I can’t find any technical data on one of our two existing air conditioners. It’s 1960s through-window technology, and it seems it might be somewhere around 130% efficient. A run-of-the-mill air conditioner today is about 400% efficient. What I do know is, when that air conditioner runs our power consumption spikes 2kW; for the cooling we’re getting, this suggests we should be using 700W. It’s costing 40 cents/hour more to run than a modern unit, and it isn’t providing us with heating. It also sounds like a jet aircraft. We don’t use it much.

If it’s replaced with a $2000 unit, the payback is 5000 operating hours. It actually operates for something like 150 or 200 hours a year, so there’s a more than 25 year payback – which isn’t outlandish, given the existing unit is 50 years old now, but I will be surprised if a unit manufactured today survives that long.

Modern units come with DRED support.

Picking an air conditioner is… complex. We’ve taken our home off gas, so we need some kind of electric heating, which I expect to run daily for a number of hours for four months of the year, and the cooling side is something that will get much less use. So, where I live, I need to optimize my “heat pump” for heating performance – COP in the lingo.

As of March 2020, there are more than 3700 air conditioners with performance metrics listed by the Australian government. Thankfully this data is available is CSV format, so can be folded, sorted and mangled. 2000 can be eliminated because they’re not single-split units, so their efficiency will suck balls. Another 450 can be eliminated because they’re not the classic wall hung variety, so will be stupid expensive. Anything smaller than 3KW and larger than 5KW is badly sized for the areas I’m looking at, so now I’m at a “manageable” 300 units. Purging others for efficiency reasons, and I’m down to less than 80. I sort for COP, and start down the list.  The first is $2550, then $1420, then can’t be purchased anywhere, then $880 (a ten-year TCO of $3000, plus installation). A feature check confirms it can be set to a weekday operating cycle and a weekend cycle; we’re off to the races. I locate a supplier who will deliver two for $1,716.00 after trying the local retailer who refuses to answer the phone.

Now for the easy task: I’ve simply got to find a tradie to install my units.