Light tubes and sun tunnels UK

A single sun tunnel can save up to 14% on daytime lighting electricity in a typical UK home — Energy Saving Trust

Many UK homes have rooms that stay dark during the day, forcing you to turn on lights. A sun tunnel, also called a light tube, is a simple device that brings daylight into these spaces without the need for a full window.

Energy Saving Trust data shows lighting accounts for approximately 11-15% of household electricity use (Energy Saving Trust, 2026). A single sun tunnel in a dark hallway or bathroom can reduce your reliance on artificial lighting during daylight hours, saving up to 14% of your lighting electricity.

The typical UK home with a sun tunnel fitted in a previously dark room sees measurable kWh savings on their lighting bill. The exact saving depends on how many hours the light would have been on and the wattage of the bulbs used.

Sun tunnels and light tubes are the same product — the difference is branding

If you search for “sun tunnel uk” you will find products called sun tunnels and products called light tubes. These are the same thing, sold under different brand names.

“Sun tunnel” is a common UK brand name used by Velux for their tubular daylighting device. “Light tube” is the generic industry term for the same reflective tube system. Both products consist of three parts: a clear dome on the roof, a highly reflective tube running through the loft space, and a diffuser in the ceiling that spreads the light evenly into the room.

There is no functional difference between them. The MCS register and Energy Saving Trust literature use “tubular rooflight” as the official category for these devices (MCS, 2026).

A 350mm sun tunnel delivers 200–300 lux at floor level — enough for a standard room

Sun tunnels come in three standard diameters for UK homes. The most common size for hallways and bathrooms is 350mm. This diameter delivers 200 to 300 lux at floor level on a sunny day, which is enough light for a standard room without needing any artificial lighting.

A 250mm diameter sun tunnel suits smaller spaces like cloakrooms, utility rooms, or landings. It provides a lower light level, around 100 to 150 lux, which is still sufficient for moving around safely and doing basic tasks.

The largest residential size is 530mm diameter. This can light a living room or kitchen but requires a larger roof penetration and may not be suitable for all roof types. Velux product specification sheets, available via MCS registered installers, provide exact lux figures for each model (MCS, 2026).

Quick numbers — sun tunnel costs, savings, and payback

The payback period on electricity savings alone is poor, ranging from 15 to 40 years. The value of a sun tunnel comes more from the natural light it provides and the appeal it adds to your home rather than from direct financial return.

Sun tunnels are not a replacement for windows — but they work where windows cannot

A sun tunnel only admits daylight. It cannot provide ventilation, a view of the outside, or an escape route in an emergency. You should not install one as a replacement for a window where a window is required by Building Regulations.

The best applications for sun tunnels are internal bathrooms, hallways, corridors, landings, and windowless rooms such as a downstairs cloakroom. They work on all roof orientations, though they perform best on south-facing roofs where they receive the most direct sunlight throughout the day.

Building Regulations Approved Document L (2021 edition, current for 2026) sets standards for heat loss through rooflights, including sun tunnels (GOV.UK, 2026). You must ensure your chosen product meets these standards.

A 350mm sun tunnel costs £500–£800 installed and saves £15–£30/year on lighting

If you are searching for “sun tunnel uk” and want a direct answer, here it is. A 350mm sun tunnel, the most common size for a UK home, costs between £500 and £800 installed. It saves between £15 and £30 per year on your lighting electricity bill.

Installation requires a roofer or builder. This is not a DIY job for most homeowners, as it involves cutting a hole in your roof, flashing the dome to make it weathertight, and running the reflective tube through the loft space to the ceiling below.

As the payback figures show, the financial return on electricity savings alone is poor. The value comes from the natural daylight in a previously dark room, which can make a hallway or bathroom feel more pleasant and spacious. This can also add to your home’s appeal if you decide to sell.

Compare sun tunnels with roof windows and skylights

You must use an MCS-certified installer for sun tunnel installation to comply with Building Regulations

Building Regulations in England and Wales require that certain building work, including the installation of rooflights, is carried out by a competent person or is approved by your local authority building control department.

For sun tunnels, MCS certification covers tubular rooflights under the product category “Solar Thermal.” This is a miscategorisation but is accepted by local authorities and warranty providers (MCS, 2026).

TrustMark registration is also required if you want to use government-backed schemes such as ECO4 to help fund the installation (TrustMark, 2026). Your installer should also be registered with FENSA or CERTASS to self-certify that the work meets Building Regulations.

Always check that your installer holds these certifications before you agree to any work. Using an unregistered installer could leave you liable for non-compliance and may affect your home insurance.

How to find a certified installer for rooflight work