Hot Water Top Tips

Don’t let your hot water system flush money down the drain – Save energy and money by looking at the different options to heat water at home.

Choose carefully how you heat your water

Most homes have a few ways to heat water – the central heating system (oil or gas) or an immersion that uses electricity. And some homes have solar thermal panels installed so they are using renewable energy to heat their water. There can be significant differences when it comes to how much energy each option uses and what it can cost.

The price of electricity is about three times the price of gas or oil. It’s generally much cheaper to heat water using your central heating system, rather than using electricity with an immersion. The exception might be during the summer, when you have your central heating turned off, or if you have an old inefficient boiler.

If your boiler is over fifteen years old, it could be time to replace it. A modern combi-boiler, which provides instant hot water, is generally considered to be more energy efficient than a ‘stored’ hot water system. It heats the water you need to use rather than heating a large tank of water that might not be used and then left to cool down again.  

You could install solar thermal panels to heat hot water. Check your budget and how much you’re willing to spend. SEAI has a grant to help towards the cost of installing solar thermal.   They are sized to ensure you’ll have about 60% of your hot water needs over the course of the year.

If you have solar PV installed, and you have an existing hot water cylinder with an electric immersion heater, then you can divert any excess energy from your panels into heating your hot water, using what’s called a solar immersion heater.

Think about when you need hot water  

Out of habit, many of us heat water and then store it for when we need it. But it would be better if we changed our behaviour and only heated water when we need it and when it will be used. For example, in the morning and evening when we take showers or clean up after dinner. That way the heat losses from the tank can be kept to a minimum.

The amount of time the water needs to be heated depends on how big and how well-insulated your hot water cylinder (tank) is, and how much water your household uses. Heating water at the same time as you have the boiler on to heat the house will be the most efficient. Try setting it for an hour in the morning and an hour in the evening. If you don’t run out of hot water you may be able to reduce the length of time that the water heating is turned on.

If you heat your water using an immersion and you don’t already have a timer, you should think about fitting one. This will allow you to set specific times to heat your water, ensuring it is never left on too long. A boost button can be very useful if you just need to top up the heat.

It’s best not to leave your immersion heater running all the time. No matter how well-insulated the tank is, it will still lose heat and the drop in water temperature will cause the immersion heater to run repeatedly, like your kettle coming back to the boil over and over again.

Stop hot water cooling down

If you have an old cylinder that isn’t insulated, then fit a lagging jacket. This should pay for itself in just a few months. You can add to the insulation effect by storing bedding and pillows around it.

If your hot water cylinder is very old, consider replacing it with a modern insulated one. Water can stay warm for up to two days and they perform much better even compared to an old-fashioned tank with a jacket on it.

Where accessible, insulate the ‘downpipes’ – these are the pipes that lead from the tank to the taps.

Heat your water to a lower temperature

If you have a hot water cylinder check that the temperature of the thermostat is set no higher than 60 degrees Celsius. Hot water cylinders need to be kept at 60 degrees, to avoid the dangers of ‘legionella’ bacteria in water that is stored in the cylinder.

If you have a combi boiler, you will not be storing water and legionella bacteria are less of a concern.  You can easily adjust the temperature of the water that comes out of your hot water taps. There is usually a tap symbol beside the controller. About 55 degrees should be enough for most.

Use less hot water

It may sound obvious – but if you are quick in the shower you’ll use less energy.

Doing this regularly can save you money. The average shower time is 8 minutes.

Most modern showers use between 10 and 12 litres per minute. That can make an eight-minute shower a 96-litre experience, so cutting the time to five minutes is one of the best ways to help save water and energy. Our top tip is to turn the water off when shampooing and then back on when rinsing.

Manufacturers have improved the performance of showerheads and taps so you can conserve large amounts of water without compromising on water pressure. If you have older, water-guzzling systems, consider replacing showerheads with newer low-flow models. Have a look at the Eco shower heads buying guide.