Why induction hob owners shouldn’t bother buying a slow cooker

Slow cookers have soared in popularity since the energy price rises – so much so that they pretty much sold out everywhere this winter.

One reason might be because they're said to use less energy than a lightbulb. But if you’re thinking of buying one to help save energy and you already own an induction hob, our advice is not to bother.

Our recent test comparing the cheapest ways to cook showed that induction hobs use significantly less energy for some cooking tasks. Read on to find out why.

See all our slow cooker reviews and induction hob reviews.

How we compared slow cookers and induction hobs

To find definitive answers, we sent an induction hob and a slow cooker to the Which? test lab and pitted them against each other to cook a vegetable soup and a beef stew.

• We chose the models we used as typical examples of each type of appliance from our lab tests. When it comes to cooking ability, other models might be better or worse than the ones we tested.

• We cooked the same recipes using the same quantities of ingredients in both appliances, so it was a fair competition.

• We recorded how long each appliance took and how much energy it used and then calculated how much it cost. Our expert testers also rated each dish for how well cooked it was.

To make our calculations, we used the current average price of a unit of energy under the government's Energy Price Guarantee – 34p per kWh.

In terms of energy costs, our results should be a useful guide.

Find out more about the government’s energy price guarantee.

Test results: veggie soup

The old adage of 'slow and steady wins the race' certainly didn’t come true when measuring the energy used to make soup. Using the slow cooker cost 31p, more than three times the cost of using the induction hob, at just 9p.

We used a stick blender to purée the soup to a smooth consistency, and included the time and energy used for this stage in our table.

The soup cooked on the induction hob was deemed 'perfect' by our expert testers, thanks to its well-cooked vegetables and smooth consistency after puréeing. The soup from the slow cooker was also well cooked but not as smooth, and was also very thick as too much liquid evaporated during cooking. This could be solved by adding a little water before serving, though.

However, the convenience of slow cooking can’t be denied. If you like the idea of a bowl of steaming hot soup without having to stand watch over a saucepan for hours, slow cookers are your friend. 

Still want the convenience of a slow cooker? See our guide to the best slow cookers for our top choices.

Test results: beef stew

When cooking our beef and vegetable stew, the induction hob once again beat the slow cooker on energy consumption. The stew took just over an hour and a half on the induction hob and cost 23p in energy. The slow cooker took just over four hours and cost nearly twice as much in energy.

The times and energy consumption figures in our table include browning the beef separately on a hob before adding the other ingredients.

It may have been more expensive, but our lab experts agreed that the stew made in the slow cooker was slightly better than the stew made on the induction hob. Although the vegetables were a little overcooked, the meat was tender and the stew had a good consistency. The stew made on the induction hob was too thin and the meat was a little dry.  

Is an induction hob right for you? See our guide to the best induction hobs to learn more.

Why did it cost more to use the slow cooker?

Slow cookers require less power than induction hobs – the slow cooker we used for this test is rated at 320W, whereas the induction hob we used is rated at 7.2kW (or 7,200W). So even though they need less power, they're used for much longer, so end up costing more. 

Our verdict

If you already own an induction hob, it makes sense to use it for cooking things such as soups and stews rather than investing in a slow cooker specifically for these dishes. However, slow cookers do have the added advantage of being able to chuck everything in and do something else while you wait, so you might choose a slow cooker for the convenience alone.

Slow cookers we’ve tested cost anywhere between £10 and £185. If you do choose to invest in one, make sure you get one that’s the right size for your needs by checking Which? reviews for the usable volume. The model we used has a stated capacity of 6.5 litres, but according to the instructions the maximum quantity you can cook in it is 6 litres – most manufacturers recommend you fill them about two thirds full.

How to work out appliance running costs

We calculated the energy costs of cooking the soup and stew by measuring the amount of energy the appliances used during our laboratory tests. This is a very accurate way of determining the cost.

However, if you don’t have access to calibrated lab equipment you can still estimate the energy cost using your appliance's power rating – you should be able to find this on the packaging, or on your appliance brand’s website. 

1. Multiply the power rating (in Watts) by the time in hours that the appliance is running, and divide this by 1,000. This is the energy consumption in kilowatt hours (kWh).

2. Multiply this figure by the cost of energy (currently 34p/kWh for electricity) to get the cost.

Do note that this equation might not be accurate for more complex products, as it assumes the product is always using maximum power.

See 10 ways to reduce energy bills for more advice on reducing your energy consumption.