Helios – what plug-in solar could generate for any address in Britain

--- Someone finally made solar panels that don't require a mortgage. Plug-in solar panels—those things you mount on a balcony railing and plug into a regular socket—are now legal in the UK, and they're about to hit the market. The catch? Nobody knew if they were even worth buying. That's where Helios comes in.

South London Scientific built this thing to tell you exactly what your address could generate. You punch in your postcode, your flat number, what floor you're on, which way your balcony faces, and Helios ray-traces the actual skyline using UK government LIDAR data—government laser scans of the ground that map every building and hill. It knows if your neighbor's block is casting shade on your panels at 3 PM in July. It knows if that tree outside your landlord's window is killing your efficiency. Most solar calculators just assume an open sky. Helios doesn't guess. It traces photons.

The privacy piece is refreshing—they don't store your address. Postcode goes in, calculation comes out, nothing is saved. That's genuinely rare in UKPropTech.

A few catches worth knowing. Most of Scotland and Wales aren't covered by the LIDAR data, so Helios falls back to a synthetic horizon which is less accurate. Trees and anything built after 2022 might not be in the system either. And here's the UK regulatory reality: plug-in kits are capped at 800W output—they're small. The safety standard isn't even finalized yet (expected mid-2026), and to earn money from exporting power back to the grid under the Smart Export Guarantee, you still need MCS-certified installation. Most plug-in owners will generate for themselves and that's it. Still, at current electricity prices, every little bit helps.

This is a glimpse of what energy independence looks like when you're renting. No roof access, no planning permission, no cowboy electrician. Just a postcode, a balcony, and a calculation telling you whether it's worth the upfront cost.