What size solar battery do I need UK?
In this blog post, we will take a closer look at what size solar battery you will need for your UK home.
We’ll cover:
How to work out what size battery you need with or without panels
How to calculate your average energy usage
How many batteries you’ll need to power your home
Choosing the right size battery is crucial for your solar energy system and your household’s energy needs. This guide covers factors that affect battery size, types of batteries, costs, benefits and how to get the most out of your solar power.
Key Factors to Consider for Solar Battery Size
1. Household Energy Use
Your annual electricity usage determines the battery capacity you need:
Average UK Household: 3,400kWh per year, 5–10kWh battery.
High User: Over 5,000kWh, 9–20kWh.
Low User: Under 5kWh.
2. Solar Panel System Size
The size of your solar panel system affects how much energy can be stored:
3.5kWp system: 8kWh per day, 8kWh battery to store excess energy.
Larger systems (4–6kWp) may need batteries over 10kWh to capture all surplus electricity.
3. Weather and Daylight Hours
UK weather varies greatly:
Sunny Areas: Smaller batteries are enough as solar panels generate more electricity.
Cloudy Regions: Larger batteries needed to store enough energy for night and overcast days.
4. Battery Type
Different types of batteries have varying capacities and features:
Lithium Batteries: 90–95% efficiency, compact, 10+ years lifespan, fast charging.
Lead-Acid Batteries: Affordable but bulky, 3–7 years lifespan
Modern Solar Batteries: Designed for higher performance and energy density, ideal for residential use.
5. Retrofitted Residential Solar Batteries
If adding a battery to an existing solar PV system, ensure compatibility. Retrofitting takes less than a day.
| Household Size | Annual Energy Consumption | Lithium Battery Size | Lead Battery Size |
|---|---|---|---|
| 1–2 people | <2,000kWh | <10.5kWh | <20kWh |
| 3 people | 2,000–4,000kWh | 11–21kWh | 21–39kWh |
| 4–5 people | 4,000–6,000kWh | 22–31kWh | 40–59kWh |
| 5+ people | >6,000kWh | >31kWh | >60kWh |
Why is Solar Battery Size Important?
Choosing the right battery size is crucial for efficiency and cost-effectiveness:
Oversized Batteries: Unnecessary expense and space usage without added benefits.
Undersized Batteries: Limits storage capacity, forces reliance on grid power during peak hours.
Proper sizing allows you to maximise self-consumption—use more of your solar generated electricity rather than exporting it to the grid.
Benefits of Solar Battery Storage Systems
1. Energy Storage
Solar batteries store excess energy generated during the day for use at night or during cloudy weather. This increases energy independence and reduces reliance on grid electricity.
2. Lower Electricity Bills
Using stored energy instead of grid power during peak times can save hundreds per year on electricity bills.
3. Backup Power
Solar batteries provide backup power during outages, so you never run out of energy.
4. Integration with Smart Meters
Smart meters optimise battery usage by discharging stored energy during peak tariff periods (e.g. Intelligent Octopus Flux).
Costs of Solar Batteries in the UK
| Battery Size | Cost (Installed with Panels) | Cost (Standalone Installation) |
|---|---|---|
| 5kWh | £2,000–£3,000 | £5,000 |
| 10kWh | £4,000–£5,000 | £7,000 |
| 15kWh | £6,000–£7,000 | £9,000 |
From February 2024 onwards, retrofitted residential solar batteries are VAT exempt in the UK.
How much energy do solar panels produce?
Solar panels output depends on their capacity and location:
A typical UK solar panel system produces twice its rated capacity daily. For example:
A standard 4kWp system generates around 8kWh per day.
Larger systems (>6kWp) can produce up to 12–15kWh daily.
Best Practices for Choosing a Solar Battery
Analyse your household’s average electricity consumption.
Match battery size with your solar panel system’s capacity.
Consider future needs like electric car charging or increased energy independence.
Go for lithium batteries for efficiency and longevity.
Get advice to match with your existing or future solar PV system.