Comfortably ahead – A tale of two heaters

Tale_of_two_heaters

Turn on your air conditioner—and knock hundreds of dollars off your heating bill. Tim Forcey describes the learnings (and savings) gained from his experiment with reverse-cycle electric heating.

Over the last 20 years my wife and I have raised a family in our 100-year-old Melbourne bayside weatherboard home. Last spring, following our third partial renovation, we installed two air conditioners in preparation for the hot summers to come—particularly so my wife and I could stay comfortable when working at home.

The two air conditioners we chose did just that, easily cooling our full ground-floor living space (128 m2 consisting of seven rooms and a hallway). Based on advice from Matthew Wright (founder of www.pure-electric.com.au), we opted for two top-of-the-line Ururu Sararas (US7s) manufactured by Daikin: one small wall-mounted unit in our front bedroom (2.5 kW rated for cooling) and one medium unit (3.5 kW) in the lounge room.

The total US7 rated cooling capacity of 6 kW contrasts with a 14 kW multi-headed unit that the salesperson said we would need. So lesson number one: avoid the up-sell if your house is reasonably well-shaded and insulated (see box for more on sizing).

Come winter, I was keen to learn how these reverse-cycle units would compare with our 20-year-old ducted gas heater in terms of health, comfort, convenience and operating cost, particularly following on from research by Beyond Zero Emissions and the ATA (ReNew’s publisher) into the potential for economic and environmental benefits from going off gas.

My findings? There were pluses and minuses when comparing the two heating methods on comfort and convenience. But when it comes to cost, the reverse-cycle air conditioners beat ducted gas hands down—not only for our home, but possibly for hundreds of thousands of homes around Australia.

Science—sort of—in the home
Starting in late June 2015 (mid-winter), I sought to heat our home on alternate days using the US7s and then ducted gas.

The US7s are heavily instrumented and can tell you the outdoor temperature, the indoor temperature, the indoor humidity and how much electrical energy they have consumed since you turned them on today, or since you installed them last year! Adding to this, I spread thermometers throughout our living areas. I also referred to our in-home electricity display that relays instantaneous electricity-use figures for our whole house from our smart electricity meter.

And for the first time in my life, often wearing a bathrobe and head torch, I journeyed out behind the bushes to the not-so-smart gas meter to diligently record gas usage.

I will not claim that this exercise was the best example of the scientific method we have seen. Variables and shortcomings had to be managed, such as failure to focus on the task-at-hand at 5.30 am before the morning coffee, Daikin’s less-than-fully-illuminating owner’s manual, and my co-occupants.

Read the full article in ReNew 133.