Hive active/British Gas - most accurate way to track energy usage - help!

takay9

I am with British Gas and meticulously track our day to day energy usage - but have noticed a discrepancy on the energy usage tracker. For instance, one day it said 76.6kwh of gas which, by my calculation (76.6kwh x 10.33p =£7.91, + 24p standing charge = £8.15). However, the £ spent says £8.89 which is almost 10% out - and I can't seem to get a straight answer of whether a) my calculations are wrong or b) which is correct, the kwh usage or the £ spent.

I have now signed up for the Hive Heating Plus trial period which, for the same day, actually say £6.40 for gas used. As much as I wish this is true, I presume this is way out but does anyone have any insight on what is most accurate?

Novice_investor101

Cant help as my BG gas smart meter doesn’t work & despite sending in readings they never update my credit balance or bill until review time, next February. 

I built my own spreadsheet & plugged all the formulas into it using the pricing on my tariff info & work off that. 

The first 7 day’s of Dec have cost £30 in gas alone (not included SC in that yet). Heating is now off again in the day. 

[Deleted User]

Do you have SMETS2 meters? If so, download and install the free App BRIGHT.

takay9

No sadly its a first generation smart meter...

Astria

takay9 said:

I have now signed up for the Hive Heating Plus trial period which, for the same day, actually say £6.40 for gas used. As much as I wish this is true, I presume this is way out but does anyone have any insight on what is most accurate?

Considering Hive only knows when the heating is on and not the rating of the boiler nor how much it's modulating, I'd say it's the least accurate and go as far as saying it's a pure estimation based on the amount of time heating has been called for.

I ignore everything that attempts to give me a £ spent and just write down the numbers direct from the meter - the ones used for calculating your bill. I use approx 4 units per day, so about £4.38 (multiply by 1.0954, or 1.10 for ease of remembering and estimation)

wild666

Gas smart meters still read in M3 so go to the meter and take the whole reading including the three digits after the decimal point, that's what I do then multiply by 11.3 to give the kWh used if it goes to more than three decimal points then use the first three figures after the decimal point. 
It could also be that when you work out the usage the CV you are using is not the one that is used on the bill. on average the CV could be between 38.8 and 40.3, this would give kWh used between 10.96 and 11.41948 kWh  so it could be that you haven't used the same CV as the one on the bill and that is what is making the difference in kWh used in producing the bill.

takay9

An update on this - interestingly I've been taking daily smart meter readings and doing the formula to turn into KwH (m3 x 39.4 calorific value x 1.02264 / 3.6). Wednesday worked out at £9.49 spend - or £10.20 if you add 5% VAT and 24p standing charge. The energy usage chart on BG app shows £11.25 - so it seems to be overestimating by around 10%. If correct, this does make me feel a bit better but also just wish it could be totally accurate..!

[Deleted User]

If correct, this does make me feel a bit better but also just wish it could be totally accurate..!

Sadly, not. Calorific values vary throughout the day. Suppliers use the average calorific value of the gas supplied during the billing period not a fixed caloric value of 39.4 as used in your calculation. Also, if the average calorific value is assessed to be 39.475 then a truncated value of 39.4 is used for billing.

takay9

Dolor said:

If correct, this does make me feel a bit better but also just wish it could be totally accurate..!

Sadly, not. Calorific values vary throughout the day. Suppliers use the average calorific value of the gas supplied during the billing period not a fixed caloric value of 39.4 as used in your calculation. Also, if the average calorific value is assessed to be 39.475 then a truncated value of 39.4 is used for billing.

Sure, but even if this was, say 41, it wouldn't be as high as what it showing on the BG app. 

[Deleted User]

takay9 said:

Dolor said:

If correct, this does make me feel a bit better but also just wish it could be totally accurate..!

Sadly, not. Calorific values vary throughout the day. Suppliers use the average calorific value of the gas supplied during the billing period not a fixed caloric value of 39.4 as used in your calculation. Also, if the average calorific value is assessed to be 39.475 then a truncated value of 39.4 is used for billing.

Sure, but even if this was, say 41, it wouldn't be as high as what it showing on the BG app. 

The BG app will also be using a fixed CV which may be different from Hive. I have no idea what CV the BG app uses. Arguably, you will happy about the lower kWh figure that you are being billed for.

Astria

takay9 said:

Dolor said:

If correct, this does make me feel a bit better but also just wish it could be totally accurate..!

Sadly, not. Calorific values vary throughout the day. Suppliers use the average calorific value of the gas supplied during the billing period not a fixed caloric value of 39.4 as used in your calculation. Also, if the average calorific value is assessed to be 39.475 then a truncated value of 39.4 is used for billing.

Sure, but even if this was, say 41, it wouldn't be as high as what it showing on the BG app. 

Surely the BG app is a pure estimation of gas usage though?