all year round and can be well covered with midday electricity.
- Control, system size and a battery increase the coverage rate – but a battery storage does not bridge a winter.
- What is decisive is the overall calculation over the year, not the wishful thinking of a self-sufficient winter.
What does «coverage rate» even mean?
The solar coverage rate answers a simple question: of the total amount of electricity that your heat pump consumes over the year, what proportion comes from your own roof instead of from the grid? A coverage rate of – let's say – one third would mean: you produce one third of the heating electricity yourself, you purchase two thirds.
This single number is often sold in a striking way and misunderstood twice over. Firstly, many confuse it with the degree of self-sufficiency of the whole house – but the heat pump is just one consumer among several. Secondly, the annual value is an average that hides the actual story: behind a medium coverage rate lie an excellent summer and a lean winter. Exactly this spread is the core of the topic – and the reason why the honest answer is more nuanced than any advertising promise. How the interaction fundamentally works is explained in the overview combine heat pump and photovoltaics; this is specifically about the question of how much of it realistically comes together.
Why is the coverage rate so low in winter?
Because two curves run counter to each other. The heating demand follows the cold: it is highest in December and January. Solar production follows the light: it is exactly then at its lowest. Short days, flat position of the sun, fog and snow mean the system delivers only a fraction in mid-winter of what it manages in June – while the heat pump conversely runs at full speed.
The result is uncomfortable, but physical: on a clear winter day the roof helps, on a cloudy one hardly at all, and at night – when heating is taking place – not at all. The largest part of the winter heating electricity therefore remains grid procurement. No trick fundamentally changes this, and anyone who promises a high winter coverage rate is selling an illusion. The good news is in the other half of the year: the transitional period and summer deliver plentifully – only the heating needs almost nothing then.
Where solar electricity really covers the heat pump well
There is one consumption that occurs throughout the entire solar season and can be excellently covered with solar electricity: the hot water. Unlike room heating, it is also needed in July – and can be timed so that the boiler charges at midday, when the roof delivers the most. Anyone who wants to raise the coverage rate starts here.
The second good case is the transitional period: on mild, sunny days in spring and autumn there is a moderate heating demand – and precisely then the system is already or still producing decently. In these weeks, the heat pump runs to a considerable extent on its own electricity. If you add hot water and the transitional period together, the noticeable, real solar share of the heat pump emerges – not in deep winter, but all around it.
Which factors increase the coverage rate?
| Lever | Effect on the coverage rate | In depth |
|---|---|---|
| System size | larger roof = more surplus for the heat pump, especially in the transitional period | PV size with heat pump |
| Control / SG-Ready | actively shifts hot water and heating buffer into the sun hours | SG-Ready & energy management |
| Hot water priority | uses midday electricity for year-round consumption | Optimising self-consumption |
| Battery storage | shifts solar electricity into the evening – but not over months | Battery & heat pump |
| low flow temperature | more efficient heat pump = less electricity demand per kilowatt hour of heat | Heat pumps in older buildings |
Classification, As of: July 2026 – the achievable coverage rate is individual and depends on roof, building, consumption profile and control. Concrete percentage values can only be seriously calculated with your data.
The most important point about the battery: it is a day-night tool, not a season tool. A home battery shifts the solar electricity from midday to the evening and thus increases the coverage rate in the warm half of the year. It does not bridge the winter – for that it would have to have a hundred times its capacity. Anyone who buys a battery to heat self-sufficiently in January is buying past the problem.
How do you honestly classify the coverage rate?
With a shift in expectations: the value of the combination does not lie in running the heat pump at zero cost, but in feeding a large additional consumer to a good extent with self-produced, cheap electricity in the first place. Self-consumed solar electricity is worth significantly more than fed-in – and no consumer in the house can absorb as much of it as the heat pump in the solar season.
Therefore, the right key figure is rarely the pure winter coverage rate, but the annual benefit: how much expensive grid electricity does the combination replace overall? This question can be realistically quantified with your consumption, your roof and your control – sweeping percentage promises, on the other hand, cannot. And it generally turns out positive, precisely because hot water and the transitional period contribute more than a glance at the cold January might suggest.
The most common sentence in consultations on this topic: «Then I'm heating with the sun.» Our honest answer is: partially – and at the right time. Anyone who comes with the idea of being self-sufficient in January will be disappointed; those who understand that the system carries the hot water almost all year round and vigorously helps heat in the transitional period, will be more satisfied in the end. The disappointed system owners are almost never those with the low winter coverage rate – it is those to whom someone promised a high one.
Frequently asked questions
How high is a realistic coverage rate?
That depends too heavily on roof, building, system size and control to name a serious blanket figure – any such figure would be a guess. As a principle: good in the transitional period and for hot water, low in mid-winter, noticeable on annual average, but never full supply. It can be calculated with your consumption data.
Can I bridge the winter with a larger battery?
No. A battery storage shifts electricity by hours, not by months. For winter coverage it would have to have a multiple of the usual size – that is neither economical nor practical.
Does the solar system cover heating or hot water more?
Hot water can be well covered all year round because it also occurs in summer and is flexible in terms of time. Room heating benefits above all in the transitional period; in mid-winter it remains mostly dependent on grid electricity.
Is the combination worthwhile despite the low winter coverage rate?
In general yes – what is decisive is the annual benefit, not January. The heat pump draws a lot of its own electricity in the solar season, which would otherwise be fed in cheaply. The economic classification is in the article combine heat pump & PV.
Does an SG-Ready heat pump increase the coverage rate?
Yes, because the control lets the heat pump run specifically when the roof delivers – especially for hot water and when charging the heating buffer. Details: SG-Ready & heat pump.
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Sources: EnergieSchweiz, FWS Fachvereinigung Wärmepumpen Schweiz, Swiss Federal Office of Energy SFOE.
Last updated: 9 July 2026 · Author: ecoEn editorial team
