low energy light bulbs

[nix-j-c]

how many low energy light bulbs, not the long tube ones, dos it take to light a room because i'd say the same amount as the classrooms have but they're tubes so i dont know how many bulb shaped bulbs you need for each tube bulb? if you understand that 'cause now i rered it it doesnt make much sense can u try and answer please?

[rojash]

I don't really understand your question either, but I can tell you this: in my small office I have 5 light fittings, each with a 15w low energy bulb that claims to be as bright as a 100w incandescent bulb - that's equivalent to 500w for the lot.

If you believe the manufacturers claims, my office should be lit up like a laboratory, but it's actually as dark as a cave in here!

[neuron]

I couldn't agree more with you rojash. I raised this question earlier this week here:

http://www.theanswerbank.co.uk/Home-and-Garden /Question481489.html

There's clearly a school of thought that these bulbs should be left on for around 10 minutes to achieve their maximum light output.

I've left these bulbs on longer than this when comparing a 11W energy saving bulb with a 60W so-called incandescent equivalent. The light output of the energy saving bulb is nowhere near the brightness of the incandescet bulb. I honestly don't know how these manufacturers can get away with these lies.

[wildwood]

The energy bulbs are supposed to be 5 times more efficient as an incandescent one so an 20w. one should emit 100w. It does so, but only close to the bulb. In a room 2x 20w energy bulbs light the room up as efficiently as about 120w of incandescent, still a considerable saving and they do last a lot longer.

Just like incandescent bulbs, the energy bulbs are not very effective for use in daylight like extra lighting in an office or shop. There, its cousin the linear fluorescent tube or halogen light is needed.

The LED lightbulbs are advancing in leaps and bounds and it won't be long before they make an affordable replacement for home lighting.

[nix-j-c]

so can you get the florescent tube lights in low energy or would you need led lights for low energy

[neuron]

Wildwood, for the life of me, I can't see that because a 20W energy efficient bulb is supposed to be five times more efficient than an incandescent bulb, it can be said that the incandescent equivalent is 100W.

I'm not questioning the arithmetic which is obviously correct, but I can't see a correlation between efficiency and equivalent wattage. The point is that a substantial amount of wattage consumed by a incandescent bulb are lost as heat. I can't see that such figures could be calculated without taking this heat loss into account.

What exactly is "efficiency" as used in this context?

I went out today and bought two 20W Philips Energy Saver Bulbs. The packaging states that each provides the equivalent of a 100W incandescent bulb. I tried them out in a closed room with no windows, left them on for 25 minutes and judged the total light output. I then replaced them with two standard pearl 100W incandescent bulbs. I'd say the energy bulbs provided about 60% of the light of the incandescent bulbs. You say I should have had about 120W of light equivalent from the energy bulbs; the packaging says I should have had 200W of light equivalent from the bulbs.

Are we now at the point where we are expected to guess how many of these bulbs are equivalent to incandescent lamps? Perhaps we are expected to put in extra light fittings just in case we need more bulbs. There certainly doesn't seem to be any consistency in these equivalent ratings and to my mind, there should be.

[neuron]

nix-j-c, conventional fluorescent tubes are already classified as low energy. I've got a 5ft long single tube fitting in my office that has a tube rated at 65W. At a rough guess, I get somewhere between 120W to 150W of equivalent incandescent bulb light from it.

LED lamps such as the arrays fitted in GU10 bulbs are very efficient and are low energy. The problem is that they've not perfected the LED to give out as much light as the 50W halogen they replace. Offhand, I think the highest output for this type of bulb at mains voltage is about 20W of light.

[wildwood]

neuron, I do not understand your bewilderment. With your little experiment you supported my postulation that energy bulbs are about 3 times more efficient than incandescent ones. 2x 20w energy bulbs would produce about the equivalent light of 120w incandescent, this is what you found it to be too. The trouble is that the 5 times equivalent claimed by the manufacturers can't be disputed because it does emit that, the light waves however are not the same as the incandescent ones, that's why they are virtually useless for brightening up a room in daylight - the linear fluorescent lights (tubes) are excellent for that especially as the tube are obtainable in different intensity; daylight, softlight, put your shades on mate etc. etc.