An expensive vacuum cleaner isn't necessarily the right one for you. So what is? Working that out is just a matter of asking the right questions.

1 What shape?

An upright model

Canister models (which lie parallel to the floor and have a flexible hose connecting the wand to the canister) are much more common here than upright models. Canisters are easier to use on stairs and in awkward places under the furniture. You can also use them for jobs that an upright can't do – like vacuuming the car.

Upright models have a built-in power head, which means they clean carpet well. If your priority is to clean a large area of carpet that's all on the same level, an upright can be a good choice.

2 What’s being vacuumed?

We no longer test for hard-floor performance because experience tells us that all models these days are good at this. But we do test to see whether the cleaning heads scratch the floor: none of the models in our test database have this problem.

Tip: If you’ve got hard floors only, buy on price.

Carpet can be more complex, because of the types of cleaning heads available. But a conventional head is all you’ll need – unless you have a problem with pet hair, or carpet that gets especially dirty. A conventional head’s also lighter and more manoeuvrable around and under furniture than either a turbo or a power head.

Tip: Unless your carpet needs more vigorous cleaning, choose a model that has a really good carpet-cleaning score (8.0 or above in our Test results).

3 Pet hair in carpet?

Our testing over the past year has included pet-hair removal. All the models in our database have a score for this task – and you’ll see that we’ve yet to find a conventional head that does it well.

If pet hair’s a problem you’ll definitely need a turbo head, or even a power head. Both use a rotating brush inside the head to sweep up and shake out dirt and pet hair. Power heads have a small electric motor in the head unit to turn the brush; turbo heads use a turbine in the main airflow.

There's one downside here, though. The rotating brush of these heads get pet hairs wrapped tightly around it, and the hairs will need to be cleared regularly.

Tip: A good turbo head will remove pet hairs well, but it’s unlikely to be any better than a conventional head at getting dirt out of carpet. A good power head will remove pet hairs really well and get dirt out of carpet better than anything else (see “Especially dirty carpet?”, below). Look for scores of 8.0 and above in our Test results.

4 Especially dirty carpet?

A dismantled power head

If your carpet often ends up with embedded dirt, choose a model with a power head. This scrubs the carpet cleaner than a conventional head can. But power heads have their drawbacks. They're bulky and awkward to use – and having a power head's brush scrubbing away is likely to cause more wear on your carpet than a conventional head (which glides over the top).

Tip: A good power head model will give you the best combination of carpet cleaning and pet hair removal.

5 Bag vs bin?

Buying disposable bags for a bag model is an ongoing cost you’ll need to factor into your purchase decision.

Bin models usually have a clip-off section that you remove and then empty into a rubbish bin.

We prefer bags for four reasons:

• 1. Their size varies, but often the bag is larger than a bin. So it needs emptying less often.
• 2. A bag is part of the model’s filter system – so when you change the bag, you’re replacing a big part of the filter system. But to keep a bin model working properly you have to clean the main filter regularly, or replace it.
• 3. Bags usually have sliding shutters to prevent dust from spilling when the bag’s removed. While some bin models also have well designed dust-disposal systems, we think bags expose you to less dust and fewer allergens during the removal/emptying process. (Also see Asthma and allergens.)
• 4. Having a bag helps muffle the noise of the air passing through the cleaner; some bin models have an annoying high-pitched whine.

For these reasons we now only recommend bag models. If you really want  a bagless, check out our "Worth Considering" models.

Tip: Before you buy, always try a vacuum cleaner in the shop.

For more features to consider when you're choosing a vacuum cleaner, see the Checklist.