Energy saving light bulb reviews: Features explained
Switching to energy saving light bulbs will save you energy and money
Types of energy-saving light bulb
There are three types of energy-saving light bulb:
Compact Fluorescent Lamps (CFLs)
These are the most common type of energy-saving light bulbs and are smaller versions of the familiar fluorescent lamps used in offices or car parks. They use 60%-80% less energy than incandescent bulbs, the most widely available and cheapest energy saving light bulbs. Common problems with buying this kind of bulb are that few can be used with dimmer switches and they can be slow to emit a good level of brightness.
Halogens
These are similar to old-fashioned incandescents in having a tungsten filament - but these have halogen gas surrounding the filament, extending the bulb's lifetime. They use 20-30% less energy than incandescents, but get hot in use.
Light-emitting diodes (LEDs)
These are by far the most expensive but also most efficient types. They can last for 25 to 30 years and use 90% less energy than incandescents.
Bayonet fittings, also known as B22 fittings, twist and click into place
Fittings
Energy saving light bulbs come in both screw and bayonet fittings, although not all bulbs will come in both styles.
Bayonet and screw fittings
Before heading off to the shops, look at the old bulb to see what type of fitting – or ‘cap’ - you need. The more commonly seen fittings may be coded on the packaging as follows:
• B22 or BC: Standard sized bayonet cap
• B15 or SBC: Small bayonet cap
• E27 or ES: Standard sized Edison screw fitting
• E14 or SES: Small Edison screw fitting
• GU10: A ‘two pin’ fitting, usually for spot lights.
• GLS: not a fitting, but an acronym. It stands for General Lighting Service and was applied to incandescent lamps that produced light all round – not directionally like a spot light. Some energy savers seem to use it now as a way of suggesting that the lamp has the same ‘bulb’ shape as the incandescent bulbs we’re all familiar with.
Small bayonet cap (B15) bulbs can be hard to find in shops. You may need to shop online for these, but be aware that many online suppliers will charge you for postage and packaging – ordering one bulb at a time may prove expensive.
Energy-saving light bulb shapes
In the past, energy-saving light bulbs were available only in large stick or, occasionally, globe shapes.
Manufacturers have now started producing bulbs that have a more traditional appearance. You can now buy candle, smaller globe-shaped, spiral, stick bulbs.
Power
Energy-saving light bulbs use less energy than typical incandescent bulbs because they are more efficient. This means they require less electricity to produce the same light as more traditional bulbs.
Size
The length and diameter of the bulb in millimetres are likely to be listed on the packaging. If your lamp has shades, you'll want to make sure the new bulb doesn't stick out and ruin the look. Measure the available space so you don't end up buying a bulb that’s too big.
Light output
Light output is measured in lumens (lm). The lumen value stated on the packaging is a useful guide as to how bright the light will be. As a general rule, the greater the wattage the greater the lumen output and the brighter the light, but only when comparing similar types of light bulb.
We've tested many lamps, including incandescent bulbs. The table below shows the maximum light output measured in our light bulb test for different wattages of different bulbs.
| Wattage and maximum lumen output comparison | ||||
|---|---|---|---|---|
| Maximum light output measured in our tests | Incandescent bulb wattage | CFL wattage | Halogen energy saver wattage | LED wattage |
| 200-300lm | 40W | 7, 8 and 9W | n/a | 5 & 6W |
| 300-400lm | 40W | 7, 8 and 9W | 28W | n/a |
| 400-500lm | 40W | 8, 9 and 11W | n/a | n/a |
| 500-600lm | 60W | 8 & 11W | 42W | n/a |
| 600-700lm | 60W | 11W | 42W | n/a |
| 700-800lm | n/a | 11 & 15W | 52 & 53W | n/a |
| 800-900lm | n/a | 15W | 53W | n/a |
| 900-1000lm | 100W | 15W | n/a | n/a |
| 1000-1100lm | 100W | 15 & 20W | n/a | n/a |
| 1100-1200lm | 100W | 20W | n/a | n/a |
| 1200-1300lm | 100W | 20W | n/a | n/a |
As you can see from our table some 8W CFLs produced no more than 300 lumens, whereas other 8W CFLs achieved an output of 500 to 600 lumens. This is a big difference in 'brightness'.
Not all bulbs of the same wattage will claim the same lumen output on their boxes. In addition to this, some bulbs don't produce as much light as they claim.
That is why it's important to look at the lumen output stated on the packaging when shopping for light bulbs and check the light output test results of our independent light bulb tests.
Start-up time
A lamp start up figure is likely to be telling you how long the lamp takes to reach 60% of its full output. If it’s within one second, it can be labelled as ‘instant full light’.
We measure light output after three, 10, 30 and 60 seconds to generate our start-up time star ratings. A quick start-up is important in bathrooms or spaces you only put the light on in as you pass through, such as landings, stairs or cupboards.
Lamp colour temperature
Colour temperature is displayed in Kelvin (K) and can give you a rough idea of the ‘colour’ of the light. An old-fashioned incandescent bulb measures 2700K. Values close to this or lower are likely to feel warmer. Some bulbs with colour temperatures of 2700K may say ‘warm white’ on the box.
Higher values of around 3500K and above are likely to feel colder. Daylight bulbs measure around 6500K and the light has a ‘blue’ appearance.
Lamp lifetime
Usually expressed in hours. A traditional incandescent bulb is expected to last 1,000 hours – generalised as one year. Most CFLs claim lifetimes upwards of 6,000 hours.
We test CFLs for 5,000 hours in our lifetime test. Halogens are tested up to 2,000 hours – their maximum claimed lifetime.
Switching on and off
The number of times a lamp can be turned on and off. Bulbs that can handle lots of switching may be handy for the bathroom. In our Which? light bulbs test we switch lamps on and off 30,000 times.
Bulbs suitable for use with dimmers
There are a number of different types of dimmer switches. A lamp’s suitability for use with dimmers, or with some types of dimmer, should be mentioned on the box.
Claimed lifetime
Manufacturers give lifetime claims in multiples of 1,000 hours. One thousand hours is equivalent to about a year’s use when the bulb is on for three hours each day.
- Read our energy saving light bulb Q&As
- Find out how to cut your electricity bill
- Need new bulbs? Try our energy saving light bulb review
