EV, HV, MPGe calculations...

It seems that you have "contracted" the Obsessive Compulsive Disorder that befalls many new hybrid owners.

If all of that REALLY makes you happy......forge ahead.
But my advice is: Worry less, drive more.

 

the problem with ben 4 is, toyota decided in their ultimate wisdom to track hv miles only when the engine is running, and the rest, ev miles. so, you really have no hv mode miles, just gasser mode.

 

This is how I am doing it (numbers rounded off). Somebody check my math and correct any wrong assumptions:

At 500 miles, my car "thinks" it has gotten 100mpg. I presume this means it has used 5 gallons of gas.:

According to the "EV%" I have been in EV 65% of the time. I presume this is base don miles driven, not hours driven.

Thus, actual miles in HV = (1 - .65)(500) = 175 miles.
175 miles per 5 gallons = 35 miles per gallon.

I would certainly expect my car to be doing better than that, but as luck would have it, my HV miles have been almost entirely uphill. Or did I calculate wrong?

If it's right, OP could do a "reset" at a pre-planned time and do the math going forward.

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NEXT QUESTION
at $2.80/gallon and 1 gallon per 35 miles:
$2.80/35 = $.08/mile (8 cents per mile)

at $0.13 per kwh and 4.0 miles/kwh
.13/4.0 = .0325 (3.25 cents per mile)

As long as my electricity rate is lower than 32 cents per kwh, then electric is cheaper?

 

You calculated it wrong. The EV percentage includes Ev time while in Hv mode, which is the normal hybrid way of operating. Since all (or at least most) of that Ev energy came from gasoline, you have to include those miles as gas miles, not Ev miles.

Bottom line, you can't use Ev percentage this way for anything.

 

I'm glad you are interested in this. I'm hoping for a Prime to be my next vehicle and have been looking for the same info. Please post your findings.

 

Here's how I calculate mode-based efficiency.

Most of the time, I'm in Ev mode all day, every day. The Eco-Diary provides miles/kWh, mpg and total miles for each day. What I do is assume that mpg=199.9 means all Ev mode, so I calculate that day in miles/kWh. If it's less than 199.9, that means I was in partial Ev partial Hv that day and I don't now how much, so I assume all Hv for that day and just use the provided mpg. Most of the time this works because I primarily use Hv on long trips.

 

The Prime keeps a log of monthly miles/kwh available to the driver.
If the owner tracks charges and they are empty to full then the EV miles are known since a full charge is 5.6 kWh

 

I don't know about you, but for me, more than 99% of my charges are NOT "empty to full".

 

I've been keeping a daily log of actual kWh charge used and EV miles driven. Those two value are not something displayed nor can be calculated from the value displayed. It is very cumbersome to record the end of EV miles driven while driving a car (since there is no other way to record actual EV miles driven) and for that record to hold, I have to keep the car on EV mode only and never switch to HV or EV Auto while still have EV range left. This record gives me actual miles driven on EV mode/kWh. However, in actuality, some amount of kWh are used for powering things other than the motor, so it still is not TRUE EV efficiency, IMO. Also, it will not give me actual HV mode mpg until the next fill up for calculation of gas used.

 

The best and most fundamental method of tracking electric and gasoline usage is to treat the car as a black box which consumes electricity and gasoline, then measure the amount of each that enters the car. Then we can compute MPGe for electricity and MPG for gasoline, and the cost of operation on each. As previously discussed, gasoline use can be computed accurately from data supplied by the car. But it turns out that the amount of electricity consumed in charging can only be determined accurately by measuring the power input to the charging adapter.

If you are using the included Level 1 charging adapter to charge the car, plugging it into an inexpensive watt hour meter such as the P3 P4400 Kill A Watt Electricity Usage Monitor (available from Amazon) is a convenient way to measure the power used for charging the battery (including any losses in the internal charger). Some Level 2 charging adapters have watt meters built in; that's worth some extra money since 230 volt watt hour meters tend to be expensive.

In pure EV driving, the amount of power used to charge the car is typically about 10% to 15% or even 20% greater than the usage computed from miles/kWh. If the engine runs during the trip, the power needed to recharge can be significantly less than the miles/kWh usage.

Example: On a 32.3 mile trip, miles/kWh was 4.6, which is 155 MPGe (= 4.6 * 33.7). Based on this MPGe, electricity consumed was 7.00 kWh (= 32.3 / 155). Actual kWh to charge was 6.59, which is 0.41 kWh less. Since the trip was uphill on the average, there was no net regeneration and the engine must have contributed at least 0.41 kWh to the electric drive system (the reduction in charging power is larger, since charging is only about 85% to 90% efficient).

Rather than waiting for an infrequent fill-up, we can closely approximate gasoline usage from in-car data. As has already been mentioned, daily miles traveled divided by miles per gallon is the number of gallons used for each trip. Unfortunately, the limit of 199.9 MPG displayed in the car means you could use up to 0.15 gallons of gasoline on a 30 mile trip without being able to measure it. If Entune shows shows daily mileage greater than 199.9, use that value instead. In the example above, the car showed the daily MPG as 199.9, but Entune showed 346.1 MPG; thus the trip consumed 0.09 gallons of fuel.

 

Is it not true that the ICE is ALWAYS running in HV mode?

 

Yes, it is NOT true.

 

Right - in HV mode the Prime acts like a 'regular' Prius, where the ICE runs as needed but stops when the car is stopped, when decelerating the battery is charged and then can drive the car solely electrically for a short while, etc.

 

In routine driving in HV mode the ICE is off ~ 30% of miles. They are all counted as EV miles so far as I know

 

Not for miles/kWh. I don't know about the Ev percentage stat.

 

I was only talking about the EV %

 

Thanks everyone for this information! I've had some difficulty finding good descriptions of HV mode. More seems available on other modes, but I've been trying to learn what goes on in HV mode. Incidentally, don't have a Prius yet, nor have I ever ridden in one. Nor have we actually seen a Prime in real life... only recently has Toyota begun to roll them out in BC. So we wait to experience firsthand....