B9 group installation
Add a battery to your existing solar
Keep your panels and store the surplus for the evening, instead of exporting it at 11.88p.
- Free survey
- Fixed written quote
- NIE paperwork handled
- Part of the B9 Energy group, in renewables since 1992
Who it suits
- You already have solarAnd export much of what you generate.
- Your use peaks in the eveningA battery covers the hours after sunset.
- You are on a time-of-use tariffCharge on cheap night units.
- Outages affect your areaA backup gateway keeps essential circuits running.
Two ways to connect
AC-coupled battery
Works alongside your existing inverter. The array stays as it is.
Hybrid inverter
Replaces an ageing inverter with one that runs panels and battery together.
Which one is right for me?
AC-coupled is the usual retrofit route because nothing changes on the roof. Where your existing inverter is nearing the end of its life, a hybrid inverter can be better value. We confirm which fits at survey.
The battery we typically fit
Sigenergy SigenStor
- Module size
- 6.02 or 9.04 kWh per module
- Modules per system
- 1 to 6
Sigenergy’s Europe warranty document gives 10 years. We can also fit the Anker SOLIX X1, built from 5 kWh modules, where it suits your home better.
Typical price
Add a battery
£3,000–£7,000
Typical installed price
- LFP (lithium iron phosphate) battery, a safer chemistry with a longer cycle life
- Hybrid or AC-coupled inverter to suit new or existing solar
- Electrical installation certificate
- NIE Networks notification
VAT 0% until 31 March 2027, then 5%. Your survey confirms the price.
What a battery can save
Indicative, from solar shifting alone. See how we work out savings.
Battery retrofit questions
Can I add a battery to solar panels I already have?
Yes. An AC-coupled battery works alongside an existing solar inverter with no change to the array, and is the usual route for a retrofit. Where the existing inverter is nearing end of life, replacing it with a hybrid inverter can be the better value option.
How much does a home battery cost in Northern Ireland?
Expect roughly £3,000–£4,500 for a 5 kWh system, £4,500–£6,000 for around 10 kWh, and £6,000–£7,000 for 13 kWh, fully installed with 0% VAT. Fitting a battery at the same time as solar is cheaper than a later retrofit because the hybrid inverter, scaffolding and electrical works are shared.
What size battery do I need?
Most Northern Ireland households land between 5 kWh and 13 kWh of usable capacity. The right figure is roughly your evening and overnight electricity use, which for a typical home is 6–10 kWh. Going bigger than your daily cycle simply adds cost that never gets used, so we size from your actual consumption data.
Do batteries work during a power cut?
Only if a backup gateway is specified. A standard grid-tied battery shuts down in an outage for safety, because it must not energise a network that engineers may be working on. Adding an islanding-capable gateway lets the battery run selected essential circuits while staying safely disconnected from the grid.
Get a battery quote
Tell us what you have now. We survey for free and give you a fixed written price.
- Free survey
- Fixed written quote
- NIE paperwork handled
- Part of the B9 Energy group, in renewables since 1992