Summer is a good time to assess refrigeration needs. Before going away on holiday, you will be jettisoning perishables. If you discover they don’t fill much space, you may start thinking about downsizing to a smaller fridge-freezer.

That line of thinking has the support of Judith Wills, author of The Green Food Bible. Wills’s stimulating book covers vast areas of ground with balanced evaluations of some complicated subjects, including refrigeration. She would like more use of old-fashioned larders, or “a cool area of the house”, so we can save energy by using a smaller fridge. She’s right about this up to a point, but the issue is complicated.

First of all, the energy savings may not be as high as you would expect. With modern A-rated domestic fridge-freezers, increasing size also increases efficiency. I compared three fridges from a well-known manufacturer: an under-the-counter larder fridge, a standard-size tall one and an “American-style” behemoth with room for twin mastodons and a lawnmower. The standard size uses around twice the energy of the smaller fridge but has 2.8 times more storage space. The largest has 50 per cent more capacity than the standard, but uses less than a third more energy.

That’s an argument in favour of size. But not in the form of an extra fridge or freezer. You’d be better off with a single unit if you really need so much capacity.

And calculating need can be difficult. Most households of my acquaintance have excess fridge-freezer capacity much of the year. This is deeply wasteful, because fridges operate most efficiently when they’re around three-quarters full.

But if you downsize to an under-the-counter fridge, what do you do when 13 people come for Christmas? Or the grandchildren invade? A few days of the year, you need the twin-mastodon unit. Bear that in mind if you’re looking to downsize. Sometimes it’s tricky being green.

thegreenkitchen@thetimes.co.uk

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