Electric & Gas Boosted Solar Hot Water: Everything You Need to Know

Solar Hot Water

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Electric and gas-boosted solar hot water systems are one of the most energy-efficient and environmentally friendly hot water solutions for homes. But why do these systems need a hot water booster switch? Are electric or gas boosters worth having?

Hot water booster switches ensure that the household has enough hot water supply during colder times or days of low sunshine when solar energy is not enough. Boosters serve as backup hot water systems, so homeowners do not have to worry about running out of heated water. Thus, booster usage is supposed to be minimal.

Choosing between an electric or gas booster when installing a solar hot water system depends on factors like availability, overall costs and maintenance, and personal preferences. How does a solar hot water booster switch work? What are the differences between the electric and gas types? Read on to find out. 

What is a Solar Hot Water Booster Switch? 

A booster switch is a device that increases the hot water supply in cases when the solar hot water system cannot produce enough hot water for household consumption. When you activate this booster switch, it taps into an alternative energy source like gas or electricity to heat your water supply. 

On a sunny day, a fully functioning solar-powered hot water system of the right size can gather enough solar energy for a regular-sized household. However, the system may not collect enough heat during cloudy, cold, and rainy days. That’s why it is beneficial to have a backup water-heating device to generate hot water when you need it, overcoming many of the problems with solar hot water systems

A hot water booster switch also comes in handy when you need more hot water than usual like when you’ve got multiple guests staying with you for an extended period. However, it does add to the cost of installing solar hot water

Modern solar hot water systems come with a thermostat that can read the water temperature in the tank. The thermostat signals the booster to activate as required. When the water reaches the right temperature, the booster switches off automatically to avoid overheating. As a result, you can turn your booster switch on without the fear of overheating or harming the water heating system. 

However, a solar hot water booster switch isn’t something you should be using daily, it’s there as a backup. If you find that you need to rely on your booster switch frequently, it may indicate an issue with your solar hot water system. 

Where is a Solar Hot Water Booster Switch Installed?

Electric boosters for solar hot water systems are typically installed inside the water storage tank. Gas boosters can be installed within the water storage tank or in a different unit connected to the nearby storage tank by connecting pipes. 

The location of the solar hot water booster switch usually depends on the type and specific model of the solar hot water system. Some electric-boosted solar hot water comes with a separate control board, or a button installed within an electrical meter box. Some electric booster models in the market offer an extra switch you can install in another spot in the house. 

Types of Solar Hot Water System Booster Switches

Solar hot water systems can have either an electric or gas booster switch based on the energy source in your home. Solar hot water manufacturers will recommend electric or gas based on which is compatible with their product. However, there are other considerations when choosing one booster type over the other. 

Regardless of the booster type you use, every booster switch should be capable of preventing the growth of Legionella bacteria in potable water in accordance with the Australian Standard AS 3498. You must ensure that your hot water system boosters meet this safety standard. When deciding on a booster switch system, speak to your local solar specialist and ask them for their advice on which type of booster is going to be best for your home, your solar system and which will prevent bacterial growths most effectively. 

Gas Hot Water Booster Systems

Gas hot water booster systems are powered by natural gas or LPG when solar power is not enough to heat the water in your tank. This gas can be stored in a storage cylinder or in a water heater located on an exterior wall (close-coupled systems), depending on the design of the solar hot water system you choose. 

For most models, gas boosters come with a thermostat, which reads the water temperature in the tank. When the water temperature dips below a set threshold, the water is pumped through the gas booster. The booster raises the water temperature to the desired point before the water gets delivered to the house. For most modern gas booster units, you only need to configure the thermostat once, and the system works automatically.

Pros of Gas Hot Water Booster Systems

The benefits of gas hot water booster systems include: 

  • A gas-boosted solar hot water system is more convenient when your home has a natural gas installation for other purposes like cooking. 
  • The monthly cost for gas boosters is easier to predict as the gas cost is more consistent than electricity, which can fluctuate because of tariffs. 
  • Gas boosters can still operate even during blackouts or power outages. 
  • A gas booster is arguably more straightforward to use because it does not require elaborate pre-settings or a solar hot water booster switch timer.

Cons of Gas Hot Water Booster Systems

The main cons of gas hot water booster systems are: 

  • If you are not using gas at your house, you will need to pay upfront for the gas supply installation. 
  • Ongoing costs for natural gas or LPG connected to your property can be higher than the electric-type boosters. Gas providers may charge additional maintenance or administration fees on top of the gas cost.
  • Although natural gas is one of the cleanest fossil fuels, using gas to create heat still involves fossil fuel combustion. 

Electric Hot Water Booster Systems

Electric hot water booster systems use electricity to heat the water supply to the house when solar power is insufficient. Like a gas-boosted solar hot water system, the electrical booster is a support system to ensure that water coming into the house is heated accordingly. 

Modern electrical boosters only activate if the water temperature is below the desired temperature and additional heating is needed. Most electric booster units come with a switchboard, which allows manual control, and a thermostat that can automatically read the water temperature. Thermostats usually come with a factory-set temperature threshold. However, you can request a technician to change this temperature threshold. Electric hot water booster systems are best to use during off-peak electricity tariff times to achieve optimum efficiency. 

Pros of Electric Hot Water Booster Systems

The pros of electric hot water booster systems are:

  • Electric-boosted solar hot water systems can be energy efficient. It only uses electricity when needed and shuts off automatically.
  • If you don’t have a natural gas connection to your house, an electric hot water booster system is more convenient and takes less time to set up. 
  • You don’t have to worry about the ongoing costs for gas providers; you only need to deal with electrical billing, which you will already have anyway. 
  • You have greater control of the energy you use because you can configure the booster to work only during off-peak tariff periods when electricity is less expensive. 

