Guide · 6 min read

What does an LED sign cost to run, and how bright should it be?

By the Smart Signs team · Updated October 2026

How much electricity does an LED sign use?

An illuminated sign uses LED modules powered by low-voltage drivers, and its power use is measured in watts. The total depends on the size of the sign, the number of LED modules and how bright it is set, so the only reliable figure is the one for your sign.

Ask for the total wattage of the drivers, or the LED load, on the specification. The figure on the driver label is its maximum rating, which may be higher than the sign actually draws, so the LED load gives a more accurate estimate. If you are replacing an old sign, ask for the old and new figures so you can compare them.

How do you work out the running cost?

Use this simple formula: watts × hours on per year ÷ 1,000 × your price per kWh. Dividing by 1,000 converts watts to kilowatts, and kilowatts multiplied by hours gives kilowatt-hours (kWh), the unit on your electricity bill.

Take your price per kWh from your business electricity bill or contract. Business rates vary widely, so use your own figure rather than an average.

What does a worked example look like?

This example uses made-up numbers only, not a figure for any particular sign or tariff. Imagine a sign drawing 60 watts, on for 6 hours a night every night, with electricity at an example price of 25p per kWh.

• Hours per year: 6 hours × 365 nights = 2,190 hours.
• Energy: 60 W × 2,190 hours ÷ 1,000 = 131.4 kWh a year.
• Cost: 131.4 kWh × 25p = about £32.85 a year in this worked example.
• Halve the hours with a time switch and the cost halves too.

How do time switches and photocells help?

A time switch turns the sign on and off at set times, for example from dusk until an hour after closing. A photocell switches it on when it gets dark and off at dawn, and the two are often combined so the sign comes on at dusk and goes off at a set time.

Both cut running costs and help keep to any consent condition on hours of illumination. They also stop the sign burning all day by mistake. Digital time switches with astronomical settings adjust automatically to sunset through the year.

Can you dim an LED sign?

Yes, if it is built with dimmable drivers or a separate dimming controller. Dimming lowers the power use and the brightness, which is useful if the sign looks too bright once installed, or if neighbours complain.

It is far easier to plan dimming into the sign at design stage than to add it later. If the site is residential, in a conservation area or opposite homes, ask for dimmable drivers from the start.

How bright should a sign be?

Sign brightness is measured as luminance in candelas per square metre (cd/m²). Councils commonly refer to the Institution of Lighting Professionals' guidance PLG05, which sets maximum luminance levels by environmental zone, from dark rural areas to busy town centres.

The busier and brighter the surroundings, the higher the luminance allowed. If your sign needs advertisement consent, the application states the luminance, and the decision may set a maximum as a condition. We design to the level that suits the location and can provide the figures for your application.

How do you avoid glare and complaints?

Most complaints come from signs that are too bright for their surroundings, shine into windows or flash. A few simple choices prevent them:

• Use static illumination only: no flashing or moving light unless it has been consented.
• Match brightness to the location, lower in residential streets than on a retail park.
• Choose halo lighting or a shielded trough light where light spill is a concern.
• Aim spotlights downwards at the sign, not outwards at the street.
• Fit a time switch so the sign goes off after trading hours.
• Keep lit signs well clear of traffic signals and avoid red and green near junctions.