Cookie policy
Last updated 27 September 2026.
We only set analytics cookies if you accept them, and we don't use advertising cookies. Everything else this site stores is strictly necessary: it's what the site needs to work, set only when you use the feature that needs it. You can change your analytics choice at any time with Cookie settings at the bottom of every page.
What we store
energy-calc-wizard-state:v1
- Type
- Local storage in your browser
- Set
- When you start a calculation
- Why
- Keeps your answers so you can move between steps and come back later. It's kept in your browser.
- How long
- Until you clear your browser's site data
wattproof-analytics-consent:v1
- Type
- Local storage in your browser
- Set
- When you accept or reject analytics cookies
- Why
- Remembers your choice so we don't ask on every page.
- How long
- Until you clear your browser's site data
sb-…-auth-token (and …-code-verifier)
- Type
- Cookies
- Set
- Only if you sign in
- Why
- Keeps you signed in so you can see your saved calculations and reports. The code-verifier cookie checks that a sign-in link was opened by the browser that asked for it.
- How long
- Until you sign out, or the sign-in expires
Analytics cookies (only if you accept)
If you click Accept on the cookie banner, we load Google Analytics to count visits and see which pages are used, so we can improve the site. It sets these cookies:
_ga
Tells visits from the same browser apart. Lasts 2 years.
_ga_91P8F89YK6
Keeps track of your current visit. Lasts 2 years.
Google handles this data under the Google Privacy Policy. If you reject, or change your mind later with Cookie settings, Google Analytics doesn't load and we remove its cookies.
Other services
- Google Maps. The satellite map only loads if you look up your roof from your postcode. Google then handles that request under the Google Privacy Policy.
- Stripe. If you buy a report, you pay on Stripe's own checkout page, which sets its own cookies to process the payment and prevent fraud. See Stripe's cookie policy.
- Our fonts are served from this site, not from Google Fonts, so loading a page doesn't contact Google.
Removing what we store
Signing out removes the sign-in cookies. To remove your saved answers, clear this site's data in your browser's settings. The calculator still works if you block cookies, but you won't be able to sign in.