Solar panels and aircon: the pairing London ignores
Published 24 Jul 2026 · GPDO Sch.2 Part 14 Classes A–B (solar) · legislation.gov.uk · checked 24 Jul 2026
Air conditioning’s biggest objection is the running cost, and the sun that creates your cooling load is also the answer to it. Cooling demand peaks in the same hours photovoltaic output peaks — the one domestic load where that is true. Heating fights the sun; cooling rides it.
How well do the two actually match?
A modern split cooling a typical London room draws roughly 0.8–1.2kW. A 3–4kWp domestic array produces more than that through most of a clear summer day. From late morning to late afternoon, the aircon runs close to free at the point of use.
The honest catch is the evening. London flats hurt most from about 5pm — exactly as PV output falls away. Two responses work. A battery shifts the surplus a few hours, at a price. Or use the array’s peak to pre-cool: run hard through the free afternoon window, let the fabric of the flat bank the coolth, and coast the evening on a fraction of the load. Pre-cooling costs nothing extra and most people never think of it.
What are the planning rules for the solar half?
Roof-mounted panels on homes are permitted development for most buildings (GPDO Part 14, Class A), with conditions worth knowing before a surveyor visits: panels must not protrude more than 200mm from the roof surface, and must not sit higher than the highest part of the roof, excluding the chimney. Conservation areas and listed buildings carry extra restrictions — in a conservation area the wall-mounted options narrow, and on a listed building you need consent. Standalone garden arrays fall under Class B, with tighter limits on size, height and siting.
GPDO Sch.2 Part 14 Class A conditions A.1–A.2 · legislation.gov.uk · checked 24 Jul 2026 · conservation/listed specifics: check your borough before committing
The two systems do not interact in planning law. Panels are assessed under Classes A–B; a heat-and-cool unit under with its own conditions — the one-per-block limit, the 0.6m³ size cap for flats, the noise calculation. Doing both at once changes neither. The Class G rules, cited.
Does this work for flats?
Harder, honestly. The roof of a block belongs to the freeholder, so panels need the same consent conversation as the outdoor unit — and communal solar on London blocks remains rare. If you are in a house, the pairing is straightforwardly available. If you are in a flat, the practical version is often the smaller one: a heat-and-cool unit sized properly, run in the cheap hours, with the solar question raised at block level where there is appetite.
One alignment worth naming: a unit that heats as well as cools pairs with panels in winter too — the same array offsets shoulder-season heating, which is what makes the combined sum work rather than the summer alone (est.).