The Insider: Why low-energy lamps are such a bright idea

With energy bills having rocketed in recent years, more households are using energy-saving light bulbs as a way to cut their electricity costs. As energy-saving bulbs have grown in popularity, so too has the range of bulbs on offer – making it that much harder to know which ones to go for when you're out in the shops.

"The sale of traditional incandescent light bulbs is being phased out as part of the Government's plans to reduce CO2 emissions, so we'll all have to switch to energy-saving versions in the next few years," says Martyn Hocking, the editor of the consumer magazine Which?. "The good news is that, as well as being better for the environment, energy-saving bulbs are better for your wallet. Although they may be more expensive to buy than traditional bulbs, they work out cheaper in the long run because they use less electricity and don't have to be replaced as often."

Although most people associate energy-saving bulbs with a poorer quality of light and slow start-up, standards in these areas have improved enormously over the past few years. Nevertheless, quality still varies from bulb to bulb, as do prices. While it's now possible to pick up energy-saving bulbs for as little as 50p, you can spend up to £9 on a single bulb. But, as ever, the best bulbs are not always the ones that cost the most.

When the consumer group Which? recently tested 16 different bulbs, it was Ikea's Sparsam stick (pictured), priced at £3.25 a bulb, which ranked top – scoring 75 out of 100. It was way ahead of the rest of the field, and was one of few bulbs to perform well in cold as well as in warmer temperatures. It lasts for an impressive 10,000 hours – but there is a slightly green hue to the light it emits.

Two of the 16 bulbs Which? tested cost a rather steep £9 – including the bottom-ranked Omicron Dimmable Multi-tube (pictured). Although this bulb starts up relatively quickly and, as the name suggests, is usable with a dimmer, it has a lifespan of just 8,000 hours and performed very poorly in colder temperatures. Overall, it scored only 59 per cent in the Which? tests.

Where to buy

Ikea's bulbs are available only from its stores or by ordering online at its website, ikea.co.uk. Similarly, B&Q's bulbs are available only in its shops or at diy.com. If you're willing to consider other brands, there are many online retailers – such as energybulbs.co.uk – stocking a wide range of energy-efficient products. You'll also find a limited selection at your local supermarket or hardware store.

The Insider is written in conjunction with the consumer group Which?. For advice on saving money on your energy bills, visit www.whichswitch.co.uk.

To get three issues of 'Which?' magazine for £3, call 01992 822 800 and quote INADVICE

Five questions to ask...

*How quickly does it start up? Some bulbs can take several minutes to reach their full light output, while others are up to speed in seconds.

*What's the bulb's lifetime? The best energy-efficient light bulbs can operate for 10,000 hours, while the worst manage only about 6,000 hours.

*Screw or bayonet? Make sure you know whether your lamp or light socket needs a bulb with a bayonet or a screw fitting.

*What shape is the bulb? If the bulb is going to be visible, you might prefer one that is shaped like a globe. Most energy-saving bulbs are stick-shaped.

*How much light does it emit? Some bulbs do not emit as much light as they claim to.