How to display true total cost savings

[bellissimo]

I see there are a couple of entities containing total cost savings, namely 'savings_total_predbat' and 'savings_total_pvbat'.

However it is not clear to me whether these are separate figures to be added together, or whether 'savings_total_pvbat' contains 'savings_total_predbat' (i.e. savings_total_pvbat' = 'savings_total_predbat' + {total savings from the PV system without PredBat).

If someone could confirm, that would be appreciated.

[gcoan]

There's explanation of all these sensors in the Output data part of the documentation https://springfall2008.github.io/batpred/output-data/#cost-saving-data

This should answer your question

[bellissimo]

Ok thanks. It says:

predbat.savings_yesterday_pvbat - A sensor which tells you how much money you saved from using Predbat vs not having a PV and battery system at all and all house load being met from grid import

which seems to imply that 'savings_total_pvbat' = 'savings_total_predbat' + {total savings from the PV system without PredBat}

[gcoan]

I've read your formulae several times and I'm not sure its right. savings_pvbat and savings_predbat measure different things, the first the saving from using predbat vs not having solar and batteries, the second the saving predbat brings compared to doing non-intelligent battery charging.

[bellissimo]

Well I interpret 'savings from using predbat vs not having solar and batteries' to mean the savings from having a Predbat managed solar and battery system.

To use an example to try and make my understanding as clear as possible:

A = Yearly cost before PV system installed: £1000
B = Yearly cost after PV system installed, but not using Predbat: £200
C = Yearly cost after Predbat installed to manage the system: £150

So I interpret the documentation as follows (taking a year's worth of use as an example):

savings_total_predbat = 'A sensor which tells you how much money Predbat saved you compared to not using Predbat' = B - C = £200 - £150 = £50

savings_total_pvbat = 'A sensor which tells you how much money you saved from using Predbat vs not having a PV and battery system at all' = A - C = £1000 - £150 = £850

or to put it another way 

savings_total_pvbat = 'savings_total_predbat' + {total savings from the PV system without PredBat} = (B - C) +  (A - B) = £50 + £800 = £850

[gcoan]

Agree it's good to have a worked example and if correct I can add the explanation to the documentation

Does this match with what you see from the predbat sensors?

[bellissimo]

Well I can't see a way to work it out from the other sensors that Predbat provides. However looking at the inverter data I can do some rough calculations to work out what the savings would have been if Predbat was not running, and it would seem that my assumptions and example above are correct (i.e. savings_total_pvbat is the total cost savings from having a Predbat managed PV/Battery system).

Reading the documentation again I think it is relatively clear, it was probably just me getting a little confused.