That washing machine marked down to £369 might be a bargain. It might also be the start of a much more expensive final checkout.

Before buying a September deal, add up the full cost: the machine, delivery, installation, recycling of the old one and the electricity it will use.

The large price in the advert is only the first number.

Start with the energy label.

Look for the machine’s electricity use per 100 washes, then work out what that means in your home.

Divide the kWh figure by 100, multiply it by your electricity unit rate, and multiply again by roughly how many washes you run.

A cheaper machine can lose its advantage if it uses noticeably more power over several years.

Capacity needs the same reality check.

 A 10kg machine is not automatically better than a 9kg model if you rarely fill it.

Which? price benchmarks show why the word “deal” needs testing: the LG F4Y510WBLN1 was listed with a six-month average price of £477 and a lowest price of £369.

The Hotpoint H 101 Anti-Stain UK averaged £373, with a lowest price of £309.

Those figures give you something better than a retailer’s crossed-out “was” price.

Then enter your Cambridgeshire postcode before you get attached to the headline figure. 

Delivery dates, charges and available services can change by product and address. AO lists £30 for connection and £25 for removing and recycling an old appliance on one Bosch model.

 Currys also lists washing-machine installation at £30, with access, stairs and a connection within 1.5 metres among its checks.

Some retailers bundle the extras. At the time checked, John Lewis listed a Samsung 9kg A-rated machine at £469 with delivery, recycling and installation included, described as worth £74.95.

Another Bosch model included delivery and recycling worth £44.95.

 A higher shelf price can therefore be the cheaper checkout.

Finally, price the old machine’s exit.

Cambridgeshire County Council’s household recycling centres accept washing machines and other white goods.

 In Cambridge, the council lists white-goods collection at £31 per item and suggests reuse routes including Cambridge Re-Use for suitable goods.

Save this checklist: machine price, energy use, postcode delivery, installation, old-appliance removal and warranty.

If one of those is missing, the “deal” is not fully priced yet.