Stay Warm While Halving Your Heating Bill

This is a summary of the thinking and steps behind reducing the heating bill in our 2000ft2 house in the UK from 16,000kWh/yr down to 7,000kWhr/yr with minimal expenditure. With the reduction in energy usage comes the option to set rooms even warmer. Please read on and see what elements you can apply.

Starting point

In 2020 we moved to our current house that was built in 2010 with some eco principles in mind. The downstairs has underfloor heating with individual room thermostats – but has a U shaped open plan for kitchen, lounge, dining and family rooms (wall between kitchen and lounge). The heating is supplemented by a gas fire in the lounge. Upstairs heating runs from one thermostat at the top of the stairs and individual TRVs on the bedroom radiators. The boiler is modern condensing type (installed 2019). Separate timers drive the upstairs and downstairs systems.

Our first year's gas usage was 16,000kWhr – just as much as our previous, similar size, house in the North of England with a 1960s system, original boiler, with one thermostat and a fire to top up the lounge. Obviously disappointing!

Key principles applied for improvement:

1. Only heat the rooms you are using, when you are using them.
2. Reduce heat losses where you can.

2 off Smart Thermostats Tuya ME81AH

Curtains and rail 3.5m wide

The original thermostats were single temperature adjustment. Our best efforts to turn down the kitchen after we had eaten and up again the following day just weren’t working.

Automation is there to help! The original thermostats used three wires – live, neutral and switched. So there appeared to be a potential to install smart thermostats - where different temperatures could be set for different times of the day. I was not sure if these would work on a timed system. Fortunately I selected Wifi versions – so although these did not have internal clocks they did read the time off the internet when switched on. I installed two of these – for the Kitchen and Lounge. They needed back-boxes (original were surface mount) but these were not too difficult to fit with all the YouTube videos to advise. The original thermostats could be fitted to a back-box so reversing the installation was possible if all went pear shaped.

I used Tuya smart thermostats – around $25/£20 from Ali-Express. Amazing value. They are supported by a nice app that is much easier to use for the detailed settings than direct on the thermostats. So now we could have a low temperature in the morning when we are mostly in and out and then the Kitchen warming up for dinner and then off, while the lounge warms up ready for the evening. The Tuya units allow for 6 periods during the day, each with its own temperature, plus the option for different schedules for weekday and weekend. So there is plenty of flexibility. We are retired and so use the one schedule all week.

The other downstairs areas, study, cloakroom and hall, were set low on the original thermostats and are used only when needed.

Upstairs was set active for 20 mins am and pm to take the chill off the bathroom and heat the towel radiators. Unused bedrooms were set low. Electric blankets make our bed lovely and warm so no need to heat the room.

The net effect of this was a reduction to 13,000 kWhr/yr. It was probably greater as the decision to reduce morning heating was made some time after the smart thermostats were installed.

The lounge was a struggle to warm, needing the gas fire on a lot of the time to top up the heating. The lounge is open plan as it has no windows. It is in the middle of one side of house with hall to front and dining room to back. Double doors to the hall but big heat losses to the dining room through a 2.9m (9’ 6”) wide gap. We considered and discarded options of sliding doors and folding doors because of reduced light and inconvenience.

Then we realised there was a 0.75m (2’6”) wide blank wall on one side of the gap and we could fit a curtain. We bought a reasonably heavy pair of ready to fit curtains and set the curtain rail at the appropriate height to give a minimum gap to the floor. The curtain rail needed modification to pull both curtains (as one) to the one side. This just needed a longer chord for the longer single span.

Fitted in February 2022 the impact was instant and huge. The gas fire has never been run since. The underfloor heating works faster and can do its job with ease. The lounge is much cosier in the evenings. A big success - warmer and heating down to 7000kWhr/yr.

With the curtains open there is no impact on light. Getting through when closed is easy via the curtain middle or either end. We still go the open plan route to the kitchen despite it being arguably shorter via the hall. Old habits die hard. The curtains cost £200 and paid for themselves in few months.

The plot shows annual usage to the date on the x axis. Using annual data removes most of the seasonal impact. However the impact of the changes is only seen during the winter when the heating is on. The smart controllers were installed before the start of the plot with their impact seen up to their anniversary (March 2022). The curtains were installed a month before the anniversary of the smart controllers. Hence overlapping. Their impact came partly during the end of the winter from February 2022 and the remaining in the following winter late 2022/early 2023.

For situations without individually zoned heating systems it looks like smart TRVs could go a long way to deliver similar outcomes. These may not have the temperature vs time capability built in but this can be delivered by routines in Alexa/Google. So worth exploring. A user on Reddit said he had used these and Alexa routines to heat just his wife’s office when she was working from home.

Please don’t be blindsided by the ‘we will use less energy if we keep the house warm all the time’. This is arguably true on an hourly heating basis. The energy required to heat up a room can be significant compared to the losses – but heat input=heat loss and heat loss is proportional to temperature difference and time. So maintaining a temperature difference all the time will use more energy.

For the avoidance of doubt I have no link whatsoever to Tuya and have not had any communication with them. However their devices have worked as I had hoped and if I had to install more I would use them again without hesitation. I used their model ME81AH that does not appear to still be available. A search on ‘ME81’ and/or ‘3A Tuya Smart Life Wifi Thermostat’ gets results that include devices that looks like the same unit. Check for 'Weekly programmable' and '6 modes per day'. Make sure to get the WiFi version and 3A for water systems (thermostat drives the room water solenoid valve).

I hope the principles outlined here can be used to make us warmer with lower energy use. Home heating is probably the biggest opportunity we have as individuals to reduce our impact on climate change. Please see what you can do. You know it make sense!