Flipping the Switch on Electric School Buses: Cost Factors: Module 2 (Text Version)
This is a text version of the video for Flipping the Switch on Electric School Buses: Cost Factors: Module 2.
Welcome to the Flipping the Switch on Electric School Buses series, where we will discuss electric school bus cost factors. Electric school bus cost factors consists of five modules. Module 1 provided information on bus capital costs and infrastructure costs. Module 2, which I'll be reviewing today, will discuss electric school bus operational costs. Module 3 will discuss electric school bus maintenance costs. Module 4 will review electric school bus incentives and financing options, and finally Module 5 will provide information on how to have some financing discussions.
So let's get started with Module 2 of the Electric School Bus Cost Factors, Operational Costs. There are generally two main costs driving operating expenses, especially when it comes to battery electric school bus, and those are the fuel or energy costs and the labor costs, and there are multiple factors that impact each of these. So the fuel and energy costs are generally affected by the efficiency of the battery electric bus, other auxiliary loads, which primarily we have seen to be HVAC or that heating ventilation air conditioning system, and then the utility rate structure because that is going to cost – that is what drives your cost of your fuel or your kilowatt hour. So labor is also the other factor, and that does include bus drivers, as well as any other support staff who might be responsible for plugging in and moving the buses. Technicians are also included in the maintenance cost. So we haven't included that within the labor.
Today I was going to review a little bit of data that NREL has on the fuel and energy costs for transit, because I want to highlight how the utility rate structure can impact the overall total cost of operational cost. So with that, let's jump into some examples.
This graph shows the fuel efficiency of three different buses. We have a battery electric transit fleet, and that's the green line, a diesel trolley fleet, which is the brown line, and a diesel transit fleet which is the gold line. So the battery electric bus, again that's the green one, and the diesel trolley fleet, brown one, they have operated in the exact same duty cycle route. So the exact same route for both buses that they drove. And the battery electric bus fuel economy was almost four times higher for the BEB than the diesel trolley fleet. Again, exact same route.
It was also almost three times higher than the diesel fleet in a varied route, which included higher average speeds. So basically the BEB had much better fuel economy in the same route, and it had much better fuel economy than a diesel in a route that was higher average speeds.
So from there we want to show you the example of energy equivalent fuel prices. So we had better fuel economy. Now we're looking at the cost for the fuel for each of those applications. And when the cost of the electricity is converted to a diesel gallon equivalent the cost is much higher than that of the diesel fuel in this case, and that's the point that we want to make. This is an unusual case of electricity cost where the electricity is actually very high. So normally I think the national average of dollar per kilowatt hour is about 0.104, and then on national average of diesel, at least based on a price report in January of this year, 2021, it was $2.35 according to EIA.
So again, this case has higher cost for electricity rates, much higher than the national average. So the fuel cost for the battery electric bus will actually offset the efficiency savings of the fuel economy, and I'll illustrate that on the next slide. So here we see fuel cost much higher for electricity than it did diesel.
This one compares the total cost per mile, so when we take that fuel and energy cost and we track that for each bus over the miles driven. And with that you can see that the same duty cycle, so again that was the green and the brown lines, they drove the exact same route. The driving costs are actually more per mile for the battery electric bus than the diesel, just because of that high electricity rate.
So even though the BEB was more efficient and it used less energy per mile, the cost of electricity offset the battery electric school bus. I'm sorry, this is battery electric bus for transit, because it was almost twice as high as the diesel fuel bus cost per mile. So the main point here is to remember that when you are considering a battery electric bus it's really important to ensure that there is a favorable electricity rate. That way it doesn't offset that efficiency.
Average high electricity rates are kind of more easier. They're more obvious to flag when looking at fuel rates, but something else to keep in mind are demand charging rates. So your normal electricity rate, if that's super high easy to notice. Something that you should keep in mind though are the demand rates and how that fluctuates and what that timing is, and how that's going to impact your use of the bus. Because adding a greater load during these high demand rate periods may cause the electricity rates to jump to peak load rates, and then that brings your average to a new high.
So this is an example of simulated hourly load profiles based off of the different types of charging scenarios or timing. So they are or what we did here with the data is that we use the load from the bus depots at different periods of time based off of the past usage and the hourly load of what the buses would require were added to those profiles. So we have our normal electricity load, and then we simulate adding the bus load to that, and then we look at how that impacts our electricity rate.
So the charts at the bottom actually shows the facility load and then the add on of the electric bus load. The blue bars are the current facility load over a year, and then we've added on top of the buses over night so that the electricity load is actually, you can see is now causing the demand chargers for overall facility load to be really high. So basically adding the school bus charging puts you into peak load and your rates increase. So this cost of electricity at the bus location, we can actually break it down to understand what's driving that peak load, and what's driving those high costs.
In this example we've broken it down into the depot just by itself. The depot plus the electricity and incremental cost as well as the total utility cost. So we have how much electricity do we normally use, how much are we using with the buses charging, and what part of that was just the bus? So this illustrates the impacts on electricity cost just for adding your charging for the buses as it adds to facility loads, and then again changes that rate of electricity to the higher demand charge.
So that was an example of how to one, understand that electricity rates can offset some of your efficiency. And then two, how to keep track of maybe those non-average rates then getting bumped up into your higher peak and demand rates. So with that, we just want to remind you to keep in mind of the two main factors driving operation expenses. And again, that's that fuel and energy cost, as well as your labor. And those variable energy costs and high electricity rates can offset the fuel efficiency savings. And so it's very important to understand the demand charges and electricity rate structure again so you can avoid bumping those rates up to the higher cost.
And then there are also other strategies to manage charging to optimize those electricity rates. So if you know that you need to add a load to charge your buses, but that it might put you in those higher demand or peak rates, just try to find a time to charge at a different time to where you won't push the load up into those demand or higher increased rates.
So thanks for listening. That concludes Module 2 of Electric School Bus Cost Factors. To complete the modules of this series please continue on to listen to Modules 3 through 5. And you can find all of the content for the Flipping the Switch on Electric School Buses series including each part of the series and associated modules, as well as handouts with the summary of information and the links to all the resources mentioned today on the Alternative Fuels Data Center's Electric School Bus page.