A turnkey 15 kWp system typically costs CHF 28,000 to 37,000 before incentives in Switzerland. After deducting the one-off feed-in incentive of currently around CHF 5,400, around CHF 22,600 to 31,600 remains – the tax deduction comes on top of that. Per kWp, this size class is among the cheapest in the single-family home range. (Guideline values, as of: July 2026)
Key points in brief
- 15 kWp is usually not a target size, but the result of full coverage: the roof allows it, so it's used.
- Space requirement: around 68 to 82 m² of roof area, i.e. 33 to 36 modules of today's design.
- Annual production on the Swiss Plateau: roughly 13,500 to 15,500 kWh – significantly more than most households consume.
- The bigger the surplus, the more important your utility's feed-in tariff becomes for the calculation.
- Per kWp, the 15 kWp class is noticeably cheaper than smaller systems – the fixed costs are due anyway.
The example calculation
| Item | Guideline |
|---|---|
| 15 kWp system turnkey (modules, inverter, installation, electrics, scaffolding, registrations, VAT) | CHF 28,000–37,000 |
| One-off feed-in incentive (KLEIV, approx. CHF 360/kWp) | – approx. CHF 5,400 |
| Remaining investment before the tax deduction | approx. CHF 22,600–31,600 |
Guideline values, as of: July 2026. Pronovo's current rates and the individual quote are authoritative. The tax deduction further reduces the effective burden – at this investment level, by a notable amount depending on the marginal tax rate.
Converted, that's about CHF 1,900 to 2,500 per kWp – at the lower end of what's possible in the single-family home range. The reason is the same as always: scaffolding, travel and administration cost hardly more at 15 kWp than at 8, but are spread over almost double the output. The article Cost per kWp explains the mechanics behind it.
Who even needs 15 kWp?
Honest answer: hardly anyone «needs» it today – and yet we regularly plan this size. That's not a contradiction. In practice, a 15 kWp system almost always comes about via one of two routes:
The roof allows it. A generous single-family home with a continuous roof area, or an east-west roof covered on both sides, quickly lands in this class with full coverage. Since the extra cost per additional kWp is small, full coverage is usually the more economical choice than an artificially downsized system.
Consumption grows predictably. A heat pump plus an electric car – or two electric cars – double to triple a household's electricity demand over the years. Anyone who sees this coming covers it properly once instead of putting up scaffolding twice.
For houses whose roof only allows half of that, it's no disadvantage – the corresponding derivation is shown in the 10 kWp article.
Where does the surplus go?
This is where the 15 kWp class differs noticeably from smaller systems. With annual production of 13,500 to 15,500 kWh and household consumption of maybe 5,000 to 9,000 kWh, a large part of the electricity is fed in – even with a heat pump and electric car. Two consequences:
The feed-in tariff becomes a real factor. What your grid operator pays for the surplus differs considerably in the region – the current overview: Feed-in tariffs compared. For smaller systems this is a minor item; at 15 kWp it visibly shifts the calculation.
Self-consumption still remains king. Every kilowatt-hour used yourself brings more than any fed-in one. The article Self-consumption or feed-in? covers how much optimisation makes sense – and the article Optimising self-consumption covers the specific levers.
On top of that comes a detail many don't have on their radar: there's also remuneration for the guarantee of origin (GO) of the fed-in electricity, depending on the utility – at this production volume, it's worth taking a look.
With or without storage?
The storage question comes up more clearly at 15 kWp than with small systems, because a lot of surplus accumulates on summer days. Our assessment remains the same: the system also works economically without it, and a hybrid inverter keeps the retrofit option open. For anyone who already has high evening and night consumption today (heat pump, electric car with home charging), the storage battery can become worthwhile sooner. The figures: Solar system with storage and Is a battery storage system worthwhile?
With large roofs, we see two thinking errors in both directions. One: «15 kWp is too much for us» – calculated on today's consumption, that's often true, except the system sits on the roof for 25 years and more, and during that time most people add a heat pump or electric car. The other: the expectation that the large surplus turns the system into a financial investment. Feed-in contributes to the calculation, but it doesn't carry the calculation. Anyone who soberly weighs up both points usually makes the size decision quickly – the roof decides, not the round number.
Frequently asked questions
How much roof area does 15 kWp need?
Around 68 to 82 m² with today's modules at 430–450 Wp, which corresponds to 33 to 36 modules. On east-west roofs, the coverage is spread over both roof halves; the usable area is smaller than the roof area on the plan because of chimneys, windows and edge clearances.
What does the one-off feed-in incentive bring at 15 kWp?
Currently around CHF 5,400 (approx. CHF 360 per kWp, as of: July 2026). Pronovo's rates at the time of commissioning are authoritative – eligibility and process are covered in the article One-off feed-in incentive.
Do I need a permit for 15 kWp?
There's no special hurdle for the system size itself – as with any system, the municipality's notification procedure and the connection request to the grid operator are authoritative. Special rules apply for protected buildings or in core zones, independent of the size.
Is full feed-in worthwhile at 15 kWp?
In individual cases that can be interesting, for instance with very low self-consumption. For most homes, the combination of self-consumption plus feeding in the rest remains the better calculation. That depends on your utility's tariffs – we calculate both variants side by side on request.
From when does an apartment-building model (ZEV) become relevant?
As soon as several dwellings in the house are meant to use the solar power. This can already come up with large single-family home systems that have a granny flat – the models compared: ZEV, vZEV or LEG?
Free initial consultation
Does your roof allow for 15 kWp?
We check the area, shading and electrics – and calculate the variants for you with your municipality's tariffs. Free of charge and without obligation.
Want to calculate yourself first? Solar calculator with official roof data →
Prefer to talk? +41 78 830 83 35
Have a photovoltaic system installed →
Swissolar-certified specialist company · ESTI installation authorisation (Art. 14 NIV) · in Zurich since 2017 · over 150 systems completed · a personal answer from the specialist company, no call centre
Sources: Pronovo AG, Swiss Federal Office of Energy SFOE, EnergieSchweiz (sonnendach.ch), Swissolar.
Last updated: 9 July 2026 · Author: ecoEn editorial team
