2023 Data Analysis

Introduction:

So one year on, how does our gas and electricity consumption compare to previous years?

 

At the end of the summer 2022 we added loft insulation (increasing from 100mm to 300mm - see post: "Insulate the Attic". We also reduced the central heating flow temperature and dropped the room temperature by about 1degC (not everywhere - we sneaked it back up in some rooms!)

 

The result:

 

 

A reduction in gas consumption of £325 per year (19%) - comparing year ending October '23 to year ending October '22

 

Lifestyle changes in the year: I retired in the summer of 2023. The year end for this data is 12th Oct 2023, so this would have had limited impact as we only put our heating on during September. We also added weather compensation to control the central heating flow temperature. This was added in mid-August, so again would have had little impact.

 

Potential Sources of Error:

My aim is to get down to purely the impact of energy saving measures. Sources off error might come from:

 

Weather in the time period	I did make some attempt to look at annual average temperatures, but it is more complex than that - eg day Vs night (when heating is mostly off). I am also unsure how much impact windchill (windy day Vs calm day) will have. These results do not take account of variations in weather from year to year, other than 2009 to 2016 should be much better given the 7 year time period.
Life style	My wife's retirement in 2019 and then my retirement in 2023 (data still to be shared) seem to make little impact.
Pandemic	The impact of my working from home and being locked down seems to have caused a big rise in energy consumption, unless there is some other big difference that year.
Energy prices	I have removed the impact of this by recording actual energy used (kWh) and then using just one rate (usage and standing charge) across the whole time period.
Inconsistent time period	I have not measured energy usage on the same date every year, so the period for each 'year' was up to 27days from the 'perfect' 365days. My estimate is that this has made a <2% error in each year's energy usage data.

 

I would be very interested in feedback suggesting any other potential causes of error.

 

My view, from the above and now seeing 2 years of post-pandemic data is that 2020/21 (ie the pandemic lockdowns) is an outlier

 

Discussion:

 

In my post: "Insulate the Attic" I stated that I thought most of this saving was due to the attic insulation. However, reading this article from University College London (https://www.ucl.ac.uk/news/2022/dec/analysis-energy-bills-how-much-money-does-turning-down-thermostat-actually-save) their model from research of 13,000 homes is £1.1 saving per year per degC temp drop per m2. For our house (186m2) this gives £205/year saving for a 1degC temperature drop.

 

I feel an experiment coming on here. We did decrease the temperature in a 'lived in' rooms in late summer 2022. However, later in the Winter we moved this back up in some rooms (for more comfort). We had also made no change in the little used rooms - these account for perhaps 50% of the external surface area of our house. So my very rough estimate would be to halve the £205 and attribute £100 for saving due to reducing the temperature.

 

I still don't believe that a reduction from 70degC to 65degC of flow temperature has much impact (eg https://www.viessmann.co.uk/en/heating-advice/boilers/what-temperature-to-set-condensing-boiler.html give the dew point  of 55degC as the maximum water flow temperature to maintain boiler efficiency. However, I have not been able to find a graph or data to tell me the benefit of the drop from 70degC to 65degC.

 

Ignore 2020/21:

Now that I have 2 years of post lockdown/pandemic data I think that 2020/21 was an outlier, most likely we were in the house for much more time and just wanted it warmer.

 

So now the comparison is:

 

Year	Gas Usage	%age Saving on previous year	Energy saving measures taken early in that year
2019/20	£2,100	baseline
2020/21	£2,690	ignore
2021/22	£1,710	19%	Smart Heating Controls (Aug) and garage central heating pipes insulated (Dec)
2022/23	£1,387	19%	Oct: attic insulation, set flow temp to 65degC, drop CH temp by 1degC
n/a	£205	12%	UCL theoretical saving for 1degC temp drop

 

Difference between 2019/20 and 2021/22 is 19% with the main changes being smart heating controls and insulating central heating pipes. Using my calculation in my post on insulating pipes in the garage, £35/year or 2%1, then a whopping 17% is down the smart heating controls.

Drop from 2022 to 2023 is temp reduction (but negated because we nudged it up during the winter, so perhaps half the UCL findings, ie £100. Leaves £200 down to loft insulation.

All the is very rough an ready. I have not accounted for weather or other more subtle lifestyle changes, so my very (very) rough summary of savings is:

 

My Current Estimate of Impact of Different Energy Saving Measures:

 

Change	Installation cost	Approx annual saving	Approx payback period
Smart Heating Controls	£1,800	£2901 +02 / -100	6-11years
Insulate Central Heating pipes in Garage	£120	£35 +/- £15	2-6years
Loft Insulation from 100 to 300mm	£1,160	£200 +/-£100	4-10years
Flow temperature from 70degC to 65degC	£0	£25 +/-£25	Instant
Reduce room temp by 1degC for some of the winter in some rooms	£0 - less comfort	£100 +/-£50	Instant

 

Notes:

1. I have used the 2021/22 gas usage of £1,710 for converting between %ages and £s so that the sequence of the changes does not bias the result.
2. While the calculation gives me 17% saving for smart heating controls I think that this is probably on the high side.

 

Oct 2024 should help confirm if 2020/21 is an outlier that can be ignored and may give more clarity to other conclusions, but also adds two new factors: I retire and the addition of weather compensation to the boiler...

...look out for a future post.