Batteries & technology
Solar batteries and panel technology
By Daniel Osei · Last checked 25 June 2026
Once solar itself stacks up, the next questions are the kit. Should you add a battery? Which panels? And what does owning a system actually involve? This page covers the hardware decisions in plain terms.
The quick version
- A battery stores your daytime solar for the evening, so you use more of your own power
- But the battery pays back slower than the panels, so treat it as a separate decision
- Monocrystalline panels are the default. Do not overpay chasing tiny efficiency gains
- Systems are low-maintenance, but the inverter is usually replaced once in their life
What a battery actually does
On its own, solar sends any power you are not using at the time straight to the grid for a few pence per unit. A battery stores that daytime surplus so you can use it in the evening instead, when you would otherwise be buying power at the full rate.
Some batteries can also keep selected circuits running in a power cut, but only if that is designed in with the right hardware. And on a time-of-use tariff, a battery can charge from the grid when electricity is cheap overnight and run the house at peak times.
Is a battery worth it?
A battery lifts how much of your own solar you use, often from around a third without one to roughly two-thirds or more with one. That is real money saved. The catch is that the battery itself costs a few thousand pounds and pays back more slowly than the panels do, often in the region of 9 to 15 years.
It tends to make most sense for households that use a lot of power in the evening and overnight, for example families or homes charging an electric car at night. It makes least sense if you use little electricity, or already use most of your power during the day.
What size battery you need
The aim is a battery that fills and empties most days, not one so big it sits half-charged. As a rough starting point:
| Household | Rough battery size |
|---|---|
| Small flat or low usage | Around 3 to 5 kWh |
| Typical 3-bed home | Around 5 to 8 kWh |
| Larger 4-bed+ home | Around 8 to 12 kWh |
| High usage or an EV | Around 10 to 15 kWh |
Choosing panels
Almost every domestic quote in 2026 uses monocrystalline panels, the standard black ones, at around 19 to 22 percent efficiency and roughly 400 watts each. The differences between good panels are smaller than the marketing suggests.
Higher efficiency mainly helps when your roof is small or awkward and you need to squeeze more power into a tight space. For most roofs, the warranty, the degradation guarantee and the quality of the installer matter more than chasing the top efficiency figure.
What owning a system involves
Solar is genuinely low-maintenance. In most of the UK, rain keeps the panels clean enough, so there is no routine servicing to budget for. The one part that does not last the full life of the system is the inverter, which is typically replaced once at around 10 to 15 years for roughly £1,000 to £2,000.
The panels themselves last 25 to 30 years or more, losing about half a percent of output a year, so a system is still producing around 88 percent of its original output after 25 years. A battery comes with its own warranty, usually about 10 years.
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Common questions
- Is a solar battery worth it?
- It depends on your usage. A battery lets you use more of your own solar, often two-thirds or more instead of about a third, but it pays back more slowly than the panels. It works best for homes with high evening or overnight use, such as families or those charging an EV at night.
- What size battery do I need?
- Roughly 3 to 5 kWh for a small or low-usage home, 5 to 8 kWh for a typical 3-bed, and 8 to 12 kWh for a larger home. Aim for a battery that fills and empties most days rather than the biggest you can fit.
- Which solar panels are best?
- For most UK homes, mainstream monocrystalline panels are the sensible choice. The efficiency differences between good panels are small, so the warranty, degradation guarantee and installer quality matter more than the headline efficiency number.
- How long do solar panels last?
- Panels last 25 to 30 years or more, losing about half a percent of output a year, so they still produce around 88 percent of their original output after 25 years. The inverter is usually replaced once, at around 10 to 15 years.
- Do solar panels need much maintenance?
- Very little. UK rain usually keeps them clean, so there is no routine servicing. The main ongoing item is a one-off inverter replacement at around 10 to 15 years.
- Does a battery power my home in a blackout?
- Only if it is set up for it. A battery gives backup during a power cut only when the right hardware is fitted and specific circuits are wired for it. Many systems are designed only to save on bills, not for backup, so ask if backup matters to you.