How electric bus charging software cuts the demand charge
A bus depot does not need a bigger electrical connection just because its buses plug in whenever they return, it needs one because nothing tells them not to all draw power at once. A demand charge is the part of a commercial electric bill set by the single highest moment of power a customer draws in a billing period, not by how much energy it uses in total. Electric bus charging software cuts that peak by deciding the order buses charge in, rather than letting the first bus draw full power immediately, spreading the same charging across more of the night.
An ETH Zurich study puts a number on the cut
Researchers at ETH Zurich built an optimization study around real service schedules from 4 real Swiss bus depots, Glarus with 7 buses, Einsiedeln with 14, Zufikon with 21 and Bern with 35, modeling a 150 kilowatt charger per bus and a demand charge rate of 12.1 dollars per kilowatt a month, the rate used in the study, not a universal price. At Glarus, charging every bus at full power on arrival reached a peak grid draw of approximately 440 kilowatts. Scheduling software cut that peak, and the demand charge tied to it, by 80%, cut the energy cost by 26%, and cut the total electricity bill by 54%, for that depot own example day.
All 3 figures describe 1 depot own example day in the paper, not a claim that every depot sees an 80% demand charge cut, since the grid capacity reduction varies by depot size, shown in the next chart.
Show the numbers
| Peak grid, power | 80 |
| Energy, cost | 26 |
| Total, electricity cost | 54 |
Run across all 4 depots, the same software cut the minimum grid capacity a depot needs by more than 40% on average. Zufikon needed 43% less, Bern needed 38% less, and Einsiedeln needed 17% less. Glarus needed no less, because its share before optimization, 9.5%, was already the lowest of the 4.
Glarus needed no less grid capacity because its minimum share before optimization, 9.5%, was already the lowest of the 4 depots, leaving little room to shrink further.
Show the numbers
| Glarus, 7 buses | 0 |
| Einsiedeln, 14 buses | 17 |
| Zufikon, 21 buses | 43 |
| Bern, 35 buses | 38 |
German operators already run this software today
A separate study from the Zuse Institute Berlin, written with IVU Traffic Technologies, a named transit software company, confirms this is not only a modeling exercise. Reading the paper directly, the researchers state plainly that power grid upgrades are not keeping pace with growing electricity demand from bus fleets, and they name 2 real Hamburg operators already running software that raises or lowers each bus own charging rate to manage cost and grid load.
King County Metro tested the same trade off in Washington State
King County Metro tested chargers from ABB, Siemens and Heliox rated to draw a combined 4.63 megawatts at once, and installed a transformer that supplies only 2.5 megawatts, about 54% of that rated total, a figure this article calculated from the 2 numbers the agency states. The Mobility House, the company whose ChargePilot software manages that gap, projects the software saves the agency approximately 1,000,000 dollars in total cost of ownership, a company figure rather than an independent measurement.
Their pilot program is an innovative demonstration of the value of interoperability and smart charging and energy management.
Gregor Hintler, The Mobility House United States managing director, quoted on the King County Metro pilot. Source 3.
In Leeds, England, the same fix paired software with a battery
At a First Group bus depot in Leeds, England, the grid import capacity at the depot restricted how many of its 14 electric buses could charge at once, in the words of a Zenobe case study of the completed project. Zenobe paired smart charging software with a 500 kilowatt hour battery rather than a larger grid connection, and the depot has cut carbon dioxide emissions by approximately 1,308 tonnes a year, Zenobe says.