Economics of the Chevy Volt and F150 PHEV

The list of retrofit/prototype/experimental EREVs just got longer.  Auburn Hills-based (why haven’t they offered me a job?) Alt-E LLC has raised the ante on its Crown Victoria conversion with the addition of a converted F150.  (Auburn Hills company showcasing converted Fords… must be some disaffected ex-Chrysler people in there!)  They’ve put their weight behind a new term, too:  REEP (Range-Extended Electric Powertrain).

I’m not a fan of pickup trucks.  Let me rephrase that:  I am NOT a fan of pickup trucks!  But if this vehicle had been in showrooms the last time I was car-shopping, I might well have bought one.  The stated highway economy of 32 MPG isn’t far from what I get with my Passat TDI, and the beast can both tow almost 5 times as much and can run a claimed 52 miles on its batteries before it needs to start its engine (presumably with nothing on the hitch, and a light foot on the accelerator).  If I had one, I wouldn’t need gasoline for more than about one trip a month.  The last 2 months have seen a lot of long-distance travel, but I would still only have needed about 33 gallons of gas; everything else would have been covered by electricity.

GM claims 50 MPG for the Chevy Volt in charge-sustaining mode.  If Alt-E’s claim of 32 MPG for the F150 conversion is comparable, it’s burning 56% more fuel for a lot more vehicle.  I’m inclined to be a bit skeptical (could the comparison be highway vs. city?) but that is still quite good.  But which is the better deal?

Whichever one is “better” depends on the use, but usage indicates who ought to convert first.  People who drive a 6 MPG vehicle across town on the last weekend of the month during the summer are a much lower priority than people who drive a 14-MPG vehicle 50 miles every weekday year-round and further on weekends.  But what’s the first thing to attack:  the pickup segment or the commuter segment?

The most expensive part of the PHEV/REEP is the battery, while the biggest savings is fuel (with engine and brake maintenance running a distant second).  We can get a feel for the benefit gained by looking first at the typical fuel savings per kWh of battery capacity, and second at the reduction in fuel consumption in charge-sustaining mode.  This needs to be calculated in fuel consumption, not mileage, so I will use gallons per 100 miles (similar to the European convention of liters/100 km) instead of MPG.

I will assume 3 driving cycles.  Cycle 1 simulates a daily commute and is 40 miles per day, starting with a full charge and no recharging.  Cycle 2 simulates a weekend of driving with 200 miles of errands or recreation, with one 75-mile out-and-return trip starting with a full charge and the remaining driving consisting of short trips with frequent recharges.  Cycle 3 simulates a vacation to visit family and consists of 300 miles of driving in 2 stages with a full recharge at the beginning of each stage.

Assuming the vehicle is driven on cycle 1 250 days/year, cycle 2 on 24 weekends/yr (2 weekends/month) and cycle 3 is driven 4 times per year (certain holidays), I get the aggregate energy consumption in the last column.

Vehicle Battery
capacity,
kWh
AER,
miles
Charge
sustaining
economy,
gal/100 mi
Fuel used
cycle 1
gal
Fuel used
cycle 2
gal
Fuel used
cycle 3
gal
Fuel savings
cycle 1
Fuel savings
cycle 2
Fuel savings
cycle 3
Annual fuel used Annual fuel
savings, gal
Annual savings
gal/kWh
Percent fuel
savings
Volt equivalent 0 0 3.33 1.33 6.67 10 533.33
Volt 16 40 2 0 2.2 4.4 1.33 4.47 5.6 70.4 456.8 28.55 86
F150 2WD 0 0 6.25 2.5 9.38 18.75 925
F150 REEV 25 52 3.13 0 3.06 6.13 2.5 6.31 12.63 98 797.25 31.89 86
Commute, mi: 40
Electric mi/yr: 11120
Interest
%/yr
Months $/kWh Residual value
$/kWh
Monthly payment
$/kWh
Volt battery
cost, $/mo
Alt-E F150
battery
cost, $/mo
0.05 72 450 135 $5.64 $90.17 $140.89
0.05 72 450 45 $6.71 $107.36 $167.75
0.05 72 450 0 $7.25 $115.96 $181.18
Annual fuel savings @ $/gal
Fuel price $2.75 $3.50 $5.00 6-year savings @ $5/gal, excluding electricity
Volt battery cost, $/mo $90.17 $174.17 $516.77 $1,201.97 $7,211.84
$107.36 -$32.12 $310.48 $995.68 $5,974.08
$115.96 -$135.27 $207.33 $892.53 $5,355.20
Alt-E battery cost, $/mo $140.89 $501.77 $1,099.71 $2,295.58 $13,773.50
$167.75 $179.44 $777.38 $1,973.25 $11,839.50
$181.18 $18.27 $616.21 $1,812.08 $10,872.50
Electric cost, $/kWh Electric use, kWh/mi Electric cost, $/yr Net savings, $/yr @ fuel cost

