Aurora, Cory Gaines, Energy, Environment, Transportation, Uncategorized

Gaines: A reality check on electric school buses

A recent Denver Post article describes how the Aurora school district added 7 electric school buses to its existing fleet of 151 total.  Sadly the article focused mainly on the politics.  Gov. Polis got in his talking points, the Republican quoted got in his, fun was had, and we all moved on with our day.  Disappointing.  For my taste, sound bites from politicians, particularly those of practiced and savvy career politicians like Polis, hide lots of detail which are important for us to know if we’re to be able to assess the decisions of those we elect.  Without details, without numbers, we’re left with the imprecision of language (fertile ground indeed for politicians).

The best way to summarize the difference between electric and internal combustion buses is that electric likely costs more upfront and less later, while internal combustion is cheaper to buy and likely more to operate.  I’m being careful to qualify my statements here because we don’t have a good handle on costs yet (also “internal combustion” is a large category with different fuels/engines to consider).  Looking into the matter has also convinced me that what you include–and what you don’t–when calculating makes a big difference.  Diesel buses are the standard choice across the country with electrics making steps into the market. Orders for electric buses are going up quickly, but are only about 1% of current rolling stock.

Running the numbers

Analyses of bus costs (electric vs. internal combustion) abound, making it tough to decide whose numbers to rely on, but I chose to analyze those of California’s electric utility (PGE).  Their estimator compares diesel to electric school buses, and should also remove any doubt that I’m trying to shade things; PGE is a big proponent of electric.

From the PGE site, we learn that diesel buses are about $90K to buy and cost about $1.11 per mile to run, including maintenance and fuel.  Electric buses cost $350K (the Post article has them at $375K) and cost about $0.20 per mile, including maintenance and fuel.  Clearly it’s cheaper to buy diesel and to run electric.  The $260K cost differential between the two, however, effectively means that any district wanting to take advantage of lower operating costs is going to need help.  Enter both the federal and Colorado state government to buy down the cost of the electric buses with big subsidies. Colorado and the feds pay 80% of the bus cost, and the district makes up the other 20%.

All the same, there are some things missing from PGE’s estimates.  There is more capital investment to electrics than just their higher purchase price.  Diesel is a known quantity.  Shops have mechanics, tools, and knowledge about how to maintain them.  Electric?  Not so much.  So add in the costs to train your mechanics and buy specialized tools.  Oh, you’ll also need to install chargers.  I couldn’t find numbers on the increase in costs for tools and training, but PGE was helpful enough to give estimates on the chargers and maintenance:  $13,750 per and $1,100 per year respectively.

I’m tempted to continue (increased sales tax costs and hidden costs like out of service time), but I think you get the point.

Continuing with the finances, the last thing to consider is the time it will take us taxpayers to realize the savings on electric school buses.  If you figure an average of 16,000 miles per year (the high end estimate on yearly mileage for a bus), and include only the costs laid out here, the payback on electric is about 20 years.  That number was startling to me because 20 years was the top end, best-case-scenario I could find for the life of the bus batteries.  In other words, right as we’d start to realize the savings, the bus would stop working.

The details matter

As you find with a full accounting of costs, the discussion of electric bus performance is incomplete.  With solid engineering you can design things to work nearly anywhere.  As I tell my students though, nature doesn’t give us things for free, and glibly misleading comments like Governor Polis’s that the buses operate “without issue” in -40 degree Alaska don’t tell you those important details.

First, with regard to Alaska, it would have been more accurate for Polis to say “bus” because there is only one electric school bus running in the whole state, hardly a reliable sample to draw sweeping inferences from.  And it does operate down to -40, just not as well.  Unlike internal combustion engines which scavenge waste heat to make the passengers comfortable, electric buses must divert some battery energy into heat (this is in addition to the basic physics of temperature:  all reactions slow with lower temperature).  To paraphrase the bus manager in Alaska, the amount of energy used to heat the bus could be more than the amount used to move it.   That is, the electric equivalent of miles per gallon on the electric bus drops by about half.  In Colorado, with its relatively milder winters, the step-down would be less, but would still be significant.  Let’s say that on the coldest days we put half our battery into heat.  The 300 mile range would then drop to 150 miles.  That’s 18 miles straight out from the depot, once around a circle, and then back on one charge.

One other thing you almost never hear about with electric vehicles is the charging rate when it’s cold.  I could not find specifics on buses, but a study on electric taxis in New York can give us a rough idea: charging rates for those batteries can be up to 3 times longer as you go from summer to winter.  That means more time out of service and higher costs (i.e. more buses to do the same job).

The right tool for the job

I look at most vehicles as tools.  Just as there would be times when using a cutting torch would be a better choice than a cut off wheel, I think there are cases where electric buses would be a fine tool:  places where there is the political will to not have as much internal combustion exhaust, where distances are small and without steep grades, and where there is some reserve in the district’s resources to absorb the costs and problems attendant with the switch.  Aurora may well be a fine location for them.  Without those conditions, however, I don’t think that they make sense (even with gigantic government subsidies to defray the cost); you’re not picking the right tool for the job.  Out in Logan County where I live, I don’t think they would work well for the same reasons.

Finally we arrive at the real point here.  You can argue whether or not an electric bus is the best tool to cart out little ones around.  It is as much a values judgment as an economic one and, in that sense, there are legitimate arguments to be made either way.  I don’t think you could fairly argue, however, that people who will not benefit from them (outside of the usual weak-tea and incomplete arguments about how electric vehicles make our whole environment better) should have to pay up to twice for them via both state and federal taxes.

If Aurora or any other district wants to take the risk that electric is the wave of the future and pay the huge cost themselves, good for them. I’d personally like to wait a bit and keep my money for my own family.

Cory Gaines, a Sterling resident, runs the Colorado Accountability Project on Facebook.


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