Solar Hot Water vs Gas Hot Water: Which is Better?

Share This Post

Whether you need to replace an old hot water system or are a new homeowner looking to install one, you’re probably having trouble choosing between solar and gas hot water systems.

Although both have pros and cons, solar hot water systems have the upper hand for their efficiency, continually improving technology, and clean energy utilisation, among others compared to gas hot water systems.

There is a lot to consider when choosing between the two. This article aims to run you through the primary considerations and general information about how they operate and why you should consider one over the other. If you’re interested to learn more, read below.

Table of Contents

How Does Solar Hot Water Work?

Solar hot water heaters work by absorbing the energy from the sun through solar collectors attached or mounted on the roof of a house. This energy is then transferred to the water inside a storage tank and pumped through the system.

More and more Australians are swapping to solar hot water systems due to the savings they bring and the fact that solar hot water systems are much more environmentally friendly. Federal and state government bodies offer discount programs and subsidies for anything related to solar as part of the push for clean and renewable energy, varying from state to state.

Solar hot water systems are often praised for their simplicity and durability, putting them on par, if not better, than conventional water heating systems. Although they are dependent on energy from the sun, you can always have a solar hot water booster switch installed in your system, ensuring that you’ve got enough hot water, even when the sun is lacking. Solar hot water systems utilise two kinds of solar collectors:

Flat Plate Solar Collectors – These are suitable for systems whose storage tanks must be mounted on the roof. These operate through copper pipes and run through a glass-covered solar collector. The heat from the sun hits the copper pipes, which results in hot water being thermo-syphoned out of the tank.

Evacuated Tube Solar Collectors – These are generally more efficient and preferred for areas with extreme cold seasons. Evacuated Tube Systems have glass tubes which are fused at both ends. There is space between the glass tubes, which is evacuated to form a vacuum. The heat pipe running through the tube ends at a manifold connected to a circulation pump that moves water to a tank, bringing in heated water. This system is not to be confused with a heat pump, which is a different device entirely. When compared, a solar hot water system vs a heat pump work very differently.

The storage tank has built-in insulation, which also allows hot water to be used during the night. Evacuated tubes are widely considered superior to other types of solar collectors since they can draw out heat from the air even when there is high humidity and no direct sunlight.

Knowing how solar hot water works, and knowing the difference between the main two types of solar hot water heaters, is an essential first step when trying to compare solar and gas hot water systems.

Pros of a Solar Hot Water System

The primary advantages of a solar hot water system are:

Savings on water heating bills – Because you are using free energy generated from sunlight instead of paying for electricity or gas, your water heating bills will be lower compared to other types of hot water systems.
Relatively low maintenance required – With fewer moving parts, and nothing dangerous like a pilot light to maintain, keeping your solar hot water system in good condition is faster, easier and more affordable.
Environmentally friendly – By using solar panels to generate power from sunlight, you’re able to heat the water in your home more sustainably, which is significantly better for the environment.

Cons of a Solar Hot Water System

The primary disadvantages of a solar hot water system are:

Relatively high upfront costs – Although solar systems are generally cheaper in the long run, the cost to get a solar hot water system is usually comparatively higher than gas hot water systems.
Dependent on the climate – Depending on where you live, solar hot water systems may not be as effective, as it is dependent on how much sunlight you get. Some areas simply don’t get enough sunlight to get the maximum amount of use out of these units.
Can only heat water – As efficient as they are, solar hot water systems are naturally limited to heating just water.

How Does Gas Hot Water Work?

There are two gas hot water systems: Gas Storage Systems and Instantaneous Gas Hot Water Units. Although both use the conventional method of heating water, their primary difference lies in whether they have a storage tank.

Gas Storage Hot Water Systems – In gas hot water systems, water is heated by a gas flame mounted below the tank — a very traditional method. These systems generally have a pilot flame which constantly burns and ignites the primary burner when needed, heating the tank from underneath. Some gas storage hot water systems use a flue system that recirculates gases around the storage tank’s exterior, boosting energy efficiency.

Most gas storage hot water systems allow temperature customisation using an adjustable thermostat. The system automatically turns on the main burner when the temperature drops too low, keeping water heated to the desired level. As hot water leaves the top of the tank, it’s refilled with cold water from the bottom.

In Australia, gas storage hot water systems are available in various sizes, from 90L to 300L, suiting a wide range of households.

Instantaneous Gas Hot Water Unit – Also known as ‘continuous flow’ hot water systems, these are in some ways similar to gas storage hot water systems but without a storage tank. Instead, water is heated by a gas burner and flows through a heat exchanger (coiled pipe). The unit will only heat the required water instead of continuously heating a full tank. Due to the absence of a storage solution, there is no heat loss from a tank, so that it can contribute to energy and cost savings.

