Battery capacity: what does kWh mean?
Battery storage is usually described in kilowatt-hours (kWh). Capacity tells you roughly how much energy can be stored, while power (kW) describes how quickly the battery can charge or discharge. These are different: a battery can have plenty of energy capacity but a limited discharge rate. Check the manufacturer's stated usable capacity and operating limits rather than assuming every advertised kWh is available in all conditions.
Look at evening and overnight usage
Start by looking at your smart-meter readings, if available. How much electricity do you use after the solar panels stop producing meaningful power? Cooking, washing, heating, electric vehicle charging and other appliances can change the answer significantly. A battery intended to cover modest evening use may be very different from one designed for a high-consumption household.
Match the battery to likely solar surplus
A battery cannot store solar electricity that the panels never generate. In winter, generation can be much lower than in summer. Your roof orientation, shading and panel output matter. For some households, a smaller battery that cycles regularly makes more financial sense than a larger one that is rarely filled. For others, additional storage is useful, particularly when electricity demand is high.
Consider your electricity tariff
Some systems can charge from the grid at off-peak times and discharge during more expensive periods. Whether this is worthwhile depends on tariff eligibility, the difference between import rates, battery efficiency, equipment settings and the cost of the system. Export arrangements also matter: storing surplus solar is not automatically more valuable than exporting it.
Backup power is a separate question
Having a home battery does not automatically mean the house will stay powered during a power cut. Backup functionality depends on the inverter, wiring, changeover arrangements and the circuits selected for backup. If resilience matters to you, ask for a specific backup design rather than assuming it comes as standard.
What should you ask your installer?
- What is the usable battery capacity, and what is the discharge power?
- How much of my typical evening use could it cover?
- How much solar surplus will be available across the seasons?
- Is grid charging supported, and which tariffs are compatible?
- Can the system expand later, and is backup power included?
For a property-specific recommendation, read about EnviroHomes battery storage and our design process, then request a survey.