Cutting energy use is important. It saves money and helps the environment. But staying safe is a must, too, especially with water systems. If you try to lower your energy bills by dropping water temperatures, you might not expect a danger. In fact, it could increase the risk of Legionella bacteria building up in your water supplies. Getting the balance right between energy saving vs legionella risk takes a bit of thinking. How do we keep water safe while making sure energy isn’t wasted?
The Legionella Risk – Why Water Temperature is a Critical Control Point?
Legionella growth can happen if the water reaches the wrong temperature. The water bacteria, like Legionella pneumophila, prefer water that feels warm to the touch, not hot, not cold. If water is kept too cool, they can’t survive. If it’s too hot, they die off. Safety rules say hot water must be stored at 60°C or more, and used hot above 50°C. Cold water should stay under 20°C. These aren’t just numbers; they mean people are much safer using that water daily. Are you checking your systems?
Energy-Saving Technologies That Can Undermine Water Safety
Energy savings are helpful but not always simple. Some technology meant to lower bills might accidentally make things risky for health. Dropping temperatures too much or using the wrong equipment lets bacteria like Legionella multiply. It’s easy to focus on cost and forget about safety. Before changes are made, always check how new systems affect water heating and storage. No one wants to swap short-term savings for long-term problems.
Heat Pumps (Air Source & Ground Source)
A heat pump works by moving heat from the air or ground to warm up water. These systems are clever and can cut the energy used for water heating. But here’s the problem: they often stop heating once water hits about 45-55°C. That’s just the right range for Legionella. Unless your heat pump system also runs hot cycles to kill bacteria, it can let risk creep in. Think about both efficiency and Legionella risk management every time.
Solar Thermal Systems
Solar thermal panels use sunlight to warm water, using less electricity. On sunny days, these can get your water hot enough to stay safe and save you pounds on energy bills. When it’s cloudy or winter, though, water might not reach 60°C. That’s when Legionella growth is more likely. If the drinking water in your building drops in temperature, someone could get sick. Always check system performance in all seasons, and have backup plans ready for cold, dull days.
2 Practical Energy-Saving Ideas That Don’t Compromise Safety
You can be smart about cutting energy use without risking anyone’s health. Don’t just think about changing the water temperature. Insulation and system upgrades make a difference, too. Here are ideas you can use, at home or at work, to keep safety first.
1. Use High-Efficiency Water Heaters with Legionella Controls
Some new water heaters don’t lose as much heat, working more efficiently. Pick a model with Legionella controls built in. These special heaters run a hot cycle now and then—this process kills off harmful bacteria, so the water is always cleaner and safer. So, if you’re replacing an old heater, look for this feature. It’s one more line of defence between you and unwanted bugs.
2. Insulate Pipes Correctly
Covering your hot water pipes with insulation keeps the heat in for longer periods. Less heat is lost as water moves through the building. That means you use less energy, and water stays at the right temperature until it reaches the tap. Pipe insulation also lowers the risk of pipes cooling down between uses, which could otherwise give Legionella bacteria a chance to multiply.
Energy Efficient Ways to Generate Hot and Cold Water
Thinking about how your water gets heated (or cooled) matters just as much as the equipment itself. Design choices at the start make a real difference later on. It’s good to review these options with safety and energy use in mind.
Energy Efficient Building Design
If you’re planning a new building or renovation, think carefully about the layout. Put water heaters as close as possible to where hot water is needed most, like sinks or showers. Run pipes in straight lines when you can. Fewer pipes means less chance for water to cool down in between uses. All these choices together help keep energy bills in check and keep water safer.
Don’t Forget Cold Water Systems – Legionella Loves Lukewarm
People often focus on hot water. But Legionella likes cold water too—if it warms up just a bit. If pipes carrying cold water pass near boilers or run through warm areas, that water can warm up past 20°C. Then bacteria have a chance to grow. You can prevent this by checking the pipes, keeping them away from heat, and using pipe lagging when needed. Testing your cold water regularly is a smart move.
