Desert Agility

EV Basis

The EV starts at its purchase price and falls when driving credits beat charging. Diesel and gas start at zero and climb. A crossing is the odometer where avoided spending has paid the car back.

Portfolio average

33,871 mi

1.41 yr · avoided +$0.4797/mi

GMC diesel

20,330 mi

0.85 yr · +$0.6259/mi

BMW 330xi

47,411 mi

1.98 yr · +$0.2424/mi

Solar driving value

$537.60/yr

7,680 kWh credited at $0.070/kWh

GMC diesel pays the purchase back at 20,330 mi (0.85 yr). BMW 330xi pays the purchase back at 47,411 mi (1.98 yr).

Baseline scenario: $13,650, 320 Wh/mi, $0.145/kWh retail, solar on, 2,000 miles a month.

Capital and horizon

$13,650
100,000 mi

EV efficiency

320 Wh/mi

3.13 mi/kWh · right is thirstier

2026 EPA combined. Pick a trim to set Wh/mi.

Solar and grid

Credit the generation rate against retail power.

$0.145/kWh
$0.070/kWh

Operating credits

$99/mo
$40/mo
2,000 mi

Credits are spread across monthly miles, so more driving dilutes the dollar-per-mile benefit and stretches payback in miles.

Combustion benchmarks

GMC Sierra diesel

$6.50/gal
11.0 mpg

BMW 330xi

$5.60/gal
27.0 mpg
$0.035/mi

$5.00 regular · same maintenance

Show the math

Combustion cost per mile is fuel price divided by economy, plus maintenance. The EV starts at the purchase price. Its slope is charging minus FSD and insurance, spread over the miles driven that month. Payback miles are the purchase price divided by the gap between those slopes.

  • Diesel = $6.50 / 11.0 + $0.035 = +$0.62591/mi
  • BMW = $5.60 / 27.0 + $0.035 = +$0.24241/mi
  • EV energy = 0.320 kWh/mi × $0.075 = $0.02400/mi
  • Credits = ($99 + $40) / 2,000 = $0.06950/mi
  • EV slope = energy − credits = -$0.04550/mi
  • GMC diesel = $13,650 / (+$0.62591/mi − -$0.04550/mi) = 20,330 mi
  • BMW 330xi = $13,650 / (+$0.24241/mi − -$0.04550/mi) = 47,411 mi

Monthly credit pool is $139. Solar value this year is $537.60.