Buying a home battery: what you really need to look out for

A home battery stores electricity generated during the day so you can use it in the evening instead of feeding it back to the grid. Sounds simple, but the right choice depends on a few technical factors that are not always clear on a quote.

In this guide we go through them one by one: how much capacity in kWh you need, what power in kW the battery can handle, whether it matches your inverter and how your consumption pattern comes into play. That way you can recognise a proposal that suits your home.

In Flanders, the meter no longer runs backwards for those who have a digital meter. As a result, solar energy that you feed into the grid yields less than it used to.

Self-consumption therefore becomes more important. A home battery or smart control helps you to use your own generated energy later instead of feeding it into the grid cheaply. What it delivers in your situation depends on your consumption, your installation and energy prices; we will work it out honestly with you.

The capacity, expressed in kilowatt hours (kWh), determines how much electricity the battery can store. Too small and you are back on the grid halfway through the evening, too large and you are paying for storage you rarely fill. It comes down to your evening and night consumption in relation to what your solar panels leave over during the day.

A household with a heat pump or an electric car that charges at night has a different profile from a couple who are rarely at home during the day. That is why we start from your actual consumption and not from a standard package. Whether a particular capacity pays off depends on your home and your consumption, so we look at that concretely during a site visit.

Besides capacity, power matters, expressed in kilowatts (kW). That determines how much the battery can deliver or absorb at any one moment. If you run many appliances at the same time, you want the battery to cover that peak rather than the shortfall still coming from the grid.

Capacity and power belong together. A large battery with too little power will not cover your peaks, while a small but powerful system runs flat too quickly. The right ratio follows from how you use electricity, not from a single figure in a brochure.

A home battery works together with an inverter. Sometimes you connect a battery to your existing inverter (AC coupled), sometimes a hybrid inverter is needed that combines solar panels and battery (DC coupled). Which route is most convenient depends on what is already in place.

If your current inverter does not match the battery you want, then you are left with an inverter that needs to be replaced or supplemented. That is an important point to clarify in advance, because it affects both the installation and the cost. In our guide on expanding solar panels we go into that in more depth.

How useful a battery is depends on what happens to the electricity you feed back to the grid and how your consumption is spread across the day. Those who consume a lot during the day get less out of storage than those who are mainly at home in the evening. It comes down to the difference between self-consumption and feeding back to the grid.

We make no general promises about efficiency or payback time, because these differ from home to home. What we do: look at your consumption profile and tell you honestly whether a battery is worth the effort in your case. That happens during a site visit.