Energy saving light bulbs: How we test energy saving light bulbs

Line up of low energy lightbulbs

In our tests, low-energy light bulbs are turned on for 5,000 hours

The best and brightest bulbs

To separate the best light bulbs from the worst, we've put three types of energy-saving light bulbs through our rigorous tests: compact fluorescent lamps (CFLs) - these are the commonest type available - LEDs, the newest type available, and halogens. 

Each light bulb goes through exactly the same test procedure under controlled lab conditions so we can recommend those light bulbs that truly shine. Discover the latest Best Buy energy-saving light bulbs here.

Bright sparks

We measure how bright the bulbs are after 100 hours of being on to find out if the level of brightness matches the manufacturers' claims, taking the average from three samples. We also test how much power they are taking to put out that light. That shows us how efficient the bulbs are.

We have also estimated annual energy costs so you can get an idea of how much different bulbs cost to run.

 

Testing energy saving light bulbs

Energy-saving light bulbs are switched on and off to see if they burn out or fade

Slow to start up?

CFLs used to be very slow to get going, emitting very little of their total light when first switched on. For the best CFL bulbs, this is no longer the case. To find out which ones are bright at start up we measure performance at 25°C, 5°C and -10°C to get the full picture.

However, even the best CFLs usually emit less than half their total light at start-up; LEDs, by contrast, instantly emit their full light.

Light bulb durability

There are three aspects to our durability testing:

  • how much light output a bulb loses over time
  • whether the five samples we leave on for 5,000 hours survive
  • whether the three samples we turn on and off 30,000 times survive.

For loss of light output we leave the bulbs on for 5,000 hours - the equivalent of five years' use - and measure the light output after 2,000 and 5,000 hours. 

Light bulbs that don't survive the 30,000 switches are not necessarily poor performers overall - but they are certainly unsuitable for places where you're likely to turn bulbs on and off frequently, such as landings or bathrooms.

Safety

We also test that the bulbs protect you from electrical shock and have adequate electrical insulation.

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