Berkeley, Calif. -- Using electricity as an automotive fuel, to most Americans, seems as alien as powering a car by Higgs bosons. Electricity, they'd say, might be fine for fueling exotic sport machines made by California start-ups -- or for tiny Japanese mobility pods -- but not the family sedans of America's highways.
What, then, should we make of Ford Fusions and Honda Accords suddenly sprouting plugs and growing battery packs? Both of these mainstream, top-selling cars have recently arrived as plug-in hybrids, expanding their maker's existing lines of gas-only models and conventional hybrids.
You can think of a plug-in as an overachieving hybrid, a vehicle that runs largely on electrons for local miles and then mostly on gasoline for longer trips. That combination -- a broadly appealing solution that splits the difference between petroleum power and purely electric cars -- has the potential to make battery propulsion acceptable to motorists put off by matters like limited driving range.
The Ford Fusion Energi, however, is less about the blending of electrons and hydrocarbons for power and more about the car's dual nature: the ability of a handsome family sedan to switch, superhero-style, from one driving persona to another.
When its 7.6 kilowatt-hour battery pack is fully charged -- that takes about 2.5 hours from a 240-volt source -- the driver can invoke the car's jazzy smooth electric-vehicle self. In the first two days of a week with the sedan, I used a button near the gearshift to select the EV Now mode, which keeps the car driving almost exclusively on its battery. In 36 miles of driving punctuated by frequent electric top-ups, I was effectively operating a spacious 3,913-pound zero-emissions electric sedan, not using a drop of gasoline.
The car's roomy interior, comfortable ride and taut steering were a welcome change from the toylike robotic feel of the Nissan Leaf compact E.V. that is my usual transportation. Among sedans that can operate on battery power, in my view, the Fusion Energi is surpassed in size and style only by the Tesla Model S.
Both cars appropriated Aston Martin's signature grille to inject some James Bond flair in their four-door profiles. But don't take the similarity too far: compared with the rip-roaring Model S, the Fusion Energi has swallowed a dose of Xanax. It glides sedately through city streets. The acceleration on highway on-ramps is adequate, but when driving solely on electricity, the car is not even as zippy as a Leaf.
Things change about 17 or 18 miles down the road, when Dr. Electric transforms into Mr. Combustion. With gasoline supplying power via Ford's 2-liter 4-cylinder engine, and assisted by the electric motor and battery pack that had been operating solo in E.V. mode, the car's output jumps to 188 horsepower. It feels like twice the oomph.
Ford has perfected smooth transitions between gas and electric power sources, so passengers have little evidence of the handoff. The cabin of the Ford Fusion Energi is also among the quietest I have experienced. Close the door and you feel practically vacuum-sealed, buffered from engine noise or vibration. Noise-cancellation technology is used to counteract any whine from electrical components.
After the switch from E.V. to hybrid operation, there is an obvious sign that hydrocarbons are powering the Fusion: the planted feel on the road now takes on a sporty quality. It becomes a fun family cruiser, especially shining on the highway, territory not usually associated with E.V. prowess.
An 80-mile round-trip drive between Berkeley to San Jose -- usually an anxious experience in my Leaf requiring a 55 m.p.h. pace to conserve energy -- was carefree in the Fusion Energi, which offers a total range of 620 miles.
Yet the Transformer-like shift has an impact on efficiency. There were several days early in the week when I frequently charged throughout the day, and therefore remained all E.V. As a result, fuel economy broke past 100 miles per gallon of gas (not including the electricity you put in the battery). The E.P.A. pegs average combined city-highway fuel at 100 m.p.g.e. A Toyota Prius plug-in, for reference, is rated at 95 m.p.g.e.
Trips that started all-electric for the first 20 miles or so but continued on for another 50 or miles registered around 75 m.p.g. And the day's travel to San Jose and back -- when I tested the limits of legal highway speeds, with air-conditioning and audio blasting -- fuel economy was a respectable 38 miles per gallon. Over the course of 227 miles, the Fusion Energi averaged 55 m.p.g.
For all of Ford's success in turning the Fusion into a 100 m.p.g. vehicle and making it a joy to pilot, its engineers made a critical mistake: they did not find a good spot for the E.V. battery pack, shoehorning it between back seat and trunk, reducing the trunk space to 8.2 cubic feet, from 12. The resulting odd dimensions leave room for about two carry-on suitcases and little else.
The 2013 Accord Plug-In, which I drove for a few days right after the Fusion, has the same problem of filling its trunk with batteries -- an even more drastic reduction from 15.5 cubic feet in the gas-powered Accord Touring model down to 8.6 cubic feet.
The Accord offers no mode to enforce E.V.-only driving. The battery can deliver the equivalent of 55 horsepower, so the gas engine is programmed to come on with very little provocation. This "blended" approach puts the Accord in the league of conventional hybrids like the Prius. The gas engine, electric motor, or both, are used in whatever way the car's computer decides is the most efficient.
The combination of power and fuel efficiency is impressive: the Accord Plug-In Hybrid delivered 49 m.p.g. on my three-day 188-mile trip around Southern California, during which I had little access to a charging plug.
With an E.P.A. rating of 115 m.p.g.e., the Accord Plug-In is the most fuel-efficient sedan in America, Honda says. That may clinch the deal for some shoppers, but others will conclude that the exterior styling, which hardly stirs emotions, is reason enough to shop elsewhere.
The Accord is a generic-looking car. Its interior is a hot mess of competing chromes, and the dashboard graphics reflect a Y2K aesthetic -- not good for a high-tech car. The wheel covers, added to improve aerodynamics on the plug-in Accord, are ultra-plastic. The charging port door wobbled on its hinge. The key fob on my test car malfunctioned, failing to open the trunk.
The plug-in Accord is the first to use Honda's two-motor hybrid system. It takes a generation or two to calibrate these systems for smoothness, and Honda is not there yet.
Neither is Ford, if the goal of the Fusion Energi is to win customers by bringing plug-in technology to the brand's best-selling passenger vehicle.
A car may be perfectly executed in almost every way, but all is for naught if it is marred by one major flaw. Engineers at Ford and Honda alike need to figure out how to offer game-changing plug-in hybrid technology in its most popular models without shrinking the trunk in the process.
Trying to understand the economics of these plug-in vehicles could quickly short-circuit your brain, considering the dazzling number of trim options on comparable gas versions and the available federal tax credits and state rebates.
Here are the basics: The Honda Accord Plug-In, sold only in California and New York, starts at $40,570. After incentives, the price is about $1,000 above the gas-only V-6 278-horsepower Accord Touring, which comes with leather upholstery rather than the plug-in model's bland "bio-foam" interior.
The Ford Fusion Energi, available nationwide at select Ford dealers, is offered at $39,495. After incentives, it still costs over $1,000 more than the 47-m.p.g. Fusion Hybrid Titanium. The Titanium model brings along sharper 18-inch aluminum wheels, a more powerful audio system and goodies like a leather-wrapped steering wheel. Gas savings over a few years will chip away at the extra expense.
Even with at their premium prices, the Fusion Energi and Accord Plug-In Hybrid could have been satisfying to mainstream consumers looking for a middle-of-the-road vehicle that can run on electricity. But their pipsqueak trunks kill the deal.
This article originally appeared in The New York Times.