What does a home battery cost, and is it worth it?

What a home battery costs depends on the house. The size, the inverter and the installation set the price tag, and none of them is the same in two homes, so there's no shelf price. The useful question isn't what it costs to buy, but whether it pays off, and that answer comes out of a calculation on your house.

In an energy subscription you never ask that question yourself. Elvy owns the battery, runs it and trades the electricity, so the value lands in a fixed monthly fee instead of a calculation you have to run. Below we go through what sets the price, what makes a battery worth the money, and when it isn't.

First of all the size. A battery is measured in kilowatt-hours, and the more electricity you want to be able to store, the bigger it gets and the more it costs. Then come the inverter that converts the current, the mount on the wall and the electrician who runs the cables. There is no shelf price, because none of those things is the same in two houses.

So the price tag on the hardware is the easy part. The hard question isn't what the battery costs to buy, but what it gives back. And that's where it starts to depend on the household.

A battery earns its money by moving electricity in time. It charges when power is cheap and is used when it's expensive, and the difference between those hours is the first source of income. If the price gap is small, there's little to gain. If it's large, the battery is quickly worth more.

On top of that there's more to be had. If you have solar panels, the battery stores the day's surplus for the evening, instead of you selling cheap and buying dear. If you have a capacity tariff, the battery can shave the peaks when the oven and the electric car pull the most at once. And the battery can take part in support services that keep the grid stable, which Svenska kraftnät pays for. How much each of them gives varies over time.

More slowly, and sometimes not at all. Without solar panels the battery lives only on the price gap between cheap and expensive hours, so the payback drags out when that gap is small. It's a calculation of its own, and we go through it in the guide on a battery without solar panels.

Its life is measured in cycles, not in years, and a battery that's meant to pay for itself over many years also has to last those years. If it wears out faster than planned, the gain is eaten up by the replacement. How the cycles work and what wears a battery we cover in the guide on battery lifespan.

That decides who carries the risk. If you own the battery, an early replacement is your cost. In a subscription it's Elvy's, because we own the equipment and replace it when it needs replacing.

Because almost everything in the calculation moves. The price gap between the hours changes from day to day. The payment for support services varies. The solar surplus depends on the roof and the season. An online calculator that promises an exact payback time has been forced to guess at all of those things, and a guess doesn't become truer for sitting in a box.

The only figure that means anything is the one worked out on your house. If you want a number, the honest answer is that it depends on the house, and the number comes from Elvy's energy analysis, not from a table.

Like a line on the monthly fee, not like an investment. Elvy owns the battery, installs it, runs it and trades the electricity for you. No upfront cost, no loan, and no payback time you have to keep an eye on yourself. We handle the optimisation against spot price, power peaks and support services in the background.

You pay a known amount and skip the calculation. Whether a battery pays off for your particular house is still a real question, but it's our job to work out, not yours.