In my office and kitchen, and nightlights for my children...
Until recently the energy-most efficient form of widely-available domestic lighting has been fluorescent; initially in somewhat harsh strip-lights for the kitchen and garage/shed, but more lately as versatile compact fluorescent lamps (CFL) shaped to fit conventional bayonet or screw light fittings and with excellent colour and low price. These are available both for mains electricity (240V AC in the UK) and 12V DC operation such as for caravans and cars and low-voltage display lighting. CFL is generally a GoodThing(TM), as it is about four times more efficient (at around 60lm/W, ie 60 lumens of light out per Watt of electrical power in) than filament (incandescent) bulbs and has a considerably longer life to boot, but its downsides are the relatively fragile tube and small but significant amounts of toxic mercury (Hg) in the tube. CFLs also by their nature require some kind of inverter or ballast that can waste significant energy.
Only just about in 2007 did LED (light-emitting diode) lamps start to match CFL in terms of efficiency, and colour rendering has improved too. LEDs are a natural for low-voltage (eg 12V DC) applications, though require some supporting electronics to protect them from spikes, reverse connections, etc. LED lighting is also available for mains operation. It is helpful to understand the notion of 'lumens' for total light output, since the many forms of lighting available have very different behaviour and efficiency.
From September 2010, c/o EU directive 98/11/EC: domestic lamps have (mainly) been required to be labelled with lumen (lm) output more prominently than Watts, which should help with direct comparisons.
A lingering limitation on LED lighting in 2012 is power (ie the amount of light produced). As of 2007 I liked my lighting bright, so for example my then desk lamp in my study was a 20W 1200lm (lumen) mains CFL. At the turn of 2010 I started using the 7W mains 'cool white' EQ60 in an anglepoise which is great, as well as 9W "warm" and 7W "cool" 12V lamps to be able to be 'off grid', and as of 2012 we now have 7W and 10W (roughly equivalent to 40W and 60W incandescents) in several fittings around the house.
(The reason that I've taken a special interest in LED lighting is because I was looking for efficient low-voltage lighting for my solar power PV project, mainly for a decent desk lamp replacement. The initial light for this project was a 16W caravan-style CFL, which was a little bit flickery and blue for my liking, and which produced noticable heat from its built-in inverter. The initial LED lighting that I supplemented this with was a 3W 180° floodlight white LED meant for car 'modding' fancy lighting effects. It was tiny, but mounted behind my shoulder shed a noticable light that filled in many dark corners and avoided the feeling of sitting in a candle-lit cave!)
Note that although the latest round of off-the-shelf LED technology in 2011--12 is passing the efficiency of CFL at 60lm/W, the theoretical maximum efficiency of 'white' lighting is about four times this, so we have some way to go still! And note that LED lamps have no 'warm-up' time, which even new CFLs exhibit.
LED lamps, often as drop-in replacements for miniature halogen display lamps, are becoming widely available in the high-street as well as over the Internet, and are passing the efficiency of the best widespread alternative, so we could be on the cusp of a small but well-lit revolution! The main barriers to household use that remain as at the start of 2012 are cost (several times that of CFL, though lasting many times longer) and maximum light output (50W halogen equivalent LEDs are still rare).
NOTE: LEDs don't like getting hot (you'll get less light and/or shortened life), so be careful if installing in unventilated flush ceiling fittings such as GU10 reflectors, and for 12V MR16s ensure that the transformer is rated 0+.
See mini reviews of various LED lamps below, divided into categories.
Measuring the performance of a lamp in lumens allows direct comparisons of light quantity (which is the service actually offered by the lamp). Comparisons based on wattage are not meaningful any more and can be misleading. Look for 1300-1400 lumens for the equivalent of a 100W incandescent bulb, 920-970 lumens for a 75W, 700-750 lumens for a 60W, 410-430 lumens for a 40W and 220-230 lumens for a 25W bulb.
- This Directive shall apply to household electric lamps supplied directly from the mains (filament and integral compact fluorescent lamps), and to household fluorescent lamps (including linear, and non-integral compact fluorescent lamps), even when marketed for non-household use. Where an appliance can be taken apart by end users, for the purposes of this Directive the 'lamp' shall be the part(s) which emit(s) the light.
- The following lamps shall be excluded from the scope of this Directive:
- those with a luminous flux of more than 6 500 lumens;
- those with an input power of less than 4 watts;
- reflector lamps;
- those marketed or commercialised primarily for use with other energy sources, such as batteries;
- those not marketed or commercialised primarily for the production of light in the visible range (400 to 800 nm);
- those marketed or commercialised as part of a product, the primary purpose of which is not illuminative. However, where the lamp is offered for sale, hire or hire purchase or displayed separately, for example as a spare part, it shall be included.
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Copyright © Damon Hart-Davis 2007-2014.