Tread lightly: Keep your kettle in check

Put the kettle on - but only with the water you need. Photograph: Graham Turner

At first glance, the idea of only putting the water you need to use into the kettle seems pretty finicky. After all, boiling an electric kettle to make a cup of tea only requires about 0.03125kWh of electricity and generates around 0.015kg CO2.

However, according to the UK Tea Council, as a nation we guzzle 165m cups of tea and 70m cups of coffee each day. If, as some figures suggest, we habitually boil twice as much water as we need, we could be needlessly wasting some 3,525 tonnes of CO2 every day.

According to the Department for Environment, Food and Rural Affairs, 97% of UK households have a kettle. Until 10 years ago, these were mostly 2.2kW appliances, but more powerful 3kW kettles are widely available now. These more powerful kettles have the advantage of boiling water more quickly and many hold more water than older designs.

The downside is that people are more likely to overfill such kettles, especially when making one or two cups at a time. A survey conducted by the Energy Saving Trust (EST) in 2006 found that 67% of people in Britain admit to overfilling the kettle each time they use it.

The EST concluded that if we each boil the water we need to make a cup of tea instead of filling the kettle every time, we could save enough electricity in a year to run nearly half of all the street lighting in the country. So this week's pledge aims to contribute to doing just that.

There are other ways to heat water for a cuppa; in a pan on a gas hob or in the microwave, for example. However, an electric kettle converts about 80% of the electricity used into energy to heat the water, while the comparable figure for a pan of water on the gas is around 40% and a microwave about 55%.

There are new water-heating devices on the market that claim to save electricity. For example, the Eco Kettle claims to use 30% less energy than a standard kettle. This product is recommended by the EST. The Plunger Kettle is a similar device, which incorporates a water filter.

With both products, you fill the main reservoir, but then decant the exact amount of water required into a separate boiling compartment. However, you can get the same result without splashing out on a new kettle simply by pouring the required number of cupfuls into a jug and decanting it into the kettle. The time you take to do so will be more than repaid by the time saved by boiling less water.

So will you be filling you kettle less for this morning's cuppa? Do you have an eco kettle? Tell us your thoughts