The 2013/2014 graph shows the night outside minimum temperature in red and the daily amount of gas used in kWh in blue. The light red and light blue are for the 2011/2012 season. You can see how I've converted my meter readings to kWh here.

It's interesting to plot this graph on a scatter chart to see the direct relationship between minimum night time temperature and gas consumption. The following graph starts frpm November 1st using the regime outlined in 'Announcement' below.

I have alos been experimenting with using 'degree day' tem,perature measurements. Degree day are calculated from a combination of both day time and night time temperatures and can be downloads from a weather station near you. According to (where you can download your local degreeday data), degree days are essentially a simplified representation of outside air-temperature data. They are widely used in the energy industry for calculations relating to the effect of outside air temperature on building energy consumption.

"Heating degree days", or "HDD, which are used below, are a measure of how much (in degrees), and for how long (in days), outside air temperature was lower than a specific "base temperature" (or "balance point"). They are used for calculations relating to the energy consumption required to heat buildings.

You can see that there is quite a tight correlation between gas consumption and degree day tempertaure. This is because I now have the heating on all day downstairs and degree day data is an 'average' of day and night temperatures.


eTRV 'Sleep' button: Since February 2011, we have been using Chalmor eTRVs on all radiators. To make major savings in gas usage, we are putting many radiators to 'sleep' during the evening cycle (including bathroom, utility room, dining room etc. etc.) using the eTRV Sleep button while having them all on during the morning cycle.

This resulted in a 20% reduction in gas usage - a great result.

March 2013 Boiler Upgrade: In March 2013 I upgraded my old 25 year-old boiler and my gas consumption increased by 50% compared to previous years. Although, the boiler is much more efficient, several things conspired to create this result. You can see this quite clearly in the cumulative gas usage graph below. Read below to find out why!

- Read about my boiler upgrade -

Reasons why gas consumption increased after the boiler upgrade: Up until the time of the upgrade in March 2013, I used eTRVs on EVERY radiator in the house (except one samll toilet) including the hall. The hall is very large and is like two rooms in size, so I used the etrv to turn it off during the evening. This reduced gas consumption significantly but meant we had to rush from room to room as the hall was pretty cold!

The upstairs toilet did not have a TRV or etrv on it. The reason for this was so that flow was maintained through the boiler when all the eTRVed rooms were up to temperature. The downside of this was that the temperature of the water in the pipes was held high all the time that the boiler was switched on. The reason for this eas that water temperature was being controlled by the thermostat in the boiler. This is a very inefficient way of running things though this was perfectly normal back when.

A modern system MUST have a room (in my case the hall) with a wall theromostat that directly controls the boiler by switching it off when that room gets to temperature thus allowing the water in the pipework to cool down. This also prevents the boiler 'hunting' (often turning on and off). The direct consequence of this was that I HAD to heat the hall, which is much more compfortable of course, but does significantly increase my gas consumption. This dramatically incresed my gas consumption during March, April and may when the central heating was still turned on.

The way round this is by using a wireless thermostat system ( such as the Honeywell EvoTouch system) that monitors each room individually and only when all rooms have reached their set temperatures does the boiler turn off. This means that I would be able to go back to how I had things before and have the hall at a lower tempertaure than other rooms downstairs. Recreating the system I had before upgrading the boiler.

Using the Honeywell Evohome and EvoTouch controller system

Take a read here to see how I have got on I'm using the Evhome system in conjunction with eTRVs from mid October 2013. I hope that this arrangement means that I will be able to reduce my gas consumption when compared to last year. By the way, I have added considerable roof insulation in September so I hope that this will also help reduce gas consumption. Time will tell!


As can be read elsewhere, I have focussed on improving things in my home to enable me to redice my gas consumption:

As can be read elsewhere and building on my experience of using eTRVs in 20011/12, I have focussed on improving things in my home to enable me to reduce my gas consumption - to recap:

  1. Improving the insulation in my loft using the LoftZone product.

  2. I have upgraded my boiler to a more efficient model as can be seen on this page.

  3. I have added a Honeywell Evohome / Evotouch controller to add 8 zones to my house.

For the last thirty years I have only had the central heating on for twice a day ( 07:30 to 10:00 and 17:00 to 21:00) and only occasionally had it on for longer. The reason for this is that my gas usage shot up dramatically whenever I did this. Years ago, this didn't bother me as I just paid the bills without thinking. That is not the case now.

I have been using this regime for only a few weeks now but I AM AMAZED. I have been running the central heating system for 14 hours a day (07:30 to 21:00) and I am using less gas than I used before when running it for just twice a day! AND THIS IS STILL THE CASE IN JANUARY 2014.

BBC's Rory Cellan-Jones: Soaring energy bills - can smart technology help? He should come to my site to see that it does!