I want an energy efficient house. However I don’t want to move or build from scratch. So I have decided to see what I can do with my 80 year old double-brick house here in Suburban Adelaide, South Australia. This post talks about the steps I have taken over the last 3 months to roughly halve my gas and electricity bills.
I once worked with a guy whose mantra was “If you can’t measure it, you can’t manage it”. So the first step was to audit my electricity use with this $40 power meter from Jaycar:
You plug this puppy in line with an appliance to get voltage, current, and most importantly the power in Watts. It can also add up the power used over time to give you the total energy used in kWh. This is really useful when the power used by the appliance varies. For example a fridge motor starts and stops over the course of a day.
So I wandered around the house for a few days, irritating my family while I plugged the power meter into various appliances and working up the results in a power audit spreadsheet (here is the power audit spreadsheet in Excel format).
Some appliances (like the air conditioner and stove) were directly wired in and couldn’t be tested using the power meter. So I worked out how to measure power from the household electricity meter. I have a really ancient one like this:
The more electricity used, the faster the ring spins. On my meter is says that every 400 revolutions is 1 kWh. So if it rotates 400 times in one hour, then I must be using an average power of 1kW. A little maths and I worked out that the instantaneous power in Watts is given by P=9000/T where T is the number of seconds it takes for the ring to revolve once. For example as I write this the ring is taking about 18 seconds to turn which means the house is using 500W. With two TVs and a few PCs running, that is about right.
To measure stuff like the air conditioner I would first make sure loads like the fridge/pool were switched off (I didn’t want them switching on by themselves half way through my measurement). It also helps to have no one in the house, as the electricity jumps up and down all the when people (especially kids) are in the house. Then I would look at the power before and after the appliance was switched on, and subtract the two measurements.
One interesting test was to switch off everything. You see I wanted to make sure there were no “phantom” load sucking power that I didn’t know about, like a suspect alarm system or IR sensor light. Switching everything off (i.e. using no electricity) was really hard – just try it! I had to chase all the kids out of the house (to avoid TVs, lights being switched on and off), and run around the house switching off the fridge, my server etc. All that was left was a few clocks (too much effort to reset) plus stuff that was permanently wired in (like IR sensor lights). The minimum was about 70W. Not zero, but about what I expected.
Electricity Audit Results
Anyway, back to the power audit results. There were some shockers. For example my sons desktop PC uses more energy off (20 hours off at 28 Watts/hr) than on (4 hours on at 91 Watts/hr). It uses more power off than my laptop does on!
Standby power was also a big problem for the older appliances like TVs and VCRs. Some of the newer DVD players were much better, drawing 0W when off.
The effect of 24 hours is interesting. Just wasting 20 W/hr adds up to nearly 500Whr/day (180 kWh/year)! Add that up across several appliances and it really starts to stack up.
There were also some pleasant surprises. Before starting the audit I was sure that my server would be the main power culprit, however combined with my DSL modem and a hub it only uses about 20W. This I totally have Linux to thank, it runs a powerful server on a 10 year old P133 PC. It’s a file server (SAMBA/NFS for both Windows and Linux machines), print server, DHCP server, firewall, SSH server for remote login, runs a small web server. All on an ancient P133 with 64M of RAM.
OK, so here are the steps I took to increase electrical energy efficiency:
- Conduct an Energy Audit to sniff out the culprits. Many surprises here, both good and bad.
- Used a Floatron to dramatically lower pool energy requirements.
- Switching off at the wall standby power loads at night, like TVs and PCs. Grumble. I wish there was a box that could do this for me, or that beeped in my kids ears when they forget.
- Swapped out nasty incandescent light bulbs for compact fluorescent (CFLs).
- Swapped out nasty halogen downlights for LED downlights.
- Encouraged the use of laptops (20W) rather than desktops (90W).
- Where possible use my laptop on mains rather than battery power, as I have read the charging/discharge cycle is only about 50% efficient
- Placed my home office equipment on a separate power board than can be switched off at night, while leaving my server running. Previously I just left everything on.
- Promised my 9 year old son an extra $1/week if he remembers to switch his PC off at the wall every day. Good training, teaches him “the value of energy”. I figure that energy efficiency is going to be a much bigger issue in his life than mine.
Most of these changes cost me very little, they mostly paid for themselves by the next power bill.
When you start to look around it’s amazing what you find. In my family room I have two light fittings which had 5 60W lights each. That’s 600W total for one room! The funny thing was that with the dark walls in that room the light still wasn’t any good for reading. Now I have a pedestal lamp with a single 11W CFL – it’s direct lighting actually makes reading easier than the previous 600W of indirect light.
