We have all experienced the phenomenal rise in the costs of domestic electricity and gas in the last few months and this has focused us on the need to better control its use. After scanning the Internet for practical advice, it came up with all of the usual advice that you would expect, use energy saving bulbs, switch off chargers, turn your thermostat down by one degree etc. etc. Although this guidance is very useful, I could not find much discussion about how much gas typical houses used throughout the year. Even in chat room discussions, I could not find too many places where the actual amount of gas used was discussed. Moreover, we all know that we use more gas in the winter than the summer but I wanted to know by how much and what were the main drivers behind the horrendous quarterly bills I had been receiving in 2008.

You can download an annual average annual gas consumption graph in the UK. An approximate guide to gas consumption according to house size from the now defunct EnergyWatch site is shown below:

I felt that I needed to gain more understanding and that if I achieved this then I would feel to be in more control. I'm happy to say that I believe that this has been achieved and my analysis of electricity and gas usage has really helped me to reduce my energy bills by more sensible use of gas central heating and electrical appliances. I hope you find it useful. Let me know if you do: Email:

Top of my list was to understand how gas use changes during the year which is clearly dependent on outside temperature, especially so during the winter. So, task number one was measure gas consumption on a daily basis. This is quite easily achieved by reading the gas meter at the same time each day. Shown on the left is a typical gas meter and if the gas used each day is to be accurate, it needs to be read to at least decimal places e.g. 10884.33. This is not at all onerous and takes only a couple of minutes.

If your gas meter is outside of the house, you might need to get hold of a gas meter box key like the one shown on the right. I'm not sure where these are available from but I'm sure they shouldn't be too difficult to get hold of.

I also started measuring the outside temperature each morning as well but I soon came to the conclusion that the outside temperature was lower at some time in the middle of the night.

As I assumed this was a key factor in how much gas it took to heat my house, I invested in a low-cost maximum-minimum electronic thermometer available from Maplin. The one I purchased will measure inside temperature and had an external temperature sensor on the end of a 2-metre lead which can be placed through a convenient window. I was now able to measure both the minimum night temperature and the daily gas consumption so I was ready to go!

The next task is convert the daily gas units used to Kilowatt Hours (kWh) as this is what your gas supplier uses to create your bill. You will need to get the exact formula from your own gas supplier. The one shown below is British Gas (Incidentally, the calorific value has changed in the last few months from 38.8386, a change that favours British Gas from a billing uplift of 1.009% [Dec 2008]):

Converting units to Kilowatt Hours
( Your local calorific value )

Of course, this is not calculated manually each time but is achieved using an Excel spreadsheet as shown below. It's quite easy to convert the calculated kWh/day to monthly and quarterly estimates and multiply by the pence/kWh charges supplied by your gas supplier on your quarterly bills.

Gas consumption analysis spreadsheet

I found the results of the monitoring very interesting as can be seen in the graph below. Before looking at the graph you should know that:

• Our house is quite a large old 1932 four bedroom detached house.

• We also use gas for cooking and heating water.

• The central heating boiler is an old Potterton Netaheat ( Boiler efficiency database ) and is not as efficient as a new condensing boiler.

The graph covers three periods of gas usage. The first period gas is used for cooking and heating the hot water tank (more on this later). For the second period, the gas central heating is only turned on for a single period in the morning. For the third period, the gas central heating is turned on twice a day - morning and evening. The two peaks show when I had the gas on all day - not something I plan to do every day.

Notes 2009/10: Towards the end September we turned the gas on once per day in the morning . At the beginning of November we had it on twice a day in the morning and evening. During March, the day time temperature has been so high we had the central heating on during the evening only essentially returning to a once a day regime. In the middle of April we have turned the gas central heating off completely and only using it for hot water and cooking. When it has been chilly in the evenings we use our wood fire.

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!

Notes 2011/12: We are now using eTRVs this year on all my radiators (see below) and we are putting many to 'sleep' in the evenings using the eTRV thus saving quite a bit of gas - we hope! We turn off all the rooms we are not using in the evening including bathroom, utility room, dining room etc.

• November 2011: Very mild compared to previous years so only had gas on once per day.

• December 2011: Gas in now on twice a day, but using eTRVs have allowed me to put most radiators on low or many put to 'sleep' in unused rooms in the evenings - this really reduces gas consumption noticeably. The eTRVs are programmed for Economy in the evenings except in used rooms and I have been over-riding the programming by turning off unused radiators downstairs in the evening as a trial. My target is to see if I can limit gas usage to less that 100kWhr when on twice a day - without being in any way uncomfortable!

• January 2012: We still having the heating on twice a day and using the eTRV sleep button to turn off unwanted radiators in the evening cycle. If we get cold during the day we light the fire. Wow! We have saved 32% of gas used so far compared to last year due to the use of eTRVs - this is projected to be 20% over the full year. This is even taking into account that we have had the heating on twice a day every day (due to 'return to nest' syndrome) whereas we often only had central heating on once a day on many days in previous years.

The 2011/2012 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 2010/2011 season.

Compared to the first year we started monitoring gas usage we have saved over 5000kW hours!

2011/12 have been much warmer than the the previous two years, though January 2012 is pretty much the same in all three years.

I've had some success - in spite of price rises!

In February of this year I undertook a trial of Chalmor ETRVs as can be seen below. I am now continuing to monitor through to January 2012 whether the use of eTRVs are continuing to reduce gas usage this winter.

The plot below shows this winter compared to last winter but care needs to be taken in interpreting the results:

• I have excluded all the summer days where gas was only used for heating and coking and averaged 13kW/hrs a day.
   

• I have plotted gas usage every day in the scatter plot below even though some days I have had central heating off, some days on just once a day in the morning and some days twice a day. This can mean a 2:1 spread in gas used for any particular nigh time temperature.
   

• Both plots should intercept at the right around 13kW/hr as this is when the central heating is off.
   

• If the eTRVs are helping me reduce gas usage, then the red line should always be below the blue line.

We will see what happens as the 2011/12 winter progresses! Come back regularly and take a look!

I used an Owl electricity usage monitor and its USB unit to look at my daily electricity profile (The OWL software is awful!).

Below is a typical day's electricity usage profile. Averaged out over 24 hours, the biggest impact on usage are all the items that are on 24 hours a day.

This day's usage peaks are as follows:

• Evening: televisions and other video equipment.

• The over night fluctuation is due to fridge and freezer.

• The 09:00 8kW peak is an electric shower.

• The 2.5kWh peaks is a kettle.

• The 3kWh peak at 13:00 is a washing machine (and a kettle on at the same time!).

Electricity

I have come across an interesting concept to save electricity - VPhase - but I'm not entirely convinced how much it would save me. Perhaps I need one on evaluation and I'd be happy to pass on my real results! Pros and cons discussion on the IET forum.

2010 to 2011 Season

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.

eTRV gas usage - From February 1st 2011

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.

Conclusions.

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.

2009 to 2010 Season

Daily gas consumption 2009/2010

2008 to 2009 Season

  Daily gas consumption 2008/2009

I hope that this helps and if you undertake a similar exercise please let me know your results and I'd be happy to publish them here. Email:

Useful links:

• Real-time Web Based Power Charting

• Combi boiler gas consumption

• Average gas consumption

• How to dramatically cut your electricity use 

• what is average gas consumption based

• Gas and Electricity price statistics

Email:

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