Photovoltaics simply explained: Chapter 1 in the Solar-Guide

In this chapter, you'll learn

• how sunlight turns into electricity – in two sentences instead of a physics lesson;
• which path the electricity takes from the roof to the socket;
• why «self-consume» is the magic word of the whole calculation.

What happens on the roof?

The core piece are the solar modules – the dark panels that you know from countless roofs. Inside them is a material that has a remarkable property: If light falls on it, electrical voltage is generated. Nothing more is needed. No motor that turns, no fuel that is burned, no noise. Light in, electricity out.

The technical term for this is «photovoltaic effect» – you don't have to remember that. More important are three everyday consequences of this principle. Firstly: The system works as soon as it is light – even when overcast, then simply with less power. Secondly: At night it produces nothing; where the electricity then comes from, we'll clarify in a moment. And thirdly: Because nothing moves and nothing wears out like in a motor, modules last for decades and hardly need any maintenance.

We can clear up one misunderstanding right here: You don't need a southern sun for solar power. The Swiss Plateau gets more sun than many think – enough that well-planned systems have been proving themselves here for years. Whether this also applies to your roof is the question of the next chapter; Chapter 10 clears up the most persistent solar errors.

Which path does the electricity take to the socket?

From the roof to your refrigerator, the electricity passes through four stages – and these can be counted on one hand:

The path of electricity, simplified. The components in detail: Chapter 3.

The only station that deserves an explanation is the second one. Solar modules deliver a type of electricity that your devices can do nothing with. The inverter – an inconspicuous box in the basement or utility room – translates it into the usual household electricity from the socket. It is, so to speak, the interpreter of the system and, incidentally, its watchdog: it monitors operation and reports if something is wrong.

Everything else – how the modules get onto the roof, what exactly the meter can do, what a battery is good for – belongs in Chapter 3, the system at a glance. For a basic understanding, the four steps are completely sufficient.

What happens to the electricity you don't currently need?

This is where it gets interesting, because a solar system does not produce according to your daily schedule, but according to the sun's. Most electricity is generated around midday – often exactly when nobody is at home. What happens to this surplus?

It flows via the meter into the public grid, and your utility remunerates you for it. Conversely, in the evenings, at night and on cloudy winter days, you draw electricity from the grid as normal, just as before. So the house is never without electricity – the system and the grid complement each other, the meter keeps both directions apart. You notice nothing of this in everyday life.

And now the magic word that determines the entire cost-effectiveness: self-consumption. A kilowatt hour that you consume yourself replaces expensive electricity that you would otherwise have to buy. A kilowatt hour that you feed in only brings the – usually significantly lower – remuneration from the utility. Self-used electricity is therefore worth more than fed-in electricity. From this one sentence follows almost everything that needs to be said later about batteries, heat pumps and e-cars: they all help to use more of your own electricity yourself. Exactly where your electricity and your money flow is calculated in Chapter 6.

Is that enough for a whole house?

The honest answer has two halves. Calculated over the year: often yes – a well-covered single-family home roof often mathematically produces as much electricity as the household consumes in the year, sometimes more. As a rough guideline value, a well-oriented system in the region delivers around 950 to 1,100 kilowatt hours per kilowatt of installed capacity and year – what that means for your roof is shown free of charge by the official portal sonnendach.ch.

The second half of the answer: the electricity doesn't always come when you need it. In summer, much more is generated than the house swallows; in winter, significantly less. A lot at midday, little in the evening. A solar system therefore does not make a normal house completely independent of the grid – anyone who promises you «autarky» promises too much. What it does is more modest but still considerable: it noticeably reduces your electricity draw and turns you into a producer. Whether that pays off depends on the roof, consumption and tariffs – the assessment is provided by the guide Is a solar system worth it in Switzerland?

Anyone who wants to delve deeper into the technology after this chapter – cell types, efficiencies, the interaction in detail – will find the complete picture in the technology guide on how photovoltaics work. You don't need it for the guide path: you now have the basic principle.

### Keep in mind A solar system is a power plant with no moving parts: light in, electricity out – and the most valuable is the electricity you consume yourself.

In brief

Does the system also produce when it's cloudy and in winter? Yes, modules also use the diffuse light of an overcast sky – just with significantly less power. In winter, the yield drops noticeably: shorter days, lower sun, fog in the Swiss Plateau. The greater part of the annual production falls in the summer half-year, and this is exactly how a system is calculated.

Do I have electricity from the roof during a power cut? In the standard version, no – the system switches off automatically during a grid failure for safety reasons. Anyone who wants to be supplied during a power cut needs a battery with an explicit emergency power function; that is a conscious additional decision, not an automatic mechanism.

Does a solar system make noise or work? Neither, in everyday life. The modules are silent, only the inverter can hum quietly – which is why it hangs in the basement. And because nothing moves, maintenance is limited to an occasional glance at the app and a check every now and then. Rain usually takes care of the cleaning itself.

Questions about your own roof? Call us without obligation – we are a specialist company from the region and will gladly explain further where this chapter ends: +41 78 830 83 35

Solar Guide: To the guide overview · Chapter 2: Is my house suitable? →

Sources: Swiss Federal Office of Energy SFOE, EnergieSchweiz, sonnendach.ch (SFOE/swisstopo); guideline value 1:1 from the technology guide (T01).

Last updated: 9 July 2026 · Author: ecoEn editorial team