Jeff Howell: what are the best low-energy lightbulbs? A: My views on light-emitting diode (LED) lamps are similar to what my views were on compact fluorescent lamps (CFLs, or "low-energy lamps") some 15 years ago. At that time CFLs cost around £10 each, so buying a CFL to replace an existing incandescent lamp was unlikely to pay for itself in terms of saved energy. Since then, electricity has tripled in price, and CFLs have become much cheaper - you can bulk-buy them for £2 each, or sometimes cheaper in supermarket promotions. Many readers were given free CFLs by their energy providers. So if you have CFLs lying around the house, then use them, and when an old incandescent lamp blows, it will be worth replacing it with a cheap CFL, especially if you are on an Economy 7 tariff, and now paying an eye-watering 19p per unit on the day-rate. At that rate, the saving between a traditional 60W incandescent lamp and its 15W CFL equivalent, used for say 1,000 hours per year, would work out at 45 kWh or units, or some £8.50. On a standard tariff of 14p per unit, the saving would be around £6.30 a year. LED lamps, on the other hand, are still expensive, although they are gradually getting cheaper. I recently bought a basket-full in a supermarket promotion for £7 each. I don't expect them to save me any money, but some readers have reported problems and premature failure, so I thought I'd give them a try. For standard bayonet-cap or Edison-screw fittings, I can't see much advantage over CFLs. I replaced some 6W CFL wall-light "candle" lamps, for example, with 5W LEDs. The brightness appears to be roughly the same - although the LEDs do seem to reach full brightness straight away, with no annoying warm-up period. Where the LED lamps do seem to score is in replacing my 240v kitchen halogen downlights (GU10 fittings) - 5W each instead of 50W. The LEDs are the same size and shape as the halogens (the CFL equivalents are much bulkier). The same applies to my 12v downlighters in the lounge. Both were simple to exchange, give a good equivalent light intensity, and yes, the 12v LEDs work fine with the existing transformers and fittings. Sadly, one of them failed after only three days. I shall be keeping an eye on this subject, and would welcome readers" comments and experiences. Treading the boards Q: We had our kitchen extended some years ago. The floor construction is wooden floorboards on joists suspended over a concrete raft. The floor has now settled, leaving a small ridge half way across the floor. What is the best option for making it level before we re-cover the floor with flexible tiles? CW, by email A: My initial reaction was to write, "Take up the floorboards and shim up the joists to level them." But then I re-read your question and I'm worried in case you really do mean that your back addition was built on a concrete raft that has settled. A raft is a concrete slab that supports the brick walls along its perimeter edges; if that is settling, you might have a structural problem. I'm sure you mean the walls have their own foundations, and that there is a separate concrete slab below the suspended timber floor. All the same, have a structural engineer or experienced building contractor look at it first, to check there is no ongoing movement. Send your questions to Jeff at Life, The Sunday Telegraph, 111 Buckingham Palace Road, London SW1W 0DT, email askjeff@telegraph.co.uk. Also visit Ask Jeff