The Great Electric Bus Takeover Has Begun (CleanTechnica Exclusive Interview)

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The US electric bus company Proterra has been making a series of rapid-fire moves into the EV transit marketplace, and it looks like you can file the latest development under Y for “you ain’t seen nothing yet.” The company has just introduced a new, improved version of its Catalyst XR EV battery that will enable transit fleet managers to place electric buses on more routes — and save more money, to boot.

The bottom-line benefit of electric transit has already convinced Philadelphia’s SEPTA managers, among others, to take the electric bus plunge. With an average turnover of about 12 years, the potential is there for the entire US bus transit fleet to ditch diesel and compressed natural gas in favor of electricity.

Proterra electric bus EV

Big Fuss Over An Electric Bus

Proterra has long been on the CleanTechnica radar, and that of our sister EV-centric site, for its purpose-build approach to designing electric buses.

While the upfront costs may be more, the company’s focus on the actual lifetime cost of ownership presents a compelling case for switching to electricity.

Fuel costs alone add up because of the amount of mileage that transit buses put in. Proterra estimates a fuel savings of $250,000 to $365,000 compared to hybrid, CNG, and diesel buses.

Access to renewable energy sweetens the pot even more by insulating transit systems against fuel price shocks, and the relatively simple design of Proterra’s bus can save tens of thousands in lifetime maintenance costs — an important consideration when you’re dealing with vehicles that are on the road all day, every day.

As for the environmental benefits, last fall we caught up with Proterra CEO and President Ryan Popple, who described why the VW “clean diesel” scandal was the death knell for diesel buses:

It’s oxymoronic. There is no level of diesel pollution you’d want to be exposed to. The end point should be moving vehicles without lighting fuel on fire.

When we got to the point where Paris had air quality as bad as China, you know something is going to change.

Electric buses provide a twofer because they improve general public health while also creating  a more attractive environment for alternative transportation, namely walking and bicycling, and for social interaction in public spaces like plazas, pocket parks, and outdoor dining areas.


Better Battery = More Routes

Last week, CleanTechnica had the opportunity to speak with Matt Horton, Proterra’s senior VP of sales and marketing, and he made it clear that Proterra is poised to expand its business by leaps and bounds.

According to Horton, electric buses in general already have an advantage over their diesel, CNG, and hybrid counterparts because batteries “really shine” when it comes to handling the start-stop-idle patterns of urban bus routes.

Proterra expects that its newly upgraded Catalyst XR battery will propel it even farther along. As with its bus design, Proterra took a bottom-up, from-scratch approach to the improved design, as Horton describes:

We do things a bit differently … we have been hiring battery engineers from the leading electric vehicle companies, for a complete redesign to work in Proterra buses in heavy duty transit.

The new battery has the same weight and footprint as the original, but packs a 28% increase in capacity. That provides a rated range of 194 miles, which will enable Proterra buses to be placed on longer routes with “high confidence.”

The improved battery means the Proterra buses can also be used on more routes in regions where the necessities of climate control interfere with battery range.

That’s where another new Proterra development comes into play. The battery’s rated range of up to 194 miles will vary depending on actual driving conditions, so the company has just introduced a proprietary “EV Simulator” that enables fleet managers to identify routes where they can place a Proterra bus with the improved battery, and to calculate their potential savings.

… Designed to visualize mass transit networks and to assess the cost savings, performance improvements and environmental benefits of battery-electric transport, the Proterra EV Simulator generates a side-by-side comparison of Proterra’s transit solutions with diesel, CNG, and hybrid technologies on specified transit routes within a chosen public transit system.

As Horton explained, until the EV Simulator came along, Proterra would send its analysts on actual routes with a GPS tracker to chart the variables — an effective but cumbersome and time-consuming method for calculating potential savings.

According to Horton, the EV simulator takes it to “a whole new level.” The new system leverages map applications from Google, enhanced by the more than 2 million miles that Proterra buses have already logged in actual driving conditions. Passenger load, layover times, and vehicle charge times are also among the variables that factor in.

