Battery storage, heat pump, e-car: Is it needed?

In this chapter, you'll learn

• what battery, heat pump and e-car actually do around the solar system – each in one paragraph instead of a sales pitch;
• why none of the three building blocks is mandatory, but all three live from the same basic idea;
• in which order it makes sense to think – and what you only prepare today instead of buying.

Why do these three terms pop up in every solar conversation?

The answer is in the previous chapter: Self-consumed solar power is roughly two to four times as valuable as fed-in power. Once that is clear, the question of every solar planning becomes: How do I get more of my own electricity into my own house?

And that is exactly what the three building blocks answer – each in its own way. The battery shifts the electricity into the evening. The heat pump consumes it, as the largest consumer in the house. The e-car fuels it, as the largest battery in the household. Three different ways, one goal.

Important for the classification: Nobody builds a heat pump or buys an e-car because of the solar system. Both come into the house for their own reasons – the heating is at its end, the next car drives electrically. The solar system does not make these decisions necessary, but it makes them cheaper. And vice versa: Those who see them coming plan the system a size larger right from the start.

The battery: shifts electricity from midday into the evening

The principle fits in one sentence: At midday, when the system delivers more than the house needs, the battery charges – in the evening, when the sun is gone and life takes place at home, it gives the electricity back. So the battery produces nothing; it shifts. That is its whole job, and for many households it is a valuable one.

Just as important is what it cannot do – three expectations that we straighten out early:

• No seasonal storage: Saving summer electricity for the winter does not work; the battery would have to be hundreds of times larger for that. Shifting takes place within the day, not between seasons.
• No independence from the grid: The battery noticeably reduces consumption, but the connection and the grid remain – and in winter they continue to supply the majority.
• No automatic emergency power: The fact that the lights stay on during a power failure only applies to systems explicitly built with emergency power capability. This is a conscious additional decision during planning, never a free extra.

Whether a battery pays off depends on the consumption profile, the local tariffs and the incentives – a real calculation, honestly derived in the battery storage guide. For the guide, the short version is enough: The battery is the biggest, but also the most expensive lever – and therefore the last in the sequence, not the first.

The heat pump: the largest electricity consumer in the house

A heat pump heats with electricity, and efficiently at that: It turns one kilowatt hour of electricity into a multiple of heat. For the solar system, it is therefore the most interesting consumer of all – it increases the electricity consumption of the house as a guideline value by several thousand kilowatt hours a year, it runs for many hours, and its consumption can be shifted in time because the house and hot water cylinder retain the heat.

This last point is the elegant trick of the combination: If the heat pump preferably heats when the sun is delivering, the hot water becomes a battery – the energy is stored as heat at midday and consumed in the evening, entirely without a battery. That is why we often say in consultations: first store thermally, then electrically.

Here too, the honest line belongs: Heat pump and solar system have opposing annual curves. The system delivers the most in summer, the heat pump needs the most in winter. The combination pays off – but calculated over the year, not in January. How the interaction works in detail, from the control to the permit and incentives, is in the guide on combining heat pump and photovoltaics.

The e-car: the largest battery – if it is at home during the day

An e-car increases electricity consumption by a four-digit kilowatt-hour amount per year, depending on the mileage. This electricity has to come from somewhere anyway – and from your own roof it is cheapest. The technology for this is unspectacular: a controllable wallbox that preferentially charges with surplus. You plug in the car, the control does the rest.

The decisive question is therefore not the hardware, but your everyday life: When is the car at the house? Those who work in a home office, have a second car or charge at the weekend get a lot out of it. Those who drive away in the morning and come home in the evening mainly charge grid electricity – even the most beautiful roof does not change this, and a serious consultant will tell you this before you buy.

Beginners should also remember one distribution rule right away: The car charges directly from the system, not via the home battery – filling one battery from another only costs losses. The profiles, operating modes and wallbox selection in detail: Charging an e-car with solar power.

In what order should you think?

The three building blocks in direct comparison – and behind them the order that has proven itself in practice:

Simplified overview – in all three cases, profitability depends on the individual consumption profile.

The common thread behind it: First come the building blocks that life brings anyway. A heat pump is planned when the heating is replaced, an e-car when buying a car – the solar system simply includes both. Then come the free levers: shifting consumption to sunshine hours, heating hot water at midday, the six levers of self-consumption in order. And only at the end the battery – as an investment that is calculated, not as a reflex.

And what if none of this is pending today? Then the most cost-effective of all strategies applies: prepare instead of buy. An inverter with a battery connection, an empty conduit to the parking space, a system size with a reserve – setting such courses costs little in an ongoing project and saves a second construction site later. The house grows into the system, not the other way around.

Go deeper on this topic

Read more from the guide: – Home batteries Switzerland: the complete guide — functionality, size, costs and the honest question of whether it pays off – Combining heat pump and photovoltaics — dimensioning, control and the annual balance in detail – Charging an e-car with solar power — surplus charging, wallbox choice and the standing time question – Optimising self-consumption: the six levers — the complete sequence, from free of charge to investment

### Keep in mind None of the three building blocks is mandatory, and all three do the same thing: use more of your own electricity yourself. Buy what your everyday life brings anyway – and only prepare the rest.

In brief

Do I have to buy battery storage, heat pump and wallbox together with the system? No – and mostly that wouldn't be smart either. It makes sense to dimension the system for the future house and prepare the connections. You can buy each building block when its turn comes: the heat pump when replacing the heating, the wallbox with the car, the battery based on real calculation.

Is the solar system worthwhile even without all three? Yes. The household electricity alone plus the remuneration for the surplus carry the calculation in many cases – the building blocks improve it, they do not base it. Those who are neither planning a heat pump nor an e-car today are still better off not building too small: Consumption grows by itself for most families over the years.

Can the e-car replace the home battery? Not reliably yet today. Bidirectional charging – the car feeds the house – is technically on the rise, but not yet a broad standard: vehicle, wallbox and billing must match. Whoever plans now calculates the car as a consumer and keeps the option open.

Solar-Guide: ← Chapter 6: Self-consumption and feed-in · To the guide overview · Chapter 8: The path to the system →

Sources: EnergieSchweiz (basics of battery storage, heat pumps and electromobility); theses and guideline values taken 1:1 from the guides S01, W01 and E01.

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