Home Battery Storage: Certified Installations and Costs

Home batteries went from a curiosity to a routine part of a solar quote in about three years, and the only official statistics on them are newer still. This page shows what those statistics say, and is careful about what they do not.

What these figures actually count

The Government publishes one dataset on domestic batteries: the installations that MCS-certified installers have registered on the MCS database. That is not the same as the number of batteries in British homes, and the difference is not a rounding error.

A battery fitted by an uncertified installer does not appear. Nor does one fitted by the householder, one supplied with a new build, or anything commercial. The Department is explicit that figures for batteries not registered with MCS are simply not available, so there is no way to scale these numbers up to a national total — and this page does not try.

Everything below is the United Kingdom including Northern Ireland. MCS runs across all four countries and never reports them separately, so there is no Great Britain figure here at all.

Installations and costs

Why this is not a count of every battery

Two limits travel with every figure above, and both come from the publisher rather than from us.

The coverage is growing at the same time as the market. The Department says the rise in registrations may be more batteries being installed, more of them being registered with MCS, or both — and it cannot separate the two. So the series tells you registrations are climbing steeply. It does not tell you the home battery market is growing at that rate, and nobody can currently say what rate it is growing at.

The recent months are undercounts. An installation is dated by when it was fitted, not by when it reached the database, so registrations arriving late land in a month that has already been published. The last edition revised eighteen months of the back series upward for exactly that reason. A dip at the right-hand end of the chart is usually the lag, not a slowdown.

What a battery actually earns you

A battery does not generate anything. It moves electricity from one hour to another, so what it earns is the difference between the price you charge it at and the price you avoid paying when you discharge it. That makes it a tariff decision much more than a hardware one.

On a single flat rate there is no difference to capture, and a battery only pays back by storing your own solar output for the evening. On a tariff that prices by time of day, the gap between the cheapest and the dearest hours is the whole return — which is why the two questions to settle before buying are what your tariff’s spread is and how much of it your usage can actually shift. The cheapest and cleanest hours page shows the spread as it stands in each region, and the smart meter replay costs your own half-hourly readings against real tariffs before you commit to anything.

If you already have panels, the arithmetic changes again: what a battery saves you is the difference between what you would have been paid to export a unit and what you would have paid to buy it back later. Export rates and import rates move independently, and the solar deployment page explains why domestic solar and household demand run in opposite directions across the year.

Bigger batteries cost less per kWh

The clearest finding in the published data is that cost per kWh falls sharply with size. The smallest band costs roughly twice as much per kWh as the largest, because a good deal of the price is the inverter, the electrical work and the day’s labour rather than the cells.

That is why this page never quotes an average cost per kWh across the bands. Such a figure would move whenever the mix of sizes moved, and would describe what people bought rather than what anything cost. The table above keeps each band on its own line, with its own average size beside its own price, so the two are never crossed.

The figures are also not adjusted for inflation. A rise between two years is a rise in cash terms and is not necessarily a rise in real terms — what energy has actually cost since 1998 shows how much difference that distinction makes over a longer run.