A buyer’s guide to light bulbs

Switching the lights off when they’re not needed is a good habit, but it takes ages for the savings to add up. The way to make a real dent in your power consumption is to switch to so-called eco light bulbs. But unlocking these savings can cost you more initially...

How do they work?

Compact fluorescent lamps (CFLs) are one of the most common eco bulbs, and sometimes get called curly bulbs for their twisted shape. Instead of using power to make a metal coil glow, these are filled with a gas which creates UV light when a current passes through it. When that UV light hits the special coating on the bulb it glows with a florescent light, creating much the same illumination out of far less electricity. They also stay noticeably cooler than regular bulbs, which is part of the secret of their success – all that heat given off by incandescent bulbs comes from wasted electricity.

Unfortunately, all this clever technology costs more than incandescent bulbs. At the extreme end of the scale a standard light bulb could be on special for 80 cents – while a top-of-the-line alternative with a 20-year lifespan could cost up to $100. These kind of figures can make the switch feel like a decision for another day.

Is the cheapest bulb the cheapest option?

Environmentally it’s not. Twenty-seven per cent of New Zealand’s electricity is still generated by burning fossil fuels like coal and gas, which pumps carbon dioxide straight into the atmosphere. CO2 emissions wrap around the earth and trap the sun’s heat, and the more CO2 we emit, the faster the world’s climate heats up. Switching light bulbs, however, has an immediate impact on electricity use, which both reduces CO2 emissions and slows demand for new generators.

But even if you forget about the impact on the environment, cheap light bulbs still end up costing you more. Buying a 25 watt CFL light bulb for $7 costs you a few more dollars on the day, but it can save you nearly $20 a year on electricity costs – or $110 over its lifetime. So whichever way you look at it, the simple switch is a smart idea.

Today’s energy-efficient light bulbs come in all shapes and sizes, so we visited www.rightlight.govt.nz and www.consumer.org.nz for the lowdown on the best bulbs for home use.

What about LEDs?

LEDs are about as energy-efficient as CFLs so are another very good choice. More impressively they last for more than 20 years with normal household use, which makes them particularly useful for hard-to-reach areas like over stairwells or in homes with very high ceilings. But they remain expensive – one light bulb can cost up to $100 – so for now are out of reach for most of us. However, LEDs are expected to continue dropping in cost and become the light bulb of choice in years to come.

Are there any risks?

CFLs and fluorescent tubes do contain small traces of mercury. High doses of mercury can be toxic, causing damage to the brain, kidney and lungs. So if you break one and gasp in fright, you could be breathing in some mercury. The Ministry of Health has assessed the risk from mercury exposure following breakage of CFLs and found that because of the very small amount of mercury contained in a CFL adverse health effects were very unlikely. It’s still recommended you open doors and windows after breaking a bulb to ventilate the room. LEDs do not contain mercury.

Bright ideas: some lighting options

*If used for three hours per day at a cost of 22.97c/kWh

Sources: RightLight. 2011. http://www.rightlight.govt.nz; Ministry of Health. 2009. Screening Level Risk Characterisation for Mercury Exposure from Compact Fluorescent Lamps. Prepared by Toxicology Excellence for Risk Assessment (TERA); Ministry of Economic Development.