How to get/track electric and gas usage / efficiency info

Discussion in 'Prime Main Forum (2017-Current)' started by srothkin, Jan 1, 2023.

  1. srothkin

    srothkin Junior Member

    Sep 9, 2008
    Ossining, NY, USA
    2017 Prius Prime
    Prime Advanced
    I've been keeping track of approximate electric cost/mile for each gas fillup for my 2017 Prius Prime. I use this to compare electric and gas rates. It lets me know when it is cheaper to plug in vs using more gas.

    Up until now I've been using data from the SmartCharge OBD device/service (from ConEd/FleetCarma) to track per trip data to help me calculate this. The relevant per-trip data provided by SmartCharge includes
    • Date
    • Duration
    • Distance (mi)
    • Gasoline Consumed (gal)
    • Electricity Consumed (kWh)
    • Fuel Efficiency Equivalent (MPGeq)
    • Starting SOC (%)
    • Ending SOC (%)
    • Electric Distance Fraction (%)
    Unfortunately, ConEd ended the SmartCharge program so it will not give me this data going forward.
    Given that the data obviously is available to an OBD device, how should I go about recording/extracting it going forward?
  2. Salamander_King

    Salamander_King Senior Member

    Nov 8, 2015
    New England
    Other Hybrid
    Disclaimer: I no longer own a PP. The following comment is based on my past experience while owning PPs.

    Unfortunately, there is no easy way to track the EV and HV portion of the trip on the PP. I am not sure how your OBD dongle worked, but I suspect the data are extracted from ECU similar to the data obtained using the Hybrid Assistant App. If so, the data for the "Electricity Consumed (kWh)" may not represent the true efficiency comparison between the EV mode and the HV mode you are after.

    Yes, it may be true that the ECU knows exactly how much kWh of electricity was fed to the motor. But to my knowledge, it does not distinguish the electricity from the wall charger vs. electricity from the regen and from the engine in HV mode. If you completed the entire trip on EV mode then you can be sure that the entire kWh consumed was from the wall, but if any of your trip data contains some EV mode mixed with HV mode, then, the data is not likely showing what you want.

    The best you can do is to track the record of Eco diary data for EV efficiency (miles/kWh), both the daily and the monthly, as well as the lifetime average, shown on Drive Monitor 2. Those numbers will indicate what EV efficiency you are getting when strictly in EV mode, thus if you are also logging the data on how much kWh of electricity was consumed from the wall when charging, then you can calculate the cost/mile for the EV portion of your trips.

    But this leaves the gap on the HV portion of the mpg. The dash mpg is for the entire distance traveled per 1-gallon gas used regardless of the driving mode. Naturally, the number is very inflated if you do a lot of EV mode drives. You can not get accurate mpg strictly for HV mode from the data provided by the car or any OBD dongle and app I know of. Again, your best bet is to keep a record of the amount of gas pumped into the tank and the distance traveled in between the fill-ups. If you have kept the number of kWh used to charge the battery from the wall, and the efficiency (miles/kWh), then you can guesstimate the distance traveled in EV mode for that period. Thus it allows for estimating the distance traveled by HV mode. But all of those data are just estimates, there are many instances when the engine is on even though it may not be propelling the car or charging the battery. Likewise, the charging session uses some electricity that does not end up in the traction battery. There is no 100% conversion of energy.