Even people who like the concept of light energy bulbs have a few common complaints: they are too slow to light up, they are a pain in the butt to throw away when broken, and they don’t provide a natural light. LED lights could answer all those problems — but at a cost.

It’s the week of Lightfair International, a trade fair that from a geek perspective probably isn’t quite as much fun as CES or the like. But the big theme this week appears to be LED bulbs which, as the name suggests, are simply a bunch of light-emitting diodes inside a single bulb.

The technology means that, just as with a computer screen, the full brightness comes on immediately (or at least quick enough to be unnoticeable.) There’s no mercury, which means that it’s much safer to dispose of the bulbs. And the color tone of the light is much closer to an old-style lightbulb than the more familiar compact fluorescent bulbs.

There are downsides though: the LED bulbs need a special circuit because the diodes run on direct rather than alternating current, and the diodes need to be kept cool while running.

That’s reflected in the costs: the star attraction this week is SYLVANIA’s ULTRA A19, a prototype which will be the first LED bulb capable of producing the same light as a traditional 100 watt bulb. The 100 watt mark is significant as traditional incandescent 100 watt bulbs must be withdrawn from sale in January under US environmental legislation.

Meanwhile Phillips has unveiled a forthcoming range that goes up to 75 watt equivalent. 60 watt equivalents are already on sale for around $40.

In the long-run, the bulbs should be good value: the manufacturers of the A19 say it uses just 14 watts (ie a potential 86% cut in electricity consumption) and will last 25 times as long as a traditional bulb. Still, that may be a hard sell to a sceptical public wary of handing over a picture of Ulysses Grant in return for a single bulb.