The Insider: Hairdryers - all you need to know to blow away bad-hair days

There's much more to buying a hairdryer than you might first think. These days, the best appliances offer much more than a stream of hot air. Some include an "ionic function", which uses negative ions to protect your hair and retain its frizz – while others come with "cool shot" functions, diffusers or built-in straighteners. In short, before you head for the high street, it's well worth doing your research.

"Whatever your hair type, a good hairdryer should be light enough to hold comfortably, and have a range of heat and speed settings that are easy to use, so that you can style your hair with the speed, heat and force that gives the best results for your style," says Victoria Pearson, of the consumer magazine Which?.

"Using just the highest heat and speed settings might make the job quicker, but it can cause damage to your hair. Choose a hairdryer with an ionic function to get softer, shinier hair, or switch to the lower speed and heat settings after an initial blast."

Hairdryers vary in price, from as little as £3.89 at Argos, through to as much as £50 for the top of the range models. But, as ever, the most expensive appliances are not necessarily the best.

When Which? recently tested 13 hairdryers, it picked out the Toni & Guy 2000W Wave Sock Pro Tourmaline TG180D (pictured) as the best on the market, giving it a rating of 71 per cent. It costs just £25. In its review, Which? said that the Toni & Guy dryer was head and shoulders above its competition, claiming that it dries hair quickly at both high and low settings. It has an ionic function, as well as a diffuser sock. It also looks stylish, and weighs a modest 420g.

The most expensive model that Which? tested – the Imetec Nutriheat, which costs £40 – was way down the list, scoring just 58 out of 100. While at the bottom of the heap was the Revlon CordMagic Folding 2000W (pictured), which scored just 49 per cent, and was marked down for its lack of versatility, as well as its loud noise and high energy use.

All of the models that Which? tested came with a "cool shot" function – although some of these were much more effective than others. The Toni & Guy appliance applies a cool shot at 35C, for example, while the Nicky Clarke Nano Detox delivers a shot at just 26C.

Where to buy

If you know which model you're after, the internet is always the best place to find the cheapest deals.

Websites such as froogle.co.uk, which compare.co.uk and pricerunner.co.uk can help you to find the retailers currently offering the best bargains. But don't forget to check for postage charges before you order. If you prefer to do some browsing, sites such as argos.co.uk and amazon.co.uk have a wide selection of hairdryers to choose from.

On the high street, shops such as John Lewis, Boots and Superdrug are all worth a look – as well as larger branches of Tesco and Sainsbury.

Five questions to ask...

How much does it weigh?

Weights of hair-drying appliances can vary dramatically – and a heavier dryer can be harder to control.

Is it ionic?

Some machines use negatively charged ions to help protect your hair, reduce frizz, improve shine and reduce static.

How long's the power cord?

Power leads can vary from less than two metres to over three. If your plug points are nowhere near your mirror, you might need to get an appliance with a longer cord.

How cool is the cool shot?

Most hairdryers have a cool-shot function, but temperatures can vary by as much as 10 degrees centigrade. The cooler the shot, the more effective it is at setting your hair.

What accessories does it come with?

Some dryers come with Afro-combs, diffuser socks, or straighteners. Make sure that you check what extras you're getting with the model you choose.

The Insider is written in conjunction with the consumer group Which?. For more information, visit www.which.co.uk/reviews/hairdryers. To get three issues of 'Which?' magazine for £3, call 01992 822800 and quote INADVICE