More on Less Power

Working in a company that helps its clients reduce their power consumption has its benefits. One of which is I have at hand quite a few tools that I wouldn’t normally invest in. A year or so ago we came across the ETrack, a power monitor which was being manufactured and sold by Bridex Harwal. They’ve since stopped production and no longer support it, but we did pick up a few units for clients as well as for our own use.

One of these we mounted in a junction box and it’s our portable power meter which we use to demonstrate how efficient our LED lights or other solutions are. One of the problems the ETrack has is its inaccuracy when measuring very low wattages - we find that anything below about 10 watts doesn’t show accurately. This is a problem because the 6.5W MR16 bulb which we sell to replace 35 - 50W halogens hardly registers on the meter…

On a bit of a power-saving drive, I brought the meter home and started measuring all sorts of stuff around the house. And what I found was quite surprising.

My computer setup is a MacBook laptop with a 17” external monitor, a couple of external harddisks, a little Epson printer and an Epson scanner. I also have an Altec Lansing speaker system, a little box fan and some assorted chargers for camera batteries and so on. Not all the equipment is on all the time and I found that typically, the whole setup consumes about 100 watts when I’m working. The little box fan alone is responsible for about 35 of those watts so the rest of the gear isn’t consuming that much really.

Still, I use my computer sometimes 12-15 hours a day so that’s still a substantial amount of power over the course of a month. As a first step, I cut back on wastage through phantom power. Above my desk is a bank of switches - I’ve now started switching off at the plug devices or chargers that are not being used.

I’ve also changed my sleep mode settings. Now before I put the laptop to sleep, I disconnect and switch off the external monitor and other devices like hard disks. I also unplug the laptop charger and switch that off too so the only power that is being used comes from the battery. I’ll monitor this and update the power savings in a month or so.

The real shock, however, came when I plugged the power monitor in to the fridge. I have an old (about 10 years) Kelvinator which we bought before the advent of energy star stickers. I like the capaciousness of this fridge which comes not just from the large size, but also the adjustable shelves and the very open interior layout. It holds the rolls and rolls of film I have and the bottles of vodka friends insist on buying us quite comfortably alongside the frozen pizzas, tomato and chilli sauce, olives, medicine and other what-nots we insist on cold-storing.

We mounted the power meter in a junction box and use it to measure all sorts of stuff. Came in useful to leave next to the fridge.

As you can see, when the compressor is running, the fridge consumes about 140 watts.

I noted the fridge was consuming about 140 watts when the compressor was running and substantially less when it wasn’t. Then one night when I checked, the monitor showed the fridge was consuming almost 500 watts! It was then I realised the fridge probably had 3 cycles: normal running, compressor cycling, heater on. As I understand it at the back of every no-frost fridge is a heating element which melts the ice build-up. This turns into water which eventually evaporates. I’m not sure if 500 watts is normal for this cycle but it did seem quite a bit.

Even more telling, over the 70 hours I had the power monitor plugged in, the fridge consumed 10.784 kWh. This works out to an average of about 3.7 kWh per day or almost S$30 per month which is almost triple that of a modern fridge. This is roughly equivalent to the amount of power used to boil water in an electric jug. For 2 hours a day, every day...

As the old thing does need some attention (slightly leaking door seals, some minor water leaking and corrosion on the edges of the doors), we decided instead to get a new one and paid a visit to our favourite appliance store, Mega Discount Store and splashed out $1280 on a new Fisher & Paykel E442B which is 3-star rated at approximately 635 kWh annually or less than 1.8 kWh per day. At projected savings of $18 per month, it’ll take almost 6 years to pay it off just in electricity savings, but I suspect we’ll do better as there are only two of us at home (most times) so the fridge isn’t opened with the frequency a typical household would see. Additionally, the old unit is bound to need attention again soon.

The new fridge arrives on Friday and I’ll post the power readings in a month or so.

Meanwhile, if you want to measure the power usage around your house, check out the Kill A Watt meter. AS they say, knowledge is power. In this case, it's power-savings.