The least efficient appliances would add an eye-watering £490 a year to your energy bills, but choosing the most efficient would cut this down to just £154. This could save you £336 a year, or £3,360 over the course of a decade.
Our new running costs tools can help you save money on your energy bills by calculating the energy efficiency of tumble dryers, washing machines, fridge freezers, ovens and dishwashers.
While some of the most efficient appliances may be more expensive up front, our research has found they will end up being cheaper over the product's lifetime thanks to lower running costs.
Heat pump tumble dryers tend to be both more energy efficient and pricier than cheaper condenser and vented models but can easily pay for themselves in energy savings. On average, condenser dryers cost £109 per year to run whilst heat pump models cost just £42.
The most energy-hungry tumble dryer we've tested is a vented model, the Hoover HL V10LG-80 (pictured below), which costs £260. The most energy-efficient is a heat pump model, the Miele TWB140 WP, which costs £800.
But the Hoovercosts more than four times as much to run.
Even though the Miele costs more upfront, it would still save you £1,580 over the course of the dryer's lifetime (around 20 years on average) due to its lower running costs.
Fridge freezers are on all the time, so it's not a surprise that big savings can be made by choosing an energy efficient model.
The Hotpoint will add £134 in energy bills a year.
Despite the significant price difference between these two (£541 for the Hotpoint and £1,599 for the LG), the LG more than pays for itself in the energy savings - ending up costing £800 less over its 18 year life despite costing £1000 more.
The type of fridge freezer people opt for will also have an impact. On average, a freestanding fridge freezer will add around £61 per year to people's energy bills, while a large American-style fridge freezer will add around £92 per year.
You could also save £55 a year by choosing a more energy efficient washing machine when replacing your current model.
On average, a washing machine will add £46 per year to people's bills if running four 40°C washes per week, but this can vary from under £20 to as much as £70 per year.
Check our washing machine reviews before purchasing new appliances to make sure you are getting the best value for money.
Ovens aren't as energy-hungry as other large appliances, such as fridge freezers or tumble dryers, but they last a long time - we estimate around 23 years from our Which? member survey.
Therefore, buying an efficient model now will lead to big long-term savings.
The average built-in oven costs £53 a year to run if used for about five hours per week at 170°C.
Perhaps what makes this more extraordinary is that the Beko is a fifth of the price, at £259 compared to £1,600 for the Smeg.
Our energy cost data comes from independent lab testing that's based on how you really use your appliances.
It often reveals big differences between A-rated machines, and in some cases B and C-rated machines that actually cost less to run.
This is because Which?'s surveys have found that most people use appliances differently to the official rating tests.
For example, the ratings for washing machines are mostly based on washing at 60°C, but most people wash at 40°C.
Which? Eco Buys are our environmentally-friendly product recommendation. Just like our Best Buys, the Which? Eco Buy is backed up by rigorous research.
Products we've flagged as Eco Buys will have a lower carbon footprint over their lifetime, all while doing their main job well.
By being energy and water efficient, Eco Buys highlight the products that match real long-term savings with outstanding performance.
You don't have to pay to be green, either. We've found Eco Buy ovens for less than £200 and Eco Buy dishwashers for as little as £330.
Read the reviews below to see all our Eco Buys. You can also see the annual running cost for every product in the tech specs section of the review.
A spokesperson from Hoover commented: 'Vented tumble dryers are less energy efficient than other types of dryers on the market. Our Heat pump models with A++ ratings for example are amongst the most energy efficient. Generally, Heat Pump models are more expensive than the entry level vented models due to the advanced technology used.
'As a business we are committed to reducing the energy consumption of all of our appliances and continue to invest in their development. Earlier this month we opened a brand-new, best-in-class tumble dryer factory in Turkey, which will provide additional capacity for the production of energy efficient Heat Pump models.'
A spokesperson from Candy said: 'We're currently making upgrades to our entire dishwasher range for 2022. This will build upon our current product collection, including the Candy CYF 6F52LNW-80, which is one of our entry level models.
'Significant investment has gone into R&D and production, and this includes plans for a new dishwasher factory which will open in 2022. The new production plant will utilise a completely new dishwasher platform and product re-engineering and energy efficiency will be a key part of the manufacturing process.'
Hotpoint said: 'According to Youreko, an independent energy consumption tool on the Hotpoint website, this appliance is not the least efficient on the market and has a £314-lifetime energy saving compared to the least efficient model in the UK. The tool rates the product out of all similar specifications in the UK, and you can see there is nothing cheaper to run at this price point, which is deemed good value for money.'
Smeg said: 'Smeg ovens offer the consumer both flexibility, speed and efficiency. The Circulaire function used in the Which? test can achieve 180°C in just 4-6 minutes. Ideal for consumers who may well be time poor. However, all Smeg ovens, regardless of their model offer an Eco function. This uses the same heating system as the Circulaire function, fan-forced convection, but achieves the temperature at a much slower and efficient rate.
'All ovens sold have to be tested and display an energy label, making it simple for customer to compare energy consumption and thus running costs. The Smeg ovens are tested on the ECO fan-forced convection function. The Smeg oven tested by Which? uses a mere compared to competitors [on the eco function] that sit at 0.69kwh and up to 0.71kwh. The Beko oven used to compare running costs in the article below uses on the same test.'
A spokesperson from Haier said: 'As a brand we aim to consistently improve and develop our products. The model that has been chosen by Which? to be tested at this time is being discontinued and is not currently listed on our website. We are however aware of its energy rating which is why we have since launched an improved and more efficient A-rated range.'
Despite Haier saying that the HW100-B14876 is being discontinued, it remains widely available from AO.com and Currys.
We have used the new price cap of 21p per kWh for all energy prices throughout this article and in our running cost tools.
All appliance lifetimes are based on a September 2020 survey of 12,000 Which? members.