PiP Fuel Efficiency: Cost per Mile

A few of us track our numbers in this spreadsheet (its also stickied at the top of the forum)

PiP Owners Spreadsheet

At about $0.05 per mile, you're doing pretty good. Looking over our spreadsheet, the numbers seem to range around $0.02 to 0.07, with a majority around the $0.05 to 0.07 range it seems (this is based on a fixed $0.12/kWh and $4.19/gallon of gas for comparison purposes).

And welcome to Priuschat!

 

welcome to p/c! i think it is a very good way to do it. cost depends on how much you drive ev and how much ice. how much are you paying per kwh?

 

When calculating your electrical costs you might need to adjust the kWh reported in the PiP to compensate for charging losses. The PiP spreadsheet uses 15%, or you could just add 3 cents to your kWh cost.

 

If you adjust your kWh used for charging losses, you could calculate your MPGe (33.7 kWh = 1 gallon) for the EV miles and then arrive at a combined MPGe as well.

I think the PiP is EPA rated at 95 MPGe in EV mode.

Miles per gallon gasoline equivalent - Wikipedia, the free encyclopedia

 

Welcome to PC! The electric cost per mile seems almost the same as gas cost per mile (less than 1/2 a penny). I imagined running on electricity to be much cheaper than gas, in order to make some financial sense. I wonder what other owners in your climate are getting in the regular Prius? That said, you are enjoying the heck out of it so not everything boils down numbers and payback. There has been many threads trying to figure out payback for a regular hybrid and it never works out in favour of the hybrid, unless you compare it to SUV and trucks.

My local rates are $0.08 per kWh and even at those rates, it takes FOREVER to make up the price premium for the plug-in. But most of my drives are short and I enjoy the electric feel so I'm willing to pay for it.

 

I've got this comparison of my savings, based on my 11 partial and full fillups since April 2012.

Total Gas Gal: 85.720 Add Gal
Total Gas $: $ 322.54 Add $
Total kWh: 1090.00 Add kWh
Total Miles: 7852.1 Add Miles

$ per Gal: $ 3.76 Divide Total Gas $ by Total Gas Gal
kWh $: $ 95.92 Multiple Total kWh x 8.8 cents per kWh
kWh Gal: 25.492 Divide kWh $ by $ per Gal.
Equivalent Gal: 111.212 Add Total Gas Gal + kWh Gal
MPGe: 70.60 Divide Total Miles by Equivalent Gal

If Typical MPG: 50.000 2012 Prius Standard MPG
Typical Gal: 157.042 Divide Total Miles by Typical MPG
Typical $: $ 590.90 Multiply Typical Gal x $ per Gal
Total $: $ 418.46 Add Gas $ + kWh $
Savings $: $ 172.44 Subtract Typical $ - Total $

If Typical MPG: 35.000 2007 Prius Standard MPG
Typical Gal: 224.346 Divide Total Miles by Typical MPG
Typical $: $ 844.15 Multiply Typical Gal x $ per Gal
Total $: $ 418.46 Add Gas $ + kWh $
Savings $: $ 425.69 Subtract Typical $ - Total $

 

ukr2: According to your calculations, you save $172 over a standard Prius. If extrapolated over a full year, you save $229. (172/0.75)

If a base PiP is $32000 and a Prius Four starts at $28500, it would take over 15 years to payback plugin premium. ($3500/229) Although I didn't compare spec of each, I'm gonna guess the P4 is much better equipped. Comparing a PiP Advanced to a P4 is even more ridiculous. Not factoring in local rebates, it's gonna take the intangibles of plug-ins in order for it to sell. (lower emissions, silence, lower carbon footprint, being first on the block, etc).

I'm hoping the next-gen will give greater EV range and lower MSRP (within reason). By relying on more electricity, the math will hopefully make PiP owning a little more sensible.


edit: payback of PiP advanced over a Prius 4 at $229 savings/year is 48 years.

 

I calculate 66.5 MPGe combined.

7852 / ( 85.72 + ( 1090/33.7) )

I didn't take your kWh --> Gallons through a $ equivalent.

 

John,
Where do you get 33.7 Gal/kWh from?

