It's one of the most frequent questions asked by shoppers interested in utility vehicles with better gas mileage: why aren't there more hybrid SUVs and crossovers?
Following the 2012 demise of the much-loved Ford Escape Hybrid, it took four years for the 2016 Toyota RAV4 Hybrid to emerge.
This year, we have the 2017 Nissan Rogue Hybrid to compete directly against the hybrid model of Toyota's hugely popular crossover.
DON'T MISS: 2017 Nissan Rogue Hybrid: gas mileage review
That's pretty much it, though. Ford has never replaced the Escape Hybrid (nor its Mazda and Mercury siblings).
The Ford C-Max Hybrid launched for 2013 didn't offer all-wheel drive underneath its tall five-door hatchback body, a lack that simply disqualified it for many buyers.
Two consecutive EPA-enforced reductions in its gas-mileage ratings didn't help its image either, and now in its fifth model year, it has languished in dealer showrooms.
2009 Chevrolet Tahoe Hybrid
For the record, Nissan also offered a Pathfinder Hybrid in 2014 (and an Infiniti QX60 Hybrid twin from its luxury brand) and had a 2016 Murano Hybrid on the books as well.
Both of those use a weak mild-hybrid system and are widely assumed to be extremely low-volume models.
Earlier on, General Motors sold almost 24,000 V-8 Two-Mode Hybrid versions of its Cadillac Escalade, Chevrolet Tahoe, and GMC Yukon full-size SUVs from 2008 through 2014.
CHECK OUT: 2016 Toyota RAV4 Hybrid: Gas Mileage Review (Feb 2016)
And that's pretty much it for hybrid SUVs in the mass market.
Sure, you can buy plug-in hybrid luxury crossovers from BMW, Mercedes-Benz, and Volvo, but those all start well north of $50,000, taking them well out of the mainstream market.
So why exactly are there so few hybrid SUVs—especially when Toyota's RAV4 Hybrid sales have been going gangbusters over the last year?
2016 Toyota RAV4 Hybrid, Catskill Mountains, NY, Feb 2016
It comes down to three challenges: aerodynamics, packaging, and market demand.
Tall wagon-like vehicles (which is the segment crossovers and SUVs occupy) create far more drag than sleek, tapered, fastback hatchbacks like the 52-mpg 2016 Toyota Prius.
And aerodynamic drag increases further when they're 6 to 9 inches off the ground—one of the requirements that earns them a beneficial "light truck" designation from the NHTSA.
CHECK OUT: Is Toyota RAV4 Hybrid SUV hurting Prius V wagon sales? (Jun 2016)
Then there's packaging: that high-voltage battery pack has to go somewhere, and the need to fit all-wheel-drive hardware on the rear axle severely limits the possibilities.
The two choices tend to be under the rear seat, or under the cargo bay. The first can interfere with folding the rear seat forward, while the second can raise the load floor.
That's not always the case, but the challenges are far greater if the pack can't sit between the rear wheels because there's an axle or a second drive motor there instead.
2012 Ford Escape Hybrid
You also have to provide pathways for cooling air to reach that pack, which is why the old Ford Escape Hybrid had a small exhaust vent in a shortened left window behind its left-rear door.
Finally, with the steady increase in corporate average fuel-economy standards, all crossovers and SUVs get better fuel efficiency these days than they did 10 years ago, meaning buyers are less likely to hesitate because of the fear of spending too much on gasoline.
That means less apparent market demand for hybrid SUVs—which don't come close to the stratospheric fuel-economy ratings of cars like the Prius or hybrid sedans, because the incremental improvement from a hybrid powertrain is reduced by the first two factors.
Continuing low gas prices aren't helping either.
Carmakers today are pretty much selling every compact crossover they can crank out, while sedans and hatchbacks require increasing discounts to move them off lots.
2015 Ford C-Max Hybrid
If gas prices soared, would they be ready to launch hybrid crossovers and SUVs with all-wheel drive?
That's a question that's one to ask your local franchised dealer salesperson the next time you're shopping for a new vehicle.