Privacy notice
How Helios handles your data.
The short version
Helios is designed to give you a useful plug-in solar estimate without storing your personal data. We don't set cookies, we don't create accounts, and we don't track you across the web. Your inputs are processed to produce a single calculation; the result is returned to your browser and we keep no record of your address. We use cookieless, self-hosted analytics to count visits, and a map and a few libraries load in your browser (details below). We also record aggregate outcome counts — which verdict, data source, and location-precision level a result used — with no address and no personal data, so we can see how the tool performs across requests.
What you tell us
To produce a yield estimate, you provide:
- Postcode — required. Resolved to a lat/lon via Ordnance Survey / postcodes.io data.
- House number or flat designator — optional.
When provided, we look it up in a local copy of
OpenStreetMap address data held on our own server, matching the
addr:housenumberandaddr:postcodetags — your house number does not leave our infrastructure for this step. If OSM has the building, we use its centroid as the panel location for shading; if not, we fall back to the postcode centroid. We never store the house number — it is used only to locate the building for this one calculation. (Some white-label deployments, e.g. councils, additionally use the Ordnance Survey OS Places API for addresses OSM lacks; this is off by default and not used on this site, and any deployment that enables it discloses it in its own privacy notice.) - Floor, balcony orientation, balcony depth — the panel-geometry inputs the shading model needs.
- Annual electricity consumption band, tariff, kit and install cost, self-consumption fraction — used to compute payback. None of these are uniquely identifying.
We don't ask for your name, your email address, or any other identifier in the calculation flow. The waitlist signup (see below) is the one place we collect an email, and only with your explicit consent.
How we process it
Your answers are sent to our server, used in a single calculation, and the result is returned to your browser. We have no database — nothing about your address or your calculation is written to disk or kept after the response is sent.
A short-lived in-memory cache speeds up repeated identical calculations. It is keyed on the numeric inputs to the solar model — the location coordinates and panel geometry — held only in memory and cleared when the server restarts; it contains no postcode, house number, name, or email. Where any future cache is keyed on address-derived data, the Helios design spec (§3.6) requires a non-reversible HMAC with a server-side secret so the address cannot be recovered from it.
Third-party services
To generate your results, our server contacts the following services on your behalf — these receive data from us, not from your browser:
| Service | Data sent | Purpose |
|---|---|---|
| postcodes.io | Your postcode (only when the offline ONS index isn't loaded) | Converting postcode to lat/lon |
| PVGIS (European Commission) | Lat/lon, panel azimuth, tilt, kWp, horizon profile | Computing annual yield from solar radiation models |
| Environment Agency LIDAR Composite | Lat/lon (resolved to OS National Grid tile names) | Building-height data for shading calculation |
| Welsh Government / Natural Resources Wales LIDAR | Lat/lon (resolved to OS National Grid tile names) | Building-height data for shading calculation (Wales). Contains data © Welsh Government / Natural Resources Wales, licensed under the Open Government Licence v3.0. |
| Ordnance Survey OS Places API | Postcode and house number — only on deployments that have enabled OS Places (off by default; not used on this site). Address lookups here are served from a local OpenStreetMap copy and contact no third party. | Authoritative building-level lat/lon — improves shading precision |
| Brevo (Sendinblue SA) | Email address (only if you use the waitlist signup) | Holding your email for the kit-availability mailing list |
Loaded directly in your browser
A couple of resources load straight from third-party servers when you view the page, so those servers see your IP address (and, for the map, the area around your result location). We don't send them your postcode, house number, or any account identifier.
| Service | What it receives | Purpose |
|---|---|---|
| CARTO basemaps | Your IP address and the map area around your result location | Drawing the map that confirms we found the right place (only shown when we have a building-level match) |
| unpkg | Your IP address | Delivering the Leaflet map library (code and marker images) |
Waitlist signup
If you sign up to be notified when UK plug-in solar kits hit the market, your email address is sent to Brevo (Sendinblue SA, Paris, France) where it is stored on a Helios list. The legal basis is your consent, expressed via the tick box on the signup form.
You can unsubscribe from any email we send, or contact us to ask for your record to be deleted. We don't store your email anywhere else — South London Scientific holds no separate copy of the waitlist.
Brevo's privacy policy is at brevo.com/legal/privacypolicy.
Analytics, cookies and tracking
Helios does not set any cookies, and does not use localStorage or sessionStorage.
We count visits using
Plausible Analytics,
which we self-host on our own server
(plausible.southlondonscientific.com) — your visit
data goes to us, not to a third party. Plausible is cookieless,
stores no personal data, does not fingerprint your device, and
does not track you across other websites. It records aggregate
page views, referrers, and a country derived transiently from your
IP address (the IP itself is not stored). There is no advertising.
Server logs
Our web server records standard access logs (timestamp, IP address, path requested, status code) for diagnostics. Logs are retained for up to 30 days then deleted.
Who we are
Helios is built and operated by South London Scientific. Council-branded versions of Helios remain hosted and operated by us on behalf of the partner.
Your rights
Under the UK General Data Protection Regulation (UK GDPR), you have the right to access, correct, or request deletion of any personal data we hold about you. In practice we hold very little — at most an email address on the waitlist, and short-lived access logs — but if you have any concerns or requests, please contact us.
Contact
Questions about this privacy notice or how your data is handled: ruaraidh@southlondonscientific.com.