Alle Insights
Perspectief
How does a battery work with solar panels?
Sofia Forsman
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A solar battery holds on to your solar electricity until you actually need it. The system stores what your panels generate while the house is using little, so you can use more of your own electricity later instead of exporting it cheaply and buying electricity back at a higher price a few hours afterwards. The idea is simple, but the real value lies in timing: when the electricity is generated, when it is used, and what it costs at each moment. This article explains how solar panels and a battery work together, and what that means for your electricity costs.
Contents
Why are solar panels not enough on their own?
Why storage matters more than it used to
How does the battery know when to charge and discharge?
Can a battery do more than lower your bills?
What does this mean for your home?
Frequently asked questions
Why are solar panels not enough on their own?
Solar panels take you a long way, but a battery lets you make use of more of that electricity even when generation and consumption do not happen at the same time. Panels generate most around the middle of the day, when many households use the least, and nothing in the evening when consumption peaks.
Without storage, a solar installation has only two outcomes for every kilowatt hour it generates. Either it is used in the house straight away, or it is exported to the grid. The share you use yourself is called self-consumption, and it largely determines what your installation is worth to you.
A battery fills the gaps between when electricity is generated and when it is used. A typical summer day looks roughly like this.
Time of day | Solar generation | What the battery does |
|---|---|---|
Early morning | Low or none | Supplies what was saved from yesterday, or electricity charged during cheap overnight periods |
Late morning | Rising | The house runs on solar, and the surplus starts filling the battery |
Midday | Highest | The battery charges from the surplus, and the remainder is exported once the battery is full |
Evening | Falling to zero | The battery discharges and covers evening consumption, which otherwise falls in the most expensive part of the day |
Night | None | The battery can charge from the grid if prices are low ahead of the morning |
The point is that a home with solar panels and a battery avoids buying electricity during exactly the periods when it costs most, and that repeats every day, all year round.
One detail is easy to miss: the battery works even when the sun does not. The price difference between the cheapest overnight periods and the evening peak can be substantial within a single day. A battery that charges when electricity is cheap and discharges when it is expensive creates value regardless of what the roof is doing.
The battery's role also shifts with the seasons. During the lighter half of the year, battery storage is mainly about capturing surplus solar generation. During the darker half, when generation is low, it is mainly about shifting the household's purchases to cheaper periods. This does not mean the battery sits idle in winter. It means the value then comes from price optimisation rather than from stored solar electricity. Batteries for solar panels should therefore be sized around the household's daily pattern, not around peak summer days.
Why storage matters more than it used to
Because the economics have moved away from exporting and towards using your own electricity. Two developments drive this, and both apply across European markets in different forms.
The first is what happens to the value of exported solar electricity. Support schemes that once paid households well for feeding electricity into the grid have been scaled back or withdrawn in a number of markets, leaving the supplier's own export payment as the main compensation. There is also a structural effect: solar installations all generate at the same time of day, which tends to push wholesale prices down during exactly the periods when households have a surplus to sell. Exported electricity is therefore worth less per kilowatt hour than the electricity you avoid buying, which carries the full retail price including network charges and taxes.
The second is that prices now move in shorter steps. Since 30 September 2025, the EU day-ahead electricity market has calculated prices in 15 minute intervals rather than hourly, which means 96 price periods per trading day instead of 24. The stated aim is to reflect generation and demand more accurately as the share of renewables grows. For a household, more granular pricing means more opportunities for a battery to charge when electricity is cheap and discharge when it is expensive, provided the electricity contract passes those price differences through.
What this adds up to is a shift in where the value sits. Every kilowatt hour you use yourself replaces one you would otherwise have bought at the full retail price. Every kilowatt hour you export earns the market price at a moment when that price is often at its lowest. The gap between those two figures is the entire case for battery storage.
Support schemes, tax treatment and export arrangements differ significantly between countries, so check what applies in your market before making assumptions about the economics.
How does the battery know when to charge and discharge?
Through automatic control that weighs up three things: how much the panels are expected to generate, how much the household normally uses, and what electricity costs at each point in the day. You do not have to follow the price curve yourself.
Without control, a battery would simply charge whenever there is a surplus and discharge whenever there is a shortfall. That works, but it leaves a good deal of value on the table. A system that combines solar generation, battery storage and price data can instead hold back from discharging in the afternoon if the evening is forecast to be more expensive, or top up from the grid overnight ahead of a cloudy day.
Two conditions are worth stating plainly. Price optimisation requires an electricity contract that follows market prices, because a fixed price gives you the same rate regardless of timing and leaves no price difference to capture. And the benefit varies by location, because price volatility differs considerably between markets and between bidding zones within them.
Can a battery do more than lower your bills?
Yes, by helping to keep the electricity grid in balance. This is revenue rather than a saving, and the distinction matters. A saving comes from electricity you avoid buying. Revenue is money paid to you for a service the battery performs.
Grid operators need resources that can respond quickly when generation and consumption do not match. These are known as ancillary services, and batteries suit them well because they can increase or reduce their power draw within seconds. A single home battery is too small to take part on its own, so households participate through a party that pools many batteries and handles the market side.
This is how Emaldo Grid Rewards works. Capacity in the battery that is not currently needed by the household can be made available for ancillary services, and the system owner receives a share of the payment. Rates are set by a market and vary over time, so they cannot be promised in advance. Availability also depends on the market you are in and on your electricity supplier arrangements. Use the Grid Rewards calculator to see an estimate for your own battery size.
What does this mean for your home?
That a solar installation with a battery gives you more ways to make use of your own electricity. You use more of what the roof generates, you buy less during the most expensive periods of the day, and spare capacity may earn revenue through ancillary services where those are available to you.
How much that adds up to depends on your own circumstances: your household's consumption pattern, the size of your solar installation, your electricity contract, where you are located, how the system is configured, and what your market allows. None of it is guaranteed, and figures from another household rarely transfer to yours.
Emaldo's battery solutions are built for this way of working, with automatic optimisation based on generation, consumption and electricity prices, and with the option to take part in Grid Rewards. If you already have solar panels on the roof, you can read more about adding a battery to an existing installation, or see how one homeowner lives with the system day to day.
Next step: find an Emaldo installer near you who can look at your actual consumption data, or get in touch if you would rather talk it through first.
Frequently asked questions
How large a solar battery do I need?
A common starting point is roughly 1 kWh of storage per kW of installed solar capacity, but what really decides it is how much electricity you use in the evenings and overnight. A household with high evening consumption benefits from more capacity than one that uses most of its electricity during the middle of the day. Ask an installer to work from your metered consumption data.
Can a battery make me self-sufficient in winter?
No. A home battery shifts electricity across hours and days, not across seasons. Where winters are dark, solar generation is low, and the battery's value then comes mainly from charging when electricity is cheap and discharging when it is expensive.
Do I need a contract that follows market prices?
Not to store solar electricity. You do need one if you want the battery to optimise against price as well, because a fixed rate offers no price differences between periods to work with.
Does a battery reduce how much electricity I can sell?
Yes, you export less, and that is the intention. Electricity used in the home is worth more than electricity exported, because it replaces a purchase at the full retail price.