An opening skylight you cannot reach by hand needs something to push it open. That something is either a small motor fed from the house wiring or a motor fed from a battery that a solar cell keeps topped up. Both do the same job from the wall switch or the remote. What differs is where the power comes from, what has to be built into the house to carry it, and what you will look after in the years that follow. This guide walks through the choice as we put it to a Sheffield household at survey.
What the two systems have in common
Strip away the marketing and an electric rooflight and a solar rooflight are the same machine. A small motor drives a chain or a spindle that swings the sash open. A control unit tells the motor when to start and stop. A rain sensor, usually a small pad on the glass or frame, tells the control unit to close the window when water lands on it. A switch or handheld remote gives you a say.
Both can be set to open a crack for background ventilation or a long way for a hot afternoon. Both fit the kitchen, the bathroom, a landing with a high ceiling or a loft room where the window is out of reach. And both, on a flat roof, usually mean an opening rooflight set on a kerb rather than a window in a slope. The sections below are about the one thing that really separates them: the power supply.
If you want the working parts in more detail, our guide to rooflight motors, rain sensors and controls covers them one by one. This page stays with the decision.
How a mains-powered rooflight is fed
A mains rooflight takes its power from a cable. That cable runs from a supply point in the house, usually through the ceiling void or down a wall, to the control unit at the window. From there a low-voltage lead goes to the motor, and a second lead to the rain sensor.
Mains supply gives a steady, predictable source. The motor does not care whether the day is grey or bright, and the window will open on a January morning exactly as well as on a July afternoon. For a room that needs regular ventilation, such as a shower room or a kitchen over a hob, that reliability is the main reason to choose it.
The cost of this is the cable. Where the ceiling is already open, because a loft is being converted or a kitchen is being rebuilt, the run is easy. In a finished room, someone has to route a cable across the ceiling void and make good the plaster. We look at that route at survey and describe it in the quote, so that getting the wire to the window is not a surprise.
How a solar rooflight is fed
A solar rooflight carries its own supply. A small photovoltaic cell is built into the window, or sits in the frame, and charges a rechargeable battery. The motor draws from that battery when the window is told to open or close. Nothing runs back to the house, so no cable crosses the ceiling and no electrical work is needed in the room below.
That makes solar the neat answer wherever running a cable would mean breaking open a decorated ceiling: a finished bathroom, a staircase with a tall plastered void, a landing in a conservation-area house where we would rather disturb as little as possible. It is also the answer where the window sits on a part of the roof far from any existing supply.
The cell does not need sun shining on it. It charges from daylight, so a cloudy day still tops the battery up, only more slowly. The window only draws power for a few seconds each time it moves, which is why a modest cell can keep up in ordinary use.
Where Sheffield roofs complicate the solar choice
A solar rooflight needs light on its cell for a good part of most days. Sheffield's hills make that less automatic than it sounds. Many terraces step down a slope, with a tall neighbouring gable or a tree line to the south. A rooflight in the back slope of such a house may sit in shade for much of the year, even though it faces a perfectly good direction on paper.
North-facing slopes are the obvious worry. They get plenty of diffuse light but little direct sun. The cell charges more slowly there, though it does charge. What matters more is how often the window moves. A loft room window that opens twice a day and closes twice a day asks little of the battery. A bathroom window that cycles many times an hour in a steamy household, and is also set to react to every spot of rain, asks more.
So at survey we do not take the compass bearing and stop. We stand on the roof or in the loft and look at what falls across the glass and when. If the answer is unclear, or the room needs heavy daily use, we put forward mains power and say why.
Comparing the two side by side
| Question | Mains | Solar |
|---|---|---|
| What does the house need? | A cable route to the window and a qualified electrician to connect it | Nothing run through the house |
| What does the roof need? | Nothing special | Reasonable daylight on the cell most days |
| Best suited to | Rooms that vent often, such as kitchens and shower rooms | Finished rooms and tall voids where a cable would mean opening the ceiling |
| The parts you will look after | Motor, control unit and rain sensor | All of those, plus the battery and the cell |
| Behaviour in a power cut | Depends on the control unit; the window may not move until power returns | Unaffected, since it does not use the house supply |
The last row deserves its own page, and it has one: what happens to an electric rooflight in a power cut.
