Get the truth about Solar Hot Water

Some Honest Solar Hot Water Answers

We often have people tell us that it is not worth installing solar hot water in Melbourne, because of our climate. So, is it actually worth it? do you actually save money? Do you end up paying the same in gas because of your booster? These answers may bring clarity to your confusion.

It’s so cold in Melbourne, so why would Solar Hot Water save me money?

You most definitely do save money! Solar Hot Water works on Ambient temperature as well as infared heat. Do you remember those cold and windy, yet sunny days, where you have to wear a jumper, but then you hop in the car and it’s stifling hot? well that’s what Solar Hot Water works like. The water inside of the panel or tube is not exposed to direct air temperature. What that means is that you do not need boosting on those days, because the water is being significantly heated.

In Victoria, you can reasonably expect to have free hot water 8 to 9 months of the year, always depending on your habits and how you are boosting your water.

It’s only worth it if you live up in somewhere like Queensland

You actually save more money in Victoria by installing Solar Hot Water than installing it in Queensland. That’s right! It’s because of the incoming water temperature. In Victoria, our cold water temperature can be anywhere from 10 to 12 degrees. In Queensland, their cold water is around 20-22 degrees. That means that if you use a gas hot water in Queensland, your using less gas. When you install a solar, the savings you see are not as significant because you had a smaller bill to start off with.

Comparatively, in Victoria, you start off with a larger gas bill with a gas hot water, because of the cold water temperature. Installing solar hot water means that your bill will significantly reduce, but you would see a larger reduction than if you were in Queensland!

Solar Hot Water boosted with a woodfire? Isn’t that contradictory?

This could not be further than the truth! When you burn wood, the carbon dioxide that is given off from the wood burning is less than 20% of the carbon dioxide that was absorbed during the tree’s lifetime. That means that if you plant a tree for every five trees worth of firewood you burn, than you have an entirely carbon neutral hot water system. Unlike electricity or gas boosting, wood is renewable, and it is a truly renewable way of boosting your solar hot water.

Flat Panels are far less efficient than Evacuated Tubes

Unfortunately, the Solar Hot Water industry is an industry which is full of misinformation. As we say to every customer of ours, you can find a systems efficiency by looking at it’s STC rating. The more STC’s a system qualifies for, the more efficient the system is. Long answer short: Yes, evacuated tubes are much more efficient in Melbournes climate. However, No, they are not greatly more efficient. You can find your systems STC rating either looking through our products, or on the ORER registry https://www.rec-registry.gov.au/sguCalculatorInit.shtml.

Solar Hot Water is so much more expensive than Gas or Electric Hot Water, why do I pay more?

When you buy a gas or electric, are you buying solar collectors? when you buy a gas or electric, are you buying a separate booster? How hot can it get in a gas or electric tank? Also, how much does the plumber charge when he is connecting all of these things up? Because a Solar Hot Water has annual fluctuating water temperature, if you had a standard hot water system, the tank would surely burst in the middle of summer. Solar hot Water tanks commonly are designed by a team of at least 60 engineers to make sure that there won’t be any disasters when the sun comes out.

When you install a Solar Hot Water, you have to remember that the water is not being heated inside the tank, the water is being heated by the solar collectors. This means that you must have cold water enter the tank, then circulate to the collectors on the roof to be heated, and then back into the tank. There is extra installation work with a solar. You must remember though, that once you have installed a Solar Hot Water, decades from when it is installed and it needs replacing, all of the pipework is already there; meaning that purchasing Solar Hot Water the second time around is greatly cheaper to install than fie first time.

Why should I buy from Insolar?

At Insolar, we have more than three decades in house expertise. We have been here since 2002, which also means we were selling these systems long before most of our competitors realized there were rebates available. We’re not here to give people cheap systems and then disappear when the rebates do, we’re here for the long run! We can find the best system for you because we do not sell only one brand of Solar, we are multi branded, each application giving a different solution to best suit every one of our customers.

Solar Hot Water With Woodheat Boosting

Solar hot water and wood heaters

Solar hot water and wood heaters make a perfect combination as in the colder months solar hot water systems usually need boosting, and this is precisely the time of year when households with wood heaters will be using them to keep warm. Why not tap some of the heat going up the flue to heat the water? In this article, we will try to give you a clear explanation of how to safely and easily use wood heaters to boost a range of commonly available solar hot water systems.

For any dwelling where wood fire is the primary source of heating and/or cooking, it makes good sense to use a wood heater or stove fitted with either a ‘wet-back’ or ‘water jacket’ to provide hot water boosting. Using a wood fire on a winter’s day to keep warm, while at the same time boosting the solar hot water system, allows households with this set-up to enjoy virtually free hot water all year round. Modern, well-maintained wood fires fed by properly dried fuel burn so efficiently that they create relatively small quantities of greenhouse gases, using the renewable resource of wood. In fact, they emit less than 20% of the greenhouse gases emitted from open fireplaces! Firewood is not a fossil fuel and can be sourced from timber planted for wood, pulp or firewood production.

