When it comes to an energy-efficient system for a cold part of Australia, there are typically two that stand out: a heat pump that has been put in right or a solar hot water system of the correct size with dependable boosting. In Melbourne and its ilk you will find heat pumps give the most consistent performance through winter; a solar set up is very efficient as long as the roof gets good light and there is some sensible back up.
I am Charlotte Redfern and I like my household advice to be of a kind that can withstand a cold Monday morning. The figures may show one system is the cheapest in southern Australia but in a home they do not always tell the whole story. You have to consider how the hot water is used, the ambient temperature, where the roof is facing, storage, electricity tariffs and the quality of the workmanship, all of which can outweigh an attractive efficiency label.
The Effect of the Cold
Efficiency is impacted by the weather in various ways. The lower the ambient temperature, the more a heat pump’s efficiency will wane as it draws from the outside air. With solar hot water, a lack of sun due to cloud, shading or short days in winter will see the solar contribution diminish. Learn more about readying hot water for Melbourne winter.
Neither technology is for that reason any less fit for purpose. It is a matter of having the right backup and controls. What is a fine system in Brisbane might require different settings or more storage capacity and frost protection in the ACT, the Tablelands or the Victorian high country.
Then There Is Winter Demand
Households go through more hot water in the winter months. People in the shower stay in longer, the bath is filled with greater frequency and guests seem to treat the bathroom like a tropical resort. Running costs will reflect this even if the system is in good order.
Mains water is colder so it takes more energy to warm it; a storage tank has to recover for longer and a heat pump will be in operation more. These are to be expected in the season and are not of themselves an indication of trouble.
Heat Pumps
A heat pump can be well suited to a cold climate if the installer abides by the manufacturer and the model is of the right operating range. By means of an evaporator coil and refrigerant cycle the unit is moving heat from the air into the tank rather than making it.
COP, or coefficient of performance, is the measure of efficiency. Under test conditions a COP of 3 will yield about three units of heat per unit of electricity. But in practice the outdoor and water temperatures, pipework, defrosting and usage will mean results are not so cut and dried.
Operating in Winter
You can get good efficiency from a cold climate heat pump in mild weather. Come a frosty morning and the tank will take its time to heat up and draw more power. Some will put an anti-frost cycle on to look after the evaporator coil, others an electric booster when demand is high or it is very cold.
In alpine or exposed spots a frost protection system is something to have. Put questions to your installer about the minimum operating temperature, how the condensate is dealt with and whether the outdoor unit is to be sheltered from the elements. Just do not put it in a box, it requires an unimpeded flow of air.
Pros and Cons
The appeal is that you use less electricity than with an electric resistance storage tank. An electric element makes heat directly from the current, a heat pump puts the heat already in the air to work. This saves on energy but the cost of buying and installing is generally more.
On the other hand the compressor and fan of a heat pump are not silent and they need room and the right electrical connections. Put one in a small courtyard in the wrong place and the noise will try the patience of light sleepers or you will have condensate on the walkway. Such things are tedious until they are not.
Solar in Victoria
There are solar hot water systems a Victorian household can put in that will do well in winter with enough solar boosting and unobstructed sunlight. The energy is free when you use it but then again an electric or gas booster will have to do more work when the winter clouds roll in and daylight is at a premium.
For where there is a risk of frost a closed-loop system is often the way to go, being able to protect the fluid in the collectors from freezing. One has to look at the system design and what is happening on site to determine the right setup; an installer will be able to put one’s mind at ease as to frost protection, maintenance and pressure.
Roof Conditions
In a sense the roof makes or breaks a solar hot water system. While north-facing roofs have been the norm in Australia, there is no reason an east or west orientation will not do, if that is where the household demand lies in the morning or afternoon. Be aware that trees, chimneys or the like can cast shade and diminish output in winter.
A word of advice before going with solar: inspect the structure of the roof, where the collector will go, the pipe runs and how easy it will be to service down the track. An unnecessarily long run of pipe will cost more to put in and lose heat. Should the roof be in the shade yet you have good photovoltaic panels, you might find a heat pump with solar PV integration a more sensible way to get your renewable energy.
Heat Pump Or Solar?
You will not find a one size fits all hot water system for the Australian cold climate. On a cloudy winter day a heat pump gives you more to go on, whereas a solar set up will draw less purchased energy provided the collectors are in the sun. In the end it comes down to the roof, the electricity supply and how much backup energy the household is prepared to use.
| System Type | Winter Strength | Common Limitation | Best Fit |
|---|---|---|---|
| Heat pump | More consistent than solar when the skies are overcast | The fan and compressor make some noise and efficiency drops in very cold air | For those who want their renewable heating to be predictable |
| Solar hot water | Running costs are minimal in the sun | Cloud and the short days of winter see a drop in what the solar can put in | Where the roof is sunny and well orientated |
| Electric storage | Reliable come rain or shine | Higher running costs and energy use | If the priority is a simple replacement or low initial outlay |
Do not take indicative efficiency figures as gospel. The COP of a heat pump is subject to the test conditions and a published number does not tell the whole story of solar performance. What is of more value is a comparison of whole-of-life costs from purchase and installation through to the time a replacement is due, factoring in tariffs and maintenance.
Safeguarding Winter Performance
Equipment for the cold should be more than a big tank and a brochure. Make sure the hardware and controls are of a piece with your climate, particularly where there are overnight temperature plunges or extended cloud and frost.
- Verify the minimum ambient and operating temperatures.
- Enquire as to the anti-frost cycle, condensate drainage and how legionella protection is handled, including the electric booster.