Water is slowed down as it flows through the coiled pipe to give it enough time to heat. As such, instantaneous gas hot water units supply hot water at a lower pressure than storage hot water systems. Depending on the model and make of the unit, hot water flows at 10 to 30 litres per minute.

Pros of a Gas Hot Water System

The primary advantages of a gas storage hot water system are:

Generally comes with 5 to 10-year warranties – A 5 to 10-year warranty is quite extensive and generous, especially for a gas heating unit.
They may contain 1-2 sacrificial anodes – Preventing corrosion within the tanks is essential, which is why many units come with multiple sacrificial anodes, which lengthen the life of the unit and improve the cleanliness of the water it heats.
Requires little maintenance – Compared to other hot water heating systems, gas powered ones are generally easier to maintain.

The primary advantages of an instantaneous and continuous flow gas hot water system are:

Cheap to run – Due to the availability of natural gas, gas hot water systems are cheaper to run now than they have ever been.
Water is only heated as needed, avoiding wasted energy – Unlike other types of hot water systems, gas heaters don’t heat large amounts of water, only the amount of water that’s needed; making them cheaper to run and more efficient.

Cons of a Gas Hot Water System

The primary disadvantages of a gas storage hot water system are:

Less freedom when choosing a model – Local water quality may influence which type of tank is required, meaning you don’t have as much control when choosing a system.
Not clean energy – Gas is not the most environmentally friendly heating source, especially compared to the prevalence of solar heating in the industry.

The primary disadvantages of an instantaneous/ continuous flow gas hot water system are:

Not ‘instantaneous’ – Since it requires some time to heat up, they are less convenient than other types of heaters available.
Not clean energy – Especially when compared to things like solar, gas heaters are generally not considered clean.

Solar vs Gas Hot Water Systems – What to Consider

Solar and gas hot water systems do the same job differently. And this difference affects the user directly (through savings, rebates, maintenance, etc.) and indirectly (clean energy for the environment). Although there is not one definitive ‘winner’ here, there is much to consider when deciding which kind of hot water system to purchase.

Below are the primary considerations:

Efficiency – It should be no surprise that solar trumps gas in terms of efficiency. Solar technology has always been about efficiency, and solar hot water systems are no different. Since they use clean and renewable energy (basically free electricity), it costs much less to heat water than conventional gas hot water systems.

Running Costs – Remember that solar hot water systems only need sunlight. No batteries, gas lines etc., need to be refilled or replaced regularly. On the other hand, gas hot water systems require gas to operate. So, in this aspect alone, solar costs you less in the long run than a gas hot water system. Both kinds of systems are considered to be easy and cheap to maintain.

Price – Despite a yearly decrease in solar technology prices, solar hot water systems remain more expensive to purchase and install upfront than gas hot water systems. The average cost of installing solar hot water systems is approximately $3,500 for the components (panels, tubing, tank, etc.) and up to $5,000 for labour and other miscellaneous components and materials. On the other hand, gas hot water systems cost roughly $770 to $1,450 for the components and may run you up to $2,000 with labour.

Although it may seem like you will be saving more by choosing a gas hot water system, do not forget that the Australian Government has incentives like discounts, rebates, and subsidies for those who install solar-powered systems. This is part of the government’s Renewable Energy Target scheme in which widespread adoption of clean energy technology such as solar is among the targets.

If you consider the energy bill savings from solar, and the rising cost of gas, oil, and petrol products, you will realise that going for a solar water heating system will save you more money in the long run.

Capacity – The only time a solar hot water heating system will win over the gas variant is when the gas hot water heating system has continuous flow/instantaneous, as it does not have any storage tanks. In every other setup, gas wins over solar due to its enormous tank capacity.

Required Space – Gas hot water systems require much more space than solar hot water systems, as the tank capacity can reach anywhere from 30 to 80 gallons. There are ‘tankless’ gas hot water systems (known as continuous flow or instantaneous hot water systems), but those kinds require exponentially more energy and electricity to heat water. Although solar hot water systems also use storage tanks, the space needed for these is nowhere near that of gas systems; some solar hot water systems have storage tanks mounted on the roof, saving space where it matters.

Conclusion

Choosing a hot water system should be an informed decision. It’s best to be aware of the advantages and disadvantages of solar and gas hot water systems. However, keep in mind that clean and efficient solar energy has become more accessible with the continually decreasing price of solar technology.

It would be a wasted opportunity to save on energy costs in the long run and be part of the movement towards clean energy. Make sure you speak to your local solar expert before making any decisions on what type of hot water system you get for your home.