Our roaming Home Energy Assessor Peter Goodyear performed an energy efficiency assessment on a home and found himself standing with the homeowner at the power meter calculating just how much energy was being used on the halogen downlights in the house.

“Recently I was performing a home energy assessment at a large two-storey house. The assessment would help the home owner improve his energy efficiency and suggest ways to further reduce his energy bills.” Peter Goodyear said, “The owner was concerned with the huge electricity bills he was receiving. I suggested that the halogen downlights within the house could be responsible. The entire house was lit by downlights and from experience I knew these could potentially have a big impact on electricity bills. Initially he had trouble believing me, so I suggested we have a look at the smart meter and I could explain how it works.”

“The client asked me what the flashing light on the box represented. I explained the light was the power usage light and as its name suggests, indicates whether power was operating within the premises. The faster the light flashes per second, the more power was being used and after 800 flashes it meant that one kilowatt-hour of electricity had been consumed.”

“‘Well, let’s time it to test the halogens.’ he said. And with that my client opened his smart phone to a stop watch application. We both fumbled on timing the start a few times, as the flashes were quick but eventually we managed to time the flashes at once every four seconds, with the lights in the study, hallway and kitchen on.”

“Then we went into the house and switched off the halogen downlights in the hall, study and kitchen. We switched off sixteen lights which used a total of 800 watts, then returned to the smart meter outside.”

“‘Let’s time it again.’ he said and we both leant over his smart phone and timed the flashes again. The power usage light flashed once every fourteen seconds with the halogens switched off.”

“My client was convinced that the halogens had contributed to his huge electricity bill and he said he would definitely get some CFL’s to replace the energy-guzzling halogens.”

If you have a smart meter you can use this simple method to calculate the electrical consumption of appliances.

The smart meter indicator light flashes 800 times per kilowatt-hour of electrical consumption. One flash, therefore means 1.25 watt-hours of electricity has been used since the previous flash.

To find how much electricity your appliance is using, divide the time between flashes into 3600 (the number of seconds in an hour) then multiply that figure by 1.25.

In the example above, the householder had various things such as his refrigerator, freezer and some cordless phones running, so one flash every fourteen seconds indicates they were using about 320 watts just for the fridges, and other devices:

3600 x 1.25 = 321 watts


With the downlights switched on the consumption rate increased to one flash every four seconds:

3600 x 1.25 = 1125 watts


The difference between these two figures is 804 watts, which is close enough to what you would expect for sixteen 50 watt lights (800W). A considerable impact on a home’s energy use which could be improved by using more energy efficient lighting such as CFLs or LEDs.

Peter Goodyear is a fully qualified Home Energy Assessor and has performed up to 150 Home Energy Assessments for Ecovantage in Melbourne since the end of last year.

Home Energy Assessments help you improve the energy efficiency of your home, by correctly identifying your energy use and providing you with solutions to reduce your home operating costs. Contact Ecovantage today for more information on Home Energy Assessments and what they can do to improve the energy efficiency of your home,03  9645 7243 (Metro Melbourne & South Australia Only)