Better Bulbs, Smarter Design Cut Home Lighting Energy Use By 15%, Study Finds

Most people don’t spend much time thinking about the light bulbs in their ceiling. But across millions of homes in the United Kingdom, outdated bulbs and poorly planned lighting layouts are quietly driving up electricity bills while leaving rooms dim and unevenly lit. A new study finds that a combined upgrade, switching to LEDs and planning the layout with free lighting-design software, cut modeled residential lighting energy use by about 15 percent while making rooms roughly 24 percent brighter.

Researchers at the University of East London and FJ&B Engineering Consultants published their findings in the journal Buildings, testing twenty carefully matched lighting setups in modeled one-bedroom flats and comparing traditional hand-calculated designs against layouts optimized with a free simulation program. The software-designed LED versions used less electricity and produced better-measured illuminance in nearly every case.

Energy bills in the UK have surged since the COVID-19 pandemic, and the government is pushing toward aggressive carbon-reduction targets. Lighting eats up a real share of household electricity, and many British homes still rely on aging, inefficient systems. According to the paper, the average Energy Performance Certificate rating of UK housing in 2023/24 sits at just 67 out of 100, with roughly half of all homes rated at a middling energy performance level.

LEDs Plus Free Software Cut Lighting Energy Use in Modeled UK Flats

The research team compared two approaches side by side. The first was the traditional method, relying on hand calculations and rules of thumb that engineers and electricians have used for decades. These older designs typically called for compact fluorescent lamps, or CFLs, the curly spiral-shaped bulbs that became popular in the early 2000s as a step up from old-fashioned incandescents.

The second approach used a professional lighting simulation program called DIALux Evo, which is free to download and widely used by architects and engineers. Researchers modeled the exact same rooms digitally, then used the software to fine-tune the placement and selection of modern LED luminaires, which generally deliver more light per watt than CFLs.

To keep the comparison fair, the team held every other variable constant: room size, wall and ceiling colors, the height of surfaces where people work or read, and the assumption that lights would run for 1,000 hours per year. The main changes were the design approach and the luminaires used.

Home Lighting Energy Savings Reached 30% in Some Rooms

The software-optimized LED designs used an average of 8.68 kilowatt-hours per scene compared to 10.25 kilowatt-hours for the manual CFL designs, a reduction of about 15.3 percent. Eighteen of the twenty scenes showed energy savings, with reductions ranging from 1 percent to 30 percent. The two exceptions were cases where the software had to use slightly more power to meet minimum brightness and light-distribution standards the older designs had been falling short of anyway.

Average brightness across all rooms jumped from about 166 lux to 205 lux, roughly a 24 percent increase. Lux is simply the standard unit for measuring how much light falls on a surface. So the optimized designs were saving energy and making rooms meaningfully brighter at the same time.

Kitchens and Bedrooms Got Brighter Under LED Lighting Design

Each room was also measured against brightness ranges recommended by CIBSE, a professional body that publishes guidance on how well-lit different types of spaces should be.

Under the old manual designs, many rooms fell short of those recommendations. Kitchens were the worst offenders, frequently coming in below the minimum suggested brightness of 200 lux. Software-optimized designs brought many more rooms into compliance. Bathrooms improved too, hitting recommended ranges more consistently.

Living rooms and bedrooms also benefited, though not perfectly across the board. In one living room, brightness actually dropped in the optimized design, from 158 lux to 114 lux. That still landed within the acceptable range of 100 to 300 lux, because the software reduced power there to save energy across the whole flat.

What the Results Mean for Home Energy Upgrades

It’s worth noting what the study can and can’t tell us. The gains measured came from a combined package: switching from CFL to LED luminaires and using simulation software to optimize layouts. Because the study didn’t include a scenario comparing the old manual approach with LEDs, or the software approach with CFLs, it’s impossible to say how much of the improvement comes from smarter placement versus simply using more efficient bulbs. The authors call this the primary limitation and want future research to pull those two factors apart.

Daylight, smart dimming, and health outcomes related to light exposure were outside the scope of the study, though researchers note that broader work connects well-designed lighting to better sleep and overall well-being.

For anyone designing or renovating a home, the combination of modern LED luminaires and freely available simulation tools offers a measurable upgrade in both efficiency and light quality over the old way of doing things. For UK policymakers facing persistent energy costs and approaching carbon deadlines, a reproducible, standards-based framework built on a free software download may be one of the most accessible tools available.

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Disclaimer: This article is based on a simulation study and does not constitute professional energy or home improvement advice. Results were modeled under controlled conditions and may not reflect real-world outcomes in all home types or locations.

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