Net 6 year savings @ $5/gal
$0.10 0.25 $278.00 -$103.83 $238.77 $923.97 $5,543.84
$0.10 0.4 $444.80 -$310.12 $32.48 $717.68 $4,306.08
-$413.27 -$70.67 $614.53 $3,687.20
$56.97 $654.91 $1,850.78 $11,104.70
-$265.36 $332.58 $1,528.45 $9,170.70
-$426.53 $171.41 $1,367.28 $8,203.70

(These figures were generated from an OpenOffice Calc spreadsheet and saved as HTML to create the table.  The spreadsheet allows you to vary the length of the daily commute.  Pardon the lack of clarity on the last section, I’m not quite sure what I meant by that part any more either.)

I realize that the VMT figures are about 30% higher than average, but they are probably representative of a substantial fraction of suburban commuters with new vehicles (vehicles have historically covered half their lifetime VMT in the first 6 years).  People with longer commutes and heavier usage patterns will have the best ROI on efficiency improvements and ought to form the leading edge of the mass-market, following the early adopters.

Several interesting things pop out of this spreadsheet.  One is the similarity of the benefits for the 40-mile commute; both save 86% over the equivalent ICE powertrain.  Even the fuel consumption is within 30 gallons.  The second is the greater savings per kWh of battery for the F150, despite a commute exactly equal to the Volt’s rated AER; if the batteries cost the same per kWh, the F150 battery has a greater ROI than the Volt’s due to the greater reduction of fuel consumption.  If you increase the commute to 45 or 50 miles, the comparison increasingly favors the F150 REEP; at 50 miles the Volt’s savings fall to 79% vs. 88%, the savings per kWh of battery are 7.5 gallons lower, and its total fuel consumption is even higher by 22 gallons (trivial, but interesting).  The major unknown is battery usage and lifespan for the Alt-E.  We know the Volt’s designers have been very conservative.

The question on everyone’s mind:  when does it pay to buy batteries to replace fuel?  This depends mostly on the price of batteries and fuel, with the price of electricity coming in third (1).  The near-future cost of lithium-ion traction batteries is falling in at around $450/kWh.  A lease payment at 5% interest with 30% residual value after 72 months gives a monthly cost of $5.64 per kWh, or $141/month for the Alt-E F150.  At today’s gasoline prices, the EREV/REEP is a slight loss.  If you are driving 1300+ miles/month and saving 3+ gallons per day at $3.50/gallon or more, that’s going to pay off nicely.

I was going to try to add a little Javascript calculator to this post so everyone could play with figures right here, but it was taking too long so I’m posting without it.  I’ll probably make a post for it.

(1) If an electric powertrain is 65% efficient wall-to-wheels and regenerative braking is included, electricity at 11 cents/kWh costs about as much as a 20%-efficient engine burning gasoline at 75 cents a gallon.  This is less than 1/3 the cost of gas at the pump today, and about 1/6 of the 2008 peak.  I remember gasoline at under $1.00/gallon as recently as the Asian Flu of 1998, but it’s a safe bet we’ll never see anything close to that again as long as it remains a major transport fuel.

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