How does a solar battery work?
Short answer
A solar battery stores the electricity your panels generate during the day but you do not use immediately. Instead of sending that surplus to the grid, the battery holds it for when the sun goes down and your panels stop generating, so you use your own solar power in the evening and overnight.
Without a battery, a typical Scottish home uses only 30 to 50 percent of the electricity its panels generate. The rest goes to the grid, often for a modest export payment. With a battery, self-consumption rises to 60 to 80 percent or higher, meaning you buy less electricity from the grid and save more on your bills.
The battery charges automatically when your panels produce more than your home is using, and discharges automatically when your home needs more than your panels are producing. You do not need to manage it manually — the inverter handles the flow of electricity between panels, battery, home and grid.
What size battery do I need?
Short answer
The right battery size depends on how much electricity you use in the evening and overnight, not just on your solar generation. A typical Scottish home benefits from a 5kWh to 10kWh battery. A surveyor looks at your usage pattern and recommends a capacity that matches your needs.
A battery that is too small fills up quickly and still sends surplus to the grid. A battery that is too large never fills completely, so you pay for capacity you do not use. The sweet spot is a battery that most days charges fully from your surplus generation and discharges fully overnight.
A surveyor checks your electricity usage, your solar generation estimate, and when you use power. If you use most of your electricity during the day, a smaller battery may be enough. If you use most in the evening and overnight, a larger battery gives better value.
Can I add a battery to existing solar panels?
Short answer
Yes, in most cases. Most existing solar systems can take a battery, either alongside the current inverter or by replacing it with a hybrid inverter that manages both panels and battery. A surveyor checks your inverter, consumer unit and available space before recommending the best approach.
If your current inverter is a standard string inverter, adding a battery typically means either fitting a separate battery inverter alongside it or upgrading to a hybrid inverter that handles both. If you already have a hybrid inverter, adding a battery is usually simpler and cheaper.
The surveyor also checks whether your consumer unit has space for the additional circuit protection a battery requires, and where the battery can be physically installed. Batteries are typically mounted on a wall in a garage, utility room or loft, and need to be kept within their operating temperature range.
How much does a battery save on bills?
Short answer
A battery increases your savings by reducing the amount of grid electricity you buy in the evening and overnight. For a typical Scottish home, adding a battery to an existing solar system can increase annual savings by £150 to £350, depending on your usage pattern and tariff.
The exact saving depends on the difference between your import tariff (what you pay for grid electricity) and any export payment you receive for surplus generation. If your export payment is low, a battery that lets you use your own power instead of exporting it gives better value.
Some batteries also support time-of-use tariffs, where you charge the battery on cheap overnight electricity and use it during expensive peak hours. This can add savings even on days when your panels generate little, but it depends on your tariff and whether your supplier offers time-of-use pricing.
Is a battery worth it for your home?
Short answer
A battery is worth it if you are out during the day (so you cannot use solar as it is generated), if your export payment is low, or if you want protection against evening price rises. If you are home all day and use most of your solar as it is generated, a battery adds less value.
The best way to decide is to get a survey. The surveyor looks at your generation estimate, your usage pattern, your tariff, and the cost of a battery sized for your needs. You then have a written quote with the total cost and the expected additional savings, so you can see the payback period for the battery specifically.
We install through MCS-certified partners, and every quote is written and no-obligation. Interest-free credit up to £30,000, subject to status, is available for systems including batteries.
