Save up to 8% on your Gas Bill by adjusting your Condensing-Combi Boiler

A recent report by the Heating and Hot Water Council (HHIC) found that households can save around 6-8% on their gas bill just by turning down the flow temperature on their condensing combi boiler. To be clear, this is not turning down your thermostat. 

What Does “Turning Down the Flow Temperature” Mean?

Most gas boilers are set up to deliver water at 80 degC, and return it to the boiler at 60 degC, having given off 20 degC to the room.  This is called 80/60 flow.  However these temperatures are too high for a condensing boiler to achieve the 92% efficiency that they are rated to.  They only start condensing at 70/50 degC, and will only reach peak efficiency at 65/45degC or lower.

Won’t this make my house cold?

It does depend on the size of your radiators and how much energy you use to heat your home i.e. how well insulated it is.

For homes with modern double-glazing, cavity walls and good levels of loft insulation, you should be able to drop your flow temperature, with no impact on comfort.  The radiators won’t get quite as hot, so if you are used to running your heating for short periods, you may need to run your heating for longer to maintain the temperature

The good news is that, it costs nothing to try it and see.  Try turning down your flow temperature and testing to see if your house stays warm. 

What kind of boiler do I need?

This tip is only suitable for homes fitted with a combi boiler (that is one that delivers hot water on demand without a hot water tank) installed withing the last 15 years. 

Safety Warning If you have a hot water tank, then you need to run at higher temperatures to prevent legionella outbreaks in your hot water tank, so this tip is not suitable for you.

How do I reduce the flow temperature?

Most combi boilers have two dials on the front: one for heating (usually with a little radiator icon over it) and one for hot water (with a little tap icon).  Some boilers have a digital display next to the dial, some have an up and down button, some just have vague markings so it is not actually possible to know what temperature you have lowered it to.  Turn the dial down and see how you get on.

Here’s a short video on how to do it: Turn Down the Boiler Flow Temperature

The above is a summary of an article published by The Heating Hub

Heat Pumps

What is a Heat Pump?

A heat pump works like a refrigerator in reverse, taking heat from the surrounding air (air source heat pump) or ground (ground source heat pump) and converting it to heat to heat your building.  For every kWh of electricity that you put in, it leverages the energy in the air or ground to give you more heat out.  Exactly how much depends on the temperature outside, and the temperature that you want to deliver the heat, so it varies through the year between about a factor 2 and 5.   Since the ground temperature is much more stable than the air temperature, a ground source heat pump is more efficient.

How much CO2 could I save?

It will vary by house and depending on the type of heat pump.  For an air source heat pump in a house in Dukes Ride, I worked out that it would cut CO2 emissions from the current 4 tons per year to 1.65 tons per year.  A saving of 2.35 tCO2/year.

How Much Does it Cost?

There is a government grant, the boiler upgrade scheme, which refunds some of your upfront costs – about £5,000 for an airsource heat pump on a house on mains gas, more for ground source heat pumps.  The installation cost is likely to be £10 – 20, 000 for an airsource heat pump and £20 – £30,000 for a ground source heatpump. 

If you have oil-fired heating, it should also significantly cut your energy bills and probably save you money over a 10-15 year time frame.  If you have gas fired central heating the payback is likely to be longer.

For a lot more detail, have a look at the Energy Saving Trust website 

What else do I need to know?

Have a read of our blog about one residents experience of replacing their gas boiler with an air source heat pump.

Because heat pumps are more efficient delivering heat at a lower temperature, you leave the heating on all the time to maintain a constant temperature through your home.  You may also need bigger radiators or underfloor heating to transmit the heat.

An air source heat pump looks, and sounds, a bit like an air-conditioning unit outside your house.  You may need planning permission, and almost certainly will if you live in a listed building or a conservation area.  Having said that, heat pumps may be a particularly good solution for historic buildings because they deliver steady heat at a lower temperature rather than cycling heating and cooling.

If you do go for underfloor heating, it’s a relatively small addition to also make the heat pump cool your house in the summer.

To find out if your home is suitable for a heat pump, try the heat pump calculator

Historic Buildings and Conservation Areas

What do I need to Consider?

Historic buildings present different challenges for energy efficiency.  You will almost certainly need planning permission for most changes and some (such as solar panels) are unlikely to be approved.  For more on BDBC’s approach to sustainability in historic buildings see our blog on Historic Buildings and Planning.

Where should I go for advice?

The Sustainable Traditional Buildings Alliance has a lot of information about measures that you might consider see STBA Knowledge Centre .  The Knowledge Wheel is a particularly good resource.

What could I do?