EV vs Gas Cost Comparison

Annual fuel savings is calculated purely from ongoing operating costs -- miles driven, gas MPG and price, and EV efficiency and electricity rate -- none of which reference either vehicle's sticker price. Purchase price only enters the calculation later, in the break-even point, which compares the price difference between the two vehicles against the annual savings this first figure represents.

Gas MPG directly changes how much fuel the gas car burns for the same annual mileage, so it moves the annual fuel-cost comparison every single year. Ownership period (years) only multiplies an already-fixed annual savings figure to get a lifetime total -- it doesn't change what the annual savings actually is, so on a per-year basis it has no effect on the annual fuel savings number at all, only on how many years that same annual figure gets summed over.

At this calculator's defaults, moving from a 55 MPG gas car down to a 15 MPG gas car raises the EV's annual fuel savings from around $327 to more than $2,300 -- roughly a seven-fold increase -- because a lower-MPG gas car burns proportionally more fuel for the same annual mileage while the EV's electricity cost stays the same. Gas MPG is the single input this calculator's fuel-savings figure responds to most strongly.

Yes -- if the combined annual fuel-and-maintenance savings work out to zero or negative (meaning the EV doesn't actually save money on a year-to-year basis given the entered inputs), the calculator reports the break-even point as "Never" rather than a nonsensical negative number of years, since a price premium can't be recouped by savings that don't exist.