Harvest Hot Water

Your Canberra heat pump hot water specialist

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Yes, they do! If you have a reverse cycle air conditioner and it works, then yes, a heat pump hot water system will work too. It’s exactly the same technology.

It’s also important not to over-state the severity of Canberra’s climate. Even in the depths of winter, the afternoon temperature is usually over 10 degrees, and that’s the best time to run a heat pump:

Mean temperatures by month in Canberra

Time of day \ MonthMarchAprilMayJuneJulyAugustSeptemberOctober
Mean 3 pm temperature (℃)23.519.114.911.410.612.615.118.3

In fact, Standards Australia recognised back in 2011 that more and more people were installing heat pump hot water systems in cool climates like Canberra. They introduced a new climate zone that year, specifically to cover heat pumps designed for cold climates. Canberra was designated the representative location for that zone. The Clean Energy Regulator’s 2017 register of heat pump water heaters listed 171 models which had passed the testing and modelling requirements for cold climate operation.

Modelling has been undertaken for all the heat pump hot water systems we provide. For example, the larger Stiebel Eltron heat pumps (WWK302 series) earn 30 STCs (Small-scale Technology Certificates) in the ACT. Each STC is equivalent to 1 megawatt hour (MWh), or 1,000 kWh of electricity. What that means is that these heat pumps use 30 MWh (or 30,000 kWh) less electricity over a ten-year period than an equivalent standard electric hot water system.

Similarly, the modelling shows that the larger Midea heat pump hot water systems use 31 MWh (28,000 kWh) less electricity over a 10 year period than a standard electric hot water system.

Cold climate features of our heat pump hot water systems

All of the heat pump water heaters that we offer have features which ensure smooth cold climate operation. Firstly, the refrigerants used in our various heat pumps boil at extremely low temperatures. For example, R134a boils at -260C. This means that even at very low temperatures the system will work, extracting warmth that exists in the air even at low ambient temperatures.

Secondly, all our heat pumps have frost protection functions. These ensure that in the event of the evaporator mechanism becoming frosted during cold weather operation, the heat pump will de-frost automatically. This process takes 5-15 minutes, after which normal operations resume.

Thirdly, when the ambient temperature falls below 5 degrees, the HP170 automatically switches to electric boost mode. This is a sensible shift that avoids placing pressure on the heat pump during the infrequent occasions when it would be operating at low temperatures. As for the HP280, when the ambient temperature falls below 20C, it switches to combined heat pump and electric booster operation.

Finally, some of our models, such as the Earthworker Reclaim and the Midea heat pumps, include electronic control panels with timers that allow selection of the optimum time to run them – normally in the middle of the day. This also provides scope to optimise their operation to match a particular household’s needs. For smaller households who typically have showers in the morning, it makes sense to set the heat pump to run during the afternoon when the air temperature is highest. It may only need an hour or two to restore the tank temperature. For larger families, longer operation will be needed, but even then this can be set for the optimum time of day. And while this means the heat pump use daytime electricity, they don’t use too much of that. If you have a rooftop solar system, even in winter you will be able to power most of your usage from your rooftop.

But my plumber says heat pump hot water systems don’t work in Canberra

Yes, well … Canberra does have a dark history on that front. Back in 2009 and 2010 when generous rebates were available, a large number of heat pumps that were poorly made or were otherwise unsuitable for use in Canberra were installed here. From product reviews we’ve seen, the electronic controllers were unreliable, the units leaked water, they were noisy and they did not withstand frosty conditions particularly well.

But that is not to say that heat pumps don’t work. Certainly poor quality products and those which have not been designed to operate in cold climates will fail, but better quality products will work perfectly well.

You might have heard your plumber say `don’t buy a heat pump. They don’t work!’ That goes back to the dark days of the rebate-driven boom in 2009 and 2010, when a lot of dodgy heat pumps were installed. And they were provided by two of the best-known hot water system companies! They failed because many of these had no frost protection mechanism, and in some cases they were poorly installed.

Surely it’s too cold for a heat pump to work in Canberra, especially in winter?

It’s true that the warmer the air is (that is, the ambient temperature), the more efficiently can heat pumps work. It stands to reason: the more warmth there is in the air, the more warmth the heat pump can extract to heat up your water. But the refrigerant used in our heat pumps boils at – 26℃, so even on the coldest winter day in Canberra – say it’s -5℃, there is still enough heat energy in the air to make the refrigerant boil.

But most of the time the heat pump doesn’t need to operate during very low temperatures. By the middle of the day, even in mid-winter, the temperature is usually over 10 degrees, as you can see from this table:

Time of day \ MonthMarchAprilMayJuneJulyAugustSeptemberOctober
Mean 9 am temperature (℃)16.312.18.35.13.95.99.813.3
Mean 3 pm temperature (℃)23.519.114.911.410.612.615.118.3

So it’s a simple matter of setting the timer so that the heat pump only runs from say 11 am to 5 pm each day. That works for most people, but heavy water users might need a slightly longer timespan. The great thing is that if you have solar panels on your roof, even in winter the heat pump will be mostly powered from your roof.