What is financially the most efficient way to effectively light a room?
SHANE VAN DE VORSTENBOSCH, director at OnSolution, investigates what is financially the most efficient method to effectively light a room.
What is financially the most efficient method to effectively light a room? The wording is critical. It is not just about being energy smart. Overall running costs also need to be considered, as well as adequate lighting levels.
When the Australian Government banned incandescent lights, it let the real power waster go unchecked. It also tried to replace it with an imposter that failed to solve the problem.
THE FIVE KEY TERMS TO UNDERSTAND
To find the best solution there are five key terms that need to be understood. The first three are electrical terms: volts, amps and watts. Volts are the potential of supply and amps are the actual number of electrons that are flowing. While both are important on their own, it isn’t until you multiply them together that they can be compared for efficiency. Multiplying them gives power. The formula is simple: P = I x E (P = power, I = current and e = volts). For example, a 240 volt light drawing 0.25 amps is using 60 watts. A downlight running at 12 volts and drawing 5 amps is also using 60 watts. Both use the same power even though one is 240 volts and the other only 12 volts.
The next two terms appear on the bill. Kilowatt hours (kWh) is simply the power times the duration it is running in hours (divide by 1000 to convert watts to kilowatts). So, a 100 watt light running for 10 hours will use 1 kWh. The final term is dollars – what you pay for electricity. It is the number of kilowatt hours times the unit rate.
Running the 100 watt light for 10 hours will use 1 kWh and cost 25 cents (assuming 25 c/kWh). Running the light for 40 hours will cost $1. So, one 100 watt light on in an office during business hours will cost about $50 a year to run.
THE AVAILABLE ALTERNATIVES
At this stage, the incandescent light bulb is looking guilty. They were normally 80 or 100 watts. They were the highest power consuming globe commonly used. Replacing them with a compact fluorescent power saver dropped the power from 100 down to 20 watts and it looked like the problem was solved. The New South Wales Government website (www.savepower.nsw.gov.au) shows how much money is saved by switching to a compact fluorescent light and, at first sight, it looks good. The figures appear to show that all facilities should now be leaner and greener.
The uptake of fluorescent lights was, however, not great. I think the answer partially lies in the need to ‘effectively light a room’. The quality of light deteriorates with time, they take time to warm up and ageng makes this worse. So, while they may last 8000 hours, by the end of their life they don’t provide sufficient lighting. Low-cost light meters are now available and can be used to demonstrate when lights are far from adequate.
In addition, they don’t last 8000 hours. If a light was left on 24 hours a day, seven days a week, then it should last a year. A light left on for 12 hours a days should last two years. In my house (where they do tend to be left on for 12 hours a day), they are replaced every couple of months.
Furthermore, they are worse for the environment. They contain more metal, plastic, mercury and other chemicals than incandescent lights, and have special instructions for disposal and in case of breakage.
Finally, they often did not fit in existing light fixtures. Smaller units are now available, but initially they were big and cumbersome. So, the proposed alternative to incandescent lights wasn’t viable.
But, the incandescent light is not actually the true problem. The downlight is. Its ‘12-volt’ label meant that it looked innocent. The reality, however, is that these are actually 50 or 75 watts, and many downlights are installed to light a room. So, rooms that were lit by a single 100 watt incandescent light are now lit by six downlights, meaning the power used for one room has gone from 100 to 360 watts.
There is, however, an emerging alternative – the halogen globe. It looks like an incandescent light, works like an incandescent light and provides the same quality of light as an incandescent light, but with 30 percent less energy. It looks like a winner, but it costs 10 times more, has more parts and still consumes a large amount of power (70 watts for a 100 watts equivalent).
In theory, they are also meant to last longer. Personal experience has shown that the promised number of hours is, however, not achieved. It may be the quality of the power in my local area, but I was fortunate to get 500 hours out of any of the types of light bulbs I installed.
The latest option is the LED downlight. The 9 watt LED downlight is now a good alternative to the 50 watt downlight. It turns on immediately, doesn’t age, provides plenty of light and can be used in existing sockets. Anecdotally, its lifespan appears to be significantly better.
THE TRUE COSTS
I did the maths for trying to light a room for 8000 hours:
|Type||Power cost||Light costs||Total|
|1 x 100-watt incandescent||$200||$10||$210|
|6 x 50-watt downlights||$600||$400||$1000|
|1 x 20-watt compact fluorescent||$40||$80||$120|
|1 x 65-watt halogen||$130||$80||$210|
|6 x 9-watt LED downlights||$108||$66 upwards (prices vary from $6 to $19)||$174 plus replacement bulbs|
Downlights are clearly the worst choice financially for lighting an area and, while a compact fluorescent is the cheapest, it is the worst choice for effective lighting. The halogen is just as expensive as the banned incandescent. LED downlights, on the other hand, pay for themselves within months. And, with LED lighting promising a much longer lifespan, the need to replace them less often will only add to their cost saving.
Extend this to a commercial facility and the maths still applies, except the replacement costs are significantly increased due to labour. So, what is financially the most efficient method to effectively light a room? My money is on LED downlights.