As for the idea that the entire US bus transit fleet could transition to electricity within a dozen years or so, Horton had this to say:

It’s probable that most if not all new sales will be battery electric vehicles. The economics are already better today and costs will continue to fall over time.

I honestly struggle to understand what transit manager would buy a fossil fuel bus.

Proterra is focused like a laser on transit systems for now, because that’s where the company sees the greatest potential for rolling an entire transportation sector over to electricity. Campus shuttles and similar fleets are also ripe for the picking.

Why stop there? Success in the transit fleet market could accelerate change in other diesel-heavy sectors, including tour buses, delivery vans, food carts, and ice cream trucks.

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Image (cropped) via Proterra.

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Tina Casey

Tina specializes in advanced energy technology, military sustainability, emerging materials, biofuels, ESG and related policy and political matters. Views expressed are her own. Follow her on LinkedIn, Threads, or Bluesky.

Tina Casey has 3150 posts and counting. See all posts by Tina Casey

32 thoughts on “The Great Electric Bus Takeover Has Begun (CleanTechnica Exclusive Interview)

  • Good report, but no context about the competition. This basically means BYD, as European bus makers are chasing the complicated half-way house of en route fast recharging, and other Chinese manufacturers are sticking to their huge domestic market.

    A question for Tina and the other bloggers following electric buses. The ride is presumably better than ICE ones, without noise and vibration. A priori, one would expect this to attract more riders. Has this been observed anywhere?

    Proterra: “We have been hiring battery engineers from the leading electric vehicle companies ..” This is an important part of a technological revolution. As the new system takes root, the pool of qualified and experienced workers at all levels expands, from production-line fitters to design engineers to maintenance mechanics to marketing people and operations supervisors. Call it network economies of learning, as companies cannot put a lock on such acquired skills. A hundred years ago, Fred Singer put foot-powered sewing machines into hundreds of thousands of villages across the world. IIRC you can find sewing-machine repairmen anywhere, like bicycle mechanics.

    • A sub-question on the “noise and vibration” front: might regenerative braking be less noisy than friction brakes? Reduced brake servicing costs could be a significant cost advantage.

      • yes, and this is just one of the ways that electric buses have lower maintenance costs.

    • I talked with someone who worked on some “bus conversions” to electric and the ride was a lot rougher for those because of the weight of the batteries. It felt like riding in a loaded dump truck. Basically a stiffer suspension was required due the the weight. Maybe if you started from the ground up designing a bus, you could make a smoother suspension.

      I really look forward to electric busses though… I think it will be great.

      • If the batteries were mounted above the floorboards and in front or behind the wheels the ride could be more “pitchy”. Also if the conversion company didn’t deal with suspension needs the ride would suffer.

        I don’t understand why some of the urban electric buses are putting the batteries on top.

        Probably don’t convert. Build a Tesla-like skateboard and put a school bus body on top.

        • Ride quality is not something Chinese carmakers are renowned for, so this could be an area where non-Chinese bus manufacturers can establish a lead and a selling point.

          IIRC the latest BYD is only slightly heavier than a diesel bus, so a priori the suspension need not be much stiffer. A Rolls-Royce is a heavy car, and by repute very comfortable.

          Firsthand reports wanted.

          • Weight should not be the issue. It’s battery placement and suspension.
            Batteries placed in front the front wheels or behind the rear wheels could lead to ‘hobby-horsing’. Placed high would add to body sway. Tesla got it right, low and between the wheels.

            Heavy cars (if engineered correctly) offer very smooth rides. It’s the light cars that bounce around on the road.

            With computer controlled acceleration electric buses could offer very smooth rides. No jackrabbit starts that sling passengers off their feet and no abrupt gear changes.

            Obviously someone can build a badly riding electric bus if they don’t pay attention to the details….

          • IIRC, one of the principles of getting a good ride is to minimize unsuspended weight. The battery isn’t at issue in that regard, but the in-hub motors would be–though I’m guessing they are not all that heavy relative to the vehicle weight. Any insight on that?

