In March of 2011, Keith Barry, writing on the Autopia blog at Wired.com, reported that a Massachusetts-based company was retrofitting Lincoln Towncars as hybrids, pitching the upgrade to fleet owners primarily as a way of cutting fuel costs:

XL Hybrids, a startup in Somerville, Massachusetts, has created a low-cost battery-powered electric motor that installs on a Lincoln Town Car in under six hours, boosting power by 20 horsepower and reducing fuel consumption 15 to 30 percent.

Given that real-world fuel economy in a Town Car seeing hardcore urban duty is 13 or 14 mpg, the hybrid conversion can pay for itself in fuel savings within 24 months, says co-founder Justin Ashton. No word yet on the per-unit cost, but expect payback time to shorten as fuel prices rise.

Ford sold over 10,000 Town Cars last year, with many of them going to livery operators who are not only struggling with fuel costs, but mandates from customers and city governments to go green.

According to Ashton, the project was designed with fleets in mind. “Before settling on an architecture, we got real-world data from fleets,” he said. ”Due to the extreme nature of their driving, their fuel bills are astronomical.”

Though there are myriad reasons for greening a fleet of vehicles, XL pitched their technology straight at the wallet. “We want to reduce fuel consumption, but we know the only way to do that is by saving people money,” Ashton said.

Excerpted from Hybrid Town Car Conversion Cuts CO2, Costs

Now Ford is mass-producing hybrid Towncars.

We wouldn’t hazard a guess as to how much fuel and money will be saved, but we suspect we’ll be seeing a lot of fleet hybrid Towncars as fleet operators hedge their bets against fuel increases. Progress in these matters often comes in small steady increments, and this is one.