During times of extreme heat, a hot water system may struggle to perform as expected, leading to inconsistent temperatures, reduced capacity or complete shutdowns. While a cold shower might seem appealing after a 40°C day, sudden temperature changes can place unnecessary stress on your body. Even in hot weather, a lukewarm shower is often the better option, which means your hot water system still needs to perform reliably, even when hot water is the last thing on your mind.
This article breaks down how extreme heat impacts different types of hot water systems, what performance changes are considered normal, and what you can do to safeguard your system during Australia’s increasingly harsh summer conditions. With our Aussie summers pushing water heaters to their limits, this knowledge can help you prevent damage, lower energy bills, and ensure optimal performance of your hot water system.
It might seem counterintuitive, but blistering heat makes your hot water system work harder and consume more energy, even though less heating is required. Here’s why.
Just as cold snaps and freezing temperatures can see water heating systems struggle, sustained hot weather can have a similar impact. As water heats, it expands, increasing internal pressure and placing additional strain on valves and safety components. High ambient air temperatures can also cause electrical components and compressors to overheat, reducing hot water system efficiency. This is a particular risk for systems with poor ventilation or those sitting in direct sun. Warmer inlet water can also alter heating cycles, and you may see inconsistent performance during peak use.
It can feel like you’re running out of hot water faster during heatwaves due to changes in usage patterns and basic physics, not because your system is failing. When it’s hot, homes use more water overall, placing greater demand on the system. At the same time, the incoming cold water is warmer than usual, which changes how hot and cold water mix at the tap. Normally, a comfortable shower temperature mixes hot water at around 60°C with a significant amount of cold water, say at 15°C. During a heatwave, if the cold water is closer to 30°C, far less cold water is needed to reach a comfortable temperature, meaning a higher proportion of hot water is used each time the tap is turned on.
Here are some problems you might see happening with your hot water system during weeks of searing weather.
Pressure relief valves are designed to protect your hot water system by releasing excess pressure. It’s normal for them to activate more frequently during heatwaves as pressure builds up because the system has less time to cool between heating cycles. However, if it flows continuously, especially when not heating, it can indicate a problem such as excessive system pressure, a failing valve, or inadequate expansion control.
Extremely high temperatures can cause your hot water temperature to fluctuate for a few reasons. The first is that high ambient temperatures may affect sensors, which can trigger irregular heating cycles. Another reason is that mixing values can struggle during heatwaves as water temperatures rise significantly. They may not adjust properly, which can cause sudden changes to the temperature of water coming from the tap. Pipes can also lose less heat compared to when you’re experiencing cold temperatures, meaning that water at the tap can be hotter than usual initially.
Most hot water systems will shut down for safety if the system overheats to prevent damage. When faced with extreme temperatures outside, electric systems automatically activate temporary thermal cutoffs when internal components or wiring get too hot. In gas systems, pilot lights can go out, while heat pump water heaters can shut down if airflow is poor. In most cases, the hot water system will automatically restart when temperatures drop to safe levels.
While you might assume that your water heater doesn’t need to work as hard in hot weather, extreme temperatures mean your system actually consumes more energy. This is because of frequent cycling and standby losses as it turns on and off more to maintain its temperature, wasting energy each time. The thermostat also needs to switch on and off as it tries to maintain temperature control, which also increases energy use. Smaller differences in the temperature of the water going into the system can also cause greater energy consumption, as the system has to regulate heating more efficiently to prevent it from getting too hot.
If you’re struggling to figure out if those hot water system drips are normal or not, here’s how to tell the difference between normal changes to expect during a heatwave and warning signs that something more serious is happening.
Prepare your hot water system for optimal performance during summer with these tips.
To better protect your system against heat-related problems, consider upgrading to heat-resistant models or switching to more energy-efficient heat pump systems. Moving away from fossil fuels toward renewable energy options, like solar hot water systems, can also improve reliability and reduce environmental impact in hot climates.
If your hot water system doesn’t already have one, installing expansion tanks or vessels is a simple way to manage thermal expansion and reduce pressure-related issues during heatwaves, while models with smart thermostats can help optimise heating cycles, prevent overheating, and adapt to changing ambient conditions. These actions not only improve energy efficiency, but they can also prolong the life of your system.
Finally, ensuring your hot water system is correctly sized for your household is crucial. An undersized system will struggle during peak usage and heatwaves, while an oversized system may waste energy and exacerbate pressure problems.
Just as your hot water system has to work harder in cold weather, scorching summer days also take a toll, often leading to the need for hot water system repairs or unexpected breakdowns. However, with a bit of DIY maintenance and regular professional servicing, you can lessen the environmental impact of rising temperatures on your hot water system. A professional assessment of your hot water system can also help you reduce your carbon footprint, cut energy costs, and keep the hot water flowing as you need it.
Want professional help to safeguard your hot water system against the heat? Call Same Day Hot Water Service on 1300 721 996 for fast, no-sweat service.
Outside temperatures affect hot water heaters by significantly changing the temperature of the water coming into the system, reducing efficiency, making the system work harder and extending recovery times.
If a hot water system’s components become too hot, it can cause an automatic safety shutdown that helps the system avoid permanent damage.
If it feels like you are running out of hot water quickly during a heatwave, it may be due to increased water usage or because the temperature of the water coming into the system is hotter, which actually causes more hot water to be used to deliver the correct temperature to the tap.
Extreme heat can affect water pressure by increasing demand, stressing pipes and weakening fixtures and therefore, impacting water flow.