BrightGridBattery sizing should start with how your home uses electricity rather than simply choosing the biggest battery that fits your budget. Solar generation, evening demand, tariff structure, EV charging and future electricity consumption all influence the right storage capacity.
What does battery capacity mean?
Battery capacity is normally expressed in kilowatt-hours. It describes how much energy the battery can store, although usable capacity can differ from the headline capacity depending on the battery's operating limits.
Start with evening electricity use
One useful starting point is to understand how much electricity the home consumes after solar generation has fallen. This helps determine how much stored energy could realistically be used.
| Battery size | Indicative application |
|---|---|
| 5 kWh | Smaller homes or lower evening demand |
| 7–8 kWh | Moderate household demand |
| 10 kWh | Higher evening and overnight demand |
| 15 kWh+ | Large electricity demand or multiple flexible loads |
Match battery size to solar generation
A battery needs energy available to charge it. A very large battery connected to a small solar system may spend much of its time underused unless grid charging is part of the operating strategy.
What if you have an EV?
An EV can consume substantially more electricity than normal household appliances. The EV should therefore be included in the overall energy model rather than automatically increasing the home battery size.
Tariffs can change the ideal battery size
If a battery can charge from the grid during lower-cost periods, its economic value can be influenced by the tariff as well as solar generation.
Battery size should follow the energy profile
The right battery is the one that can be used frequently and economically without creating unnecessary upfront capacity.
Calculate your battery size
Use your electricity consumption, solar generation and tariff to determine an appropriate battery capacity.
Check Your SavingsFrequently asked questions
What size battery do I need with solar?
The correct size depends on solar generation, evening electricity demand, tariff structure and other flexible loads.
Is a 10kWh battery enough for a house?
It can be suitable for some homes but not others. Household consumption and solar generation should be assessed first.
Should I get a bigger battery if I have an EV?
Not automatically. The EV is itself a major flexible electricity load and should be included in the overall system design.
Can a battery charge from the grid?
Some battery systems can be configured to charge from the grid, depending on the equipment and tariff.
Sarah Kimani
Systems Designer at BrightGrid Energy
