The price frame
Solar Panels and Battery Cost: The Published Prices
Every figure here is from a named source with a date. None is ours, so none is flattering.
DESNZ Solar PV cost data 2025/26 (published 28 May 2026), South East mean; Octopus Energy, battery-only installation (April 2026 prices, read 7 October 2026); Energy Saving Trust, "Battery storage" (page last updated 6 October 2026); HMRC VAT Notice 708/6, energy-saving materials and heating equipment. DESNZ means are installed costs from MCS installation records, including VAT where applicable. Octopus adds a £500 non-refundable deposit. The Energy Saving Trust figure is a general guide.
A Worked Price: What Combinations Cost
Using the DESNZ solar rates and pricing each battery from Octopus’s published £3,947 (5 kWh) and £5,336 (10 kWh) — a straight line through those two points, which is £278 per extra kWh — the sums come out like this:
| System | Solar (DESNZ) | Battery (Octopus line) | Total | VAT effect after March 2027 (+5%) |
|---|---|---|---|---|
| 3 kW solar only | £5,577 | — | £5,577 | £279 |
| 3 kW + 5 kWh battery | £5,577 | £3,947 | £9,524 | £476 |
| 4 kW solar only | £7,436 | — | £7,436 | £372 |
| 4 kW + 5 kWh battery | £7,436 | £3,947 | £11,383 | £569 |
| 4 kW + 10 kWh battery | £7,436 | £5,336 | £12,772 | £639 |
| 5 kW + 5 kWh battery | £8,607 | £3,947 | £12,554 | £628 |
| 5 kW + 10 kWh battery | £8,607 | £5,336 | £13,943 | £697 |
| 6 kW + 10 kWh battery | £10,329 | £5,336 | £15,665 | £783 |
Totals are sums of published figures, not quotes; an installer fitting both together should come in below the sum (see below). VAT: 0% to 31 March 2027, then 5%, so the last column is the added cost if the same price were charged at the reduced rate. DESNZ Solar PV cost data 2025/26 (published 28 May 2026), South East mean; Octopus Energy, battery-only installation (April 2026 prices, read 7 October 2026); HMRC VAT Notice 708/6, energy-saving materials and heating equipment
Read the table the way an installer would: the solar half does most of the work and most of the cost, and the battery is a large share of the total for the saving it adds. Our solar panel calculator shows what each combination earns back.
Fitting a Battery With the Panels Is Cheaper Than Adding It Later
Octopus publishes two prices that let you test this without any opinion from us. Two panels with no battery start at £6,663. Twelve panels with a 10 kWh battery cost £11,115. The difference is £4,452 for ten more panels and a 10 kWh battery — less than the £5,336 Octopus charges for the same 10 kWh battery installed on its own, by about £884, before counting the panels.
The reason is the fixed costs: one scaffold, one visit, one set of electrical work, one commissioning and, with a hybrid inverter, one inverter doing both jobs. The Energy Saving Trust says the same: you should be able to save money installing storage at the same time as solar panels because the installers are already on site and can integrate the panels with the battery as part of the same job. If you are going to want a battery, the cheapest time to buy it is with the panels. If you already have panels, our battery storage installation page covers the retrofit routes.
Cheaper to fit together is not the same as worth fitting. In our model the battery adds about £133 a year to a 4 kW system on a medium-use home, a payback of 30 years on its own price. Whether it earns its place depends on your tariff, your use and whether backup matters — see our solar and battery storage page.
Why Two Quotes for the Same Panels and Battery Differ
The published prices are a frame, not a forecast. These are the things that move a real quote, in roughly the order they matter:
- The roof and access. Slate and in-roof systems cost more than standard on-roof; a high or awkward roof needs more scaffold.
- Hybrid or AC-coupled. One hybrid inverter doing both jobs is cheaper than a solar inverter plus a separate battery inverter.
- The battery’s size and make. The marginal cost of extra capacity is low (about £278 per kWh on Octopus’s line), but capacity you cannot use is wasted money.
- Backup. Whole-home backup needs extra hardware and wiring; essential-circuits backup needs less.
- An EV charger or heat-pump readiness. Both change the sizing and sometimes the consumer unit.
- Your consumer unit and earthing. An old unit may need replacing before anything is connected.
Octopus’s own numbers show how much is fixed rather than variable: two panels cost £6,663 before any battery. That is why very small systems look expensive per kW, and why the DESNZ rate falls from £1,859 to £1,721 per kW above 4 kW.
