The Center for Transportation and the Environment (CTE) with the Midwest Hydrogen Center of Excellence (MHCoE), Cleveland State University (CSU), and the Stark Area Regional Transit Authority (SARTA) investigated the relationship between ambient temperature and fuel economy for zero-emission buses. This study builds upon previous efforts by incorporating daily-level data into the analysis, allowing the team to capture extreme temperature values that would be masked in an evaluation of monthly data.

The Study Team collected data from eight transit agencies, four that deployed hydrogen fuel cell and four that deployed battery electric buses. The agencies were located in variable climate conditions, ranging from hot (southern California) to cold (northern Minnesota), and included one from Europe. Of the four battery electric bus transit systems, two used "en-route" recharging systems.

The results of the analysis showed that for temperature drops from 50-60 degrees to 22-32 degrees Fahrenheit (F), battery electric buses lost around 32.1 percent efficiency, while fuel cell electric buses dropped 28.6 percent. For those planning fleet replacement, however, the rate of fuel consumption is only one consideration. The cost of acquiring vehicles and building refueling/recharging infrastructure may be more important than the cost of fuel. Accordingly, a transit agency that expects to swap out its diesel for zero emission buses on a one-to-one basis will need to consider vehicle range for the zero emission buses.

For this reason, the Study Team also looked at the effects of weather on bus range. While the "en route" recharging data could be analyzed for efficiency, it could not readily be compared to other EV buses for effects on range, so the transit agencies using these buses were removed from the range analysis. The loss in range going from 50-60 degrees F to 22-32 degrees F was greater for battery electric buses (37.8 percent decrease) than for fuel cell electric buses (23.1 percent decrease). Since battery electric buses typically have a smaller range than fuel cell electric buses even under optimal conditions, this may be an important consideration for transit agencies located in cold weather climates that are seeking one-to-one bus replacements.