installing a lightbulb

LED bulb buying guide

A few years ago, LEDs were confined to the display panel of your clock radio. Now they’re a viable option for almost every lighting task.


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This guide illuminates how to find the right LED for you. We’ve surveyed the market to let you know what’s available, what bulb’s right for a particular job and which LEDs give the best value for money.

Why is this report free?

This report is available free to all New Zealand consumers with support from EECA (Energy Efficiency and Conservation Authority), the government agency that works to improve the energy efficiency of New Zealand's homes and businesses, and encourages the uptake of renewable energy.

If you'd like to support our work as a non-profit organisation, consider making a donation. We’ll use your contribution to work for positive change.

Spotlight on light bulbs


LED bulbs are the most efficient and durable of the lot, but also the most expensive. However, prices have fallen considerably since we first tested them in 2013. They use up to 80 percent less energy than incandescent bulbs, while producing the same amount of light. Most LEDs should last at least 15,000 hours – that’s more than 13 years if used every day for three hours.


A compact fluorescent lamp (CFL) is a scaled-down version of the fluorescent tube lights common in offices and commercial buildings. They use a small tube filled with glowing gas. CFLs are generally cheaper than LEDs and have a lifetime of at least 6000 hours, about six times longer than incandescents but significantly shorter than LEDs. They take a few seconds to reach full brightness and tend to fade over time. Frequent switching can shorten its lifespan.

Halogen lamps

Halogen lamps are a type of incandescent bulb, but are about 30 percent more efficient. They’re most commonly found in the home as low voltage downlights and spotlights.

Incandescent bulbs

Incandescents are the direct descendants of the first light bulb patented by Thomas Edison in 1879. They work by passing an electric current through a wire filament. They are far less efficient than other types of lighting and have a shorter lifespan.

Brightness: watts vs lumens

Watts measure power consumption, whereas lumens measure light output. Wattage isn’t the best indicator of an LED’s brightness. We found there is considerable variation in the efficiency of LED bulbs.

Generally, LEDs produce the same amount of light as an incandescent bulb that has five to six times the wattage.

Incandescent bulb (watts) Equivalent LED (watts) Light output (lumens)
40 <7 420
60 8-10 720
75 11-12 930
100 ≥14A 1300

AGLS bulbs are now available in the 40W to 100W equivalent range.

If you want to replace an existing incandescent bulb with an LED, use the wattage of the old incandescent as a guide. The packaging of LEDs usually indicates the equivalent wattage of incandescent bulbs that produce a similar brightness.

If you want to buy an LED to replace a standard incandescent bulb, chances are the LED will appear brighter than the equivalent incandescent. This is because the beam angle of LEDs is narrower, so the light comes out more focussed.

Types of LED bulbs

Before heading off to the shops, check what kind of bulb you want to replace. The majority of light bulbs are described by a system of series designations. The most common are:

GLS (General Lighting Service) standard bulbs

Available with screw and bayonet bases, which have the designations Exx and Bxx respectively. The xx refers to the base’s diameter in millimetres.

R-Series reflector bulbs

These are often used as floodlights and downlights. They are numbered by the size of the bulb’s diameter in millimetres, R80 for example.

PAR-Series security lights and self-contained exterior floodlights

PAR38 is a common type; the 38 is the diameter of the bulb in multiples of eighths of an inch. PAR38 bulbs are 121mm wide.

MR16 and GU10 spotlights

MR16s have two thin pin bases (called GU5.3 bases), while GU10s usually have thick turn and lock “top-hat” bases. The main difference between them is GU10s run at 240V, while MR16s run on 12V and require an external transformer. There are MR16 lamps available with GU10 turn and lock bases.

Where to buy them

LED bulbs are available at most supermarkets, hardware stores, and specialised lighting and electrical shops.

What to look for

There are LED bulbs available for nearly every lighting task in your home, but there are a few things to consider.

The long lifespan of LEDs makes them ideal for hard-to-reach fittings you’d like to change as infrequently as possible, such as above stairways or in high ceilings.

If you want to use a dimmer you need to buy dimmable LED bulbs, and ensure your dimmer switch is compatible with the dimmable LED bulb (it will say on the packaging).

Replacement bulb or dedicated LED fitting

A dedicated fitting houses the LED and its associated electronics – the bulb is fixed to the fitting and can’t be changed like a regular light bulb.

A replacement bulb is an LED that can be retrofitted into an existing fitting to replace an incandescent, halogen or CFL.

A dedicated fitting is designed to manage the heat that concentrates at its base; overheating can shorten an LED’s lifespan. If you’re installing lights as part of a renovation, or if you’re building a new house, then we recommend dedicated LED fittings. Note that if the fitting fails you’ll have to replace the whole unit.

If your house has recessed downlights with incandescent or halogen bulbs, it is better to replace the entire fitting with a dedicated LED downlight fitting, instead of just changing the bulb. Just replacing the bulb with an LED is likely to overheat the LED and shorten its life. In addition, most older downlight fittings require generous clearances to ceiling insulation and can allow draughts through the hole in the ceiling lining. Modern dedicated LED downlight fittings combine energy efficient lighting with better airtightness and insulation can be abutted to or even laid over them. You will need an electrician to install them for you.

