While it would appear at first glance that all laundry detergents promise slight variations on much the same things, our tests have shown vast differences in ability to get your clothes spotlessly clean. Since most people are too busy thinking about more exciting things than laundry detergents (we hope!), we've taken on the task and nutted out what you need to know to get the most mileage and best results from your next wash.

A fraction of the cost

Depending on which laundry detergent you decide on, you may be able to use half (yes, half!) the recommended dose, saving yourself money and giving the environment a bit of a break. In the past we've tested top performers and they were just as good at half the recommended dose, and others we tested performed well at half the dose on particular types of stains. While we can't test every dose variation, experiment with your detergent to see whether you really need a full cap to get a wash you are happy with.

Powder or liquid?

Powders

Still the best for general soil and stain-removal performance. However, the ones we tested were used on soiled swatches that are equivalent to old, in-ground,stubborn stains, so they were vigorously put through their paces. We found that washing performance is better on fresher stains, which are what you mostly find in typical laundry.

Liquids

Have a lower impact on the environment, with most getting good ratings for recycling and greywater reuse. Many eco-friendly liquids will do a good job of freshening up lightly soiled and coloured clothes. However, if you rewash or use a pre-wash or in-wash product for stain removal, you're negating the liquid's low environmental impact. It's best to stick to top-performing powders for heavier soiling and whites, which will also help whites from going grey or yellow over time.

For high-efficiency machines that use very little water, a suitable liquid detergent is the best way to avoid white powdery patches being left on your clothes. In some cases, ½ to ¼ dose of a top-performing powder detergent pre-dissolved in warm water can also do the trick.

Which costs more in the long run?

Cost per wash unit pricing (usually per 100g) is a great way to compare costs, but it's not entirely accurate for laundry detergents because of the vastly different dose recommendations between brands, so use our cost-per-wash figures for a better comparison. And try using a fraction of the dose - it will save you money, and still clean your clothes while helping the environment.

What about us sensitive skin types?

Enzymes

Target protein, starch or biological-based stains such as grass or blood. Different enzymes target different stains. Enzymes are known to cause irritation, so should be avoided by those with sensitive skin.

Optical brighteners

Coat the fabric with fluorescers that absorb ultraviolet light and re-emit it as blue light, making the clothes look whiter and brighter even though they don't actually remove any dirt. Products with brighteners are best avoided by people with sensitive skin.

What about the environment?

The number of washes per pack is an important consideration – the more you can get, the less package waste, so the better for the environment. Buying larger packs, or when on special, will usually be more cost effective, but transfer bulk purchases to an airtight container to maintain performance.

Another consideration is phosphates, which contain phosphorus, which help soften the water and keep extracted dirt in suspension. But high levels of phosphorus can lead to excessive growth of blue green algae in inland waterways. P means low phosphorus (<7.8 g/wash) and NP is for no phosphorus or less than 0.5%.

Is it worth washing in warm or hot water?

When we had results for the highest- and lowest-performing detergents, we retested these in both top and front-loader variants to see whether a warm wash (40 degrees C) would produce a great difference in results. Generally, there's an overall benefit, but only by a couple of per cent. However, one top loader comes out marginally worse when washing with warm water and one comes out much better. Basically, it really depends on which stains you are trying to remove. Some detergents perform better in cold water than warm with some stains. There's more info in our laundry detergents test.

OK, so I've settled on washing in cold water

Washing in cold is an excellent way to save money and power consumption. However, washing in cold means a waxy film can build up inside your machine – more so if you use a fabric softener. To clean your washing machine, regularly run a full-wash program without clothes (or a cleaning cycle if your machine has one) with a good detergent and hot water. Alternatively do a warm or hot wash every few loads. For more information,see our washing machines article.

Can I use top-loader detergent in a front loader or high-efficiency top loader?

It's best not to use top-loader detergent in a front-loading machine.

The reason for this is that front-loading machines use much less water in general, and use much more mechanical action (turning). They have an anti-foam ingredient in their detergent formulations, which means that if you use top-loading detergents in the same amount it's possible for the front loader to build up too many suds in the machine. These suds can mean that foam builds up between the outer drum wall and the inner drum of the washer, and can create a suction issue, causing the motor to burn out. This is called "suds lock".

If you've got heaps of top-loader detergent left over, you can use it in your front loader or high-efficiency top loader to use it up, but use a lot less of it in your front-loader wash (half to quarter dose).

Smelly detergents

There are fragrance free detergents available in the market place, but most tend to have a fragrance of some description, if anything just to let the manufacturer sell more product by putting different fragrances into the same basic formula. Assessing fragrance is very subjective, so take a good whiff before you buy, as some smells can be quite grating for some, but smell like nothing at all to another.