Feature

LEDs Can Slash Your Total Lighting Wattage

By Victor Bivell

LED lighting has arrived and it can slash the power needed to light your property. In my case, I've just reduced the total lighting wattage for our home by two thirds - from 3,144 Watts to 1,033 Watts. The reduction in the high use areas such as kitchen, dining, lounge and bedrooms is even more dramatic - from 2,825 Watts to 735 Watts or 74 per cent.

It was easy to do. To begin, all I needed was a bit of time and a methodical approach to find all the light bulbs in and around the house and jot down their type and wattage. I wanted to add up the wattage of every light bulb to find out our total lighting wattage. I was a bit shocked to discover I supported 75 light bulbs with a combined wattage of 3,144 Watts.

As we completed a major extension only three years ago and had installed more compact fluorescent bulbs than I care to remember paying for, I'd been under the impression that our home lighting was energy efficient. The audit proved that well and truly wrong. In the old part of the house I found numerous incandescent light bulbs with surprisingly large wattages, and there were also some big Watts in the ancient fluorescents that I knew were there.

Because light bulbs come on individually it's easy to think of them as separate and small power users. But when you think of all the lights together as a single system, 3,144 Watts or 3.144 kW is a major appliance in the same category as our electric solar hot water booster which draws 3.6 kW and our reverse cycle air conditioner which can draw up to 2.9 kW.

Clearly there were some easy savings in energy and running costs to be had.

On the big numbers side, the biggest saving was replacing two very old heat lamps in the bathroom. We never used these except on very rare occasions when we needed a very bright light or someone accidently flicked the wrong switch. The heat lamps were 350 Watts each so it was easy to replace these with two 9 Watt LEDs. 18 Watts replaced 750 Watts, and being daylight colour they seem just as bright.

In the high use areas of the house, the biggest reduction was in replacing 9 halogen downlights that were 50 Watts each. There are seven in the lounge and two in the kitchen. They were put in when we did the extension and I had it in my mind that they were low wattage, about 20 Watts each. In fact they were 50 Watts each for a total of 450 Watts. I replaced them with 5.5 kW LED downlights that just slotted into the existing fittings. So 450 Watts became 49.5 Watts. Looked at another way, at 49.5 Watts we could run all nine downlights with slightly less power than needed to run just one of the old 50 Watt downlights. That's impressive.

I also replaced all but one of the numerous compact fluorescents put in as part of the extension and renovation. That hurt a bit as they are 25 Watts each and there were 28 in total in the lounge, dining, kitchen, hall, bedrooms, bathrooms and landing.

These were replaced with 9 Watt LEDs. 700 Watts became 252 Watts. Again, a huge gain in efficiency and saving on future running costs for these high use areas.

The one light I didn't replace is high in the stairwell and too hard and a bit dangerous to reach. That can wait until it burns out.

Left: The Philips 5.5W 12V LED downlight used to replace 50W halogen downlights.
Right: The 9W Osram LED globe used to replace 25W compact fluorescent globes.

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There were also some other good savings around the house.

The very old incandescent flood light for the backyard clothesline was 275 Watts. It's replacement is a 13 Watt LED floodlight. That's a 21 fold gain in efficiency.

Also outside, the front verandah light was a 100 Watt incandescent globe. It is now a 9 Watt compact fluorescent that was made redundant from another part of the house. One day I'll replace it with a 4 or 5 Watt LED but in the meantime I'll get some useage out of it.

Likewise, some of the lamps around the house were already 9 Watt compact fluorescents but as they are not high useage I'll replace them at some future time when they burnout or I get another efficiency rush.

Two exceptions were a 50 Watt halogen desk lamp that was replaced with a new 8 Watt LED lamp, and a 28 Watt incandescent lamp in the entrance hall that was replaced with a 4 Watt LED.

I dropped the two halogen lights in the range hood from 20 Watts each to 10 Watts each with no noticeable loss of light, and I replaced the broken 25 Watt oven light with a 15 Watt globe.

In the garage I replaced three very old fluorescent globes with two compact fluorescents. That reduced the combined wattage from 108 to 46. I may still try a 14 Watt LED at some stage.

I left the other eight ancient fluorescents in the shed, toolshed and carport as they are very low useage and it is not worth the high cost to change the fittings.

Cost wise, the make over was not too painful. I bought 44 LEDs, two compact fluorescents, two halogen rangehood lights and an oven light for $560.00. I think that's good value. The LEDs should last 15,000 hours each, so if we stay put I don't expect to change too many more light bulbs in the next 10 or 20 years.

I also spent $180 on buying and installing two new bayonet light fittings in the garage to replace the dying fluoros, and $7 on a new desk lamp.

I expect to get the outlays back in savings reasonably quickly. With a family of five, lighting gets a good workout, and even more so in winter when it's dark at five and lights may stay on until late in the evening.

Under the old 2.8 kW of high and medium use lights, it wouldn't take too many lights and too many hours to notch up a few kilowatt hours each evening. Under the new 0.7 kW of high and medium use lights, it is going to take four evenings to use the same number of kilowatt hours. And the improvement in running costs starts with our next power bill.

The payback time will vary with each light, but let's look at one high use example - the dining room lights which get a good work out every night. Let's say this averages four hours per night. Where we used to draw 100 Watts we now draw 36 Watts, a saving of 64 Watts, 256 Watt hours per night or 1 kWh every four nights. We pay about 25 cents per kWh and the four LEDs cost $51.80 which is equivalent to 207 kWh. So it will take about 828 days or 2.2 years to recoup the cost.

Clearly, property owners who change to LEDs can slash their total lighting wattage and their lighting running costs.

Likewise, for owners of rental properties, LEDs can reduce the costs for tenants, perhaps making it easier to ask for a higher rent or lease or make the property more appealing to the right tenants.

Another benefit of going down the energy efficiency route is that it means any future solar photovoltaic system that gets installed on the property can be smaller and cheaper, as can any future energy storage system.

For me, the next question is what to do with two boxes of used lights bulbs? One, full of ancient high wattage incandescents and halogens, will go out with the next council clean up. The second box is full of good compact fluoros that will be farmed out to family, friends and a charity shop.

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