Hardware · Case file
AlphaESS warranty, backup and who you call
Updated
All-in-one marketing can hide a small inverter. A 10 kWh battery behind a low-power inverter will not run a house the way a Powerwall illustration suggests.
The ownership question
Ask for the capacity warranty at the end of the term and the UK contact that is not the sales rep. Check the specific Smile or successor model. Backup output and pass-through power are model-specific and easy to over-claim.
Who it still suits: homes that want a single cabinet, a moderate discharge rate and a price below the premium backup brands.
A September 2026 figure for AlphaESS
Take a 10.1 kWh pack, cycled about 320 times, at 90% round trip. Charge at 11.0p, and value what comes back at 29.6p. Export given up is priced at 10.0p. About 1829 kWh a year of the charge is treated as spare solar from 4 kWp that might otherwise have been exported. Delivered energy is about 2880 kWh. After charging cost and lost export, the figure saves about £555 a year. Set that against £6,880 fitted, which is a September 2026 illustration at the temporary 0% residential rate, not a quote. That is a simple payback of about 12.4 years on these assumptions. Nudge the night rate up by 4p and see if you still like it.
In most single-phase houses in Britain, 3.6 kW is in the band where G98 connect-and-notify is often enough. Export can still be capped. Agree that before the inverter is ordered. The figure uses 10.1 kWh and 4 kWp, which is enough to tell two quotes apart if they assumed something else.
At a steady 600 W evening load, 10.1 kWh lasts about 16.8 hours. A 3 kW kettle only works if the inverter can deliver it. Capacity on the badge does not answer that.
VAT, paperwork, refusal
Where the job is a qualifying install in a home, the 0% rate runs to 31 March 2027 and is due to become 5% after that. This figure prices the work at £6,880 on that basis. It does not apply to a shop, and it does not apply to a battery you buy and fit yourself.
I would not sign off a 10.1 kWh install from a video call. Someone has to open the consumer unit.
If you already own AlphaESS, do not rip it out because a headline frightened you. Photograph the serial, keep the installer details, and ask them what the warranty path is this month.
Common questions
Is the price on this page a quote?
No. £6,880 is a September 2026 illustration for a 10.1 kWh example at the temporary 0% residential rate. Your survey replaces it.
Will it stay on in a power cut?
Only if a gateway or essential-load board was designed and paid for. A standard grid-tied battery turns off with the grid. On this 10.1 kWh example the inverter is 3.6 kW, and backup is still a separate line.
What paperwork should I keep?
Keep the MCS certificate where the job is certified, the electrical certificate, the DNO record, the schematic, the warranty registration and a photo of the schedule. For an illustrated £6,880 job, that folder is part of what you bought.
What if the cheap rate is not 7p?
Then the figure changes. This page used 11.0p as a charge rate and 29.6p as the rate avoided. A smaller gap means a worse payback. Read the live tariff.
Sources
Want a price for your house?
The figures above are a rough guide. An installer still needs to see your fuse board, where the battery will go, and whether you want power during a blackout.