Consumption surprises

I've had my shiny new Flukso running for five days now. Man, what a rude shock I got…

I knew that we were a high-consumption household, but didn't realise how bad it was. Our base load was around 1 kW! So, I started looking around for the main culprits. One of them was no surprise: I'm running a mid-2008 Mac Pro with eight Xeon cores 24x7. Together with its UPS and a few bits of associated gear (5.1 sound system and external disk), that draws a cool 300 W.

So, step 1 is to move all the services I want 24x7 to a Mac Mini that draws all of 10 or 11 watts, and turn off the Mac Pro when it's not being used. That's a $650 saving per year right there!

The next thing I picked up is a second fridge that I have in the garage. That thing is 14 years old and on its last legs. It turns out that it almost never turned off, pretty much permanently drawing 150 W. That thing is headed for the dump, to be replaced with something energy efficient, or maybe not to be replaced at all. No fridge at all is a lot cheaper than a new energy-efficient one…

Taking care of these two knocks my stand-by consumption in half. Not bad. That Flukso will have paid for itself in three months!

We also have a 9 kW ducted air conditioning system. It gets used rarely and, on the days where I use it, I don't mind paying for it, even though it's expensive. After all, that's why I got it in the first place. But what I didn't know is that the system has a heater around the sump. The job of the heater is to stop the refrigerant from liquifying and pooling at the lowest point of the system, which is the compressor. If the compressor tries to pump liquid gas, that's instant compressor death because liquids are not compressible.

The astonishing thing is that this heater is on 24x7 and consumes 160 W! Never mind that we don't use the aircon for at least seven months out of twelve. So, turning off the aircon at the switch board in autumn and spring makes another big difference. The only glitch is that, after turning the power to the unit back on, we have to remember not to actually run it for the next 24 hours, to make sure that heater has had enough time to turn the liquid back into gas.

With that taken care of, I'm now down to a stand-by load of about 200 W. I've identified some of that. Various wireless access points, modem, external backup disks, TV on stand-by, stereo on stand-by, cordless phones, etc. For many of those things, turning them off isn't worth the hassle. For example, the TV draws all of 3 W when on stand-by. I also measured a Sharp microwave that is 24 years old and still working fine. Gratifyingly, that microwave draws only 2.5 W when not in use!

I still have to figure out where about 95 W of the remaining phantom load are coming from. Oven and hotplates don't draw any significant amount, as far as I can tell. I can't measure those directly because they are wired in, so I need to compare consumption by turning them off at the switchboard. The Flukso isn't super-accurate with my 400 pulse/hour meter at low power levels, but it doesn't look like there are worthwhile savings there. And I don't really want to walk into the garage to turn on the hot plates every time I want to cook…

Other possible culprits: alarm system, smoke detectors (unlikely), another microwave that I haven't measured yet, a coffee machine, and maybe one or two other things I don't even know I own…

Still, this Flukso is probably the most cost-saving device I own besides my PV system. I've just ordered a bunch of energy-efficient MR16 bulbs for high-use areas, to get rid of those pesky 50 W halogens. I think I can save around $1500 per year all up without taking things so far that they become inconvenient.

So, thanks Flukso!

My only complaint is that the Flukso has turned me into a consumption fanatic. Oh the power of knowledge…


DriekdeGadgetfreak's picture

Nice story! Should have done this before the PV-system.



petur's picture

2 days ago it was our yearly meter check, and thanks to using flukso to be more energy efficient, we knocked off 700KWh compared to the year before. Main changes were an even less consuming NAS, several devices on timers so they are off completely at night. I also used a more accurate powermeter for checking individual devices.

the_roggy's picture


fusionpower's picture

Nice post. Its always interesting to read other peoples experiences.

Some thoughts i had about some of the items you listed.

The alarm system, check the battery is ok as otherwise it could be wasting a bit of power constantly trying to charge rather than float the battery.

The smoke alarms (mains powered) will probably use more power that you would think but unless you have dozens of them they don't add up to much. Here is an excellent article on the subject.

Also the garage fridge. There is a very nice article here about converting a deep freeze into a super efficient fridge (0.1kWh per day!). It may be worth a look.

michi's picture

Thanks for the tips!

The alarm system draws 10W pretty much permanently. It has a large brick-style power supply. I haven't checked the specs on that but, from its weight, it's a transformer supply, not a switched one. I might check the current requirements. If feasible, replacing that supply with a switched one could save a few watts.

Only two smoke alarms in my house, and I think I can safely ignore them, with routers, backups, wireless access points an the like contributing far more. Even if I disconnected the smoke alarms, I'd never notice.

I saw that article, thanks! It's a nice idea. For now, I'm simply doing without the second fridge. If it turns out that I really need one, I'll probably get an energy-efficient model.



icarus75's picture

Going from a 1kW to a 200W base load means you're now the proud producer of 800 negawatts. And with just a bit of 'maintenance' you can keep on producing them. Way to go!

michi's picture

True :-)

I find it personally satisfying that we are consuming less simply because that's the Right Thing. And, obviously, I don't mind saving $1500 per year :)

It's also satisfying that, the way it looks, our house will be a net producer of electricity. Over 12 months, we'll probably generate around 5-10% more than we consume. I'll have to wait for another 11 months to see how accurate my estimates are. At worst, we'll be breaking even; at best, we'll put back more than we take. That's nice to know :)


michi's picture

I now have a full year's worth of data, both production and consumption. The long and short of it is that, for every kWh we import, we export 1.6 kWh. So, our house has turned into a net producer of electricity, which is gratifying.

In terms of return on investment (taking into account feed-in tariffs for Queensland, Australia), the system pays us $2,200 per year. That's in contrast to the $2,400 annual electricity bill we used to get, so we are about $4,600 better off in terms of cash flow per year.

After three years and six months, the system will have paid for itself. Thereafter (assuming no change in the current feed-in tariff), it will pay us nearly $200 per month, tax free.

Putting the whole thing through a return-on-investment calculator, annualised ROI is 28% after tax, that is, around 37% pre-tax. If only I could find other investments that, risk free, return 37% per annum… :)