How Do You Get Power to an Electric Rooflight?

There are three ways to power an electric rooflight. Run a cable through the ceiling or roof void from an existing circuit, which is easiest while the ceiling is open. Chase or surface-run it down a wall to a fused spur. Or fit a solar unit with its own panel and battery, which needs no cable at all and is the usual answer in a finished room.

Which one applies to your house is decided by the ceiling above the rooflight and by what is on the floor above it. That is a survey question, not a catalogue question, and it is the single largest variable in the price of an electric rooflight.

Route one: through the ceiling or roof void

The electrician takes a feed from a suitable existing circuit or a dedicated spur at the consumer unit, runs it through the joist void or above the ceiling line, and terminates a fused connection unit within reach of the rooflight opening. We terminate into the control gear from there.

This is the route to have. On an extension under construction it is trivial, because the electrician is already on site and the ceiling is a set of open joists. On an existing house it is available more often than people assume, particularly where there is accessible loft space over the room or where the rooflight sits in a rear-return roof on a two-storey Ipswich terrace. The cable drops down beside the opening and the only disruption is one small access point.

The cost, on top of the rooflight itself, is £180 to £400 where the ceiling is already open. It wants doing at first fix, before insulation and plasterboard, and that timing is what people get wrong.

Route two: down a wall

When there is no void to run through, the cable comes down a wall to a spur. Two versions, and they are not equivalent.

1. Chased in. Cut a chase, run the cable in capping or conduit, plaster over, redecorate. Invisible when finished, which is the point. It adds cost and it adds a decorating job that is not ours.
2. Surface containment. Trunking or conduit on the face of the wall. Cheap and quick. Fine in a garage or a utility room. In a new kitchen extension it undoes the reason you built the extension.

There is a third variant worth naming: lifting floorboards in the bedroom above, running the cable in the joist void and dropping it down beside the opening. Practical where the floor is boarded and carpeted, expensive and unwelcome where it is engineered oak laid last month.

On a finished room, the realistic figure for cabling of any of these kinds is £350 to £900 including making good, and it goes higher where the run is long or the access is genuinely awkward. Getting a cable into a completed flat roof build-up is its own problem and is covered on getting power to a rooflight in a finished flat roof.

Route three: solar, and no cable at all

A solar opening rooflight carries a small photovoltaic panel on the frame, a rechargeable battery, the actuator and the rain sensor, all self-contained. No mains cable, no chased wall, no electrician, and no Part P consideration because there is no fixed mains connection to make.

On a retrofit into a finished room this collapses an awkward job into a straightforward one, and it is the option we recommend most often on existing houses. The unit costs more than the mains equivalent, roughly £1,750 to £2,500 fitted for a like-for-like roof window replacement against £1,600 to £2,300 for the electric version, but you save the entire cabling item. On a finished room that maths usually lands in solar’s favour before the decorating is even counted. The full comparison is on mains or solar powered rooflight.

The honest caveat is Suffolk in January. Ipswich sees roughly 45 to 55 hours of bright sunshine across the whole of December and about eight hours of daylight a day. Modern panels charge from overcast daylight rather than direct sun, so what you get in midwinter is fewer operating cycles per day, not a dead unit, and the rain sensor draws so little that it keeps working regardless. Where it turns marginal is a north-facing or heavily shaded unit that you want to cycle several times a day. We check orientation and shading at survey and say so plainly if it is borderline.

Choosing between them

Who does which part

We are skylight installers, not electrical contractors, and the boundary is worth stating plainly. The electrician owns everything from the consumer unit to the fused connection unit: circuit selection, cable sizing, RCD protection, testing and the certificate. We own the opening, the structure, the upstand, the flashing, the rooflight, the actuator, the control gear, the commissioning and the sensor set-up.

Notifiable work under Part P in England is new circuits, consumer unit work, and electrical work in a room containing a bath or shower. A fused spur added to an existing circuit outside those locations is not notifiable in itself, but it must still be carried out to BS 7671 and certified. We work with electricians registered under a competent-person scheme so notifiable work is self-certified. Use your own if you would rather, and we will give them the technical requirements in writing before the job. The detail is on the electrical side of an electric rooflight installation.

Get the route surveyed before you order

Powering an electric rooflight is the part of the job that varies, so it is the part we price with a real figure rather than a caveat. Tell us the room, the roof type and roughly where the property sits, and we survey the structure and the cable route together. One written price, fixed after survey, with a 10-year workmanship guarantee on the installation.

Request a fixed quote, or read how an electric rooflight actually opens and how long the installation takes if you are still working out the shape of the job. Everything sits under electric skylight installation.