No.385 of 650 · approved, not built MP: Sir Oliver Dowden (Conservative) England

Hertsmere

Hertsmere has 1.4 MW of clean power (all solar) approved and still not built: enough to supply a year's electricity to 500 homes. Britain's grid bottlenecks still add to bills here: about £92 a year per household, £3.9m across the constituency's 41,939 homes.

Not visible
here

No big wind farm on the national grid is mapped to this constituency, so no switch-off payments show here in national data. Smaller wind farms on the local grid can still be paid to switch off — invisibly. The £ figure for this seat is a floor, not a zero.

how we worked this out

1.4 MW

of clean power — all solar — approved and still not built, enough to supply a year's electricity to 500 homes. Approved at least two years ago; waiting on the grid, not on planning. That is 0.1× the renewable capacity actually running here.

5 projects · planning database (REPD), July 2026 · how we worked this out

£3.9m

is what the grid gap costs this constituency's 41,939 households in a year between them — £92 each, about 51 days of one home's electricity.

The £92 per household is a national figure — identical in every GB seat. Only the seat total varies, with the number of households · NESO · how we worked this out

The waiting list

5 of 5 waiting projects · years since approval

Willows Activity Farm, Colney Heath - Solar Array 0.2 MW

4.2 YRS

Unit 2, York Crescent - Solar Panels 0.2 MW

3.7 YRS

Multi Storage, Cranborne Industrial Estate - Solar Panels 0.2 MW

3.3 YRS

Blanche Lane, South Mimms - Solar Panels 0.6 MW

2.9 YRS

NIBSC, Blanche Lane - Solar Panels 0.2 MW

2.7 YRS

Every approved, unbuilt project

approved 24+ months ago, still not generating · planning database, July 2026

Site	Technology	Enough for	Capacity	Approved	Waiting
Blanche Lane, South Mimms - Solar Panels	Solar Photovoltaics	200 homes	0.6 MW	2023-08	2.9 yrs
Unit 2, York Crescent - Solar Panels	Solar Photovoltaics	100 homes	0.2 MW	2022-11	3.7 yrs
NIBSC, Blanche Lane - Solar Panels	Solar Photovoltaics	100 homes	0.2 MW	2023-12	2.7 yrs
Willows Activity Farm, Colney Heath - Solar Array	Solar Photovoltaics	100 homes	0.2 MW	2022-05	4.2 yrs
Multi Storage, Cranborne Industrial Estate - Solar Panels	Solar Photovoltaics	100 homes	0.2 MW	2023-04	3.3 yrs

Plus 2 more approved within the last two years.

Batteries

projects of 10 MW and above · planning database, July 2026 · what batteries do →

Site	Size	Status	While discharging
Hilfield Lane, Aldenham - Battery Energy Storage	170 MW	approved, not built 2026	could supply ≈596,000 homes

What this page does not show

Smaller wind farms on the local grid are also switched off; national data does not show it, so the £ figure here is a floor, not a zero. Offshore wind is counted nationally, never per seat. The planning database can run a quarter behind reality.

Electricity does not travel from a particular project to particular houses. Everything generated goes into the national grid and everyone draws from that shared pool, so "enough for X homes" is a way of sizing the electricity — not a claim that these homes would be powered by this site. Battery storage is counted separately from generation: it moves power in time rather than making it.

Planning statuses come from the government's planning database (REPD), which records what was decided and when, but not why. Where a project was refused we say so and name the authority; for the reasons, look up the planning reference on that council's own register. How to check any figure on this page →

Read the full method, including everything we cannot see →

What has Sir Oliver Dowden said about the grid in Parliament? Search Hansard →

See the full league table Data (JSON)