What a watt of plug-in solar actually costs in Britain

Plug-in solar is sold in pounds and used in watts, and almost every piece of coverage since the law changed has quoted the first and ignored the second. That is how a £449 kit gets called the cheapest way into solar when it is one of the worst-value products on the approved list, and how a £989 kit gets called expensive when it is among the best. Price per watt is the only comparison that survives the difference between a single 400W panel and a 1260W pair, and nobody in the UK was publishing it, so we are.

This page is the index and the method behind it. The underlying data is the same file that drives every price on this site, and it is downloadable as a CSV under a Creative Commons attribution licence. Take it, check it, argue with it.

The index since it started

Three readings in, and the third is the one that matters. Read the two percentages against each other: the median fell 14% while the best available rate fell 34%, from £0.69 to £0.45. That gap is the whole story. If the market were repricing, both would move together. Instead the middle barely shifted and the floor collapsed, because not one seller on this list has cut a penny. A trade merchant simply arrived selling its own-label kits at roughly half the going rate, and Octopus Energy entered at £0.71. Every fall we have recorded since 19 August is composition, not price cuts, and anyone reporting this as "plug-in solar prices are falling" has the mechanism wrong.

Trade against consumer, and why the gap is not what it looks like

From this reading the index is also split by route to market, because the two are no longer telling the same story.

A watt through consumer retail costs exactly twice what a watt through a trade merchant costs. That headline is real but it would be lazy to stop there, because two different effects are stacked inside it and only one of them is about the channel. The same kit is only modestly cheaper on a trade counter: the UKSOL 890W ground mount is £951.60 at City Plumbing against £1,089 direct from UKSOL, a 13% difference that is roughly what you would expect from trade terms. The larger part is product, not channel. City Plumbing has built its own kits, pairing commodity Jinko and DMEGC panels with a Hoymiles inverter, and prices them at merchant margins rather than consumer-brand margins. That is what halves the number, and it is a far more interesting development than a trade discount.

The practical version for a reader: the cheapest legal way into plug-in solar in Britain today is a plumbers' merchant's own-brand kit, and you do not need a trade account to buy one.

Which City Plumbing kit is which register entry

There is a problem with buying the cheapest kits on the market, and it is worth stating plainly. City Plumbing does not print register model codes against its listings, so a buyer standing on that page cannot do the one check that everyone, including us, tells them to do. We have matched them ourselves.

To be explicit about the standard of evidence: these matches are ours, not City Plumbing's. Each rests on two things agreeing, the total panel wattage and the inverter. The shop's "HiFlow" branding is the Hoymiles HF-800-WB named in the register entry, and that is what separates the two 940W entries from one another, since the other pairs the same panels with an HMS-800-2WB. We think that is solid, and we are publishing it rather than sitting on it because a buyer needs it today. If any of it is wrong, from City Plumbing or from a reader who has a box in front of them, tell us and we will correct it here with the date attached.

Every priced kit, ranked by what a watt costs

Sorted cheapest per watt first. No affiliate links anywhere on this page, and Plug Solar Hub earns nothing from any seller of a compliant kit.

Three things the index shows that a price list does not

Size buys itself, and it is not close. The 1260W UKSOL Pro Max is £0.78 a watt and the 460W UKSOL Pro Compact is £1.85, the same manufacturer, the same inverter class, a difference of 137%. The fixed costs of a plug-in kit, the inverter, the plug, the cable, the type testing, the delivery, do not shrink when the panel does. If you have the wall or the ground for two panels, buying one is the most expensive decision available to you.

The mount is a bigger line item than anyone admits. The identical UKSOL 890W kit is £0.95 a watt on a hybrid mount and £1.07 on a ground mount, and that is at the cheapest seller for each. At Argos and UKSOL direct the ground mount version is £1.35. Before you compare two kits, check you are comparing the same mounting, because the frame can move the per-watt figure further than the panels do.

The cheapest entry ticket and the best value are now almost the same product, and that is new. For the first three weeks of this market the cheapest kit was always the worst value: on 5 September the floor was a £449 PatioSun Lite at £1.12 a watt while the best rate was £0.69. Today the cheapest kit outright is a City Plumbing Jinko 940W at £432 and £0.46 a watt, and the best value is its DMEGC 1030W at £468 and £0.45. The floor and the best rate have converged, because the thing setting the floor is no longer the smallest box but the cheapest supply chain. The £449 PatioSun Lite is still on sale, still 400W, and now costs seventeen pounds more than a kit with 540 more watts in it.

How the index is calculated

The rules are deliberately dull, and published so anyone can reproduce the number.

• The basket is every kit showing Compliant on the ENA G98 Type Test Register that has a retail price on a seller's own page. Approved kits nobody sells are excluded, and there are currently thirty of them.
• The price is the lowest we can find, inclusive of VAT and delivery, read on the seller's page rather than taken from a press release or a comparison site. Where a seller's checkout differs from its listing, the checkout total is used.
• The denominator is total panel wattage, not inverter rating. Every compliant kit is capped at 800 VA of export, so inverter rating would make every kit identical and tell you nothing.
• The statistic is the median, not the mean. The range runs from £0.45 to £1.85 and a single ground-mount outlier would drag an average around.
• One price per kit, so a model sold in five places counts once, at its cheapest. Where a single register entry covers several mountings or panel sizes, as EcoFlow’s does across thirteen price points, we take the cheapest configuration the entry actually names and record which one it is.
• Readings are taken when the register moves, not on a fixed calendar day, and every reading is dated and kept.

What the index cannot tell you

Four limits, and they matter more than the number while the series is this young.

• The basket is not held constant. This is a median of what is on sale on the day, not a fixed basket tracked over time, so a fall can mean prices dropped or simply that a cheaper maker arrived. In this reading it is entirely the second.
• It is weighted towards UKSOL, because UKSOL is six of the eleven priced kits. That is a fair description of what a buyer meets in the shops today, and it is not a manufacturer-neutral average.
• It says nothing about quality, warranty or whether the thing arrives. Lead times are tracked separately on where to buy. One of the cheapest entries is a pre-sale from a seller whose checkout charged £100 over its listed price on another product. Per watt is a price measure, not a recommendation. It prices the hardware rather than the electricity, which is why we now also publish what each kit costs per unit of electricity it generates.
• It excludes the thirty approved kits with no public price, and if those land cheaply the index will fall sharply, which would tell you about supply rather than about anyone cutting margins.

Using or quoting this index

The index is free to use, including commercially, with attribution to Plug Solar Hub and a link to this page. If you are a journalist, an analyst or a manufacturer and you want the underlying rows, the price CSV carries every priced kit with its seller, channel and the date it was read, the full register CSV carries all one hundred and nine approved kits including the eighty-nine nobody sells yet, and the history CSV carries every reading we have taken. If you think a figure is wrong, tell me and I will check it against the seller and correct it with a dated note, which is what happened to the PatioSun Duo on this very page: it was published at £549 and a reader found the checkout charging £649.

I have no commercial relationship with any manufacturer or seller of a compliant kit, there are no affiliate links on this page or on the register tracker, and the only thing I want from you is that you check the model code against the register before you plug anything in.

Sources: ENA G98/G99 Type Test Verification Register, Plug-in Solar device type, register read 4 September 2026; individual seller pages on the dates shown in the table. DESNZ Plug-in Solar Device Interim Product Specification v2.0, 16 July 2026, for the 800 VA cap. Educational information, not financial or electrical advice.