Helios. Is plug-in solar worth it?
Helios. Is plug-in solar worth it? A free calculator estimating what plug-in solar could generate for any UK address.
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What is Helios. Is plug-in solar worth it??
"Helios. Is plug-in solar worth it?" is a free online calculator by South London Scientific that estimates whether plug-in solar panels are worth it for your specific home in the UK. Users enter their postcode and optional house/flat number to see how much energy they could generate from a balcony or wall-mounted solar kit, accounting for shading from nearby buildings.
The tool resolves your postcode against Ordnance Survey data, uses ray-tracing on Environment Agency LIDAR data to map surrounding buildings and shading, then queries PVGIS for annual energy yield based on the shading found. It lets you select panel orientation (south, east, west), floor level (ground floor is 0, higher floors clear more obstructions), and your annual electricity usage band. The calculator shows a visual sky plot with grey areas showing blocked sky and gold arcs tracing the sun's path on midsummer, equinox, and midwinter.
Helios is designed for UK homeowners and renters considering plug-in solar kits (typically 0.8 kWp with two panels and a microinverter, capped at 800 W inverter output by UK rules). It helps you weigh the financial viability before buying, noting that DIY socket installs cost £0 but compliant hardwiring by a registered electrician may be needed until the plug-in safety standard lands (expected mid-2026). Most owners earn nothing for exported power since DIY kits can't get MCS certification for the Smart Export Guarantee.
The tool stores no data — your address isn't saved, and the postcode is only used to pinpoint your building for calculation. It provides estimates, not financial advice, warning that real yield and savings vary with weather, day-to-day electricity use, and installation details. Self-consumption defaults to 60%, and the calculator should be refreshed quarterly for time-of-use tariffs.
Helios. Is plug-in solar worth it? pricing
Pricing model: Freemium
Free tool with no paid tiers. £0 assumes a DIY socket install. If compliant hardwiring by a registered electrician is needed (until the plug-in safety standard lands expected mid-2026), users should add the electrician's cost themselves. No subscription or payment required to use the calculator.
Helios. Is plug-in solar worth it? pros
- Free to use with no paid plans required
- No address storage — complete privacy
- Uses accurate Ordnance Survey postcode data
- Ray-traces buildings from Environment Agency LIDAR
- Queries PVGIS for authoritative annual yield data
- Visual sky plot shows shading clearly
- Gold arcs show sun path on midsummer, equinox, midwinter
- Accounts for floor level impact on obstructions
- Lets you choose panel compass direction
- Accommodates different annual electricity usage bands
- Shows realistic savings assuming 60% self-consumption
- Notes UK 800 W inverter output cap for plug-in kits
- Explains Smart Export Guarantee limitations for DIY kits
- Includes electrician hardwiring cost option
- Helps avoid expensive installation fees before buying
Helios. Is plug-in solar worth it? cons
- UK-only — only works for British addresses
- Plug-in solar kits not legally available in Britain yet
- Provides estimates, not financial advice
- Real yield varies with weather conditions
- Real savings vary with day-to-day electricity use
- Assumes exported energy earns nothing for most users
- Self-consumption rate is fixed at 60% default
- Requires manual refresh quarterly for time-of-use tariffs
Frequently asked questions about Helios. Is plug-in solar worth it?
What is plug-in solar?
Plug-in solar panels let you generate electricity from your balcony without expensive installation fees or planning permission. UK rules cap plug-in kits at 800 W inverter output, so most kits sold here are around 0.8 kWp — two panels and a microinverter.
When will plug-in solar be available in the UK?
Plug-in solar is currently in regulatory limbo in Britain — the kits available elsewhere in Europe aren't legally for sale in Britain yet. The plug-in safety standard is expected to land mid-2026, and the tool tracks the market to notify users when things change.
Do you store my address?
No. The tool has no database and your address isn't stored. Your postcode is resolved against Ordnance Survey data and house/flat number is used only to pinpoint your building for this calculation, not to store your address.
Why do I need to enter my house number or flat number?
The house number or flat number is optional but helps pinpoint your specific building for the calculation. Postcode is required, but the house/flat number improves accuracy without storing your address.
What does the floor number affect?
Ground floor is 0. Higher floors clear more obstructions from nearby buildings but also shift the solar peak season. The calculator uses this to determine how much sky is visible for solar generation.
Which compass direction should I face my panel?
South is typically best in the UK for maximum generation. However, east and west orientations still produce well. The tool lets you select the direction your panel will point to calculate accurate yield.
Can I earn money for exported power with plug-in solar?
Most owners earn nothing for exported power because the Smart Export Guarantee needs an MCS-certified install, which DIY plug-in kits can't get. The value is in what you use yourself (self-consumption), which defaults to 60%.
Do I need an electrician for plug-in solar?
Until the plug-in safety standard lands (expected mid-2026), the compliant route is a quick hardwire by a registered electrician. DIY socket install costs £0 but may not be compliant until the standard is in place.
What does the visual sky plot show?
Grey areas show the sky blocked by nearby buildings (derived from LIDAR data). Gold arcs trace the sun on midsummer, the equinox, and midwinter. Where a gold arc dips into the grey, the sun is hidden at that time.
Are these savings estimates reliable?
These are estimates to help you weigh it up — not financial advice. Real yield and savings vary with the weather, your day-to-day electricity use, and how the kit is installed. The calculator should be refreshed quarterly for time-of-use tariffs.