Solar battery storage: a practical guide
Understand how battery storage works, where battery-only systems fit and what to check before choosing a system.
- How batteries work with or without solar
- AC-coupled and DC-coupled systems
- Capacity, inverter power and system design
- The information worth checking before you buy
What does a solar battery do?
Solar panels generate electricity during daylight, while homes often use more electricity in the evening and overnight. A battery can store surplus generation and make it available later. Depending on the system and tariff, it can also charge from the grid at suitable times.
Do I need solar panels to use a battery?
No. Solar is common, but it is not essential. The best arrangement depends on whether you are adding storage to an existing solar system, planning a new solar installation or looking for a battery-only system.
With solar panels
Surplus solar electricity can be stored rather than exported, then used when the panels are producing less. For a retrofit, a separate AC-coupled battery system may allow the existing solar inverter to remain, subject to compatibility and design.
- Consider solar generation and evening use together
- Check the existing inverter, metering and export arrangements
- Avoid assuming that every battery works with every solar system
Without solar panels
A battery-only system can charge from the grid at suitable times and supply stored electricity later. This can be useful where a time-of-use tariff makes off-peak charging worthwhile, but the tariff, controls and expected usage all matter.
- Start with daily, monthly or annual electricity use
- Consider how much of a typical day the battery should cover
- Allow for charging losses and the system’s power limits
AC-coupled and DC-coupled systems
These terms describe where the battery connects in relation to the solar inverter. They are useful when comparing options, but you do not need to choose the architecture on your own.
AC-coupled
The battery has a separate inverter or AC charger connected on the home’s AC side. This is commonly considered for retrofits and for battery-only systems. An existing solar inverter can sometimes remain in place, but the equipment, metering and protection still need checking.
- Often a practical retrofit route
- Can be used without solar panels
- Provides a separate route for grid charging
DC-coupled
A hybrid inverter manages the solar panels and battery on the DC side. This is commonly considered for a new solar installation or when an existing inverter is being replaced. The panels, battery, inverter and grid connection need to be designed as one system.
- One hybrid inverter can manage solar and storage
- Can reduce the number of conversion steps in some operating conditions
- Must be matched to the panels, battery and electrical design
How much battery storage do I need?
Most people do not know which model or capacity they need. Your electricity use is a better starting point than guessing a product. Use a daily, monthly or annual kWh figure from your bill or smart-meter app.
We can then consider solar generation, evening and overnight demand, future loads such as an EV or heat pump, available space, location, mounting and whether backup is required.
Electricity use
Daily, monthly or annual usage gives us a sensible starting point.
Solar generation
Storage should be considered alongside how much solar is available to charge it.
Location and space
Indoor or outdoor conditions, mounting and available space can affect the choice.
Future plans
EV charging, a heat pump or backup may change the design.
Capacity and inverter power are different
Battery capacity is measured in kWh. Inverter or charger power is measured in kW. Both matter, and a larger figure in one does not automatically mean the other should be larger.
Capacity (kWh)
This is how much energy the battery can store. Usable capacity, reserve settings and the battery’s operating limits can differ from the headline figure.
- Consider typical evening and overnight use
- Compare the capacity with likely solar generation
- Allow for future changes in consumption
Power (kW)
This is how quickly the system can charge or discharge. It also affects how much demand can be supplied at once, subject to the inverter, battery and electrical installation.
- High-demand appliances may need more power
- Power is not the same as storage capacity
- The proposed inverter or charger must be matched to the system
What should I check before buying?
The right questions depend on whether the project is a new system, a retrofit, a battery-only installation or an expansion. These checks help avoid an attractive but incompatible parts list.
Frequently asked questions
These are useful starting points. A final recommendation still depends on the actual equipment and electrical design.
Often, yes. An AC-coupled system can be a practical retrofit because the existing solar inverter may remain in place, subject to compatibility, metering, space and the electrical design.
Yes. A battery-only system can charge from the grid at suitable times and supply stored electricity later, subject to the tariff, controls and system design.
AC-coupled storage uses a separate battery inverter or charger and is commonly considered for retrofits or battery-only systems. DC-coupled storage uses a hybrid inverter to manage solar and batteries together and is commonly considered for new solar systems.
Start with your electricity use, especially evening and overnight demand, then consider solar generation, future loads, space, battery limits and backup requirements. The Battery Builder can use your daily, monthly or annual kWh figure as a starting point.
Not automatically. Backup needs compatible equipment, switching and a design for the circuits that need to remain powered.
Tell your installer and FIT licensee before making changes. Adding battery storage or changing metering can create notification or scheme-specific requirements.
Ready to explore your options?
Use the Battery Builder to share your electricity use and priorities, or visit our installation page if you want a complete solar and battery project discussed.
Return to the Energy Storage hub for product categories, further guidance and the main routes.