Mark Harris

They cost more at first, but most will save you money in the end

If you're fed up of changing lightbulbs all the time, compact fluorescent lamps (CFLs) promise an unbeatable combination - very low running costs and a lifetime eight (or even ten) times as long as normal lightbulbs. There are some drawbacks, however, that might put you off. For a start, CFLs can cost over thirty times as much as a standard bulb to buy, even though you'll get the money back - and savings beside - eventually.

Light weights
CFLs come in a wide range of shapes and sizes (see picture, right) but they are all heavier and larger than conventional bulbs. The lightest models are twice as heavy, and the heaviest ones can be more than ten times the weight of standard bulbs. This might mean they're too heavy for some flexible desk lamps, for example, or too long or bulky for special fittings like spotlights.

Power mad
Like fluorescent strip lights, CFLs produce light by passing an electric current through gas in a tube, making the tube's coating glow brightly. They are much more efficient than normal bulbs, which turn most of the electricity into heat. In fact, a CFL can run around five times as long as a normal bulb on one unit of electricity (see Savings, below).

Location limitations
To get the largest savings from your CFLs, it makes sense to use them where they're likely to be on for fairly long periods - a living room or hallway for example. They're not suited to situations where they'll be turned off and on frequently, like automatic outside security lights. This is because they take a few minutes to reach their full brightness, and some flicker briefly when switched on. When considering CFLs, bear in mind also that they cannot be used with dimmer switches or electronic switches (like many security timers).

Light show
Always try to see a CFL in action before you buy - the light they produce is often a slightly different shade than you might be used to.For this reason, avoid mixing CFLs and normal bulbs in the same room.Think about the fitting or shade it will be used in as well - the bulky adaptor at the base of the CFL can sometimes obscure light. No CFL will produce perfectly spherical illumination like normal bulbs. This means the brightest part of the light may be masked, by part of a shade for example. Brighter CFLs tend to be bigger than dimmer ones.

Nice but dim
There are other reasons why you might end up with less light with a CFL. On the packaging, manufacturers say which CFL you need to give the nearest equivalent light output of normal bulbs (25W, 60W and so on). We've grouped the bulbs by these recommendations. Even at the start of it's life, though, some CFLs do not produce as much light as the bulb they are meant to replace. And as they get older, the light output of all CFLs will decrease - sometimes by as much as a half. Add to this the fact that CFLs will produce less light still in cold conditions and there's a chance you may be disappointed with them.

Getting the light right
If you want to be sure of getting enough light, you may want to buy a CFL which the manufacturer says is equivalent to a higher wattage bulb; a 75W-equivalent CFL to replace a 60W bulb for example. This will decrease the energy saving, but the CFL will still save you money in the long run.

No lifetime guarantee
Although nearly all manufacturers claim a lifetime eight or ten times that of normal bulbs, a few CFLs in our test failed long before that. The more often you have to replace a CFL, the less money you will save; you may want to choose a lamp that shone through our longevity tests.
All the CFLs on test will save you money eventually. The older, cheaper models, like the Philips Comfort or Prismatic range, will save you money most quickly. Newer models, like the Osram Dulux or Philips EnergySaver lamps, will cost more but are generally smaller and lighter. CFLs are not always a suitable replacement for normal lightbulbs, so try one or two around the house before deciding which ones to replace.

The amount of money you can save with CFLs depends on the design you choose, how long it lasts but most importantly on how bright a light you want. You'll save the most by using CFLs to replace bright, higher wattage bulbs. If you don't want a CFL, buying normal bulbs in 2 or 4 packs will save you money. However, because most of your money goes on running the lightbulbs (not buying new ones), replacing 100W lightbulbs with dimmer, 60W bulbs will save you more.

The tests, carried out in conjunction with the Dutch consumer organisation, include a lifetime test where we use the bulbs just as they would be in real life. The table below is based on the 5,000 hour results, but the CFLs will face another 5,000 hours of use before our tests are complete. We tested one of each "family" of CFLs completely, and used those results to give information for the other bulbs in the table. Every bulb was tested for efficiency.

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