Cons of Electric Hot Water Booster Systems

The downsides of electric hot water booster systems include:

  • If you fail to run your electric hot water booster system at the correct times, you may pay for more electricity than expected. Low electricity bill is one of the reasons why people choose solar hot water systems in the first place. 
  • Electric hot water boosters can be more complicated to set up and calibrate as you need to run in only off-peak hours to use less electricity.
  • You may need to install an additional clock device to automatically turn on or off the electrical booster at certain times to achieve energy efficiency, depending on the model
  • This booster system can’t heat the water supply during electrical power outages or blackouts.

Gas vs Electric Hot Water Boosters

Gas and electric hot water boosters have been proven effective in heating water to the desired temperature when solar energy is not enough. The type of booster best suited for you depends on the energy sources available in your area. 

An electric booster for solar hot water systems is considered more convenient because electricity is a more widely available energy source. However, gas boosters have a more straightforward functionality. The availability of natural gas in recent years is another reason to consider a gas booster switch.

If you don’t already have gas running to your house, you will need to pay for gas supply installation to operate a gas-boosted solar hot water system. However, many gas booster models installed outside the water tank will most likely conserve more energy because water is only heated as required.

The automated nature of electric boosters within the water tank makes this type trickier to set up if your goal is to minimise operating costs. You may need to set a timer to ensure your booster only uses electricity at lower tariff times. If you don’t set the electric booster properly, it will cost you more than a gas booster. However, speaking with your local solar specialist can help resolve these issues. They will be able to set up your booster switch so it’s as effective as possible, regardless of whether you choose gas or electric. 

How Do I Turn On My Solar Hot Water Booster Switch?

Electric and gas boosters can come with a dedicated button or a controller to turn on the power for the booster. The location of this switch depends on the system model you purchase and the manufacturer’s specific design. 

For most electric-boosted solar hot water systems:

  1. Look for the power switch or button of the booster and turn it on. The power switch may look similar to a light switch and is typically located in the electrical box.
  2. Keep the switch turned on. The power switch allows the electric booster to activate when the system thermostat senses that the water in the tank falls below the set temperature. Typically, the booster unit turns off when the water temperature reaches the desired level. If the water temperature drops again, the unit re-activates automatically.
  3. If there is a solar hot water booster switch timer connected to the electric booster, you will need to locate the timer switch and turn it on to activate your electric booster. 

For most gas-boosted solar hot water systems:

Although some gas boosters are installed inside the water tank, many gas booster models follow the in-series or instantaneous format. For this model, the gas booster is outside the water tank and installed between the main tank and the hot water outlets in the house. 

  1. For gas in-series systems, locate the gas booster device connected to the water tank.
  2. Turn on the switch. Leave this button switched on if you wish the gas booster to activate when needed. Leaving the switch turned on does not mean that the booster will heat the water continuously. It will only heat water that is below the predetermined temperature. 

Some active solar hot water systems have a dedicated controller that allows you to switch the booster on or off when desired. There are also high-tech solar hot water systems with digital capabilities that enable you to turn on and control the booster via a tablet or smartphone. 

When Should I Turn Off My Solar Hot Water Booster Switch? 

You should turn off your solar hot water booster switch when the house is empty or if there is enough solar power to heat the right amount of water. When you switch your booster on again, it may take some time to get hot water on days when solar energy is insufficient. 

If you want your hot water supply to be available on demand, you should not turn off your solar hot water booster switch. Most electric and gas boosters have automatic functionality. They only operate when the system thermostat senses that the desired water temperature is correct. However, if you have an electric booster with no timer and use flat-rate electricity, you may want to turn it off at certain times to save energy. 

You can also turn off your booster switch when the house is empty for several hours. Take note that when you turn off your booster switch, you may have to wait more than 30 minutes for it to produce hot water. 

How Long Can I Have My Solar Hot Water Booster Switch On For? 

There’s no harm in keeping your solar hot water booster switched on. Modern boosters only activate when the water temperature is below the expected level. It turns off automatically when the water is heated. Leaving your solar hot water booster switched on will not cause overheating or damage to the system parts. 

Is a Solar Hot Water Booster Switch Worth it? 

If your priority is to have enough hot water supply at home, a solar hot water booster switch is worth having. No matter how abundant solar energy is in your area, there will always be darker, colder, or rainy days that will keep your solar hot water system from keeping water hot. 

Hot water is essential for modern living and daily household activities like cleaning, cooking, and washing. During winter, people rely on hot water to offer comfort when dealing with cold temperatures. 

Having electric or gas boosters added to your solar hot water systems allows you to enjoy the benefits of having a steady hot water supply at all times. For many people, these benefits are worth paying for, and improve the convenience of solar hot water compared to heat pump alternatives

Related Questions 

Should I Turn My Solar Hot Water System Off When on Holidays?

Turning on or off your solar hot water system for a long time without proper circulation of hot and cold water can result in overheating and physical damage. A solution to this issue is to turn on the system’s “holiday mode” or “recool function” so it can cool down and function well even when no one is using it. 

Check your owner’s manual or consult the manufacturer on the best way to manage your solar hot water system if it does not have a “holiday function”. 

How Do I Reset My Solar Water Heater?

A hard reset of the system usually requires the service of a qualified technician, but you can reset several solar water heaters by pushing the power button. Some models have a reset button on their dedicated controllers. Consult the owner’s manual to verify the resetting process. 


This article is published in good faith and for general informational purposes only. JFK Electrical does not make any warranties about the ongoing completeness and reliability of this information. Always seek personalised advice on solar energy to ensure any recommendations suit your property and scenario.

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