In the kitchen I replaced 4 nasty 60W Halogen downlights with 3W(!) LED downlights:
The LED versions aren’t quite as bright, and my wife Rosemary wasn’t very happy with them at first. However we are now quite used to them. Compared to CFLs they were expensive at $30 each, but I figure the payback is a little over 1 year. Thats one good thing about working out the numbers with something like a power audit, you can make educated decisions on where it is a good idea to spend money.
Also, I have to admit there is just a good feeling about being efficient. Not everything in life reduces to economic, dollar based decisions like payback period. Sometimes it just has to feel right. That’s enough.
Hacking my House – Insulation and Air Conditioning
To attack the gas consumption we had a hard look at our insulation and air conditioning options.
In August 2006 my wife Rosemary was shivering through our vicious Australian winter and suggested we get a reverse cycle (heat pump) type air conditioner. Actually in Australia we are blessed with fairly mild winters (it rarely gets to freezing). However as a result building codes are lax, and most houses have single glazed windows and poor insulation. During a winters day when it’s 15C outside, it’s often 15C inside. I have several Norwegian and Canadian friends say that their coldest winters have been in Australia!
The current, socially accepted solution, is to bolt a massive reverse cycle ducted air conditioner onto the energy sieves we call houses. In winter they heat, in summer they cool. These air conditioners can draw up to 8kW and often require a 3 phase power connection to the house. When I step outside on a summers day I can hear them roaring all over the neighborhood. Our electricity companies are creaking under the load, especially in summer, as more and more are being retrofitted to older homes like mine.
Our house (which is gas heated) was unpleasantly cold in winter. In summer it was too hot, our old evaporative air conditioner just wasn’t cutting it. So we asked for a few quotes on reverse cycle air conditioning. About $15,000 plus the cost of a three phase connection. Plus I figured significant ongoing electricity bills. Running 8kW means $1.20/hour and rising each year as electricity costs go up. Ouch.
So I decided as a first step to look at our insulation. No point pumping all that heat into/out of the house if the insulation was just going to let it all leak out again. Sure enough, our insulation was shot, so I arranged to have new insulation put in.
The more I thought about it, the more I felt bad about a big reverse cycle air conditioner. So I decided to upgrade our evaporative unit, by getting new ducting (the ducting was ripped) with a high insulation standard. We have mainly dry heat here in Adelaide, so evaporative is fine most of the time, and it draws between 500 and 1000W, a fraction of a heat pump.
After reading about household heat loss, I realised that my standard, single glazed windows were a big problem. Swapping to double glazed windows would be a big job (new frames in all windows) so after some research I decided to install some special laminated glass called Pilkington Comfort Glass that has insulation properties almost as good as double glazing.
Curiously, a few people I discussed this with thought I was wasting my money. Why not, they suggested, install some nice looking new window frames for the same money? I figure this is evolution at work, these people will be naturally selected out of the population if we ever face energy shortages.
Results – House 2.0
We installed our new insulation and windows in August (end of our winter). That day we switched off our gas heating and it wasn’t needed again. Normally we would still be using it (off and on) until October. So we are far more comfortable and using less energy. Nice.
We experienced the first warm weather in November; a week of 30C plus. I only needed to switch on the (evaporative) air conditioner at the end of this week, and then only right at the end of the day for a few hours. This is amazing – last year we had the air con running all day in weeks like that. When I walk outside I can hear the roar of air conditioners (big nasty reverse cycle heat pumps) all over the neighborhood. At night we open up the house to capture the “cool” night air inside. Then in the morning we shut the doors. The only problem we noticed is that the air inside gets a little stuffy. So we have started using a couple of fans, just to give the cool air some movement. Ceiling fans would be perfect I think.
Since then we have had several weeks of 40C weather. The inside temperature hasn’t been above 25C, although on the hotter days we run the evaporative air conditioner most of the day, on a moderate power setting. Last year, before the house 2.0 upgrade, even at full power the air con just wasn’t up to it.
We just received our latest electricity and gas bills. Electricity dropped from $509 to $272, and gas from $413 to $168. Gas usually drops this time of year, so the true test will be next winter. However it’s still the lowest gas bill we have had in years.
Energy efficiency, or Negawatts can be considered a really cheap, easily available new power source equivalent to at least halve our current energy consumption. Low hanging fruit. Much smarter than building new power stations, and lowers the bar for converting across to renewables.
I am working on some related projects:
- We have just had a solar hot water system installed. This should drop the gas bill even further, as we get almost all of our water heated by the sun now. Totally makes sense in a country like Australia.
- We are getting a 2 kW grid-connect solar electric PV system installed.
- I am recycling a small car into a Electric Vehicle (EV)! Totally out of my depth on this one (it’s very mechanical) but slowly making progress.