In addition to the different available lengths, the buses are sold with a variety of propulsion systems: conventional diesel, compressed natural gas (CNG), diesel-electric hybrid, hydrogen fuel cell, overhead electric wire and battery electric.

To accommodate the change, the Thermo King air conditioning system was moved from the rear of the bus to a roof mount location over the front axle.

New Flyer found that the move improved the weight balance of the bus, and when combined with enhanced insulation, contributed to the vehicle running quieter.

To improve interior aesthetics, visible fasteners were eliminated and molded plastic surfaces were introduced.

[5] Beginning with the 2026 model year, the XDE60 will be discontinued as New Flyer was unable to find a powertrain compliant with new regulations taking effect around that time.

[7] Massachusetts Bay Transportation Authority was the lead agency for the XE60, ordered in January 2019[8] and placed into service on July 31, 2019.

[10] The original battery electric Xcelsior bus, offered as an XE40, used a permanent magnet traction motor built by Siemens.

[13] On-route rapid charging is provided through an overhead pantograph designed to be interoperable with the SAE J3105 standard supplying 300–450 kW.

It has a Siemens ELFA3 traction motor, Lithium Manganese Cobalt (NMC) batteries, and electric roof-mounted HVAC(s).

[23] Earlier New Flyer fuel cell buses were based on the preceding Low Floor chassis, designated H40LFR, and integrated by an outside vendor.

[27] Project management was performed by The Center for Transportation and Environment (CTE) with support from the Federal Transit Administration, who provided a US$2 million grant under the Integrated Mobility Innovation Program.

[28] The first three Xcelsior AV buses are scheduled to be tested by CTtransit in 2021 on the CTfastrak bus rapid transit (BRT) line, over a dedicated right-of-way 9 miles (14 km) long, connecting New Britain and Hartford, Connecticut.