Calculating EV %

Hi all, been great to read through all the Prime discussion here since purchasing our Prime last year. Prior to the Prime we had an ordinary ICE vehicle which made tracking efficiency information nice and easy - each fill I would record the amount of petrol in along with the distance since the last fill, couldn't be simpler.

With the Prime, I thought this would be only slightly more involved after spying the EV% on the dash information. It wasn't long before I was aware that the EV percentage calculated also included EV time when in Hybrid mode - energy I would associate with the petrol engine, rather than being related to electrical 'plug' energy.

I think I have a reasonable way of segregating the two energy sources in my spreadsheet - and hence calculating an EV % that is actually what I would have expected: EV (plug energy only) vs HV time (petrol) - and I would be interested in your opinions.

The main inputs in calculating a more accurate EV% are:

• Total kWh from the plug from fill to fill.
  
• Total trip distance from fill to fill.
• Daily Km/kWh from the EcoDiary daily record.

The most onerous part of the data is recording the daily km/kWh information. Once I have this, I take an average of the prior 30 days km/kWh. Then, to calculate EV% my formula is:

= kWh charged since last fill * average of the last 30 days km/kWh (excluding zero days) / trip distance

For my last fill, we used 36.79 litres (9.719 US gallons) and 75.90 kWh combined to go 1,306kms (811.5 miles). The EcoDiary average km/kWh was 6.924km (4.302 miles). Provided the EcoDiary is giving me accurate figures I can then calculate an EV% of 40% vs the percentage provided by the car of 62% for that trip. I then use my EV% to determine 526km of total EV driving, with 780km using petrol/hybrid battery.

I don't believe I have seen anyone recording the EcoDiary daily records to calculate EV% so figured I would share. I had figured that the EcoDiary may be my only option, regardless of whether or not the EcoDiary km/kWh was accurate.