Is it time to invest in LED lights?

When electric lighting replaced candles, whale oil and kerosene lamps about 80-100 years ago, the incandescent bulb became our main type of light. Incandescent bulbs work by tungsten filaments becoming white hot and giving out light. To get whitish light, the filament has to reach 3025°C, where 90–95 per cent of the electrical energy dissipates as heat rather than light, meaning they use an awful lot of electricity to create a small amount light.

The next innovation was Compact Fluorescent Lamps (CFLs), where electrical energy causes electrons to collide with mercury gas molecules, which subsequently release light as they revert to a stable lower energy state. Because not as much heat is generated, they are about four times as efficient as incandescent bulbs and last eight times longer.

More recently, LED (light emitting diode) light bulbs have appeared. In LEDs, silicon layers are spiked with chemicals that create either an excess of electrons or a shortage in a patchwork across the wafer. An intrinsic electric field keeps things in this state, and when an electric current is applied, the excess electrons are freed to move to fill the areas with shortages, releasing energy as light in the process. The upshot is there are no moving parts or any thin filaments to burn through and that makes for great reliability. They are more than five times more efficient than incandescent bulbs.

Do they need a special installation?

Most energy saving lamps are designed as retro fit and don’t require any rewiring, and all bulbs are available in common sizes and base caps, so it is pretty easy to replace your current light with an LED. Even down-lights recessed into the roof cavity and dimmable versions are available.

However, it’s likely that fitting LEDs as recessed down-lights could shorten their life. Even though they are very efficient, LEDs still create a small amount of heat and if this isn’t allowed to dissipate it can affect the sensitive electronics in the lamp. A good clearance space around the lamp will help reduce heat build-up. Because of their heat-sensitivity LEDs aren’t suitable for fully enclosed spaces that can heat up, such as waterproof outdoor light fittings. It’s a good idea to ask your LED retailer for advice on how suitable your current fittings are.

For both LED and CFL bulbs, it’s also much more expensive to make them in dimmable versions and dimmers also cost about $100 each. A cheaper alternative may be to just have lights on different circuits so you can switch some off.

How do they stack up against CFLs?

The long life of LED lights and CFLs makes them particularly useful where it is difficult to replace bulbs, such as in areas with high ceilings and also saves on the ongoing cost of purchasing new lamps.

Whereas CFLs take from 2-60 seconds to brighten fully, LED bulbs reach full intensity almost instantly, and both can be purchased in varying shades of white from very warm to cool white.

LEDs are about 1.5 times more efficient than CFLs.

CFL bulbs contain small amounts of toxic mercury, raising safe disposal issues, but LEDs do not contain any mercury.

Costs vs savings

When they first came on the market in 2009, LEDs were pretty pricey with an average bulb sitting around the $100 mark. But the price of LED bulbs has been falling quite rapidly (whereas other bulb prices are stable).

We compared LEDs with the other two main types of bulb in the table below. Assuming an annual use of 2000 hours or 5.5 hours per day, and if we include the cost of replacement bulbs at expected intervals and keep electricity at 30 cents/kWh, the incandescent bulb, while having a very cheap initial outlay, proves to be dramatically more expensive. LEDs on the other hand, while more expensive up-front, are the cheapest in the long-run.

So if you changed 5 x 75W bulbs from incandescent to LED and used them on average for 5.5 hours a day, then over five years the incandescent bulbs and electricity would have cost $1145 – versus only $315 for the LED lights. That’s a whopping saving of $830 on just five lights!

There would also be an environmental saving on carbon dioxide production. Each kWh of electricity generated in NZ produces 0.13 kg of CO₂, so using five LEDs would save 3100 kWh of electricity, which represents a saving of 403kg of CO₂.

As you can see in the table, you can break even on a change from incandescent bulbs to LEDs within a year, and from there the savings build. And if electricity prices continue to rise, the greater the saving and the more LEDs become superior.

The verdict

LEDs are the future and mean savings for your pocket and on our energy generation and CO₂ emissions. If finances are tight, CFLs are currently a cheaper alternative than LEDs and are still more sustainable than incandescent bulbs. So to save money and the environment, whether you choose LEDs or CFLs, phase out incandescent bulbs.