With the high cost of electricity, solar panels are looking like a savvier investment every day, particularly given lower installation costs and higher panel efficiency than a few years ago.
But, what about a battery installation? Is it really worth it? Well, the answer really depends on a lot of factors you should consider.
It’s not just about the energy saved
The simple argument is that a home battery is good, because the power you generate can be stored and used at a different time. And if you don’t generate enough solar power to top up the battery, a time-of-use tariff with cheap off-peak electricity lets you store it and use it when energy prices are high.
That’s great in theory, but you have to also think about the cost of the battery and, effectively, how much it costs to store each kWh of electricity over its lifespan.
Batteries degrade
All batteries degrade over their life. That is, they hold less and less with each use, until they eventually break. The standard way manufacturers quote this is by stating how many charge cycles a battery can take.
For example, the typical 5.32kWh battery will deliver 6000 charge cycles at 80% depth of discharge. That is, you can use 80% of its capacity daily for that many charge cycles. That gives us a total of 25,536kWh of power stored over this lifetime.
Given that such a battery costs around £1500 if bought directly, the battery effectively costs around 6p per kWh to store the electricity over its life. If you can fill this for free with solar power, then that’s the cost per unit of electricity, which is a lot less than the current 26.53p per kWh price cap for electricity.
If you have a cheap time-of-use tariff with a super-off-peak rate around 16p per kWh, then you can top the battery up, and you’re effectively paying 22p per kWh for electricity, which isn’t that much cheaper than the standard unit price.
However, with standard off-peak electricity often around 21p per kWh, you’d be paying 27p per kWh, which is more expensive.
Do your calculations
While there’s some benefit to buying super off-peak power, the main benefit from a battery is if you can top it up for free using solar power. And that’s if you can buy a relatively cheap battery with a long life. Being able to charge a battery depends on the size of your solar array and whether there’s enough spare power to charge the battery.
For people with smaller arrays, you’re less likely to have enough spare solar to charge the battery as frequently as you’d like, and may find it better to get paid around 15p per kWh for exporting power instead.
With any installation, it’s worth checking all of the specs so that you get a realistic idea of what you’d save, what the total cost is and how long the payback will take.
