So, you've got your fancy new washing machine set up in your laundry and you've noticed an extra door, drawer or compartment that was absent on the old clunker it replaced – chances are that's the automatic detergent dosing system, a feature that increasing numbers of manufacturers are offering on their high-end appliances.

But what exactly is an automatic detergent dosing system, and more importantly, will it improve your washing experience?

On this page:

• How does auto dosing work?
• Miele Ultra detergent vs third-party detergent
• Miele's TwinDos automatic dispensing system
• Should you get an auto-dosing washing machine?

How does auto dosing work?

An auto-dosing washing machine contains an internal detergent reservoir filled with liquid detergent.

The machine automatically draws a precise measure of detergent for each wash cycle (either a pre-set amount or an amount calculated by the machine), which in theory means better wash performance, and in practice means you can generally go for about a month or so between topping up your detergent.

Generally, the reservoir is a recyclable detergent cartridge, but may also be an onboard tank.

Can you choose your own detergent?

Manufacturers sell preloaded cartridges which you can slot straight into your machine, with detergent they claim has been specifically designed for your washing machine for superior washing performance.

As you can imagine, these detergents can be fairly expensive compared to some of the cheaper brands you can get from the supermarket (though recent rises in grocery costs have very much evened the score, especially for the more premium brands). You may also just have a favourite brand of detergent you'd prefer to use. In which case, there's usually an option to fill the reservoir with the third-party (liquid) detergent of your choice.

You can also dose your detergent manually, just as you would with a conventional washer, but if you're going to do that then perhaps it's not worth paying a premium for an auto-dosing machine in the first place.

Miele Ultra detergent vs third-party detergent

We wanted to see how an automatic dosing detergent stacks up against a leading commercial detergent, in terms of cleaning performance and cost per wash.

Our theory was that cost per wash would be higher with the proprietary detergent, but that would be offset by better performance.

So we conducted a basic comparison in our lab.

There are a number of different auto-dosing systems on the market, and each will have different performance results and cost, but for our test we compared Miele Ultra with one of Australia's leading premium detergents using the same TwinDos-equipped Miele front loader.

Miele's TwinDos automatic dispensing system

One of the first movers in the automatic dosing space, Miele's TwinDos automatic dispensing system is unique in that it has not one but two cartridges, each with a different liquid inside. The first is an enzyme-based detergent, the second is an oxygenated bleach.

There are two advantages to this two-cartridge system:

1. Keeping components separate can help them last longer (the same reason there are different layers in your dishwasher tablets – it's to keep bleach and enzymes separate).
2. It gives you more control over your laundry. If you're dealing with particularly nasty stains or doing a load of business shirts you can dial up the bleach to get your whites their whitest again, or dial it down if you don't need it.

We compared an automatic dosing detergent with a leading commercial detergent.

Here's what we found 

1. Manufacturers recommend using more detergent than you probably need

The recommended dose for both detergents is much higher than we expected.

To give both of them the best possible chance we opted to use the manufacturer's recommended dose for a full-capacity laundry load, which was actually very similar for both: 80 grams of third-party detergent powder vs 82ml of Miele Ultra (46ml of phase one and 36ml of phase two).

That's a lot of detergent, and from years of testing in the laundry we've found you can get a great wash from as little as a third of that amount.

The first time you use TwinDos you have to navigate through a complex series of menus to select the settings you want

Interestingly, a drawback of the auto-dosing system is that the first time you use TwinDos you have to navigate through a complex series of menus to select the settings you want. But the good news is for most users this only needs to be done once, at initial setup (or not at all if you're happy with the defaults).

The machine then varies the dosage automatically, depending on the size of the load, the program selected and the user selected soiling level.

The only other time the dosage settings would need altering is when switching to a different type of detergent.

2. Premium third-party detergent is slightly more expensive than Miele detergent

Of course, you can (and dare we say should) use significantly less of either detergent if you want to, but assuming you follow the directions to the letter, what's the comparative cost per wash?

• Third-party detergent: 96 cents per wash
• Miele Ultra: 90 cents per wash

Detergents regularly go on sale in the supermarket. We picked ours up when it was on sale, which makes it significantly cheaper, though still slightly more expensive than Miele Ultra. That said, we used a relatively expensive detergent for our test – there are much cheaper ones available, and many of them work just as well as the expensive premium brands.

As for the auto-dosing detergent, other auto-dose washing machine manufacturers also sell their own proprietary detergents, at a variety of price points, so depending on the system you choose your cost per wash will be different.

You can assume Miele Ultra, as a two-part system from such a high-end brand, will be among the more expensive options, but realistically you're not using an auto-dosing system to cut costs.

3. A proprietary auto-dosing detergent doesn't mean cleaner clothes

We expected that proprietary auto-dosing detergents would cost more than the many detergents you'd buy at the supermarket but that's ok, because it's going to get your clothes cleaner, right? Wrong – we found performance was actually very close. In fact, the third-party powder ever so slightly outperformed the Miele product.

We've only looked at one system in a very simple test however, so it's possible other systems will perform differently.

Should you get an auto-dosing washing machine?

Using an auto-dose washing machine's not going to save any money, nor will the extra expense get your clothes any cleaner. (While we can't say for certain how systems from other manufacturers stack up, we're pretty sure they'll perform very similarly.)

But because automatic dosing systems can often be used with your own third-party liquid detergent, you can get the best of both worlds – the option of using your favourite detergent, with the convenience of letting the appliance dose it for you.

Auto-dosing washing machines have great potential to help the elderly or people with disabilities

For most of us this brings a new level of convenience to our laundry, but it also has great potential to help the elderly or people with disabilities who may have trouble getting detergent into the washing machine.

Parkinson's disease, arthritis and even cataracts are just a few of the afflictions that can make it really hard to manipulate that little scoop of detergent.

If you've got a system where you can take the reservoir over to the sink where spills aren't an issue and refill it once a month, or have a friend, relative or caregiver that can top it up for you when they call in, you can remain largely self-sufficient in the laundry despite physical challenges.

Stock images: Getty, unless otherwise stated.

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