Skip to main content

Plug-In Solar Costs and Payback in the UK: The Method, Not a Guess

This page is about the United Kingdom market only. It explains how to work out what a plug-in solar system would cost to run in the UK and how to calculate your own payback time — not one headline number that applies to everyone. Where German prices or rules appear for comparison, they are labelled as German, because German costs, subsidies and export rules do not apply here.

Before you read on: plug-in solar is not yet lawful to use in the UK. See the current legal status for the full timeline. The Government made the regulations that will change this — the Plugs and Sockets etc. (Safety) Regulations 1994 and Electricity Safety, Quality and Continuity Regulations 2002 (Amendment) Regulations 2026, SI 2026/848 — on 16 July 2026, with a stated commencement date of 27 August 2026. Until commencement, and until a product meeting the final Interim Product Specification is actually on sale here, nobody can give you a verified UK installed cost, because no lawful UK retail market exists yet. Everything below is a method for you to apply once one does, not a promise about what you will pay or save.

Why nobody can give you one honest UK payback figure

Every “plug-in solar pays for itself in X years” claim you will see between now and commencement is being made without a real UK price to plug in. That is worth sitting with. A payback figure needs two verified numbers: what the system costs installed, and what it saves you per year. Right now, the UK has neither in a form you can trust:

  • The cost side is unsettled. No kit certified against the final UK Interim Product Specification is confirmed on sale, so retail prices you see quoted today are for products that may not match the eventual standard, or are German/EU prices with no UK duty, VAT treatment or retailer margin applied.
  • The installation route is still splitting in two. Until 27 August 2026, the only route that is unambiguously compliant is a hardwired connection to a dedicated circuit, fitted by a competent registered electrician, notified to your Distribution Network Operator (DNO) under Engineering Recommendation G98. That adds a labour cost on top of the hardware, and we have no verified UK figure for it to quote you. From 27 August 2026, a genuinely plug-and-socket route opens for kits meeting the Interim Product Specification, which should remove that labour cost — but only for products built to that spec.

So rather than assert a number, this page gives you the calculation itself, built around figures you can source and verify yourself, plus the real cost and saving drivers so you know what you are plugging in.

What will actually determine your cost

1. The hardware

A plug-in solar kit is one or two panels plus a microinverter, typically capped at 800 W AC output under the UK’s new rules (see the SI 2026/848 detail above; the same 800 W ceiling, measured at the inverter, is the German convention too). Panel count and mounting hardware (railing clamps, wall brackets, ground frame) change the price, and none of it is fixed by regulation — only the inverter’s output ceiling is.

2. The installation route

This is the single biggest UK-specific cost variable, and it is exactly what SI 2026/848 is designed to change. Before 27 August 2026, current guidance treats connecting a generator to an existing socket circuit as unsafe practice: UK ring final circuits are built around a single supply point at the consumer unit, and injecting current at a socket can alter how residual current devices (RCDs) and protective conductors behave, which is why the compliant route has meant a dedicated circuit fitted by an electrician rather than a spare kitchen socket. A hardwired install is not cheap to add on top of an 800 W kit, and it also is not really “plug-in” solar in the sense the marketing implies. After commencement, a kit meeting the Interim Product Specification, using a plug approved under the amended Plugs and Sockets etc. (Safety) Regulations 1994, should be installable into a normal socket without an electrician — that is the entire point of the reform, and it is the cost saving the regulations exist to unlock.

3. Grid notification

Notifying your DNO under G98 does not itself cost money — the Energy Networks Association’s “fit and inform” process lets an installer commission a compliant, Type Tested generator first and notify the DNO within 28 days, with no upfront approval fee. The Government’s July 2026 consultation response also proposes amending G98 to fit the new plug-in category, and separately indicated support for a limit of one plug-in microgenerator per circuit. Confirm the up-to-date position on your own DNO’s site before relying on any of this, because the amended G98 text was not yet published at the time of writing.

What will determine your saving

This is the part that actually decides whether a system is worth buying, and it is true regardless of what the hardware costs.

