What are Depot charging & Opportunity charging for Electric Buses and Trucks

If you're new to medium and heavy-duty electric vehicles charging industry, you might often wonder about the terms like Depot charging, Opportunity charging, Overnight charging, on-route / en-route charging…etc. What are they actually mean? Is there any industry definitions or specifications for these terms? What output capacity each of them can offer? This post may help you to understand some basics around these terms.

What is Depot charging (a.k.a Overnight charging)

The name says it all. Electric buses / eTruck operators charge their fleets overnight at the hub or depot where they park. This approach assumes that the vehicle runs for only one shift a day, and stay idle throughout the night (or a longer duration at depot), and usually have a battery that is large enough to support the daily required range when fully charged.

Depot charging is mostly with an output of 30-50kW via plug-in charging using wall cabinets or mobile chargers; it is rare (or there is no real need) to go for a higher capacity (>100kW) or via induction charging at a depot. That is why overnight charging is often referred as '"slow charging' (though the same 30-50kW is seen as fast charging for passenger cars charging). 

Overnight is also the most economic charging solution for the medium and heavty duty vehicles.. Buses and trucks can use less expensive, slower chargers, given the long idle period, which also helps the fleet operators to reduce their up-front capital investment. In addition, with overnight charging , electric fleets can also benefit from the cheaper electricity in the night.

What is Opportunity charging?

Opportunity charging is a widely used term in the eMobility Industry, which is generally seen as the opposite of “depot charging”. However, there is no benchmark definition on what opportunity charging really is. Opportunity charging, also referred to as “on-route charging” or “fast charging (meaning, faster than typical depot charging of medium to heavy-duty electric vehicles)”, can be simply defined as the process of a bus charging while it’s on-route.

While a bus is executing its normal schedule, it can stop and charge for a short amount of time at appointed locations on the route where high power chargers (either with a plug-in , pantograph, or wireless connection) are installed. These on-route chargers, therefore, provide the opportunity for the bus to charge briefly before it continues its route.


Thus, neither of these terms refer to the power of the charger's output or its location, but rather refers to how a charger is used by the operators to charge their electric vehicles. The same charger (regardless of its capacity), can be used for either slow or fast charging. there is no hard rule that all the depot chargers are slow or the opportunity chargers are faster. 

Image source: McKinsey Energy Insights

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