Is it still cheaper to fill up an EV versus a gas car? Yes, but it’s complicated.

As electric rates have risen and gas prices have fallen, it’s a closer comparison.

A fuel nozzle in a car at a Shell gas station in California.David Paul Morris/Bloomberg

One of the big advantages of switching to an electric vehicle over the past few years has been the cost savings from swapping electrons for gasoline. But rising electricity rates, declining gas prices, and increases in the cost of fast charging on the road have complicated the savings calculation.

A year ago, EV drivers were saving a ton of money by avoiding the gas pump. Charging an EV at home at rates averaging 27 cents per kilowatt-hour meant filling the entire battery of a Chevy Bolt would cost about $18. With gasoline over $4.30 a gallon, filling the tank of a comparable gas-powered car like the Mazda 3 would cost $57.

Lately, the calculus has changed. Electric rates jumped to an average of 39 cents and gas has dropped to $3.37. Now, the Bolt costs $25 to top up and the Mazda 3 is down to $44.

But the Mazda can go 409 miles based on an EPA-estimated 31 miles per gallon versus the Bolt’s EPA-estimated range of 259 miles. So, at current prices, the Mazda costs 10.9 cents per mile and the Bolt 9.8 cents per mile. (The EV and gas-car pairings in this story were selected from Autoweek’s related comparisons.)

The calculation could shift again soon in favor of the EV, however. National Grid has won approval to slash its home electricity prices down to 14 cents a kilowatt-hour plus distribution charges starting this summer, and Eversource is likely to follow suit. At the new National Grid rate, filling the Bolt’s battery costs just $9, or less than 4 cents per mile, plus the utility’s distribution charges.

The electricity price spike happened because the region relies heavily on natural gas for generating power. But over the long term, adding more wind, solar, and other renewables will reduce prices, Ingrid Malmgren, policy director at nonprofit Plug In America, said.

“Adding more renewable energy power sources will . . . bring back big cost savings to EV drivers in New England,” she said.

The vast majority of EV owners charge at home, but the savings calculation is different when charging an EV at a DC fast charger on a road trip. In a recent Boston Globe survey of four different charging networks, prices per kilowatt-hour ranged from 20 cents to 70 cents. After price hikes by several of the networks this month, however, the lowest price seen was 26 cents.

And the math can work out differently for different cars and EVs, such as the base version of the Tesla Model 3 versus a Mercedes A 220. Filling the Tesla costs under $20, or 7.2 cents per mile, versus almost $46 to fill the Mercedes with regular gas, or 12 cents a mile.

Moving into a price range beyond the Autoweek comparisons, with a Lucid Air Grand Touring EV, which costs $138,000, and a Mercedes-Benz S 580, which costs $125,000, the electric vehicle has a larger cost advantage, in part because the Lucid can go 516 miles on a full charge and the Mercedes requires premium gasoline.

Filling the battery of the Lucid at home would cost $46 or 8.9 cents per mile of range. Premium gas in Boston is $4.15 a gallon, so filling the Mercedes would cost $92, which works out to 21.8 cents per mile.

And none of these calculations take into account the benefits to the environment from driving an EV, which stand even after accounting for the impacts of electricity generation and battery manufacturing.

“As expensive as gasoline is now, it would be even more expensive if drivers had to pay the full cost of their travel,” said Matt Casale, a director at the Public Interest Research Group. For example, gas taxes don’t cover the cost of building and maintaining roads, he noted, while traffic causes air and noise pollution along with emitting greenhouse gases.

The bottom line? Consumers and the environment still benefit from EVs, despite the many variables involved.