Helios runs LIDAR-based plug-in solar math for any British address
The browser tool ray-traces LIDAR to estimate balcony solar yield and payback per address, reflecting UK rules like the 800 W cap and MCS export limits.
By Ryan Merket ยท
Why it matters
Balcony solar is poised to go mainstream in the UK, but the economics hinge on site-specific shading and self-consumption. A per-address, LIDAR-aware calculator gives renters and homeowners a quick, realistic read before they buy.
Helios, a browser tool published at Helios, lets people in Britain punch in their postcode and see what plug-in balcony solar could generate at their specific address and whether it might pay back.
What it does
Users enter a UK postcode and optional house or flat number to pinpoint a building, then choose their floor level, balcony orientation, annual electricity usage band, kit size (0.4 kWp or 0.8 kWp), and tariff assumption. The app estimates annual generation, bill savings, and a simple payback period, and it shows two visuals: a map of the panel location and a sky view that highlights where nearby buildings block the sun.
The site stresses it stores no addresses. In its words: "We have no database - your address isn't stored." A separate privacy page is linked from the tool.
How it works
According to the page, Helios resolves postcodes against Ordnance Survey data, ray-traces surrounding buildings from Environment Agency LIDAR to model sky obstruction, and queries PVGIS for annual yield given the shading. Floor height and orientation come from the user, so a fourth-floor south-facing balcony will score differently from a ground-floor north-facing one.
The tariff model includes options like a standard variable rate and several Octopus and British Gas plans, plus an advanced section to set kit and install costs, self-consumption, and an export rate. The output frames savings primarily as self-consumption because, per the site, most DIY plug-in kits cannot claim the Smart Export Guarantee without an MCS-certified install.
The UK plug-in context baked in
Helios encodes two realities of the emerging UK balcony-solar market:
- UK rules cap plug-in kits at 800 W inverter output, per the site, so most kits here are around 0.8 kWp (two panels with a microinverter).
- A new plug-in safety standard is expected mid-2026; until then, the compliant route is a quick hardwire by a registered electrician, which users can add as an install cost in the calculator.
Because SEG export typically requires MCS certification that DIY kits cannot obtain, the calculator defaults export earnings to zero and focuses on daytime self-use. Time-of-use tariffs use a typical-day model; the site says it refreshes these assumptions quarterly.
Scope and caveats
These are planning estimates, not financial advice. Yield and savings will vary with weather, usage, and how the panel is actually mounted. The method depends on LIDAR data the page attributes to the Environment Agency; Helios does not specify how shading is handled for addresses outside England. The tool also does not disclose who operates southlondonscientific.com or when the model was last benchmarked against measured systems.
For people waiting out the UK regulatory limbo, Helios offers an email alert when compliant plug-in kits become available domestically; signups are managed via Brevo.