Is a battery worth adding to the solar panels you already have? The West Yorkshire sums

Yes if your house is empty in the day. Probably no if someone is home using the solar as it comes off the roof. A 3.5 kW system in West Yorkshire produces about 2,678 kWh a year, and in a working household more than half of that leaves for the grid. Each of those units earns around 8p on a Smart Export Guarantee tariff. Buying one back at six o’clock costs 26.32p under the present Ofgem cap (1 October to 31 December 2026). A battery earns its keep in the gap between those two numbers, every evening of the year.

Working it through on a 3.5 kW semi

Picture a Leeds semi with 3.5 kW of panels on a south-west roof. This part of the country gets 850 kWh per kWp a year (PVGIS), and allowing 0.9 for a typical roof brings the system to about 2,678 kWh. With nobody in from nine to five on weekdays, roughly 1,500 kWh of that heads to the grid.

• Sold to the grid: 1,500 kWh at 8p brings in about £120 a year.
• Kept in a battery: those 1,500 kWh replace units you would otherwise buy at 26.32p, which comes to about £395 a year.
• What the battery adds: about £275 a year, before any extra from filling it on a cheap overnight tariff in winter.

Set that £275 against the battery quote. Treat it as a ceiling, because no battery catches every exported unit: a June day makes more than it can hold, and each charge loses a few per cent on the way through. Your survey swaps it for a figure based on your own export readings. Flip the battery switch on the calculator to see the same effect on your bill.

When we would tell you to leave it

All a battery does is shift electricity from midday to teatime. Shift a small amount and you save a small amount. Three households we would steer away:

• Someone is in all day. Retired, working from home or looking after small children. Run the washing machine, dishwasher and kettle while the sun is up and you may already use 60% or more of your own solar. That leaves the battery the scraps, and the sums rarely add up.
• There is little to export. Take 2 kW on a north-east roof in Halifax, exporting perhaps 500 kWh a year. Stored, that is worth about £132 a year in place of £40. The gap is real but small to set against a battery.
• The inverter is on its way out. String inverters fitted in 2011 or 2012 are close to retirement. Swap yours for a hybrid inverter and a DC-coupled battery and you often do better than adding an AC battery to tired kit. The surveyor will say which route suits, and the quote moves with the answer.

AC-coupled or DC-coupled: which one you get

An AC-coupled battery brings its own inverter and wires into your consumer unit, leaving your panels and existing inverter alone. Systems on the Feed-in Tariff usually go this way, since the generation side stays untouched and the generation meter carries on as before.

A DC-coupled battery shares a hybrid inverter with the panels. One fewer conversion makes it a little more efficient, and it looks tidier. It only comes into play if your hybrid inverter has a spare battery port, or the old inverter is going anyway. Both kinds need an installer who is MCS-certified for battery storage, and both get notified to the network operator, which in West Yorkshire is Northern Powergrid.

The VAT on a battery: 0% until 31 March 2027

Home batteries have been zero-rated in Great Britain since February 2024, and it makes no difference whether one arrives with new panels, joins old ones or goes in by itself. That rate runs out on 31 March 2027. From 1 April 2027 it is 5%, which the Budget on 28 October 2026 confirmed. The tax point decides the rate, and for most jobs that means the invoice date. Have the battery fitted and invoiced by 31 March 2027 and you get 0%. Paying a deposit in time does nothing for the balance. Our VAT deadline page explains why.

The January price cap could widen the gap

Today’s cap, 1 October to 31 December 2026, sets electricity at 26.32p a unit plus 54.83p a day (Ofgem figures for the GB average, paying by direct debit). The next one, for January to March 2027, is due on 25 November 2026. The Cornwall Insight forecast, updated 14 October 2026, points to a yearly bill for a typical home of about £1,999 against £1,723 now. Export rates do not follow the cap, so each rise in the unit rate makes stored solar worth more. Figures as of 6 November 2026.

Six things the survey looks at

Nobody can size a battery from a web form. Before a figure goes on paper, the free survey with the MCS-certified installation team checks these six things:

• The inverter: make, age, hybrid or string.
• Your real export, read from Smart Export Guarantee statements or the smart meter.
• What you use in the evening, which decides the battery size.
• Whether the consumer unit has room or wants upgrading.
• Where the battery will live: a garage, a utility room or an outside wall. Bedrooms and escape routes are off the list.
• Backup circuits for a power cut, if you want them, since they have to be wired in on the day.

Then comes the quote: fixed, in writing, with 0% VAT taken off and the installer’s name and MCS number on it.

Your house, your numbers

Try the calculator with the battery on and then off. If the gap looks worth chasing, book a free survey. We ring to check your set-up, the installation team measures up and a fixed quote follows. If it does not stack up for your house, you will hear that from us. Starting from scratch instead? Solar panels and a battery explains what a new system involves, and the Leeds page talks through the city’s roofs.

Questions people ask about this