Is gas boosting better than electric boosting of solar hot water in Canberra and Queanbeyan.
As a supplier and installer of all types of hot water systems I am asked the above question more times than I can count. In 99.9% of all cases, I recommend electric boosting over gas boosting.
This answer is based on the installation and operating costs along with the possible maintenance costs. I also base it on the environmental impacts and the way the system is installed. I will explain costs in this post. Click on What are the environmental differences? or What are the installation requirements? if you would like to know more.
Supply installation costs versus the expected savings in energy costs.
The supply and installation of a gas boosted system costs between $700.00 and $2000.00 more than an electric boosted solar hot water system of a similar size.
Typically, in Canberra, the electric boosted system uses $50.00 worth of energy more than the gas boosted system per year.
If we divide the $700.00 additional installation cost for a gas boosted system by the yearly difference of $50.00 we get fourteen. Fourteen is the minimum number of years it takes to make up the difference between energy costs and installation costs.
The above costs are based on the assumption that both types of solar hot water systems are operating efficiently and have been installed as per the manufacturer’s instructions. From my experience in Canberra, many are not installed properly and are not operating anywhere near their optimum efficiency.
Did you Know?
It is possible to reduce the cost of electric boosting to as low as 72KW per year. At 40c per KW this is less than $30.00 per year. Apart from turning the gas booster off all together, it is not possible to do that with a gas boosted solar hot water system.
All hot water systems require at least one service every 5 years.
Considering that a gas boosted system has a continuous flow hot water system and solar bypass valve attached to it, the maintenance costs of gas boosted systems can be significantly higher than electric boosted systems. If a solar bypass valve fails, expect to pay around $400.00 to have it replaced. If the continuous flow system fails expect to pay around $1600.00 to have it replaced. If an electric element or thermostat fails, expect to pay a total of around $365.00 to have them both replaced. In most cases, spare parts for gas boosted solar hot water systems are more expensive than spare parts for electric solar hot water systems.
In our experience, most home owners are afraid to fiddle with things that look as complex as continuous flow, hot water boosters. Therefore, they leave them turned on all year round, blissfully unaware when the solar bypass valve, the pump, a sensor wire, the solar controller or another valve has failed. The end result can be overheating in the collectors leading to the rapid deterioration of sensors, steam and air release valves, the breakdown of the sealants used in the joints and collector tubes that have seized into the manifold. If left too long it will lead to pump failure and frozen and split flow and return pipes.
Electric systems are much simpler and owners have been more conscious to remember to turn the booster off.
Overall, I would say electric boosted solar hot water systems cost less to own and operate than gas boosted systems.
Electric boosted systems can be significantly cheaper to run than gas boosted systems if they are installed for optimum efficiency and performance.
Why I am qualified to give advice on this subject. I am a licensed plumber and gasfitter with a restricted electrical licence. I also graduated from the Solar Hot Water Institute which operated in Mossvale, NSW. I have been installing and repairing all types of hot water systems in this region since 1985. I am also a former President of Master Plumbers ACT and a former Director of Master Plumbers Australia.