The 2010/2011 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 2009/2008 season.

Notes 2010/11: During October, November and December 2009 we have been lighting fires using logs. As the temperatures have been so high this has meant that we have not turned the central heating on in the evenings thus saving a total of over 2000kWatt/hr - a complete month's average usage! We intend to use up this 'heating bank' during the next cold snaps in January and February 2010. It's got very cold during January 2010 so inevitably we have had the gas on longer, however, we have used less gas due to the use of open fires using free logs!

Chalmor eTRV trial: From February 2011 I am trialling 'eTRVs' - electronic thermostatic radiator valves.
I hope that by using timed programmes on several individual radiators, I should be able to reduce my gas usage by a goodly amount.

The blue dots is my gas consumption in January, February and March of 2008, 2009 and 2010. The central heating is on twice a day and I have removed those data points for when I had it on just once a day or when I had it on all day. The red dots are for this February using the eTRVs. I subtracted 13.5kW hours each day which is the average used for heating hot water and cooking.

Note: For the complete month of February 2011, gas was turned on twice a day (a total of 6 hours)

Note: Main savings seem to be in the evening when most radiators except for bedroom are 'low'. We have a log fire in the living room most evenings.

Note: I subtracted 13.5kW hours each day which is the average used for heating hot water and cooking.

Note: Average saving looks to be around 23% so far.

Note: February was much warmer than previous years but March seems to be rather warmer and I am having the gas turned on only once per day - in the morning.


  1. For the month of February I have clearly saved a goodly amount of gas - probably around 20%. The reason for this is that I am able to turn the radiators down using the timer capability in the evening period when we have a open fire in the living room.

  2. I believe the eTRVs are much more responsive to room temperature changes and have much less hysteresis than the old mechanical TRVs. I had a similar issue with the thermostat on my hot water tank until I installed an electronic version.

  3. I have found them more convenient for turning radiators off sporadically as temperatures increase as spring comes.

  4. Am I convinced they have benefits? Yes.