100 ways to save the planet

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E-Cube

Invented by British engineers, the £25 gadget significantly reduces the amount of energy used by fridges and freezers, which are estimated to consume about a fifth of all domestic electricity in the UK. If one was fitted to each of the 87 million refrigeration units in Britain, carbon dioxide emissions would fall by more than 2 million tonnes a year.

Trials are under way with supermarkets, breweries and hotels. One of the largest, the Riverbank Park Plaza hotel in London, fitted the device to each of the hotel's 140 major fridges and freezers. David Bell, chief engineer, says energy use decreased by about 30% on average - enough to slash the hotel's annual electricity bill by £17,000.

Because air heats up much more quickly than yoghurt, milk or whatever else is stored inside, this makes the fridge work harder than necessary. With the cube fitted, the fridge responds only to the temperature of the food, which means it clicks on and off less often as the door is open and closed.

Water butt

If you live in an area of the country that endures regular hosepipe bans during the summer, you may struggle to keep your garden watered during the dry months. Almost 100,000 litres of rainwater falls on our roofs each year so by collecting it in a water butt, you have a ready source of water that can help keep your garden looking lush and green. Tesco stocks a range of plastic water butts in various styles and sizes depending on your taste and budget.