Working out Central Heating running cost

mac.d

Talldave wrote: »

I read the meters weekly and my Excel spreadsheet works out the weekly kWh (I just update the calorific value from the bill each month). The weekly figures show the seasonal variations clearly. The calculation to get from m3 to kWh should be on your bill.

How do you do this on your spreadsheet? For my own heating I'm happy enough just to monitor the monthly meter readings but I'm thinking of adding weekly gas meter readings to a spreadsheet to keep a closer eye on winter heating for someone who uses their heating a lot at this time of year.

victor2

mac.d wrote: »

How do you do this on your spreadsheet? For my own heating I'm happy enough just to monitor the monthly meter readings but I'm thinking of adding weekly gas meter readings to a spreadsheet to keep a closer eye on winter heating for someone who uses their heating a lot at this time of year.

You can make it as simple or as complicated as you like...
Simple way:
Column for the date, column for the reading, column for the calculated kWh (multiply the difference between this reading and the previous one by 11.2), column for the cost (kWh x rate x 1.05 for VAT), cost divided by days between readings for daily cost.

From that you can get more sophisticated, by including your standing charge and the actual calorific value used by your supplier on your latest bill (which may change slightly when each bill comes), which means using the formula shown on your bill for calculating the kWh from the units.
You can put calorific values in a table and look them up in the formula. That way you keep a history of CVs, and can just enter a new one whenever it changes on your bill, without changing the formula.
You can then graph your usage for comparison in future years, or if you make significant changes, such as getting a new boiler.

It goes on, beeen doing it for years!

AndyPK

It's a good, worse case calculation.


But as said, measurements over 1 week, give a better idea

mac.d

victor2 wrote: »

You can make it as simple or as complicated as you like...
Simple way:
Column for the date, column for the reading, column for the calculated kWh (multiply the difference between this reading and the previous one by 11.2), column for the cost (kWh x rate x 1.05 for VAT), cost divided by days between readings for daily cost.

I'll have a go with this simple version thanks, you lost me in the next paragraph.

Talldave

mac.d wrote: »

How do you do this on your spreadsheet? For my own heating I'm happy enough just to monitor the monthly meter readings but I'm thinking of adding weekly gas meter readings to a spreadsheet to keep a closer eye on winter heating for someone who uses their heating a lot at this time of year.

Easy - as an example from my spreadsheet, cell R5 (the gas kWh entry) contains the formula:
=(P5*Q5*1.02264)/3.6


where cell P5 is m3 of gas used (this week's reading minus last week's reading) and cell Q5 is the calorific value (currently 39.1).


I auto drag/copy the calculations down a row each week.


Cell Q5 actually contains: =$Q$4 as cell Q4 in the row above contains the value of 39.1 from a bill dated that week. That prevents the drag/copy function incrementing the calorific value to 40.1 during the copy. When the calorific value changes, I put a new manual entry in (say in cell Q9) and then the subsequent rows (Q10 onwards) will be =$Q$9.


If your meter is imperial, the conversion equation is:
=(P5*Q5*2.83*1.02264)/3.6

northernsoul

For your interest (hopefully) I have recently been taking hourly readings of my central heating usage (no other gas used other than for the central heating). This is from 29/10/19.
Inside temperature at start of test in room where thermostat is is 15.3C. Boiler (Valliant ecotec plus 837 - 28kw output) set at 65C. Stat target set for 19.5C. Outside temp at test start time of 09:20 on the 29/10/2019 is 5C. Outside temp increased to 11C then fell back to 8C at end of test at 21:20. Readings taken every 60 minutes for each 60 minute period. Temperature also recorded by separate thermostat. Stat is a Honeywell CM927.
100 year old terrace house. Only insulation is roof insulation in attic, but attic only heated to number 1 on radiator TRV.

time , usage (in m3) , cost (inc vat) , temperature of room reached , stat temperature indicated.

60 , 1.08 , £0.43 , 17.5C , 18.5C
120 , 0,50 , £0.20 , 18.8C , 19.5C
180 , 0.56 , £0.22 , 19.1C , 19.5C
240 , 0.48 , £0.19 , 19.7C , 20C
300 , 0.35 , £0.14 , 19.9C , 20C
360 , 0.29 , £0.12 , 19.5C , 20C
420 , 0.43 , £0.17 , 19.8C , 20C
480 , 0.35 , £0.14 , 19.8C , 20C
540 , 0.22 , £0.09 , 19.8C , 20C
600 , 0.37 , £0.15 , 19.9C , 20C
660 , 0.26 , £0.10 , 20.0C , 20C
720 , 0.33 , £0.13 , 20.0C , 20C

Total gas usage for 720 minutes (12 hours) 5.22 m3
Total cost £2.08

harrys66

any chance of uploading your spreadsheet please?

Tom99

dan~ wrote: »

Hello, I didn’t count in standing charge and it’s not a lot and I have to pay it regardless but I did forget about VAT but that’s only going to be small at 5%.

The 4.1p is what we’re locked into with BG until 2021 so nothing I can do about that, when I was looking at the big 6 they were all basically the same, but that’s my fault.

On that website where it says unit rate, I guess I put on 4.1 as my rate?

If it’s correct then I’m very happy, I always thought it costed more to run it which is why I’ve been so stingy with having it on

If you look at your bill you should be able to work out how much each unit of gas costs. For example on my bill 156m3 cost £58.61+ Vat = £61.54 or 39.45p per m3 unit.
If you use that method you do not need to worry whether your meter is metric or imperial nor the conversion rate to kWh.

[Deleted User]

Hi,

northernsoul wrote: »

time , usage (in m3) , cost (inc vat) , temperature of room reached , stat temperature indicated.

60 , 1.08 , £0.43 , 17.5C , 18.5C
120 , 0,50 , £0.20 , 18.8C , 19.5C
180 , 0.56 , £0.22 , 19.1C , 19.5C
240 , 0.48 , £0.19 , 19.7C , 20C
300 , 0.35 , £0.14 , 19.9C , 20C
360 , 0.29 , £0.12 , 19.5C , 20C
420 , 0.43 , £0.17 , 19.8C , 20C
480 , 0.35 , £0.14 , 19.8C , 20C
540 , 0.22 , £0.09 , 19.8C , 20C
600 , 0.37 , £0.15 , 19.9C , 20C
660 , 0.26 , £0.10 , 20.0C , 20C
720 , 0.33 , £0.13 , 20.0C , 20C

Total gas usage for 720 minutes (12 hours) 5.22 m3
Total cost £2.08

I'm quite intrigued by your figures here.


5.22 m3 x 32 (roughly) to kwh = 167.


Then cost £2.08/167 = 1.245 (inc vat) per kwh.


So, who is your supplier, seems such a cheap rate.


Edit: Oops, , sorry got it wrong.


Thanks to victor2 for correction,


'You multiply m3 by 11 to (roughly) get kWh. 32 is the multiplier if you have an imperial meter, measuring hundreds of cubic feet'

victor2

[Deleted User] wrote:

Hi,

I'm quite intrigued by your figures here.

5.22 m3 x 32 (roughly) to kwh = 167.

Then cost £2.08/167 = 1.245 (inc vat) per kwh.

So, who is your supplier, seems such a cheap rate.

You multiply m3 by 11 to (roughly) get kWh. 32 is the multiplier if you have an imperial meter, measuring hundreds of cubic feet.