Your import tariff

A plug-in system without a battery saves you money by displacing electricity you would otherwise have bought from your supplier at your import rate. Under the current Ofgem price cap (1 July to 30 September 2026, Direct Debit customers in England, Scotland and Wales, including VAT), the standard variable electricity unit rate is 26.11 pence per kWh, with a daily standing charge of 57.19 pence. That is a live, published figure you can use as a benchmark — but check your own tariff, because many households are on fixed deals above or below the cap, and the cap itself is reset every three months.

Your usage pattern during daylight hours

This is the driver most guides skip, and it matters more than the tariff. A plug-in inverter feeds electricity into your home’s wiring the moment it is generated. Whatever is drawing current at that instant — a fridge, a router, a laptop charger — takes it from the panel first, because that supply is electrically nearer than the grid. Anything the panel generates beyond what your home is drawing at that moment is not stored and, without MCS certification, is not currently eligible for any export payment either — it simply goes to the grid unpaid. A household at work all day with nothing running at midday will capture a small fraction of a system’s rated output; a home office, a fridge-freezer or a heat pump changes the sum considerably. Before estimating a saving, look honestly at what draws power in your home between roughly 9am and 4pm, since that is the window most likely to overlap with generation in the UK.

No export revenue for now

Unlike a full rooftop solar installation registered under the Microgeneration Certification Scheme (MCS), which can register for Smart Export Guarantee (SEG) payments for exported electricity, plug-in solar kits sit outside MCS certification. That means, on current guidance, any generation you do not use yourself is not paid for. Your entire saving comes from import avoided, not export sold. Any future change to that position would need its own verified source before you rely on it.

The calculation method

Use this structure once you have real numbers for your own situation — do not use the example figures as UK defaults, they are placeholders to show the arithmetic.

Step What you need Where to get it
1. Installed cost Verified UK price for a compliant kit, plus installation cost if the socket route does not apply to your case Retailer quote for a product confirmed compliant with the Interim Product Specification, once such products exist
2. Expected annual generation kWh/year for your panel’s size, orientation, tilt and location The EU Joint Research Centre’s free PVGIS tool (re.jrc.ec.europa.eu/pvg_tools), which models output from postcode, orientation and tilt using satellite irradiance data
3. Self-consumption ratio The share of that generation you would actually be drawing power to use at the time it is produced Your own judgement of daytime occupancy and appliance use — there is no UK-verified average to cite yet
4. Usable annual saving (kWh) Row 2 × Row 3 Calculated
5. Annual saving (£) Row 4 × your import unit rate (e.g. 26.11p/kWh under the current Ofgem cap) Calculated, using your actual tariff
6. Simple payback (years) Row 1 ÷ Row 5 Calculated

Two things this method deliberately does not do: it does not assume an export payment (because none currently applies), and it does not assume a fixed percentage of rated output will be “usable” — that number depends entirely on when your household draws power, which you have to assess honestly rather than take from a marketing page.

We have built this exact method into an interactive tool: enter your panel size, region and rate to see the range for yourself, in the plug-in solar savings calculator.

What a battery changes

Adding a battery lets you store midday surplus and use it in the evening, when UK households typically draw more power — which can meaningfully raise your self-consumption ratio in Row 3 above. It also roughly doubles or triples the up-front cost, so it does not automatically shorten payback; it depends on how much of your generation you were otherwise losing unpaid. Run the calculation both with and without a battery using the same method before assuming storage is worth it for your case.

The German comparison, labelled as Germany

For context only — this is not a UK price. In Germany, a complete 800 W Balkonkraftwerk kit is commonly quoted around €500–€700 before any local subsidy, with several cities (Berlin, Munich and Hamburg among them) offering additional grants that can reduce the effective cost further, and VAT on such kits removed since January 2023. Germany also allows up to 2,000 W of panel capacity behind that 800 W inverter, registration is a single online step in the Marktstammdatenregister, and there is no separate DNO notification at all. None of that — the price, the subsidies, the registration process, or the panel headroom — is the UK position, and nothing here should be read as a UK estimate.

What to do with this now

Build your own version of the table above using PVGIS for your generation estimate and your actual tariff for the saving side, so you are ready to plug in a real installed cost the moment one exists. Do not buy and connect anything before 27 August 2026, and do not assume a product on sale today will match the eventual Interim Product Specification. Check the legal status page for the latest before acting.

Sources