Understanding efficient light bulb packaging

An energy efficient bulb box has lots of useful information on it to help you choose the right light for you.

Base type

Bayonet or screw fitting. Both kinds of light fixtures are common throughout New Zealand, but you do have to use the correct base type for the fixture.

Colour temperature

We measure how warm or cool a light is in kelvins (K) and refers to the colour. A "warm" light provides a more yellow light, whereas a "cool" white light has more blue - the higher the number of kelvin, the whiter the light.

A warm white is usually around 2,700 - 3,000 K, suits most rooms and is similar to the light you'd expect from standard incandescent bulbs. A cool white is usually around 4,000 - 6,500 K, is good for task lighting and gives the ‘bright' light you might prefer to use in kitchens, bathrooms and offices.

Light output

The brightness of a light is measured in lumens (lm) - the higher the lumens, the brighter the light.

A 75 watts (W) standard incandescent, 18 - 20 W CFL, 52 W halogen and 12 - 15 W LED all produce around 900 lumens.


The number of hours a bulb should last when in use.

Standard incandescent bulbs have a typical lifetime of 1,000 hours, CFLs around 6,000 - 8,000 hours and LEDs at least 15,000 hours (based on manufacturers’ information).


The amount of mercury a bulb contains. CFLs must not contain more than 5mg of mercury. Halogens and LEDs contain no mercury.

Light efficiency

How efficiently the bulb converts electricity into light is measured in lumens per watt (lm/W). The higher the lumens per watt, the more efficient a bulb is.


How much energy the bulb uses is measured in watts (W). The higher the wattage, the more the bulb costs to run.

Incandescent equivalent

The wattage of the standard incandescent bulb that emits the same amount of light.

A 75 W standard incandescent is approximately equivalent to an 18 - 20 W CFL, 52 W halogen and 12 - 15 W LED.


The voltage the bulb is designed to work with. New Zealand has 230 volts.


Shows if the bulb can be used with a dimmer or other electronic switches.