- Do not be tempted by the smallest tank; the storage has to be in proportion to what the house requires.
- Also check on clearances, pipe insulation, noise ratings and whether off-peak tariffs or solar PV are a fit for the way you live.
Storage Size
There is a fine line with storage. Insufficient and you are left with a cold shower or the booster is called into action; too much and recovery is slow and heat is lost. A family with teenagers and a large bath, or several heading to work at once, is not in the same position as a couple with modest requirements.
Have the installer lay out the usable volume, the recovery time and the backup plan. “Four-person household” is just a figure on a census form. Peak usage and the kind of fittings in the shower are more telling.
On Running And Installation Costs
The bottom line on a heat pump is determined by daily use, the climate, the tariff and the unit itself. You can make a rough calculation of annual demand against seasonal efficiency but a quote ought to reflect the realities of operation, not the best laboratory COP.
Then there is the matter of solar boosting. In winter the system may turn to its electric booster, and if that is set to run in peak hours any savings are eroded. Off-peak is cheaper but the tank must have enough to cover the household timetable.
Installation is another place for surprises
It is rarely as straightforward as putting in a new tank. There could be a need for plumbing changes, a tempering valve, roof access, electrical work or a new base of concrete. Upgrades to the switchboard or hard to reach areas will show up on the invoice.
Put it in writing. The quote should spell out the warranty, commissioning, disposal of the old unit, the type of booster and circuit and so forth. I have known homeowners to be so taken up with the rebate they miss the total for the installation. A discount is a good thing but it will not suit an unsuitable system.
The rebates on hot water systems in Australia
The rebates on hot water systems in Australia are not set in stone; they will vary according to what funding is on the table, the technology and installer you go with, and where you are. A heat pump for instance can put you in line for Small-scale Technology Certificates (STC). Those in Victoria would do well to also look at Solar Victoria for their eligibility and the rules around approved products or installers.
While an STC rebate on a heat pump hot water system is a way to lower the cost up front, its worth is contingent on the certificate arrangements, installation date, location and the system itself. It is worth asking if the discount has been factored into the quote and who is to handle the paperwork.
Before putting pen to paper on a contract in Victoria, have a read of the hot water rebate details from Solar Victoria. The application process, funding and even which products are in favour can be subject to change so do not put any stock in a rebate figure from an old social media post or article.
Other states and territories, the ACT included, have their own programmes to be aware of. But a rebate should not preclude an independent comparison; one should commit only after the total installed price, warranty and energy use have been verified.
Ready For Melbourne Winter
Homeowners in Melbourne would be wise to get their hot water in order before the first morning of ice sets in. With the system still running as it should, see to the tank, valves, pipe insulation and outdoor unit clearance, and review the booster settings.
- Make sure there is no corrosion or leaks to be found on the tempering valve or any exposed pipes and connections.
- Give the area around the heat pump’s air intakes a clear of leaves and debris.
- Verify that condensate is draining off properly and not pooling by the foundation or on a path.
- See that your timer is set to the tariffs and the household’s routine.
- Put the temperature to the test at the tap and put in for a service call if you spot any issues.
- Make sure you know how the frost protection works and what the plan is for a protracted cold spell.
One-Day Household Check
Time is short? Then put safety and controls ahead of any cosmetic tidying. Be on the lookout for anything amiss: a tripped breaker, odd noises, water that is inconsistent or too hot, or damaged insulation. Leave the electrical and refrigeration parts alone.
Winter lends itself to a bit of usage comparison too. Note down the recovery time, if the tank is being run dry at peak times and how much the booster is called upon. An installer will find that more telling than “it seems to be costing me”.
Common Questions Answered
Which System Is Cheapest To Run?
If you have a solar hot water system in the right spot and the sun is out to meet demand, running costs can be minimal. But a heat pump will give you more consistent savings when the clouds roll in and is perhaps the more sensible option if the roof is in shade. In the end the cheapest is a matter of climate, tariff, what the household demands and the cost of installation.
What Is The Main Heat Pump Downside?
Upfront expense, the noise from the outdoor unit, having to deal with condensate and a drop in efficiency in the cold are the principal drawbacks. Some will resort to an electric booster when things get demanding. Properly installed with the right controls these are less of an issue but they are not going to vanish.
Do Heat Pumps Work In Cold Climates?
Many do, provided you choose the right model. You want to see the data on cold-weather performance, anti-frost cycle and operating range. In alpine country or where there is a lot of frost, take some professional counsel.
What Is Most Efficient In Winter?
It is hard to name a winner across the board. A heat pump is the more predictable bet in winter since it does not need the sun. On a good day with little shade, a solar hot water setup might consume less of the kind of energy you have to buy.
How Much Electricity Does A Heat Pump Use?
That is determined by the COP, the size of the tank, showering habits, ambient temperatures and whether the booster is in play. As a rule it will use less of an electric current than a resistance storage tank to do the same job but for the exact figures you need the model data and to know your own consumption.
Are Heat Pumps Eligible For Rebates?
Under the right circumstances and with an approved product you may be able to claim STCs or state incentives. Do not assume it is the case; have the installer put it in writing and check the government programme in question first.
Choose For The Whole Winter
In Australia’s colder climes the most efficient hot water system is the one that fits the home, not the one the marketing says it is. A conventional system has its place for those wanting low cost and simplicity, as does solar on a roof with dependable sun, while a heat pump will see you through mixed weather with good efficiency.
Make a comparison of the likely running costs, warranty, backup energy, storage and the full price once installed. Get it sorted before the cold comes and you will not be left in the laundry over a cup of tea trying to work out why the booster has taken on a mind of its own.
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