CFL Low Energy Lighting

Advantages

Use around 80% less electricity

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Yes they really do! Compared to standard incandescent bulbs

Last 5-15 times longer than a
standard bulb?

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Under ideal conditions, using a figure of 70% of the quoted figure is a better guide. In addition standard bulbs appear to last longer than the sometimes quoted 1000 Hrs. Avoid the cheap ones the light output appears to fall of noticeably with time (based on a couple of fitting with an expensive and cheap bulb next to each other). I use 7000 hours as the life for cost comparison purposes, this corresponds to 3 hours a day use for around 6 years.

Disadvantages

High cost

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Vary between just under £0.50 and £9 - these costs are falling all the time

Can be heavy

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Put a higher strain on cable and termination when fitting suspended by cable.

Can be larger than a standard bulb

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May not fit some light fittings although a larger variety of fittings and smaller bulbs are rapidly becoming available. In particular GU10 type replacements may not fit all types of fitting.

Less tolerant of frequent switching

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Frequent switching shortens the life, manufacturer's figures are for ideal conditions

Take time to reach full output

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Approximately 30 seconds to reach full intensity - can be disconcerting

Light colour not the same a standard bulbs

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Depends on your preferences but they are different tending to be whiter. The newer types are much better in this respect.

Confusing variety of types and costs

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Be cautious the cheaper ones typically have a shorter life and can have a lower output in lumens per watt.

Manufacturers inconsistent with economy ratings

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Some manufacturers rate them as 'A' others as 'B' on the energy efficiency scale

Incompatible with dimmer switches

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This is now only partially true since bulbs are becoming available that can be dimmed, however they are expensive.

Light output drops with time

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It is slow but noticeable when comparing old & new bulbs of same wattage

Don't like being operated on their side?

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Appear to have a higher failure rate operated horizontally also poor connections sometimes especially with cheap fittings

Not all bulb types available

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Mainly bayonet, screw and GU10 at present but the range is increasing all the time.

Can flicker occasionally when switched off

When fed from very long cable runs (e.g. lights switched from the top and bottom of stairs) the capacitive coupling across the cables can cause the lights to flicker occasionally when switched off. This is quite rare.

Contain a small amount of mercury

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Modern designs contain only a very small amount but it does vary by manufacturer. Provided the bulbs are disposed of properly this isn't an issue.