What the Money Buys: A Modelled Payback
For a 4 kW south-facing array on the Hampshire coast and a medium-use household (2,500 kWh a year, part of the day at home), at the 26.32p price cap and the 12p export rate, our model gives a benefit of £699 a year from the panels and £832 with a 5 kWh battery. Against the DESNZ cost of £7,436, the panels alone repay in about 11 years; the whole system, at £11,383, in about 14 years. The Energy Saving Trust gives 9 to 13 years for solar, so the model sits in its range. Everything depends on how much of the day you are home and what you pay for electricity, which is why the calculator lets you change both.
Solar Panels and Battery Cost: Questions Answered
The questions we are asked most, answered against published prices.
On published figures, a 4 kW solar system averages about £7,436 in the South East (DESNZ, £1,859 per kW up to 4 kW), and a 5 kWh battery costs £3,947 on Octopus’s battery-only price list (April 2026) or around £4,600 on the Energy Saving Trust’s figure. Together that is roughly £11,383, before any difference from fitting them together. Octopus lists 12 panels with a 10 kWh battery at £11,115.
Yes, and the published prices show it. Octopus lists 2 panels with no battery from £6,663 and 12 panels with a 10 kWh battery at £11,115: £4,452 more for ten more panels and a 10 kWh battery, against £5,336 for the same battery fitted on its own. The Energy Saving Trust says the same: installers already on site can integrate the panels and battery in one job.
Often not on its own. In our model a 5 kWh battery adds about £133 a year to a 4 kW system on a medium-use home that is part of the day in — a payback of 30 years on its own price. The Energy Saving Trust says savings “won’t always be enough on their own to justify the cost”. A cheap overnight tariff, an electric car or heat pump, or backup can change that.
The Energy Saving Trust, as quoted by Octopus, gives 9 to 13 years for solar. Our model gives about 11 years for a 4 kW system on a medium-use home. A battery lengthens the whole-system payback because it adds more cost than benefit.
There is 0% VAT on installing solar panels and batteries in homes until 31 March 2027 (HMRC VAT Notice 708/6), including a battery on its own since 1 February 2024. From 1 April 2027 the reduced rate of 5% applies, about £569 more on a 4 kW system with a 5 kWh battery.
The roof (slate and in-roof systems cost more than standard on-roof), scaffolding and access, the inverter and whether the system is hybrid or AC-coupled, the battery’s size and make, whether backup is wired in, an EV charger, and whether your consumer unit needs upgrading. Octopus’s own list shows how much is fixed: two panels cost £6,663 before any battery.
There is no general grant for either. The Warm Homes: Local Grant covers eligible low-income or low-EPC homes through your council, and funds batteries only where they complement solar PV; the Warm Homes Loan Scheme offers lender loans up to £15,000 for a battery and £15,000 for solar PV.
Where these figures come from
Every figure above comes from a published source or from arithmetic on one. Read 7 October 2026. Where a source updates, the page should be re-read before a figure is reused.
- DESNZ Solar PV cost data 2025/26 (published 28 May 2026), South East mean — £1,859/kW up to 4 kW; £1,721/kW for 4 to 10 kW
- Octopus Energy, battery-only installation (April 2026 prices, read 7 October 2026) — 5 kWh £3,947; 10 kWh £5,336; Tesla Powerwall 3 £7,999; £500 non-refundable advance payment
- Energy Saving Trust, "Battery storage" (page last updated 6 October 2026) — typical lifespan 10 to 12 years; 5 kWh around £4,600, range £1,500 to £10,000; typical system 10 kWh; savings "won't always be enough on their own to justify the cost"; stored energy is less efficient than direct use
- HMRC VAT Notice 708/6, energy-saving materials and heating equipment — zero rate for installation to 31 March 2027, 5% from 1 April 2027; batteries qualify on their own from 1 February 2024
- DESNZ Warm Homes: Local Grant policy guidance (July 2026) — batteries only where they complement solar PV; MCS installer to MIS 3012
- DESNZ Warm Homes Loan Scheme rules (September 2026) — battery loan cap £15,000; government pays lenders up to 20% of the loan, to be passed on as a lower interest rate
- EU JRC PVGIS 5.3, PVGIS-SARAH3 2005-2023, 14% system loss — modelled yields
- Ofgem energy price cap, 1 October to 31 December 2026 — electricity 26.32p/kWh (Direct Debit)
- Octopus Outgoing, region H (OUTGOING-VAR-24-10-26, from 1 March 2026) — export 12.0p/kWh
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