How lowering peak power demand can reduce your EV fleet charging costs

Sashko Stubailo

November 15, 2023
May 16, 2023

 Lowering the cost of operations is top of mind for most fleets, and the cost of diesel and gasoline fuel has always been one of the biggest components of operational cost. Switching to electric vehicles (EVs) can help reduce fuel costs, but comes with a variety of new challenges around calculating and understanding those costs in the face of complex utility rates.

Previously, we've shared general advice about lowering costs. In this article, we'll go over a specific example of a utility rate and a single truck, and see the costs for different charging scenarios. What we'll find is that, depending on your situation, your peak power charges might be as much or higher than your per-kWh energy charges.

We'll also cover how using EV operations and charger management software like Flipturn Connect can help fleets manage all of this more easily, simplifying adoption of medium- and heavy-duty EVs.

The two main aspects of most utility bills: energy costs and power costs

Let's say you drive a class 8 electric truck 100 miles, and use 200 kWh of energy from the battery. How much will it cost you to recharge that truck back to 100%? It turns out the answer is a bit more complicated than just a certain number of dollars per kWh. There are two very important questions that can dramatically affect the result:

  1. When was it charging? Many utility plans have different rates for different times of day. For example, in one Southern California utility rate, power is most expensive between 4pm and 9pm.
  2. What was the maximum power level at which it was charged? Many utility plans charge you an additional rate depending on the peak power level used throughout the month, even if that peak power demand was only for a short period of time. As we'll see below, these costs can often be similar or even higher than the time of use rates.

Depending on how the calculations work out, your best bet for reducing costs could be to charge at a cheaper time, lower the peak power of charging, or both. Let's look at an example.

The utility rate details for our example

For our example, we'll use a specific utility rate, the SCE general service time of use rate number 2 (TOU-GS-2). Here is a summary of the winter rates under TOU-GS-2. You can find all the details about this rate on SCE’s website. As mentioned above, the rate has two main components:

Time of use energy charges, dollars per kWh:

Name Time Cost
Mid-Peak 4pm - 9pm $0.1391 / kWh
Off-Peak 9pm - 8am $0.1385 / kWh
Super-Off-Peak 8am - 4pm $0.0913 / kWh

Maximum power rates and demand charges, dollars per kW:

Name Time Cost
Mid-Peak Demand and Generation Charges 4pm - 9pm $9.16 / kW
Facilities Related Demand Charge All times $20.79 / kW

As you can already see, there are a lot of different aspects to factor in when trying to optimize costs. Let's see how a few different scenarios can play out:

Different cost scenarios for charging a class 8 truck

Let's look at the example of the specific truck above, which drove 100 miles and used 200 kWh of energy. How much will it cost to charge it back up to 100% under the assumed utility rates?

Because demand charges are determined across a whole month, we'll calculate the results for a whole month's charging, assuming we will charge once per day. For simplicity, we'll also assume that the truck charges at a constant power output rate. Usually, the power output will be decreased significantly as the vehicle nears 100% charge, but that doesn't dramatically affect the calculations below.

Scenario 1: Fast charging during peak time

Truck charges at 100 kW from 5pm to 7pm

  • Time of use energy costs: 200 kWh * 31 days * $0.1391 = $862.43
  • Maximum power costs: 100 kW * ($20.79 + $9.16) = $2,995
  • Total cost: $3,857.43

Scenario 2: Slower charging during peak time

Truck charges at 100 kW from 5pm to 7pm

  • Time of use energy costs: 200 kWh * 31 days * $0.1391 = $862.43
  • Maximum power costs: 40 kW * ($20.79 + $9.16) = $1,198
  • Total cost: $2,060.43

Scenario 3: Fast charging during off-peak time

Truck charges at 100 kW from 9pm to 11pm

  • Time of use energy costs: 200 kWh * 31 days * $0.1385 = $858.70
  • Maximum power costs: 100 kW * $20.79 = $2,079
  • Total cost: $2,937.70

Scenario 4: Slower charging during off-peak time

Truck charges at 40 kW from 9pm to 2am

  • Time of use energy costs: 200 kWh * 31 days * $0.1385 = $858.70
  • Maximum power costs: 40 kW * $20.79 = $831.6
  • Total cost: $1,690.30




As you can see, in this example, charging the vehicle more slowly results in more immediate cost savings (about $1,800) than charging quickly at the off-peak time (about $900). So it's important to consider several different charging management approaches to find the one that saves your fleet the most money.

Charging multiple trucks and other scenarios

The examples above are for one truck and one charger. How would they generalize to, say, 20 trucks?

The time of use energy rates would just be added up, but the demand charges depend on whether the trucks are all charging at the same time, and at what power levels. So, for example, if all the trucks are charging at the same time, then the demand charges stack up. But if the trucks are charging in multiple shifts, that can help keep the demand charges low.

There are also other ways to reduce costs, like subscribing to rates designed specifically for EV charging and adding on-site battery storage and solar, which add an additional dimension to these cost calculations. We'll cover those in a future article!


When trying to charge your electric fleet in the cheapest way, it's important to consider all of the different dimensions of your utility bill, including time of use rates, demand charges, and other fees.

Depending on your specific situation, the highest impact savings might come various places, like charging at a different time, lowering your charging power, making sure your vehicles aren't all charging at the same time, or something else.

Save on energy costs with Flipturn Connect

Doing all this math and management manually can get complicated pretty quickly, especially for fleets with mixed vehicle types and those that are scaling up the number of EVs in their fleet.

Flipturn Connect provides cross-system visibility for fleet EV and charger operations so you have all the data and insights you need to make decisions that will reduce costs and maximize ROI. With Connect, you can monitor and manage your EV fleet in one place and use key data to take measures that will reduce your electricity costs, like automating charge scheduling, tracking energy and power consumption, and keeping tabs on your daily electricity costs.




 Click here to read more about Flipturn Connect, and schedule a demo at!