Up and down the country our homes and workplaces are filled with over 650 million light bulbs, allowing us to work, rest and play even when the sun has set.Yet for something we rely on so heavily, they are not particularly good at their job. An old fashioned light bulb with a tungsten filament was only five per cent efficient - 95% of the energy you put in wasn't turned into light. Most of it was wasted as heat. During its lifetime it got through as much energy as contained in three tonnes of coal. In this country we currently use about a fifth of our electricity on lighting. More efficient alternatives, then, are good for both the environment and our bank balances.
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