CFLs were by then beginning to get a bad reputation

2. dubna 2013 v 5:22 |  solar photovoltaic system
Besides, CFLs were by then beginning to get a bad reputation. Few lived up to their claim of longer life, especially when they were switched on and off repeatedly, or used in recessed ceiling lights where heat could build up and fry their inbuilt circuitry. Meanwhile, the procedures for dealing with the hazardous mercury vapour in spent or broken CFLs made people wary of having them around the house.

Fearing a consumer revolt, Congressmen who had backed the legislation rushed to repeal it. In the event, the prohibition on the sale of inefficient 100-watt incandescents was put off until October 2012. Californian retailers ceased to restock them in January 2011. But the prohibition is now in force, and people are grumpy. Though LED bulbs, which have a total-cost-of-ownership significantly less than that of sodium or other forms of industrial lighting, have proved their worth to municipalities and businesses, they have yet to do the same for residential users.

That is hardly surprising, given an up-front cost of anything from $25 to $60 (before possible rebates from utility companies) for an LED bulb that has a luminous flux equivalent to the 100-watt incandescent variety. To the average householder, it does not matter that such bulbs pay for themselves-by using considerably less energy than incandescents-in three to four years, and go on putting out useful light for 20 years or longer. What does matter is that swapping from incandescents or compact fluorescents to LEDs makes a big hole in the family budget in the here and now.

Your correspondent plans to upgrade his original 4.2 kilowatts worth of indoor and outdoor lighting with LED equivalents, one lamp at a time, as the existing bulbs (mostly compact fluorescents) burn out. Replacements for 100-watt flood lights tend to cost around $40 a piece. But the popular 60-watt-equivalent can now be had for as little as $14.

Not all LED lamps, however, are created equal. Some of the cheaper ones have a chilly blue cast. None has quite the full complement of colours of the profligate tungsten-filament bulb, with its wide pallet of wavelengths in the visible spectrum.

The usual measure of a light source's ability to reproduce colours faithfully is the Colour Rendering Index (CRI). By convention, incandescent bulbs are assigned a CRI of 100. Cheap LEDs can have a CRI of 50 or less. A really good one-such as the $50 Philips LED bulb that won the Department of Energy's $10m "L-Prize" for exceeding all the set requirements for a 60-watt-replacement-has a CRI of 93. Most LEDs have CRIs of 80 to 85. It is thus worth checking the quality of the light an LED bulb produces before splurging on a six-pack of them.

It is also wise not to take claims of an LED bulb being dimmable too literally. Though many are, they usually require approved dimmer switches. That can mean replacing existing switches along with the bulbs.

That said, these are early days. Like their industrial brethren, LED bulbs for domestic use will get better, cheaper and have more features. Your correspondent is particularly excited by the prospects of being able to communicate remotely with his lights at home via Wi-Fi and the internet. He also looks forward to being able to program the colour they produce on the fly. Solid-state lighting makes all this, and more, possible.

Bulbs like the Philips Hue or LIFX can have their brightness, colour and timing of when to come on and go off controlled wirelessly from a smartphone. The Philips programmable LED uses a separate router box, but the Australian LIFX bulb has the networking electronics built into the bulb itself. The LIFX can even be set up to change colour to music.

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