Whilst solar hot water system retailers generally have a range of systems available that use either electricity or gas for boosting, few have any detailed knowledge or keep in stock the specialised equipment needed to integrate wood heaters for this purpose, so finding out how to do this is not always straightforward. Hot water boosting from wood fires can be done in two ways, namely: –

1. Wet-Backs:

A ‘wet-back’ within the firebox – this is generally the preferred option, because of the more efficient heat transfer to the water. ‘Wet-backs’ are available with many wood stoves, ovens and furnaces and also for a small number of ordinary wood heaters. They should not exceed 5 kW in rated water heating capacity if they are being used only for domestic hot water boosting and not also for central heating purposes.

We recommend ‘wet-backs’ be installed only where they are available as a standard option from the fire manufacturer, as they can reduce the operating temperature in the firebox and this can affect the performance of the wood fire and this must be taken into account in its design to ensure the fire burns efficiently and complies with air quality standards.

2. Flue Water Jackets:

A way of converting existing wood fires that have an accessible flue (i.e. not set into a masonry chimney) to also heat water heater is to install a flue ‘water jacket’ that replaces the first section of standard flue. Flue ‘water jackets’ are generally made of stainless steel and can fit a variety of flue sizes.

Why boost at all?

Wherever you live in Australia, solar hot water systems perform well and provide at least 70% of a household’s annual hot water needs. Appropriately sized systems provide all of a households hot water needs in the summer and most of the needs in the autumn and spring, but will still require some form of supplementary heating, particularly in winter in the southern regions. Also, in order to ensure that no dangerous bacteria breed in the hot water system, our health codes require that all solar hot water systems be installed with an additional heat source as an integral part of the system so as to guarantee that the temperature of the stored water is raised to at least 60°C before being used. So the booster not only guarantees the water is hot enough during extended cloudy periods, especially in the winter, it also ensures your hot water is safe to use all year round.

Most people who install ‘wet-back’ or ‘water jacket’ boosters will also have either an electric element or a gas booster connected. This means that if they have not lit the fire on days of low sun radiation, or they have an unusually high hot water demand, they can simply switch on the electric or gas booster.

No Explosions Please!

Electric and gas boosters have thermostats to switch them off when the hot water systems storage tank reaches a predetermined temperature, normally 65°C. Wood heaters, on the other hand, are an ‘uncontrolled heat source’ (as are solar hot water collectors). This means that the input of heat from the firebox to the hot water storage tank cannot be easily and quickly switched on or off, so wet-backs or water jackets will just keep on adding heat whilst the fire is going. We recommend that you never cut off the water flow to the wetback, as this can cause a potentially explosive build-up of steam!

There are two options for dealing with this concern safely. Both options require the hot water storage tank to be located above the wood heater and sufficiently high so as to ensure the wetback or water jacket always has water in it. These boosters utilise the thermosiphon1 principle to transfer heat up to the hot water storage. As the water heats up, it is critical that the flow of hot water up to the storage tank and the return of cooler water back down to the wetback must not be impeded by any flow constrictions. Draining the system and running the fire with an empty wet-back or water jacket is not a good idea either, as this can dramatically reducing its lifespan, causing it to burn out very quickly.

Option 1: Connecting to Mains Pressure Solar HW storage tanks

Using wood fires to boost mains pressure solar hot water systems works very well with the traditional roof mounted ‘close-coupled’2 solar tanks, because the solar tank is located above the level of fire. Most solar hot water storage tanks supply water at mains pressure and therefore require a specially designed heat exchanger, which is installed just below the level of the solar hot water storage tank. The heat exchanger is a simple device, with one copper pipe inside another larger copper pipe. The larger outer pipe usually has the water from the wetback flowing through it and is ‘open vented’3 at low pressure, whilst the inner pipe absorbs heat from the outer pipe and is connected to the mains pressure solar hot water storage tank. The outer pipe has an extension rising up to a small open vented make-up (or ‘header’) tank situated just above the centreline of the main storage tank.

Any boiling first happens at the make-up tank and any water lost to evaporation is replenished at the make-up tank. Many solar roof tanks, particularly in cooler areas, have glycol (a frost resistant heat transfer fluid) going through the solar collector panels and a separate heat exchanger within the solar tank. In these types of systems it is fluid from this glycol circuit that the water from the wetback heats in the heat exchanger suspended below the solar unit.

Option 2: Connecting to Low Pressure Solar HW storage tanks

Some solar hot water systems have the storage tanks ‘open vented’ so that the main body of stored hot water is not under mains pressure. These systems either rely on gravity feed to supply the hot water to the house or they have their own internal heat exchanger coil inside the tank, with the water inside the heat exchanger coil supplying the house at mains pressure. Water jackets and ‘wet-backs’ can be safely connected directly into the low-pressure open vented main body of these tanks, so with these systems a separate heat exchanger is not required.