Risk Assessments Before Any Energy Saving Initiative
Think risk management before making changes. It’s not enough to guess that waste is lower with a new system—check what changes it makes to the water temperatures. Hire an expert if you’re not sure. Risk assessments examine every step in the water loop in your building. Are there dead legs? Do pipes run through hot spaces? Will new energy-saving tricks let water linger in bad temperature zones? Finding risks before they cause harm protects everyone.
Compliance is Not Optional – Know the Standards
Rules for water safety are strict, and for good reason. In the UK, you can’t pick and choose which ones to follow. You need to know and act on them. The main guidance for Legionella includes these:
- HSE Approved Code of Practice L8 (ACoP L8): Sets rules for risk checks and steps to keep people safe in business water supplies, including regular monitoring.
- HSG274 Parts 1-3: Explains how to apply the main code to different systems, like both hot and cold water setups or bigger cooling towers.
- Department of Health HTM 04 01 (for healthcare premises): This sets tougher safety checks for hospitals, care homes, and clinics, where patients are at more risk from waterborne bugs.
Maintaining a Balance between Energy Efficiency and Legionella Control
You don’t have to choose: you really can have energy savings and water safety together. Balance means not skipping checks or letting new tech lower safety standards. Regular checks and a strategy are the real keys. Focus on how you insulate, how you control temperature, and if people can help spot problems early. A building with good risk management gets the best of both worlds.
Work With Experts to Get It Right the First Time
Getting professional help takes the stress out of doing this yourself. Water safety specialists know the rules and can check your systems thoroughly before issues start. Here’s what they do:
- Comprehensive Legionella risk assessments: They inspect your site, test water, and spot weaknesses quickly.
- Smart, safe energy-saving strategies: Their advice is practical: how to save energy, but never risk water safety. You get a plan that matches your building’s setup.
- Ongoing compliance with regulations: They help keep paperwork straight, arrange re-testing, and update you if guidance changes, so you never fall behind the law.
FAQs
How can businesses save energy when heating water?
Businesses wanting to save energy can add thick lagging to hot water cylinders and pipework. That stops heat from leaking away. Using new, efficient heaters with timers or thermostat controls cuts waste, too. These actions can lower energy bills while reducing risk, so water stays the right temperature.
Is it safe to turn off hot water systems during weekends or holidays to save energy?
It sounds simple, but switching off hot water systems fully isn’t a great idea. Water in tanks cools to temperatures where Legionella can multiply. If you do turn off the system, be sure to run it to full temperature and flush out all taps before anyone comes back. Otherwise, you could cause real danger to your health. Think before you switch off.
Are water-saving devices like low-flow taps or aerators a risk for Legionella?
Low-flow taps and aerators help save water, but they’re not perfect. Less water moving means it can stay in pipes longer, allowing Legionella to build up. They can also create more spray, spreading germs if present. To limit this risk, clean these devices regularly and make sure water keeps moving through the system.
Does reducing water heater temperature to save energy increase legal liability?
Yes, it does. If you try to save energy and set heaters too low, you risk a legionella outbreak. That can put people at risk and land your business in trouble with the HSE. You may even face fines or worse. Always keep your hot water at 60°C or above and check that you’re meeting all safety guidance.
Is Legionella risk higher in newly built energy-efficient buildings?
Surprisingly, yes. Some new “green” buildings have clever designs, but sometimes they accidentally help Legionella grow. Lots of insulation, long pipe runs, and complicated layouts might mean water sits still or doesn’t get hot or cold enough. Always carry out a full risk assessment on any new site to keep people safe from the start.
We are proud to share our experience and knowledge and take pride in offering this to all clients when required. If I, or one of the team can help then please schedule a meeting via the office or get in touch via one of our social media platforms.
- Top 10 Best Legionella Risk Assessment Companies in the UK (2026) - June 24, 2026
- Coagulation and Flocculation in Water Treatment: What’s the Difference? - April 7, 2026
- What is the Chain of Infection and How to Break It? - March 27, 2026
