Short answer
A home battery goes on its own circuit, in a place that is dry and cool and where it has space around it. It works together with the inverter and with a meter in the meter cupboard, so it knows when to charge and when to supply. The location and fire safety are more important than most people think.
Who this article is for Anyone considering a home battery. Connecting it is installation work; the choice of location we make together.
What a battery does
During the day your panels produce more than you use. Without a battery that goes into the grid. With a battery it goes into the battery first, and in the evening you take it out again. You then use more of what you generate yourself.
Whether it pays off depends on your consumption, on the rates and on what happens with feed-in charges. I would rather work it out honestly than tell you a story: for a family that uses nothing during the day and a lot in the evening, it is more attractive than for someone who works from home all day.
The location is the first question
A battery belongs:
Four requirements that decide where it may and may not be mounted.
- dry and cool, not in full sun, not in a damp cellar
- with space around it, usually a few tens of centimetres on all sides
- not in an escape route and not right next to the meter cupboard under the stairs
- on a solid, non-combustible wall, because they are heavy
A garage, utility room or plant room is usually the best place. The brand's manual gives the exact requirements, and they are binding for the warranty and for the insurance.
The connection
It gets its own circuit, and usually a meter in the meter cupboard too, so the system sees what is happening in the house. In a hybrid set-up the panels and battery are served by the same inverter; a separate battery comes with its own inverter.
Important to know beforehand: not every battery works with every existing inverter. If you already have panels from brand A, a battery from brand B can sometimes only be connected with an extra box, or not at all. That is the first question I ask.
Keeping going during a power cut
Many people want this, and it is possible, but not automatically. A separate provision is needed that disconnects the home from the grid before the battery starts supplying. Without that separation you would send voltage into the grid during a fault, exactly where an engineer is working.
In practice you choose one circuit or a small group of circuits for the backup supply: the fridge, the central heating, a few sockets and some lights. Keeping the whole home running is usually not possible, and is rarely needed.
Safety and the insurance
Report a battery to your insurer. Some policies set requirements for the location or the brand. Do that before it is installed, not afterwards.
The same applies to the installation itself as to solar panels: the DC side is where it goes wrong if the work is sloppy. See solar panels and fire safety.
From my own work
A customer wanted the battery in the meter cupboard under the stairs, because there was just enough room. That is exactly where you do not want it: no ventilation, no space around it and the escape route next to it. It is now in the garage on a brick wall, with space around it and a switch by the door. The same function, considerably more sensible.
When to call an electrician
- You are considering a battery and want to know whether your meter cupboard can handle it
- The battery needs to work with existing panels from another brand
- You want part of the house to keep going during a power cut
I look at the location, the meter cupboard and how it works with what is already installed. View the packages and make a request.
Frequently asked questions
Can I keep going on a home battery during a power cut?
Only with a separate provision that disconnects the home from the grid. I then usually choose a few circuits: fridge, central heating, some lights and sockets.
Does every battery work with my existing inverter?
No. Brands by no means always work together. That is the first question I ask before anything is ordered.
Do I need to report a battery to my insurer?
Yes, and do so before it is installed. Some policies set requirements for the location or the brand.
Further reading
A dynamic contract and a home battery: is it worth it
With a dynamic contract the battery can charge when electricity is cheap. That works, provided you let it be controlled automatically.
The net metering scheme is ending: what changes for my panels
Your panels keep generating just as much. What changes is the value of the electricity you feed back.
Feed-in charges: why you pay for your own electricity
More and more suppliers charge for feeding your solar power back into the grid. Your bill shows what that costs you.
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