  1. Thermosiphon is the process of heat rising and in so doing it sucks cooler water into the bottom of the solar collector or wet-back/water jacket when there is a flow-and-return circuit.
  2. Close-coupled’ refers to solar hot water systems where the solar storage tank is on the roof above the solar heat collector panels – the heat is transferred to the water in the tank above by Thermosiphon.
  3. Open-vented’ is a term that describes a hot water storage tank that delivers gravity fed water (i.e. water pressure will be governed by the height of the tank above the water outlet). These tanks are ideal for use where an uncontrolled heat source such as fire or solar is used to heat the water. The header / make-up tank is fitted with a ball cock to replenish the water in the main tank as it is being used.

Watch our video on Woodfire Boosted Solar Hot Water.

Choosing the right Solar Hot Water System

Choosing the right Solar Hot Water System

If you’re an experienced builder, Architect or plumber, or if you’re just building your dream home, we are sure to have the right system for you. In Victoria, new homes must have a six star rating. This means you must have a Rainwater tank, or a Solar Hot Water system installed to acheive your efficiency rating.

Here in Victoria The Sun will heat anything from 60 to 80% of your hot water year round.  In the summer, not including rainy or very cloudy days, almost all you yoru how water will be solar heated. But in the winter with short days and not much bite in The Sun the domestic hot wate rwill need to be boosted ( from say 30 degrees on a normal winter’s day) up to 60 degrees Celcius.  You acn choose to do this by Gas, Electricity or Wood Fire (backed up by electricity).  Your choice of boosting method will be the first step in determining which system will best suit your needs.

The size of your family (or home if you want to consider re-sale) will determine the size of the system, but as a general rule with solar Big is Beautiful – the larger the volume of wtaer that is being heated by The Sun in your solar tank the more days of rain and cloud you can get through without needing to burn energy to boost.

System efficiency is another consideration when choosing your solar hot water heater:-

1.   The amount af area pointing to The Sun (i.e. facing NORTH) in your solar collector is the main determinant of efficiency,

2.  There are varying efficiencies in solar collectors. In order of efficiency : evacuated tubes, high performance (Titanium coated) flat plate collectors and normal flat plate collectors, and finally Heat Pumps (that absorb heat from the ambient air temperature).

3.  The angle of the solar collector is another factor that influences efficiency. in Victoria we are about 37 degrees South which means that The Sun’s rays hit a solar collector on the pernindicular (no reflection) when the collector is set at 37 degrees at the Equinox (March 20/21 and September 22/23).  It is possible to set up the collectors at an even steeper angle to sacrifice some Summer over efficiency and get better winter gain. There are some wind load factor considerations with flat plate collectors if mounting frames are used. Close coupled systems with heat exchangers may need small adjustments if angles greater than 28 degrees are used.

4.  Glycol systems involve a heat exchange process which means approximately 5% efficiency loss

5. If wood fire is used as a boosting method then the efficiency of the solar collector becomes far less important as the wood fire in combination with The Sun will take care of most of your winter hot water needs.
Common mistakes made when buying a system include:

  • Buying the cheapest system could mean that the buyers of the home constantly run out of hot water.
  • If the booster is not be powerful enough, and two people have a shower at the same time, they could both be fighting over hot water.
  • If the solar hot water collector’s angle is too low, it could mean that the booster will be running more often, using more gas/electricity and a larger than average gas bill.

Where do we go from here?

Once we know which system suits your buildings needs and quote any additional components that may be needed to work effectively in Victoria, we can start to assess installation requirements.

Generally on a new home you would already have your own contracted plumber who will be completing your taps, vanities, laundry i.e. your homes reticulation. In order to have our plumber install the solar hot water system, we must ask; Has the other plumber run gas to the site? Are the hot & cold lines already installed? Such questions can make the installation price vary greatly. It will obvioulsy cost you more to have a separate plumber install the system because of the second callout fee.

Because of our years of experience and expertise in the industry, we find that the best way to approach new builds is to have your plumber call us and we can offer them training on Solar hot Water installation free of charge. This means that your plumber can be trained on installing the system, can quote you confidently on the install, and they will have the knowledge and training to complete installations in the future. That’s right, we give free plumber solar training to all our builder customers, this saves you time and money!

We are also happy to assess plans that you may have for a future new build, give a recommendation for a system, give our opinion on where tanks/panels/boosters should be installed, and liaise with your architects and plumbers to give you the best solution possible. We always strive to have each and every one of our systems installed to the highest level of effectiveness here in Victoria. If you require some help in choosing a system, have a look at our New Homes Recommendations.

So If you’re looking at a large project with acres of new homes, or if you’re building your dream home yourself and need advice on energy efficiency, request a quote or phone us on 03 9328 4884.

Solar Hot Water and Woodfire Boosting Video

Solar Hot Water and Woodfire Boosting Video – Part 1

Solar Hot Water and Woodfire Boosting Video – Part 2

We also have an article on Solar hot Water and Woodfire heaters with additional information.