I just determine the kWh cost with my 8.8 cents/kWh, and divide it by Gas $/Gal to get equivalent Gas Gallons.

 

The appropriate comparison to make for the base model is to a Prius three due to the cloth seats. However plugin adds heated seats and remote A/C which are not in the three, so add 1k for that.
CA residents basically get $4k back
End-of-year incentives due to 0% APR and additional cash back from TFS made the base plugin cheaper than a three after all rebates and incentives.
Appropriate comparison for the advanced model is to a Prius five, not a four.

 

Miles per gallon gasoline equivalent - Wikipedia, the free encyclopedia

It would be 33.7 kWh = 1 Gallon.

Note, I also assumed your kWh is measured at the wall rather than at the battery.

@ $0.088/kWh your gallon gas equivalent should be $2.9656, but since the PiP is about 95MPGe on electric you save money the more you drive EV !!

 

I did get $2500 off my taxable income too.
AND I'm not paying for 1/2 my kWh. The office isn't charging me.
Plus I enjoy only getting gas once a month. (I had a few partial fillups because I reset my Fillup Trip by mistake !!!)

If I was focused on Payback, I would buy a Scooter.

I owned the 2007 Prius and liked it. I LOVE the PIP.

 

Also, what's the Payback in drinking that Beer verses a Glass of Water???

 

i knew your decision wasn't based on economics. I didn't buy my prius based on payback either. Your numbers got me thinking about math, that's all

 

95 MPGe is with 0.2 gallon of gas and 29kWh/100mi combined. If you drive in the city so that ICE doesn't trigger, it can be as high as 117 MPGe (29kWh/100mi).

He is getting between 25.6 and 29.4 kWh/100mi so that's 116 to 132 MPGe on electricity. His gas efficiency is 57.4 to 63.2 MPG.

PiP is very efficient with either fuel.

 

Here are some simple ways to calculate costs:

One full charge (for me) is always less than 3 kw-hr (usually 2.85 - 2.95 kw-hr measured by Chargepoint or watt meter). This includes all possible charging losses between the wall and the battery My estimated miles per charge is about 14, but has been down to 13.5 and as high as 15. My actual miles drivien is usually about 0.5 to 1 mile more than the reported number. This is for 30-45 mph city driving. When I'm at 60-65 on the freeway it is more like 10 miles. For most people (without heat, A/C, etc) you will get from 10-15 miles per full charge on level ground.

Therefore: (3 kw-hr) / 10 or 15 miles = 200 to 300 w-hr per mile; or 2 cents to 3 cents per mile given a cost of $0.10/kw-hr.

If I compare this to a long term average from the PIP's display...I see about 349 kw-hr for 1876 miles. This calculates out as only 186 w-hr/mile, but does not include any charging losses. The PIP, reportedly takes 2.7 kw-hrs per charge "into" the battery. If it consumes 2.85 - 2.95 at the wall, this is a loss of about .15 to .25 kw-hr or around 5% - 9%. This is lower than the 15% number I keep seeing referenced. I don't know where the 15% number comes from, but I do not think it was measured, but maybe comes from Toyota or some place else. This number is most likely the combination of both charging and discharging losses. I do not think it makes sense to double count the discharge losses, because we can't distinguish these from just driving, friction, motor efficiency, etc.

Given the same driving conditions (except maybe use of heater/defroster) with gas it will be 45 - 55 mpg and gas cost $3-$4/gal. At 50 mpg this is: ($3/gal) / (50 miles/gal) = $0.06 per mile. $0.08 for $4 gas.

You have to be paying $0.30 - $0.40 per kw-hr to be losing with electricity overall.

But wait, there's more....

Since many times you are driving short distances to the store, restaurants, school etc, these short trips at low speed tend to be at the lowest watt-hrs per mile, thus lowest end of the costs per mile. But if you where to drive these with gas you would typically not get the car warmed up yet...these trips would have usually been at maybe 25 mpg for the first 5 minutes. The comparison here is like 1.5 - 2.0 cents per mile (electric @ 10c/kwh) to 12 - 16 cents per mile (gas $3 - $4); a clear win for electric even at 50c/kwh.

Mike

 

I believe the consensus is 15% at 110V and 10% at 240V but there are definitely variations based on ambient temperature and state of charge.