Prius Prime 2017 - Comparing Electric vs Gas cost

Electric
electric bill total= $100.34
Total kWh used = 706.47
14 cents per 1 kWh
car full charge = 27.7 miles
car battery uses = 6.3kWh
89 cents per charge
0.03 cents per mile
________________________________
Gasoline
$3.10 per gallon
car gets about 50-64 mpg with no charge
0.06 - 0.04 cents per mile on pure gas

________________________________
BUUUUT I can only charge at home since Pittsburgh doesn't really do the whole plug in scene and work doesn't allow it. Also I drive 38 miles round-trip between work and home.

 

I'm pretty sure he was talking about usable, although I figure it to be ~ 5.5 kWh

 

Don't include fixed charges

 

Not including the flat rate it would be 2.7 cents per mile. Rounding up that's still pretty much 3 cents.

 

$/mile really does make comparisons much simpler.
Gas costs are either very simple, or extremely complicated. Pump price is easy. Costs to society, your kids society, and global politics makes it extremely complicated.
Electricity is fairly straight forward but can range from under a penny/kWh up to over 40cents/kWh (or even more at some of the worst pay chargers).

For us, our cost per kWh is $0.05/kWh which translates into 1.25-1.5 cents per mile driven.
This cost will remain the same for the next 35 years or so.
Granted, it also required us to pay a fair amount up front.

 

Sure would! On my PiP, I usually pay about 3 cents per mile for gas and electricity combined. But I never pay to charge except at home.

 

The stuff is cheap when you can ignore a 10% difference.
Ask the ICErs how they feel about a 10% price jump

 

Flipped numbers ?

 

I don't believe so. 5cents/kWh divided by 4miles/kWh = 1.25 cents/mile.

I noted 1.25-1.5 cents because the model 3 is new and I am not sure if I will get 4 miles/kWh or slightly less.

 

You are right, the combined petrol + electricity should be calculated.

My work commute of 90 miles takes 0.9 gallons and one full charge from home:
0.9*270 + 2.77*6.3 = 260 cents per 90 miles = 2.9 cents a mile

 

I admit that I pine for a Prime sometimes. It would be even better for my typical drives than the PiP. Still, I just filled up today for the first time this month thanks to fewer trips beyond EV range. Went 1134 miles on 8.002 gallons and 85 kWh that I paid 11.2 cents per kWh for. Plus the free electricity I get at work and church. That's a new record by almost 200 miles, btw. Cost per mile was 2.68 cents. Also a record, which was remarkable because it was also the most I've ever spent on gas for this car. With a Prime, I might only fill up twice a year aside from big trips.

 

$ per km/mile doesn’t make a good comparison bc gas prices fluctuates. So $/km today will be different tmr.

I just got a chargepoint record of a full charge at approx 6kw. I will adjust the table based on this.

 

True, but I'm not sure why you mention it. Any cost comparison between electricity and petrol will be affected by changing prices for the energy.

 

Yes, that's why I have a reference comparison table between electricity rates and the equivalent fuel cost. This way if you're in a high electricity rate region, you can compare with your local gas prices and know what type of savings or costs when running in EV.

Also I just checked my model. Yes, the original table is correct at 6kw for the EV range about 40 kms for rated disance. The 17 kw is to convert it to 100kms so I can properly compare with gas price metrics at L/100kms.

Net Electricity is $ per kwh
The 3 columns to the right is equivalency in gas prices in $ per Litre

The variables are:
6 kw for 40 kms rated; 35 kms for low eff; 43 kms for high eff
4.5 L/100km rated; 5.5L for low eff; 4.2L for high eff
10% charging efficiency loss built-in

Net Elec Rate; Rated Eff; Low Eff; High Eff;
$ 0.129 $ 0.50 $ 0.47 $ 0.50
$ 0.150 $ 0.58 $ 0.55 $ 0.58
$ 0.200 $ 0.78 $ 0.73 $ 0.78
$ 0.250 $ 0.97 $ 0.91 $ 0.97
$ 0.300 $ 1.17 $ 1.09 $ 1.16
$ 0.350 $ 1.36 $ 1.27 $ 1.36
$ 0.400 $ 1.56 $ 1.45 $ 1.55
$ 0.450 $ 1.75 $ 1.64 $ 1.74
$ 0.500 $ 1.94 $ 1.82 $ 1.94
$ 0.550 $ 2.14 $ 2.00 $ 2.13
$ 0.600 $ 2.33 $ 2.18 $ 2.33
$ 0.650 $ 2.53 $ 2.36 $ 2.52
$ 0.700 $ 2.72 $ 2.55 $ 2.71
$ 0.750 $ 2.92 $ 2.73 $ 2.91

Since electricity rate doesn't fluctuate as much, then one can just glance at the gas prices columns (the 2-4 columns) and reference to the equivalent electricity charge.

Or, if you're at public chargers that charges by kw, then you can also compare using the equivalent gas prices. For instance, there's a public charger here that charges $0.33/kwh.........that means to use that charger the equivalent gas price (for Prius Prime only) is around $1.35/L of gas. Current gas prices is $1.55/L, so the savings is merely $0.20 per litre by using this public charger.

 

Do you mean 17 kWh per 100 Km ?

That would be more consumption than EPA, which measured 25 miles per 6.2 kwh charge *
Since 25 miles is ~ 40 Km, 100 Km is 6.2*2.5 = 15.5 kWh

Actually, EPA measured 133 MPGe in combined driving from the meter which is
133 miles per 33.7 kWh,
133/33.7 = 3.94658 miles per kWh
3.946587537 miles = 6.365463769 Km
So 100 Km uses 100/6.365463769 = 15.71 kWh

---
That is the arithmetic. Which I suppose is of some interest but choosing EV has these advantages:

• Much nicer driving experience
• Much less pollution in areas that rely on renewables or natural gas for electricity
• Keeps money in the domestic economy
• Keeps money out of the hands of oil rich despotic regimes

These are high value advantages. They should be considered. Certainly at price parity or close to it, EV miles are a no brainer.

 

that's the built in efficiency loss. The table only models pricing based on the distance, not the actual battery capacity to distance. So to charge 15kw you need to draw approx 17kw from the grid.

(100kms/40kms)*6.2kw*1.1 = 17kw for 100 kms, with efficiency loss

 

NOT KW. The correct unit here is kWh.
Watt is a unit of power
watt*hour is a unit of energy

6.2 kWh per 25 miles already has the charging losses included for 240v EVSE charging.

 

Is L2 charging more efficient than L1 charge? I have anywhere from 6.4kWh to 6.8kWh of charge reading from 0 mile EV range to full charge on L1 at wall using KillAWatt meter. After measuring a couple of months, I decided to use 6.7kWh average as my daily full charge. 6.2kWh seems to be low to me. Just curious.

 

yup

 

How are you guys calculating your cost of electricity?

I just got my utility bill for the past month and it's $58 for 260 kWH of electricity. That's with all the taxes and crap added in.

That works out to $0.22 / kWH.

If it takes 6.3 kWH to charge my batteries, that's $1.40 / charge (L1, not L2)

I typically get about 28 miles per charge. If we double that, it's 56 miles for $2.80.

My ICE mileage is right about that as well (~56 MPG), and gas right now is hovering around $2.80 / gal in my area.

So it looks like I'm breaking even as far as cost of EV vs. gas.

If gas prices continue to rise, I'll be saving money with my EV.

How in the world are there people getting electricity at 4 cents / kWH ?

Or are we folks here in AZ just getting royally screwed by APS and SRP?