Your own solar power isn't free – but it's by far the cheapest charging energy for an electric car. Its true cost is the forgone feed-in remuneration: roughly 6 to 14 Rp. per kilowatt-hour depending on the utility. Grid electricity at home, by contrast, costs around 25 to 35 Rp., and public charging noticeably more again. The condition for the cheap tariff from the roof: the car is parked at the house during the day. (Guideline values, as of: July 2026)
Key points in brief
- Solar power is never «free»: every kilowatt-hour charged into the car would have earned money if fed in – that's its true cost.
- This forgone remuneration is roughly 6 to 14 Rp./kWh depending on the grid area – a fraction of the grid purchase price of 25 to 35 Rp.
- Public charging, especially at a fast charger, is the most expensive variant – your own roof the cheapest.
- Over the year, the difference adds up noticeably with a four-figure charging need – depending on mileage and parking times.
- The cheap tariff only applies if the car charges during the day: anyone who only charges at night is charging grid electricity – at the grid price.
Why solar power isn't free – but almost
The widespread idea goes: the system is paid off, the sun doesn't send a bill, so the car charges for free. That sounds good, but calculates wrong – and anyone who knows the correct calculation understands their own system better.
Every kilowatt-hour from the roof that flows into the car could have taken a different path: into the grid, for remuneration. This forgone feed-in remuneration is the true price of the self-consumed electricity – economists call that opportunity cost, we call it the honest figure. Depending on the utility and model, it lies between the statutory floor and around 14 Rp. per kilowatt-hour (the comprehensive tariff comparison shows the differences in the region).
That's the bad news for the free-charging idea – and at the same time the good news for practice: even calculated honestly, electricity from your own roof is the cheapest charging energy there is. A fraction of the grid tariff, with no subscription, no app, no charging-point fee.
Three price tags for the same kilowatt-hour
Where the electric car charges decides the price – and the range is bigger than many think:
| Charging location | What the kilowatt-hour costs | Assessment |
|---|---|---|
| Your own roof (surplus) | roughly 6–14 Rp. (forgone remuneration) | the cheapest variant |
| Grid electricity at home | roughly 25–35 Rp. | solid basis, mainly at night |
| Public charging / fast charger | significantly above that, depending on the provider | the most expensive variant – for on the road |
Guideline values, as of: July 2026. Your local electricity tariff, your grid operator's tariff sheet and the charging providers' prices are authoritative – all are adjusted periodically.
The logic behind the table is the same one that carries the entire self-consumption calculation: self-consumed solar power is worth roughly two to four times as much as fed-in power – and hardly any device in the household can take as much of it on a sunny day as a car with a half-empty battery. The electric car is therefore not just a new consumer, but the most grateful taker of the midday surplus.
What does that mean over the year?
An electric car increases electricity demand by a four-figure number of kilowatt-hours per year, depending on mileage. Multiplying this amount by the difference between the grid purchase price and the forgone remuneration – roughly 10 to just under 30 Rp. per kilowatt-hour depending on the tariff area – gives the order of magnitude of the savings potential: with a suitable profile, a notable three- to four-figure franc amount quickly adds up over the year.
We deliberately don't give an exact figure – it would depend on mileage, parking times, your grid purchase tariff and your feed-in tariff, and would be wrong for your case. What can honestly be said: the effect isn't a matter of a few Rappen, but one of the most noticeable items a solar system delivers in everyday life – provided the one big condition is met.
The condition everything hinges on: when is the car at home?
The cheap roof tariff only applies to electricity that actually comes from the roof – and the system produces between morning and evening. A car that's parked at the company car park during that time inevitably charges grid electricity at home, at the grid price. No wallbox changes that.
This parking-time question decides the whole calculation, which is why it comes first in every reputable consultation: home office, second cars and weekend chargers get a lot from the cheap tariff; the classic commuter with night charging gets little. For them, the home tariff is still cheaper than the public charging point – it just then has little to do with solar. How surplus charging works technically and how much each everyday profile gets out of it is covered in the electric car and solar guide.
And the technology – doesn't that cost too?
In fairness, the investment side belongs here too, even though it's pleasantly lean. The expensive piece – the car – is there anyway; the solar system usually is too. What solar charging additionally needs is a controllable wallbox that preferentially charges with surplus, and possibly an energy management system that coordinates multiple consumers. These are one-off items, while the cheap charging tariff recurs with every sunny day – what the wallbox itself costs is covered in a separate article.
Anyone still planning the system is best off laying the groundwork right away: an empty conduit to the parking space and reserve at the meter box cost little within the ongoing project. And anyone who wants to shift the charging need further into the sunlight hours will find the remaining levers – from the timer to control systems – in the guide Optimising self-consumption.
«So I'm charging for free then!» is one of the most common sentences when the electric car comes up in a consultation – and we gently correct it every time, because the honest version sounds almost as good. We then show the three price tags: what the kilowatt-hour from the roof «costs», namely the forgone remuneration; what it costs from the grid; and what the charging point demands on the road. For most people it clicks at this point – not because of the big numbers, but because of the logic: electricity from the roof isn't a gift, but it's unbeatably cheap as long as the car is there when the sun shines. And that's exactly where enthusiasm diverges: the home-office household charges practically only from the roof for weeks in summer, the commuter barely sees the effect. That's why we never calculate with brochure savings, but ask about everyday life first – the answer to that is worth more than any sample calculation.
Frequently asked questions
Is charging with your own solar power really free?
No – every kilowatt-hour charged into the car would have earned remuneration if fed in, and this forgone remuneration is its true price: roughly 6 to 14 Rp./kWh depending on the utility. That's not free, but a fraction of the grid tariff – and thus the cheapest charging energy there is.
How much do I save per year if I charge with solar power?
A blanket figure would be disreputable – the savings potential depends on mileage, parking times and your tariffs. The order of magnitude: with a four-figure charging need and the tariff difference of roughly 10 to just under 30 Rp./kWh, a notable amount adds up per year with a suitable profile. The honest calculation is done with your own figures.
Is solar charging worthwhile in winter too?
In winter the roof delivers little surplus – winter charging comes predominantly from the grid. Solar charging is a summer and transitional-season programme; calculated over the year, the effect nevertheless remains significant, because the sunny half of the year can cover most of the charging.
Do I need a storage battery to charge the car cheaply?
No – the car charges most cheaply directly from the roof, not via the detour of a home storage battery: filling one battery from another only costs losses. A storage battery can buffer the daytime surplus for night charging, but whether that pays off is a separate consideration – you don't need it for surplus charging during the day.
Is public charging always more expensive than at home?
As a rule, yes, especially at a fast charger – there you're also paying for comfort and speed. For on the road, that's the fair price for flexibility; for everyday life the order is clear: first your own roof, then the house connection, last the charging point. Anyone who can charge at home drives most cheaply.
Free initial consultation
What does your everyday charging cost – calculated honestly?
We calculate with your tariff, your mileage and your parking times instead of brochure figures – and plan the system and wallbox so that as much of the cheap roof electricity as possible ends up in the car.
Prefer to talk? +41 78 830 83 35
Charging station from a specialist company in Zurich →
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: ElCom (electricity price overviews); tariff sheets of the regional grid operators; ranges taken 1:1 from the tariff guide (R14); experience from ecoEn GmbH's consulting practice, Zurich region.
Last updated: 9 July 2026 · Author: ecoEn editorial team
