lightbulbsA popular frugal habit and one I subscribe to is turning out lights when a room is not in use. I find it a waste when the house is ablaze and everyone is in the same room.

But how much are we actually saving by getting into the habit of turning out the lights?

Well I like cold hard data, so I did some calculations and was a little surprised by the results.

I complicated things a  little by deciding to also compare the old fashioned incandescent light globes and the new CFL globes. I wanted to see for myself if all the fuss was warranted. So I did a comparison first between the cost of using the CFLs compared to incandescent, and then a comparison of the savings per year that can be made by reducing light globe usage.

The results are based on the following assumptions:

  • Cost of electricity is at $0.17130 per kilowatt hour – this amount came straight off the back of my most recent electricity bill. Obviously this amount will differ depending on region and provider.
  • The initial purchase costs of each light bulb is based on the home brand cost of bulbs at my local supermarket. Again differing costs will result in different results.
  • The average lifespan of each light bulb I pulled from here.
  • A 20W CFL globe is equivalent to a 100W incandescent globe.
  20W CFL Globe 100W Incandescent Globe
Initial Cost $3.50 $0.60
Average Lifespan 8,000 hours 1,000 hours
No. of incandescent bulbs to CFLs   8
Total Purchase Cost $3.50 $4.80
Cost to run per hour @ $0.17130 $0.003426 $0.01713
Running Cost over 8,000 hours $27.408 $137.04
Total Cost over 8,000 hours $30.908 $141.84
Total saving per CFL $110.932  

 

Now for savings made by turning out lights when not in use.

Let’s say our hypothetical household of 4 is using all 100W incandescent globes and the average usage for all the lights around the house is 20 hours total per night (5 hours in the lounge, 3 hours in the kitchen, a couple of hours in the bathroom, a few more hours in each bedroom, porch light…) or 7,300 hours per year.

  • Total cost @ 7,300 hours per year based on $0.17130 / kilowatt is $125.049.

Our hypothetical household decides to work on the habit of turning lights off when a room is not in use and they reduce their usage by 3 hours to 17 hours per night or 6,205 per year.

  • Total cost @ 6,205 hours per year is $106.29165
  • Total saving is $18.76 per year

Now let’s assume that our household is using all 20W CFL globes.

  • Total cost @ 7,300 hours per year is $25.0098
  • Total cost @ 6,2005 hours per year is $21.25833
  • Total saving is $3.75 per year 

Is it worth it?

  • Obviously, going off the above calcs, converting to CFLs is definitely worth it. My only caveat is that we should consider disposing of these bulbs safely or recycling them so that the mercury (small as it is) is not ending up in landfill. Contact your local council to find out about safe disposal in your local area and recycling alternatives for these bulbs.
  • For zero effort we’re still saving money by turning lights out. Three dollars isn’t something to get excited about, but it’s not costing any effort to save this. And of course, the savings are greater depending on how much you currently use and how much you can reduce your consumption by.
  • Add to the savings in electricity the fact that turning the lights out when they’re not in use will make them last longer, so you are also reducing the overall cost of purchase as well.
  • By turning out the lights, we’re saving more than just money, it’s reducing our consumption of non-renewable resources. When you compound this reduction in light usage with all the households in Australia and beyond, the overall environmental savings add up.
  • Turning out lights is just one way to reduce our electricity consumption and the cost of the bill. Add to this reducing TV time, turning appliances off at the wall, using the dryer less, using the air con or heating less and the savings become more significant.
  • And lastly (a personal opinion), I think that teaching children to turn lights out when leaving a room and electronics off when they’re not in use is one way to teach them responsibility, to be aware of their surrounding and to teach them that what they do has an impact on others and the world around them. Awareness and responsibility are a couple of of the life skills that I hope to impart to my kids. How many adults do you come across everyday who don’t want to take responsibility for themselves?

So to sum up, getting into the habit of turning out the lights when they’re not being used isn’t going to save you a fortune (and probably won’t even cover the cost of a cup of coffee), but I don’t think that that’s a reason not to do it anyway. At the end of the day, we’re not so much talking about usage as waste. By leaving lights on in empty rooms we’re not using power, we are wasting it.

What do you think?

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