Instead of being measured in watts, light is now measured in lumens – the latter measures brightness while the former calculates the amount of energy used, and with LEDS and compact fluorescent lamps (CFL) now popular, the level of brightness is a more accurate measure of how much light a bulb will give you. For a basic idea of how many lumens you need for a room, start by multiplying the length by the width of your room to get the square footage. Next, work out the ‘foot candle’ – how many lumens you need per square foot. In general, a sitting room or bedroom need about 10-20 lumens per square foot, while a bathroom or kitchen requires stronger lighting, at 70-80 lumens per square foot.
Colour temperature is also important – it tells you how ‘warm’ (yellow) or ‘cool’ (blue) a light is. It is measured in Kelvins (abbreviated to K) and the higher the number, the ‘cooler’ the light, so 6500K is at the cool end of the spectrum and resembles daylight, while a wax candle has a very warm glow of about 1000K.
For living and bedrooms a Kelvin range of 2200-3000K is recommended whilst for kitchens it is 2700-5000K and bathrooms 3000 – 5000K.