Which home battery do I need?
Which home battery you need lies, for most households, between 3 and 10 kWh of storage, and often above that with a heat pump or electric car. You get the exact number from your own usage, not from a national average.
In this buying guide, you calculate step by step which capacity, which power and which connection suit your situation.
How do I know which home battery I need?
You'll know which home battery you need once you've answered three questions: how much energy you want to store, how much power you want to use at once, and what you connect the battery to. With those answers, you can compare the home batteries in the range on the points that matter to you, instead of on the biggest number on the box.
Storage is expressed in kilowatt-hours (kWh), power in kilowatts (kW). Go through the three choices in this order:
- Capacity: how many kWh you store per day and use yourself later.
- Power: how many kW the battery can charge and deliver at the same time.
- Connection: a regular wall socket or a dedicated circuit in the meter cupboard.
Always start with the capacity, because it determines the biggest part of what a home battery does for you.
How many kWh of home battery do I need?
How many kWh of home battery you need is determined by your electricity use in the evening and at night, not by your annual usage. The battery charges during the day with solar power you don't use right away and delivers that power again as soon as your panels stop generating.
According to Milieu Centraal, a household with solar panels uses an average of around 30 percent of its own generated electricity directly. With a home battery, that rises to about 60 percent. The capacity determines how large that extra share becomes for you.
How do you calculate the capacity of a home battery?
You calculate the capacity of a home battery by comparing two numbers: the solar surplus you feed back during the day and your usage between sunset and the next morning. The lower of the two numbers is the capacity you actually use per day.
Say your panels have 9 kWh left over on a sunny day and you use 6 kWh in the evening and at night. Then 6 kWh of usable storage is enough. You can read your hourly usage in your energy supplier's app or with a P1 meter, a little box that reads the data from your smart meter.
Why isn't a bigger home battery always better?
A bigger home battery isn't always better, because you only benefit from capacity that you fill and empty again every day. A battery that structurally stays half full pays for itself more slowly. In winter, the solar surplus is also so small on many days that even a modest battery doesn't get full.
The rule of thumb of 1 to 1.5 kWh of storage per kWp of solar panels gives a first direction, but doesn't take your evening consumption into account. If you also charge at cheap moments through a dynamic energy contract, then extra capacity can pay off.
How big should a home battery be for your household?
How big a home battery should be for your household depends mainly on the number of occupants and on major power users like a heat pump or an electric car. The table below gives guideline values for the capacity; your own evening consumption remains the deciding factor.
| Household | Guideline capacity | Notes |
|---|---|---|
| 1 to 2 people | 3 to 6 kWh | lighting, cooking and appliances in the evening |
| 3 to 4 people | 6 to 10 kWh | higher evening consumption from cooking, laundry and screens |
| With a heat pump or electric car | 10 kWh or more | preferably modular and expandable |
If you're at the top end of a group, for example a family of four with induction cooking and a dryer, you'll more likely end up with a 15 kWh home battery. If you work from home a lot and already use plenty of solar power directly during the day, then less storage is enough.
How many kW of power does your home battery need?
Your home battery needs enough power in kW to run the appliances you switch on at the same time. Capacity tells you how much energy fits in it, power how fast that energy can come out. If your kettle, induction hob and washing machine together need more power than the battery delivers, you simply draw the difference from the grid.
In Flanders, power plays an extra role. There, the capacity tariff is based on the average of your highest quarter-hour peak per month over the past twelve months. A home battery with enough power can flatten those peaks by stepping in at moments when lots of appliances are running at once.
How much power does a home battery deliver through the power outlet?
A plug-in home battery delivers a standard power output of 800 watts through the power outlet, including with the Zendure SolarFlow 2400 AC and the Anker SOLIX Solarbank Max AC. On a dedicated circuit in the meter cupboard, that rises to 2,400 watts with the Zendure and 3,500 watts with the Anker.
A power output of 800 watts is enough for lighting, fridge, TV and router at the same time, but not for an induction hob at full power. A plug-and-play home battery is therefore an easy way to start; for heavier evening peaks, have an installer set up a dedicated circuit.
Which home battery should you choose if your power usage is going to rise?
If your power usage is going to rise, choose a modular home battery that you can expand later with extra battery modules. That way you're not paying now for capacity you won't need until a few years from now, for example after getting a heat pump or an electric car.
The Zendure SolarFlow 2400 AC works with AB3000X batteries of 2.88 kWh each and grows up to 17.28 kWh with six modules. The Anker SOLIX Solarbank Max AC starts at 7 kWh and can be expanded up to 42 kWh. So when buying, choose a system whose maximum capacity matches your expected usage a few years from now.
Which home battery should I choose for backup power?
For backup power, choose a home battery with a backup power function and reserve part of the capacity for outages. That reserve isn't available for your daily solar power, so add it to the capacity you've calculated for your evening usage.
A plug-in home battery doesn't power your entire house during an outage. Models with a backup power function then supply electricity through a power outlet on the battery itself, where you can plug in your fridge and router, for example.
Choosing a home battery with help from TechPunt
Choosing a home battery with help from TechPunt starts with your own numbers: your evening usage, your solar surplus and the connection in your meter cupboard.
If you're torn between two capacities, or between a plug-in model and a dedicated circuit, our customer service team is happy to help you by phone, email and WhatsApp. We ship the Zendure and Anker SOLIX home batteries from our own warehouse in Barneveld.
