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8 February 2021

Five tips to reduce your heating bills

Find out how to reduce your heating bills and improve your home's efficiency. So you'll not only save money, but also keep warm and cosy
Father and son checking radiator_main 386084
WhichEditorial team

Your central heating system is likely to be the biggest contributor to your household bills. Which means it's the first place you should turn your attention to if you're looking to save money.

Heating and hot water accounts for 62% of a household's energy bills on average, according to the Energy Saving Trust. With a gas bill for a large home topping £1,600, it's easy to see how small improvements to your heating efficiency can lead to serious pounds and pence saved.

Here, we take you through what to consider if you want to have the healthiest and most efficient central heating system possible.

If you're just looking for a new boiler, make sure you read our guide to five things you need to know before you buy a new boiler.

1. Do you have a clean radiator system

Making sure that your system water (the water that lives in your pipes and radiators) is clean and free of sludge will mean that your heating system is more efficient. It’s also good for the ongoing life of your boiler and central heating system. 

A clear sign that your system may be overly sludgy is if you have cold spots on your radiators, or if some radiators take an age to heat up compared to others. 

Which? has seen research carried out by Enertek International, who are an independent company offering innovative services to the gas, oil and renewable heating industry, that suggests a heavily sludged heating system can increase your bills by as much as 25%.

If you're getting a new boiler, a clean system is also essential to validate the manufacturer's warranty on your new boiler. Ensure that your installer completes the Benchmark commissioning documentation to confirm that this has been done.

You can check how dirty your system water is yourself by simply bleeding a little into a container from your radiator valve. 

However, be aware that much of the dirt in the system will sit at the bottom, so bled-off water may appear to be quite clear, even in dirty systems. If your system water looks dirty and is in need of a clean then you have a few different options.

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Do I need a power flush?

Here are the different types of ways your system can be cleaned: 

  • Gravity flush: A gravity flush can be done yourself if you're a competent DIY enthusiast. It simply means draining the water in your radiator system and replacing it with new clean water.
  • Power flush: A power flush will be more effective at removing sludge from your system, but it does require specialist equipment and can be expensive. A power flush should cost around £250 for a five radiator system and an additional £30 for every additional radiator.
  • Chemical flush: A chemical flush is a lighter clean with a chemical that will help to more gently ease the muck out of the radiator. A chemical flush doesn't require high pressure equipment, so should be a bit cheaper than the full power flush treatment.

After either of these processes, a chemical inhibitor should be added to the system water to prevent further sludge build up. This should cost around £20 and will help to protect your system water. 

It's important to remember that if you ever add system water to top up the pressure of your boiler system, then more inhibitor will need to be added to keep the concentration at the correct level.

Products like magnetic filters, which cost from £90, can also be very effective at keeping your system water in a good state. They capture materials within a sealed system, that predominantly come from the radiators, and keep your system water clean.

In areas with particularly hard water, a water softening filter is a sensible precaution to prevent limescale build up on critical boiler parts - such as the hot water heat exchanger. 

2. Is your boiler on the correct setting?

You only really need to have your boiler on its highest setting in the very depths of winter. Otherwise your boiler is needlessly heating water up to a very high temperature and wasting energy. It could also mean that your condensing boiler doesn't even condense (scroll down to find out more).

You can adjust the settings on your boiler manually, but realistically it isn't practical for you to check the weather every day and then tweak your boiler's settings. The good news is that there are products out there that will do all of this manual adjustment and fine tuning for you. 

Weather compensating thermostat and load compensating thermostat

Both of these devices cost around £100 and adjust the settings on your boiler to suit the temperature. So during a really cold snap, when you need your radiators nice and hot, they will raise the boiler temperature.

But during the majority of the year, they reduce the temperature and make your heating system much more efficient. 

The key difference between them is:

  • A weather compensating thermostat adjusts the settings on your boiler to suit the outside temperature
  • A load compensating thermostat does this to suit the inside temperature of your home.

If you only have your heating on intermittently, this may lead to longer warm-up times - but it will benefit you in the long run through efficiency savings as your boiler will be on less.  

To learn more about heating controls and how to get the most out of your boiler, head to boiler controls and thermostats.

3. Are your radiators balanced?

You could have clean system water, but a shoddily balanced heating system will result in you spending more money heating up your home than you need to. 

The image below shows the impact of an unbalanced heating system on a typical household. In an unbalanced system, when you set the thermostat to 20 degrees, the upstairs might actually reach 23 degrees. While downstairs, where most of us spend the majority of our day, will still be too cold. 

If you turn the thermostat up, until downstairs reaches a comfortable temperature, then upstairs is overheated. 

The end result of the poorly balanced system is that the thermostat is set at too high a temperature, which will lead to higher bills. Turning down your thermostat down by just one degree can save you £75 a year on your heating, according to the Energy Saving Trust. 

If you are having a new boiler installed, your system will need to be re-balanced. After the installation, you should insist that your heating engineer provides proof that your system has been balanced before paying for the installation. Ask to see the engineer's benchmark agreement, or simply run the heating for a few hours to check that your system is properly balanced. 

For tips on what to ask your heating engineer, and what to expect from a proper quotation, see how to get the best boiler installation.  

4. Do you have a condensing boiler?

If you're not sure if you have a condensing boiler or not, check to see if your boiler has a condensation drain pipe, like the one above, in addition to the flue gas pipe. If there's no condensation pipe, you don't have a condensing boiler. 

All modern boilers, whether they're combi boilers, system boilers or heat-only boilers, are condensing boilers. Condensing boilers reuse previously wasted heat from the boilers exhaust gases. 

Condensing boilers are at least 10% more efficient than old style boilers, so can save you substantial amounts of money each year on your heating bills. 

If you decide it's time to change your boiler, make sure you check which are the best and worst boiler brands before you buy.

5. Is your boiler actually condensing

Condensing boilers recover heat that would usually be lost from combustion gases, by condensing water vapour within the gas. This releases heat energy which is then transferred into the cooler, returned water from your radiator system. The water then leaves your boiler, piping hot, and is passed through your radiator system. And so on.

Critical to this process is that the returning water is the correct temperature. Condensing boilers only condense if the return water is at around 55 degrees or lower. If it's at a higher temperature than this, then your boiler is not condensing.

The easiest way to make sure your boiler is condensing is to not set the temperature of the boiler too high. A water temperature of 70 degrees on the boiler should ensure that it condenses. However, if you have a dirty or poorly balanced system, then this will also impact on the return temperature of the water to your boiler, and its ability to condense.

Somewhat depressingly, due to poor installations, there are thousands of condensing boilers installed every year that do not condense. So do not deliver the promised efficiency gains. 

If you want to know whether your condensing boiler is condensing, you can check the temperature of the water return flow pipe with a digital thermometer. Simply measure the temperature of the water from the outflow pipe, and the inflow pipe. A healthy heating heating system will have a 20 degree difference.

If you've decided that you will need a new boiler to make your central heating system as efficient as possible, make sure you read our guide to everything you need to know before you buy a new boiler

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