Last month, the U.S. Postal Service (USPS) announced a 10-year, $6 billion dollar contract with Oshkosh Defense for new mail trucks, but only 10% will be electric. Now Congress is considering legislation that would make more of the fleet electric, Reuters reports.

The USPS is in desperate need of new delivery vehicles to replace its aging fleet, but the decision to give most of the new vehicles internal-combustion engines has proven controversial.

It seems to counter President Biden's goal of making the entire federal vehicle fleet all-electric, and given their long anticipated lifespans, these mail trucks could be producing tailpipe emissions for many years before they're converted to electric power—usually expensive and impractical—or replaced entirely. Oshkosh Defense also has no apparent experience with battery-electric vehicles.

So, on Monday, 17 Democrats introduced new legislation in the House of Representatives requiring at least 75% of the new fleet to be zero-emissions vehicles, for no less than 50% of medium/heavy-duty vehicle purchases to be zero-emission through 2029, and for all new vehicle purchases to be zero-emission after January 2040. That could open the door to EV specialists like Workhorse, which missed out on the original contract.

USPS Next Generation Delivery Vehicle - Oshkosh Defense

USPS Next Generation Delivery Vehicle - Oshkosh Defense

"We welcome and are interested in any support from Congress that advances the goal of a Postal Service vehicle fleet with zero emissions, and the necessary infrastructure required to operate it," the USPS said in a statement to Reuters. "With the right level of support, the majority of the Postal Service’s fleet can be electric by the end of the decade."

The phrase "right level of support" is key, as U.S. Postmaster General Louis DeJoy previously told lawmakers that an all-electric contract would have cost up to $4 billion more.

The USPS has tested electric trucks before, with positive results, and an all-electric or extended-range electric powertrain was previously thought to be the favored solution in the search for a replacement for the current Grumman LLV mail trucks.

"LLV" is short for Long Life Vehicle," and the current fleet has lived up to that name. Many of the vehicles are now 30 years old—10 years past their maximum intended lifetime. The current plan has Oshkosh providing 50,000 to 165,000 vehicles over 10 years, with the first deliveries scheduled for 2023.