          • I have this tucked away in a Google Doc –

            “A stock 2007 Ford Focus was compared with an identical vehicle modified with 66 lb (30 kg) of ballast fitted to each wheel. The weight was distributed between rotating and nonrotating unsprung masses as to broadly replicate Protean Electric’s PD18 (18-in diameter) wheel-hub-motor unit. The project plan included three phases of analysis and testing.

            Phase 1 focused on modeling of different modifications, including suspension spring, bushing, and damper rates, and different tires and pressures, and their effects on the IWM-equipped vehicle. It was determined that simply fitting a standard Focus ST suspension (an upgrade on the stock base car) would be a good practical solution.

            In phase 2, the stock vehicle was modified with the Focus ST suspension. This setup included revisions to the front and rear spring rates, dampers, and the rear antiroll bar. In phase 3, the Focus with the modified ST suspension was retested. The process included a subjective vehicle assessment, objective ride and handling tests, on-road shake measurements, and two-post shaker rig measurements.

            The studies concluded, and the presenters argue, that while the vehicle carrying the greater unsprung mass at each wheel did display perceptible differences compared with the stock vehicle, those differences were minor and can be mitigated using “normal engineering processes within a product development cycle.”

            By fitting the upgraded ST-level suspension to the car replicating one equipped with Protean PD18 in-wheel motors, the vehicle’s handling and on-center tracking were improved back to reference. Overall, the effort conducted by Protean Electric, Lotus Engineering, and Dunamos may help convince skeptics that the addition of 30 kg of unsprung mass per corner will not adversely impact overall vehicle dynamics and can be addressed fairly easily with cost-effective countermeasures.”


            And I have this –

            “Hub or wheel motors have been used in prototype electric cars and trucks, though none are yet in volume production. They are quite common in electrically assisted bicycles and other personal transportation vehicles.

            Now, Michelin has taken the hub motor idea one step further with its Active Wheel. Besides the electric drive motor found in all hub motors, the Active Motor also includes the vehicle’s suspension and brake components.

            Along with a small but powerful main drive motor, a second motor powers the active suspension system that’s fitted vertically across the diameter of the wheel. The suspension, which is now electrically controlled, can automatically and very rapidly correct for pitching and rolling. Response times of just 3/1000ths of a second are claimed. Finally, a ventilated brake disc is fitted inside the rim. Because it’s larger in diameter than a conventional brake disc, the disc depth is smaller, allowing more compact packaging.

            According to Michelin, the Active Wheel greatly simplifies vehicle design because an engine gearbox, clutch, transmission shaft, differential, and shock absorbers are no longer needed. Besides being simpler, the vehicle can be substantially lighter and thus more energy efficient. Packaging propulsion and suspension components in the wheel frees up space at the front of the car, which could be used to improve the absorption of impact energy.

            Other advantages include the potential for a flat floor and more efficient interior packaging.


            I haven’t followed up to see if anything has been published in the last couple of years. If you’ve got time to check and report back what you find it would be appreciated.

            There must be some sort of fatal flaw that isn’t brought out in these two articles. The advantages seem to be too good to be ignored given that there’s no “except” factor….

          • Hey, thanks, Bob! Fascinating. I’m not sure that we need to give up on those ideas, though: I first heard about CVTs back in the early 80s and had long concluded that there must be, as you put it, an ‘except’ factor. Now they are nearly mainstream, with most manufacturers using them in at least a couple of models.

          • I found the BYD bus to have about the same ride quality. I was surprised at how loud it was. No rumbling diesel but for city buses (as compared to school buses), most are already on NG which is not terribly loud. The motors have a whine that is much more audible in a bus vs in any EV I’ve been in.

            The noise level was better than any fossil fuel powered vehicle I’ve ridden in…but not the EV silence I was expecting / hoping for. I’m sure this could also be improved with more intentional focus on noise generation in motor design and in the sound dampening materials used on body panels around the motors which I believe were in the hubs on this bus:


          • There really is no reason the buses have to be loud. However it is possible for an EV be to be loud. If you make the cabin and frame very stiff and of hard materials, the interior can act as an echo chamber. Think of vibrating a big metal can.
            Sound deadening and acoustic design is necessary. Unfortunately, corners are often cut needlessly.

