A mains-powered electric rooflight stops where it is. If the power fails while the rooflight is shut, it stays shut. If it fails while the rooflight is open, it stays open until the supply returns or you wind it closed by whatever manual route that model provides. Solar models behave differently, because they run from a battery and keep working through a power cut.
The motor holds its position
An electric skylight opens with a small actuator, either a chain or a spindle, driven by a motor and a control unit. The motor moves the sash only while it is being fed. When the supply drops, nothing pushes the sash further, and the actuator holds it where it is. It does not spring shut and it does not fall open.
That is the good news. The sash cannot slam, and nobody is hurt by a rooflight that moves without warning. The less welcome part is the open case. A rooflight left ajar for ventilation will stay ajar through a storm, and an electric rain sensor cannot close it when it has no power to do so.
Which models can be moved by hand
This is the question to ask before you buy, because manufacturers differ. Some electric windows have an emergency release, a hand crank or a key-operated chain. Others do not allow the sash to be moved by hand without risk of damaging the drive. Never force a window that has no manual route.
We put the answer in your quote for the unit we propose. For each product it says whether a power cut leaves you with a manual fallback and, if it does, how it is used. If your rooflight is out of reach, on a stairwell or high ceiling, that fallback needs to be something you can use from the floor, with a pole or a switch within reach, and we raise this at survey.
Solar models and batteries
A solar opening rooflight has a small panel on the frame and a rechargeable battery in the control unit. There is no mains cable, so a power cut in the house does not touch it. It carries on opening, closing and responding to its rain sensor from stored charge.
It has its own limit. After a long run of dark days in a Sheffield winter, particularly on a north-facing slope or under a shaded terrace street, the battery can run low. Use the wall control to see its state, and a window that has not charged well may move slowly or stop. This is the trade-off we explain at survey. Our page on electric or solar rooflights goes through which suits which roof.
Rain sensors and closing when you are out
The rain sensor is a small plate on the glass or frame. When water lands on it, it signals the control unit to close the rooflight. During a power cut, the signal arrives but the motor has nothing to act on. On a mains unit, an open window stays open. On a solar unit with charge in the battery, it closes as normal.
| Type | Window position | Rain sensor | Recovery |
|---|---|---|---|
| Mains electric, no back-up | Stays where it is | Cannot close it | Resumes when power returns |
| Mains electric with a back-up battery | Can still move for a time | Works while charge lasts | Battery recharges from the mains |
| Solar | Moves normally | Works from the battery | Panel recharges the battery |
If you are often away, the simplest precaution is to close the rooflight before you leave. Rain sensors are a convenience for when you are at home or out for the afternoon, and they are not a substitute for shutting up the house. Our guide to rooflight motors, rain sensors and controls describes how the parts relate.
What happens when the power comes back
What a control unit does when the supply returns varies by make. Some wait for a command, and some run a short calibration before they accept instructions. Read the sheet for your model. If the window has been left open in the rain, check the area beneath it, because wet timber and plaster is what the sash is there to protect.
Power cut or something else?
A rooflight that has stopped responding is not always a power cut. Check whether other devices on the same circuit are working. Then look at the wall switch or remote, which may need new batteries. A tripped breaker, a fuse in the control unit or a loose connection will give the same symptom. Use the circuit or the unit as a pointer to the cause, and do not lift covers off a control unit yourself. A qualified electrician handles anything involving mains. Our page on whether an electric rooflight needs an electrician explains who does what.
Planning for it at survey
We look at four things when the rooflight is for a room you want to keep ventilated.
- Where the supply cable will run, and whether the circuit can carry it.
- Whether a back-up battery option exists for the model.
- Whether the position on the roof lets a solar panel charge in winter.
- How you would close it by hand if you had to.
Those answers belong in the life plan, which lists the actuator, the control unit and the sensor as the parts most likely to need replacement, and says how each is swapped. Reaching a motor or a pane is mostly done from inside, so the roof covering usually stays put and the job stays short.
If you are choosing now
Ask for the manual fallback and the back-up options in writing before you decide, whichever model you favour. Our free survey covers them, and the fixed quote sets them out with the life plan, under our 10-year guarantee. The electric opening rooflights page shows the full range, and if you already have a manual roof window, read about making a manual roof window electric.