As most consumers are familiar with incandescent bulbs and how much light these put out, CFL packaging indicates both the actual and equivalent wattages.
Generally, a multiplication factor of five is used, so a 15W CFL is claimed to give the same light as a 75W incandescent. Our testing (along with a recent test by the University of NSW) indicates this is only true in the best cases, particularly after the CFL has been in use for a while. For most bulbs, you’re better off using a more conservative multiplication factor of four – that is, assume a 15W CFL will be closer to a 60W incandescent.
What to look for
Colour temperature CFLs are available in three colour temperatures, which basically means three different types of light. The colour temperature is measured in kelvins and indicated on the bulb and its packaging.
- Warm White (3000K): yellowish light, similar to that from an incandescent bulb. This is a good choice for living areas and bedrooms, where a cosy comfortable light is desired. All bulbs on test are “warm white”.
- Cool White (4000K): white light, similar to that from fluorescent tubes, and suitable for offices, kitchens, bathrooms and any other room where a whiter light is wanted.
- Daylight (5000K or more): blue-white light equivalent to outdoor daylight.
Shape The shape of a CFL isn’t a factor in its brightness, but does determine the direction in which most light is thrown. A folded tube emits most of its light out of the sides and should be installed lengthways so the side faces out. A spiral emits light from its end as well as its sides and end, so is probably a better choice for a downward pointing light fitting.
Dimmable Several types of CFLs are suitable for use with dimmer switches, but check the packaging to make sure you have the right type.
Instant light Modern CFLs activate almost instantly with a reasonable light output, so in most cases they’re suitable for use in stairways, cellars and other areas where you need immediate, bright light. Nevertheless, for these areas and other rooms where you typically only switch on the light for a few minutes, choose a bulb with a faster warm-up time so it reaches maximum output faster.
Light fittings There’s no performance difference between bayonet cap (BC) and Edison screw (ES) mounts on light bulbs. However, the light fitting itself can make a difference – whether it has an effective reflector dish, the size and translucence of the glass and so on. Small enclosed light fittings can trap heat even from a CFL and reduce the bulb life, so these aren’t ideal. If you find a particular light fitting isn’t putting out enough light, a brighter bulb may be the answer, but also consider replacing the light fitting with one that has a better reflector.
Don’t turn a CFL light on and off any more than you need to, as rapid on-off-on again switching can shorten their lifespan. Switching several times a day is not a problem, and don’t be afraid to turn them off when you leave a room; just avoid doing this several times an hour, day in day out.