            An EV bus manufacturer that realizes the advantage of quietness and smoothness can take advantage of this to generate demand. There are people that don’t like to ride in or live near noisy vehicles.

          • It didn’t feel like resonance as I would expect with a large frame vehicle that might magnify any EV whine but just unmanaged motor noise. I’m no expert but would love to see improvements in this space because as you noted, EVs can be quiet…and thus, should be quiet 😀

          • If the motor and controller are not isolated from the frame, its just a big megaphone.

          • Was the bus quieter at low speed? You do seem to be going pretty fast, especially for a bus. An in city route would be much slower average speed and I would hope it would result in a quieter experience as well.

      • Electric buses require a different suspension design; this was one of the earliest things they figured out.

    • If there are studies on use of EV bus over ICE bus, it would have to be outside the USA. Since there have been so few in use here so far.

    • New Flyer is also competing.

    • New Flyer (Canadian) is also competition. 120 mile range for the current model, working well in Winnipeg and Chicago.

  • Nice article Tina. Wonderful to see such progress. Thank you!

  • Great to see a sweetening of the value proposition with longer range and the capability to run climate control on the bus.

    Sales figures? Market share figures? The “takeover” will “have begun” and the value proposition will be “compelling” when fleet managers demonstrate it by purchasing them in volume. This will happen when the price and TCO is clearly, undeniably compelling.

    • The counterpoint is that fossil fuel companies have trillions invested in NG and LNG infrastructure and are pushing hard for “Clean NG” buses to takeover mass transit. If anything, it’s an ugly bump in the road but worth noting just how much money is pushing NG vs EVs.

    • Price and TCO is already clearly and undeniably compelling but I think a lot of transit agency managers are worried about reliability of a new design.

        • Nope, that study doesn’t even CONSIDER BEV buses. (Which shows you what the problem is.) They don’t bother to analyze them. It’s strictly a CNG vs. diesel analysis.

          Were you thinking of some other study?

          Before failing to consider BEV buses, it casually assigns a price to them which is significantly higher than today’s price quotes.

          • Well the fact is that BEV buses sales volume is a trickle. Transit operators tend to be fairly rational creatures, looking at total cost of ownership, finding capital for new equipment, minimizing risk and hassle, and so on. It the proposition is “undeniably compelling” then what’s up? I suggest that the perception among transit operators is that the proposition is not undeniably compelling. It’s hard to even find much data. Here’s a link from CA air resources board, really pushing hard for this tech and the best they can say is “TCO may be cheaper for BEV” and “more data needs to be collected”. So if it’s undeniably compelling, then we need to get that word out. Feel free to offer up a link. Thanks

  • Its always sweet to read about battery tech improvement then range

  • By definition, buses and trains spend a lot of time around pedestrians. Some are getting on or off, while many are passers-by. Both are breathing the same air those buses or trains are passing through. It will be much easier to breathe when the diesel fumes are no longer part of the ride, or a walk down the same route (I almost cringe every time I see another jogger along such stretches, usually several times a week). This will be a major, major improvement for downtowns and other densely populated neighborhoods. Cleaner street-level air will put some real meaning into the general goal of making cities “more livable.”
    If it helps keep mass transit affordable, so much the better. Our last fare hike in the local commuter rail was to cover rising diesel fuel prices (they didn’t follow fuel prices back down). I wonder if this battery engineering and design work with city buses will spill over into the locomotive market (especially commuter rail and yard switch engines)?

    • Think of all the buses, driving in short loops around airports. Surely it is time to convert those over.

    • What made me angry was seeing idling school busses with their exhaust pipes on the passenger side at lung level of the elementary school kids it’s supposed to transport. As an engineering prof of mine was fond of saying: “One out of two engineers ought to be shot!”

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