For non-recessed fittings, retrofitting LED bulbs is cheaper and easier than installing dedicated LED fittings, but remember to check you get the same base type and a similar shape, brightness, colour temperature and beam angle.

Warm white or cool white

An early complaint with LEDs was they were unsuitable for general ambient lighting because of the harsh white light they produced. Models capable of producing a warmer white light are now widespread. If you’re after a bulb for your living room or hallway, a warm version is a good choice to avoid a cold feel, but cool lighting is fine for the bathroom or laundry.

Colour temperature
Colour temperature refers to the light’s colour characteristics. It varies between warm, like the yellow light of an incandescent bulb, or cool, like the bluish light of some fluorescent lamps. It is measured in Kelvins (K). The higher the K, the cooler the light.

Warm white (2700K – 3000K) brings out the warm colours in your home and is great for living areas.

Cool white (4000K) is a bluish-white light that improves the contrast between colours. Suitable for work areas where contrast is important.

Beam angle

The beam angle measures how the light spreads out from the bulb. Beam angles of LEDs vary greatly and depend on their application. The shape of an LED bulb determines the direction light is emitted. However, when buying downlights ensure you get a bulb that emits light only from its end.

Narrow angle bulbs – less than 30 degrees – are usually used when placing multiple downlights close to each other, such as in a hallway or when lighting cabinetry. Larger beam angles are used with high-power LEDs for floodlighting. If you’re replacing incandescent or halogen lamps with LEDs, make sure the beam angle is similar to the old bulb.

Very large beam angles are sometimes found in pantries or walk-in wardrobes. As beam angle increases, you require more lumens (light output) to maintain the light’s intensity.

Life expectancy

LED bulbs have a claimed life expectancy of between 15,000 and 50,000 hours, so can be expected to last for more than five years of normal domestic use. However, their lifespan can be considerably reduced if they get too hot, as can happen when they are retrofitted into recessed downlights and spotlights. Make sure they have a way to dissipate excess heat or replace the entire fitting with a dedicated LED downlight fitting.

Care should be taken if you’re installing LEDs in environments where they are likely to be exposed to steam. The bulb housing contains a small electronic circuit which can short if it gets damp. LEDs retrofitted into bathroom heater units will probably have a reduced lifespan due to increased temperatures generated by heat lamps.

One thing that won’t affect the lifespan of your LED bulbs is frequent on-off switching. They also reach their full brightness instantly – in contrast to some CFLs which can take up to a minute (although warm-up times have improved in recent years, and “instant-on” CFLs are available).

Both LEDs and CFLs fade over time, but this is more pronounced in CFLs.

Energy savings and payback time

Despite the higher upfront cost of LEDs compared to other technologies, you can expect to save money in the long run through reductions in your power bill.

Let’s compare a mid-range LED to a standard incandescent bulb. The LED has the same brightness as a 60 watt incandescent while only drawing 9.5 watts. The LED costs $18 and has an expected lifespan of 15,000 hours, while the equivalent 60 watt incandescent bulb costs 50 cents but lasts for 1000 hours. If the light is on for three hours each day the incandescent will use $17.08 worth of electricity in a year, compared to $2.70 for the LED. That’s a saving of $14.38 per year.

The LED will have paid for itself in a little over a year. It will then keep going for another 12 years if used for three hours every day, while the incandescent bulb will need to be replaced every year. These figures show you shouldn’t wait for your incandescent bulbs to blow – it’s more cost effective to replace them with LEDs now.

What to look for

Before you buy an LED replacement, here are some features to consider.

  • Wattage: Most LED packaging shows the equivalent wattage of an incandescent bulb of a similar brightness. Use this as a guide when replacing an old incandescent bulb.

  • Brightness: Lumens measure light output. For example, 720 lumens is about the brightness of a 60W incandescent bulb, while 1300 lumens is equivalent to a 100W incandescent.

  • Colour temperature: Choose LEDs that produce warm white light for living areas. Cool white is more suitable for work areas where contrast is important.

  • Beam angle: This is the angle at which light spreads out from the bulb. Narrow angle bulbs (300 or less) are good for hallways or for lighting cabinetry, while wider angles are best for illuminating a living area or floodlighting.

  • Base: Make sure you get the right bulb for the right fitting. GLS are standard light bulbs and come in screw and bayonet bases. MR16s and GU10s are used for downlights, R80s are used for indoor floodlights, and PAR38s are used for outdoor floodlights and security lights.

  • Fitting: A dedicated fitting houses the LED and its associated electronics. If your house has recessed downlights with inefficient incandescent or halogen bulbs, it is better to replace the entire fitting with a dedicated LED downlight fitting. If you just change the old bulb with an LED it can often lead to overheating and shorten the LED’s lifespan.

Why is this information free?

This database is available free to all New Zealand consumers with support from EECA (Energy Efficiency and Conservation Authority), the government agency that works to improve the energy efficiency of New Zealand's homes and businesses, and encourages the uptake of renewable energy.

If you'd like to support our work as a non-profit organisation, consider becoming a Consumer member or making a donation. We’ll use your contribution to work for positive change.