In the world of automotive propulsion, the hierarchy of complication goes something like this: Pure electric cars are simple; internal combustion engines, with many more parts and those explosions, are complex. Hybrids, which make the two work in concert, are extra complex.

Honda’s Clarity Plug-In Hybrid calls for a new category: so-complex-it-makes-your-head-spin. To combine the benefits of electric propulsion with the reassurance of internal combustion, Honda brought in two electric motors and a 1.5-liter gasoline engine. Like a small company of actors putting on an epic play, each fills a variety of roles. Those vary based on whichever of the dozens of possible mode combinations the driver engages via buttons, paddles, and pedals.

Throw in a bunch of weight-saving aluminum, and this convolution yields a plug-in hybrid that can go 47 miles on battery power (340 miles total), gets the equivalent of 110 miles per gallon, and delivers a respectable 212 horsepower, in a large, comfortable package that starts at $33,400. This is the system's third generation, having appeared first in the Honda Accord Hybrid introduced in 2014. The new version in the Clarity is lighter and smaller, with greater power and power density.

The logic behind Honda’s newest addition to its dedicated line of electrified vehicles is simple: function as an electric as much as possible, and use the engine to maximize efficiency by charging the batteries or directly powering the wheels—whatever makes the most sense at the moment.

Honda

The system follows a gnarled decision tree to maximize efficiency. Say you start in the default Normal mode, with the battery charged (just 2.5 hours to fully top off from a 240-volt home hookup.) The Clarity will disengage the engine and operate on battery power alone, letting the propulsion motor drive the wheels. If you baby the throttle, you can keep it that way, even hitting the 100 mph top speed in electric mode. If you floor it, the engine will kick in to help drive the wheels and produce maximum acceleration.

As the 17 kWh battery drains, the Clarity will automatically modulate use of the gasoline engine—a four-cylinder that boasts an industry-leading 40 percent thermal efficiency—based on the driving conditions. The engine will supply electricity to the propulsion motor directly, via the second electric motor that functions as a generator, and may also drive the wheels directly at medium and highway speeds.

That’s a key differentiator: Where most hybrids link their engines to the wheels with a continuously variable transmission (which cycles through a range of gear ratios instead of discrete gears), the Clarity uses a lighter and simpler single speed transmission and a direct connection to the wheels. This circumvents the efficiency losses that come any time the engine acts as a generator. When the engine drives the wheels directly, the loss is zero, and that power can either be supplemented by the motor’s propulsion or replace it entirely, if the driver wants to conserve battery use.