Compact fluorescent light bulbs use only 20 to 30 per cent of the energy required for a normal incandescent light bulb. They are more expensive, but on the plus side they last a lot longer. In ideal circumstances, a CFL can last up to 15 times longer than a normal light bulb. In reality, though, this is seldom the case. Spikes, or surges in electrical supply can affect how long they last, and turning them on and off frequently also affects their lifespan. So far so good. But, apart from the problems associated with mercury, CFLs have also come under fire for the length of time they take to warm up and also for the quality of light they emit. Manufacturers are addressing the issue, but in the meantime most environmentalists agree that the future is non-toxic light-emitting diode (LED) lighting. LED lights are currently still very expensive, but scientists are working to reduce costs. When the lights become more affordable, they will last 50 times longer than traditional incandescent bulbs, have around the same energy efficiency as CFLs and contain no toxins.