Donnachadh McCarthy: The Home Ecologist

However green you are, you can still slash your energy use at the flick of a switch
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It is a more powerful tool for the green cause than any solar electric panel on the market – and yet it could be yours for a tiny fraction of the cost. The revolutionary eco-gadget is the humble light switch. By far the simplest and easiest way to save lighting energy in the home is to turn on the lights only in the room you are using.

How many of us come home in the evening, flick on the hall light, go into the kitchen to make a cuppa, turning the kitchen lights on too, then head upstairs to change out of the suit, leaving the bedroom lights on, go to have a pee leaving the loo lights on, pop into the study to check on our e-mails, leaving the PC and lights on, and finally trot downstairs to flop out in front of the telly to watch the evening news with the living room ceiling and wall-lights on, oblivious to the resultant emissions in our wake?

The maximum amount of lighting required while watching telly is an 11 watt energy-saving bulb in a nice ambient table-lamp. But the above trail of destructive homecoming habits can result in anything between 600 to 13,000 watts worth of lighting blazing away, lighting empty rooms - depending on how many lamps you have in each room and how many disastrous halogen bulbs you have.

And let me kill the old canard about turning lights off wasting more energy than it saves. There was a modicum of truth in this way back in the Fifties, when fluorescent lights first came on the market. When up and running, fluorescent tubes are extremely efficient. However the first generation used a starter motor that consumed about half an hour's worth of electricity to get things fired up.

So, back then, it did make sense to turn them off if leaving the room for less than half an hour. Modern tubes however, take use about 30 seconds worth of electricity to get them started, so it is almost always worth turning the lights off when leaving an empty room.

There is another aspect to switches that frequently comes up in my home and office eco-audits - and that is simply the lack of them. Please, please, if you are building a new home or simply refurbishing your current home, try to have as many light switches as possible. In many so called "modernised" living rooms or kitchens, the owners have no choice but to turn on all 10 to 20 down-lighters, even if they only need four or five at that particular time. Even worse off are those unfortunates who were conned into installing computerised light switching. Most households that I eco-audit that have had these loony systems installed are in despair, as they need to call in a lighting engineer any time they go wrong or when they want to turn half the lights off in a room.

So my three golden eco-rules for switches are, simply: turn them off; the more switches the better; and for your sanity's sake, keep them software free. If you stick to these simple rules you will save as much electricity as many a solar electric installation.

Donnachadh McCarthy works as an eco-auditor and is author of 'Saving the Planet Without Costing the Earth' (