. . . This latest report provides data and analysis on 12 Proterra BEBs and eight CNG baseline buses from August 2015 through December 2016. . . .
Foothill Transit paid an average of $0.17/kWh for electricity for the BEBs and $0.96/gge for CNG. An apples-to-apples comparison of fuel cost—i.e., the cost for the CNG buses and the Proterra electric buses on the same route—found the average per mile cost for the electric buses was $0.41 per mile, including $0.04 per mile
reflecting the expected energy loss of approximately 10% during charging. The estimated cost for the CNG buses on the same route was $0.50 per mile
. . . .
The overall bus miles between roadcalls (MBRC) for the electric fleet decreased from more than 9,000 during the period of the first report to just over 6,000
.This is higher than the target of 4,000 MBRC—but much lower than that of the CNG buses, which achieved more than 29,000 MBRC.
NREL found that the propulsion system-related MBRC was 16,405 for the BEBs compared to 56,710 for the CNG buses. However, the energy storage system (ESS)-related MBRC for the BEBs continues to climb, now surpassing 300,000.
After removing accident- and warranty-related items for both fleets, the average per-mile maintenance cost for the data period was $0.21/mi for the BEBs and $0.22/mi for the CNG buses
—including scheduled and unscheduled maintenance. Although the totals are very similar, the BEBs have lower scheduled maintenance costs ($0.07/mi) than the CNG buses ($0.11/mi). . . .
The on-route fast chargers have operated reliably with minimal issues; Foothill Transit’s combined BEB fleet (17 buses) has been charged more than 119,000 times since the fast chargers were installed. Availability of the two charging heads was 98% and 99%. Proterra reports that the high voltage batteries are showing little to no signs of capacity degradation to date, and current estimates show they may last for up to 12 years.*
Foothill Transit and Proterra reported several key lessons learning since the beginning of the project:
- Short-range, on-route-charged buses are inflexible and cannot be deployed at other service routes that do not connect to an on-route charging location.
Transit agencies bringing in electric buses should review potential routes and consider the ones that best fit how BEBs operate based on driving range, duty cycle, and charging opportunities.
Transit agencies should adjust route schedules to accommodate BEB charging time; this is part of the transition from conventional technology buses to electric buses. An agency may need to add deadhead miles prior to the start of the route depending on the location of the in-route charging station and availability of an in-depot charger.
The higher use of air conditioning lowers the effective range in hotter months; schedules need to be adjusted.
Charger availability is important for successful deployment. Foothill Transit installed two charger heads at its charging station to avoid downtime for charger unavailability. . . .