We list your products whether you take part or not. Here is what you can do about it.
Wattcheck lists what vendors publish and what the public registers record, and puts the two side by side. Your listing exists either way — so the useful question is whether it is accurate, and that is free and takes minutes.
The three things a vendor can do here
1 Correct your listing
Free, always. Prices, photographs, product links, your description and your short trading name go live as you submit them; the figures a compliance check is built from go to a person with a datasheet first. How claiming works →
2 Embed the savings calculator
Paid. The calculator from this site, running on your product pages, over your catalogue and your prices, at your visitor’s own postcode. Described below.
3 Buy a labelled placement
Paid, and always disclosed. It is a separate block outside the comparison table. It does not move a single row, and it does not change a word we publish about you.
What the calculator embed does
1 Asks for a postcode
Geocoded through postcodes.io, then modelled at those exact coordinates rather than against a national average.
2 Models a real year
PVGIS v5.2 — the European Commission Joint Research Centre’s solar model — annual and month by month, at their default 14% system losses.
3 Caps at your inverter
Generation is clipped at the kit’s AC rating. Plug-in arrays are deliberately oversized, and a calculator that ignores clipping overstates what a buyer actually gets.
4 Ranks your kits
Scoped to your catalogue and ordered by payback at that postcode. The ordering is genuinely different in Truro and in Aberdeen, so it is an answer a static table on your own site cannot give.
Why you cannot simply build this
PVGIS explicitly forbids browser and AJAX access, so a script on your product page cannot call it. It has to be proxied server-side, cached so a free public API is not hammered, and kept correct as the model versions move. That is what already runs behind a versioned API for this site.
The honesty discipline comes with it, and it is the reason the numbers are worth putting your name on. Only self-consumed electricity counts as a saving. Export is valued at nothing. Clipping is deducted. Every assumption is printed beside the figure, which is what the CAP Code expects of a savings claim, and the self-consumption share stays adjustable by the visitor rather than quietly set to something flattering. A prettier calculator that overstated savings would be worth nothing to either of us.
Getting an embed
Email hello@wattcheck.co.uk with your site and roughly how many products you sell, and we will come back with what an embed would look like for you. There is no self-service sign-up yet, deliberately — better to get the first few right than to ship a checkout.
An embed carries a small credit back to Wattcheck. That is part of the deal, and worth being upfront about.
What money buys here, and what it does not
This is the whole commercial policy, stated once so it cannot drift into two versions.
Correcting your listing is free and always will be. There is no tier that makes a product look more compliant than it is. A site that sold accuracy would be selling the only thing it has.
Paid placement is labelled, every time it appears. The disclosure is a database column that cannot be blank and a renderer that cannot make it conditional, because undisclosed paid prominence is a banned practice under the DMCC Act 2024. The slot sits outside the comparison table, is drawn from a separate query, and there is no code path from it into the ordering.
Neither an embed nor a placement changes a verdict. On the comparison a paying advertiser’s own kit still reads “not yet verified”, in the same words as every free listing. Nothing on the register side of the site is for sale at all: the device pages carry no advertising and never will.