The profitability of a solar system rests on four figures: net investment (after incentives and tax effect), annual production, self-consumption share, and the two electricity prices – what grid purchase costs and what feed-in brings. Anyone who knows these figures can calculate the annual benefit themselves in five minutes. This article shows the method and a complete example – with guideline values for you to replace with your own figures. (As of: July 2026)
Key points in brief
- Four input figures are enough: net investment, production, self-consumption share, electricity prices (purchase and feed-in).
- The annual benefit consists of two parts: avoided grid purchase plus feed-in remuneration.
- The self-consumption share is the strongest lever – every kilowatt-hour you use yourself is worth a multiple of one fed in.
- Calculate conservatively: the lower end of the range for yields, the upper end for costs.
- A reputable quote discloses exactly this calculation – with your figures instead of blanket values.
Which figures belong in the calculation?
Four – and all four can be specifically determined for your house instead of assumed as a blanket figure:
1. The net investment. The starting point is the system cost according to the quote – the cost guide provides the guideline-value bands. Deducted from that: the one-off feed-in incentive, any local incentives, and the tax effect of the investment deduction. What remains is the amount the system actually has to earn back.
2. The annual production. As a guideline value, a system in the region produces around 950 to 1,100 kilowatt-hours per installed kilowatt-peak per year – depending on orientation, tilt and shading; the derivation is in the article on yield per kWp.
3. The self-consumption share. How much of the production you use yourself – typically a quarter to a third without special measures; more with control, a heat pump or an electric car. The article Self-consumption or feed-in explains why this figure carries so much weight.
4. The two electricity prices. The grid purchase price (typically 25 to 35 Rappen per kilowatt-hour, depending on the utility and tariff) determines the value of self-used electricity; the feed-in tariff (typically 6 to 14 Rappen) determines the value of feed-in. Both are stated in your grid operator's publications.
This gives the core formula for the annual benefit:
Annual benefit = (self-consumption × grid purchase price) + (feed-in × feed-in tariff) − operating costs
The complete example calculation – step by step
Let's take a typical 10 kWp system on a single-family home – all figures are guideline values for you to replace with your own:
| Step | Calculation | Result |
|---|---|---|
| Investment (guideline value) | according to the 10 kWp cost band | CHF 24,000–30,000 |
| − One-off feed-in incentive | around CHF 360/kWp | − CHF 3,600 |
| − Tax effect (individual) | depending on income/canton | − several thousand CHF |
| = Net investment | roughly CHF 17,000–23,000 | |
| Annual production | 10 kWp × 950–1,100 kWh | ~9,500–11,000 kWh |
| Self-consumption (30%) | ~3,000 kWh × 30 Rp. | ~CHF 900 |
| Feed-in (70%) | ~7,000 kWh × 6–14 Rp. | ~CHF 420–980 |
| = Annual benefit (before operating costs) | ~CHF 1,300–1,900 |
Illustrative example calculation with guideline values, as of: July 2026, without obligation – your quote, your tariff and your tax situation are authoritative. The tax effect is individual; the ranges deliberately show bandwidths rather than false precision.
If you set the annual benefit against the net investment, the example system lands in the order of magnitude that the articles on payback and the question «is it worth it?» also cite: typically between ten and fifteen years – with a module lifetime of 25 to 30 years. The years after that are the real profit.
Two notes on reading the table. First, the range of the feed-in value: between 420 and 980 francs there's more than a factor of two – that's the real difference between the tariff areas in the region and the reason the calculation has to stand with the tariff at your address. Second, the self-consumption lever: if the share rises from 30 to 40 percent, around 1,000 kilowatt-hours move from the 6-to-14-Rappen column into the 30-Rappen column – depending on the tariff, that's 160 to 240 francs more per year, every year, without a single extra franc of investment.
How do I calculate honestly – and how do I spot number-dressing?
