Do Electric Rooflights Work in a Power Cut?

Not all electric rooflights rely on the same thing, so the answer changes with the type fitted.

A mains unit with nothing behind it is the simplest and the cheapest, and it simply stops. Whatever position it was in stays put until the supply returns. That is usually fine, but it matters if the window was open when a storm arrived.

Some electric roof windows come with a small battery pack, or have one as an option. It keeps the motor and its controls alive for a while after the mains drops. The point is usually to let the sash close, which is the move that matters when weather is coming in.

Solar versions work in a similar way, only the battery is charged from a panel on the unit and not from the house. They carry on through a power cut because the house supply is not involved. A run of dull days will leave the battery low, so the better units shut themselves before it runs flat. For more on how they compare, see electric vs solar rooflight.

We do not quote battery life in hours, because it differs by make and model. Ask for the maker's information on the model you are looking at, and have the answer written into the quote so it is on paper before work begins.

Most outages are brief, a flicker or a few minutes, and a sash that stays where it was left does no harm. Planning matters more for a long outage on a wet night, when a window open to the weather is a nuisance, or when a window is stuck shut on a hot evening.

• Stuck shut: the room simply loses its extra ventilation until the power is back. Other windows in the house still work.
• Stuck open: this is the one to plan for. A narrow opening is far easier to live with than a wide one, so some people keep the sash at the vent position when they go out.
• Half-way: a motor that stops mid-travel leaves the sash where it is. A manual release lets you finish the move.

Our answer on whether you can leave a rooflight open overnight goes further into the vent position, which is the safest place to leave a sash if the supply might fail.

Many electric roof windows can also be shut with a pole or a release, even when the motor will not move. Whether yours can is a question for the quote, not an assumption. A window out of reach, above a stair or a bath, is the one where it is worth asking.

Rain sensors rely on the same supply as the motor. If the power is off, so is the sensor, which means it cannot close the window for you. Our page on the rooflight rain sensor covers this.

A neat installation allows for the awkward day. The control sits where you can reach it, the manual release is easy to find, and the wiring is labelled at the consumer unit so an electrician knows what each circuit does.

We also tell you what the unit does when the power returns. Some motors stay put, others run a short reset, and a few close fully. None of this is hard to live with, but it is better to know before the first outage than during it.

Planning for it at the quote

The easy way to avoid surprises is to decide what you want to happen before the unit is chosen. If the rooflight sits over a bedroom or a bathroom, you may want it to close without mains. If it sits over a stairwell you rarely use, a mains-only motor may be enough.

• Say whether the room is ever left with the window open when you go out.
• Ask for the back-up option to be shown on the itemised quote.
• Check that a manual way of closing the sash is possible and who can reach it.

The cost differences are set out in electric rooflight cost. Our electric opening rooflights hub lists the units we fit, and opening options appear on every quote we write after a free survey.