Put the savings calculator on your own product pages.
The same calculator that runs on this site, embedded on yours, answering “what would this kit save me?” for your visitor’s own postcode — over your products, at your prices.
What it 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 one
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 an embed does not buy. It does not change where your products rank in our comparison table, and it does not change anything we publish about them. The checks and the advertising are deliberately separate businesses — see the comparison, where a paying advertiser’s own kit still reads “not yet verified”.