By four principles that every honest profitability calculation shares:
Set conservative figures. The lower production range, realistic (not optimistic) self-consumption, and for market-price tariffs the cautious annual average instead of the best quarter. Anyone who calculates this way and comes out positive is rarely disappointed in reality.
Don't forget operating costs. Meter, any insurance adjustment, reserve for the inverter replacement after 10 to 15 years – the items are manageable, but they belong in the calculation; the article on maintenance costs puts them into context.
Electricity price trends as sensitivity, not as a bet. Rising grid purchase prices improve the calculation – but a reputable calculation already works with today's prices and treats increases as a reserve.
Know the warning signs. An exact payback figure in the sales conversation («9.2 years!»), electricity price increases of several percent a year calculated in as a base, missing operating costs – these are the patterns of number-dressing. What's reputable is ranges with disclosed assumptions; that's exactly how you can recognise a good quote.
The most valuable tool in our consultations isn't the finished figure, but the open calculation: we lay out the four input figures side by side and calculate together – with the real tariff for the address, the real consumption profile, the real quote costs. Almost always the same thing happens: the client starts turning the levers themselves. «What if we run the washing machine at midday?» – then self-consumption rises, and the calculation shows it immediately. This understanding is worth more than any glossy forecast: anyone who understands their own calculation buys the right system – and then operates it correctly too.
Frequently asked questions
Can I really calculate profitability myself?
Yes – with the four figures from this article and your grid operator's publications, you can arrive at a robust order of magnitude. What your own calculation doesn't replace: the specific roof assessment (production) and the quote (investment). But you can trace through any quote's calculation – and that's exactly what you should do.
What self-consumption share is realistic?
Typically a quarter to a third of production without measures. Significantly more with simple consumption shifting, a heat pump or an electric car. Be wary of calculations with high blanket assumptions without justification – the share depends on your everyday life, not on the brochure.
Should I calculate with rising electricity prices?
As a sensitivity, yes – as a basis, no. A system that pays off with today's prices is a solid investment – rising prices improve it. A system that only pays off with assumed price jumps is built on sand.
How does a storage battery change the calculation?
It raises the self-consumption share, but costs its own money – the storage question is a separate calculation with its own rules. The sensible sequence is: first calculate the system cleanly, then check whether the consumption profile supports a storage battery.
Why doesn't anyone give me an exact payback figure?
Because nobody can honestly know it – it depends on the weather in a given year, tariff developments and your behaviour. What's reputable are ranges based on conservative assumptions. An exact figure in a sales conversation isn't a sign of competence, it's a warning sign.
Is photovoltaics worth it in Switzerland?
For most single-family homes with a usable roof, yes – the system produces electricity for around 8 to 15 Rappen per kilowatt-hour, while grid electricity costs significantly more in the Zurich region. How well it pays off depends on the four figures from this article: net investment, annual yield, self-consumption share, and the difference between the electricity price and the feed-in tariff. The more you consume yourself – for example with a heat pump or electric car – the clearer the calculation.
When isn't a solar system worth it?
With heavily shaded or very small roofs, with a roof that needs renovating within a few years, or when almost all the electricity is fed in instead of self-consumed and the feed-in tariff is low. Moving away within a few years also shifts the calculation, because the system's value isn't always fully paid at sale. In these cases we calculate honestly – and sometimes advise against it or recommend a smaller system.
Free initial consultation
Your calculation, laid openly on the table.
We calculate your system with the four real figures for your situation – the tariff at your address, your consumption, conservative bands. To check for yourself, not to take on faith.
Want to calculate yourself first? Solar calculator with official roof data →
Prefer to talk? +41 78 830 83 35
Photovoltaic installer for your region →
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: Guideline values from the linked guides (cost, EIV, yield, tariffs — each with its own source basis), tariff publications of the regional grid operators. Example calculation illustrative and without obligation; the individual quote is authoritative.
Last updated: 9 July 2026 · Author: ecoEn editorial team