The wiring question
New fixed wiring in a home is electrical work, and it is covered by Part P of the Building Regulations. A mains rooflight therefore needs an electrician to make the connection, and we use a registered electrician who can certify the work. A solar rooflight does not need new house wiring, so that step disappears.
We tell you at survey which route your quote takes and who does it. Where an electrician is needed, the quote says so and the connection is planned alongside the roof work, so cables are in place before the ceiling is boarded. The rules on who may connect it are set out in does an electric rooflight need an electrician.
The glazing side is regulated separately. Putting a new opening into a roof is notifiable, and we make that notification for you. Who inspects depends on your address and on the route chosen, and it does not change what you have to do.
What wears, and what that means for each choice
For an opening rooflight, the life plan in our written quote spends most of its words on the motor. The glass and frame outlast the moving parts. What ages first is the electric side of the window: the motor and its chain, the control unit, the rain sensor and, on a solar window, the rechargeable battery.
On a mains window that list is short, and the supply never wears out, because it is the house. On a solar window the battery is one more part with a life of its own. A rechargeable battery loses capacity with age and use. The cell itself has no moving parts and changes more slowly.
What matters is how each part is replaced. We specify windows whose motor and battery can be swapped from inside the room, through the opening, without lifting the roof covering or disturbing the flashing. The life plan names each part, says how it comes out, and says whether the roof is touched. At year 5 we suggest a check of the seals, the sensor and the operation, and we mark the same for year 10.
How we help you choose
At the free survey we look at four things, and the answer usually falls out of them.
The room. A kitchen or shower room that needs regular venting leans towards mains. A bedroom or landing that only opens now and then suits either.
The ceiling. If it is already open or about to be, a mains cable costs little extra. If it is a finished, decorated ceiling, solar saves the damage.
The light. We check what shades the glass through the day, not just which way the slope faces.
The roof type. Pitched slate or tile roofs, and flat roofs with a kerb, both take either system. On a flat roof the kerb gives space for cabling, which makes mains easier to route there than on a steep slope.
The same window can often be offered both ways, so you can compare the two quotes side by side. If you already have a manual window and wonder whether it could be converted, see can a manual roof window be made electric. The hub page on electric opening rooflights covers the full range, and we cover Sheffield and the towns within 30 road miles in South Yorkshire and north Derbyshire.
What changes the price of each option
We do not quote figures in an article, because the number depends on your roof. What we can do is list what moves it. Window type and how large an opening it fills come first. Then the roof: a pitched slope with tiles or slate needs flashings cut to suit, and a flat roof needs a kerb and a sealed joint to the covering.
The power choice adds its own items. A mains window adds the cable run, the electrician's visit and any making good to the ceiling. A solar window adds the cell and battery within the product, but takes away the cable and the plastering. Blinds and insect screens, if you want them on an opening window, add to either. Setting these side by side in one written quote is the quickest way to see which option suits your budget.
Blinds, screens and the finish inside
An opening skylight with a blind is a different animal from one without. A blind fitted to the sash should work with the motor, so that neither fouls the other, and some blinds are motorised too. On a solar window the blind motor may have a battery of its own. We settle this at survey, with the ceiling finish and the room's use in mind.
An insect screen is worth asking about for a kitchen or bedroom window that will stand open on summer evenings. It sits in the reveal, and the window still closes onto the seal. The lining round the opening should be neat and light in colour, because it bounces daylight into the room, and the reveal is finished in the same visit as the window.
Choosing between mains and solar
Does a solar skylight work on a cloudy day?
Yes. The cell charges from daylight rather than direct sun, so it keeps working under cloud, only more slowly. The window draws very little power for each movement.
Can I change from solar to mains later?
It can be done if a cable can be routed to the window. We would normally decide this before the roof work, so the route is planned and the ceiling is not opened twice.
Which is better for a bathroom?
If the bathroom is finished and decorated, solar avoids opening the ceiling. If the room gets a lot of steam and the window is set to react to rain as well, mains gives the motor a steadier supply. We look at the light and the use before we recommend one.
Does either option affect the guarantee?
We give a 10-year guarantee on the fitting itself, and it applies to either power source. The parts carry the maker's own terms.
Will I need to replace the battery on a solar rooflight?
A rechargeable battery loses capacity as it ages. We specify windows where it can be changed from inside the room, and the life plan says how.