The cost to charge an electric vehicle includes more than the cost of buying electricity form the power company. The charging infrastructure, including the charging hardware on the car and at the charging sites, inevitably adds to the EV charging cost. The costs of purchasing and maintaining this equipment must be recovered via direct payments by EV customers, additional fees for EV charging or public subsidies.
The table below shows how AC Propulsion's Reductive(tm) Charger reduces overall charging cost by minimizing both vehicle and charging site hardware requirements. The supporting financial and usage assumptions are shown in Attachment 1 below.
| Type of charging station | Onboard charger | Offboard charger | ||||
| AC Propulsion Reductive(tm) | Conductive opportunity | Inductive opportunity | Inductive one-hour | Quick-charge | ||
|
Power rating |
kW | 20 | 6.6 | 6.6 | 25 | 100 |
|
Recharge rate for EV @ 200 Wh/mi (Driving range per hour of charge) |
mi/hr | 100 | 33 | 33 | 125 | 500 |
| Total cost | ||||||
|
Total charging cost |
cents/mi | 2.4 | 3.6 | 4.6 | 5.3 | 7.5 |
|
Cost penalty vs. Reductive(tm) |
% | 0 | 52 | 93 | 124 | 216 |
( Typical gasoline fueling cost = 4.5 cents / mile @ $1.35 / gallon, 30 mpg )
The Reductive(tm) Charger minimizes charge site cost by keeping the charger with the car. Since the Reductive(tm) Charger is GFI compatible and operates at unity power factor, only power outlets are required at the charge site.
The Reductive(tm) Charger reduces vehicle cost by integrating the charger with the drive system. High cost charger components are "borrowed" from the drive system during charging so the incremental cost for the charger is low. The Reductive(tm) Charger provides for charge rates up to 20 kW, at least 3 times faster than other onboard charging systems.
Descriptions and hardware requirements for the charging systems analyzed here are included as Attachment 2 below.
| Type of charging station | Onboard Charger | Offboard Charger | ||||
| AC Propulsion Reductive(tm) | Conductive opportunity | Inductive opportunity | Inductive one-hour | Quick-charge | ||
|
Power rating |
kW | 20 | 6.6 | 6.6 | 25 | 100 |
|
Recharge rate for EV @ 200 Wh/mi (Driving range per hour of charge) |
mi/hr | 100 | 33 | 33 | 125 | 500 |
| Station investment cost | ||||||
|
Charging station hardware cost |
$ | 300 | 150 | 3,000 | 15,000 | 150,000 |
|
Annual cost of capital |
% | 10 | ||||
|
Cost recovery period |
years | 3 | 6 | |||
|
Cost recovery requirement |
$/month | 10 | 5 | 97 | 484 | 2,779 |
|
Station utilization(% of time at rated power) |
% | 25 | ||||
|
Total energy delivery |
kWh/month | 3,600 | 1,188 | 1,188 | 4,500 | 18,000 |
|
Investment cost allocation |
cents/kWh | 0.3 | 0.4 | 8.1 | 10.8 | 15.4 |
|
Cost per mile for EV @ 200Wh/mi |
cents/mi | 0.0 | 0.0 | 0.6 | 0.8 | 2.1 |
| Station maintenance | ||||||
|
Maintenance expense as % of cost |
% | 5 | 5 | 15 | 15 | 15 |
|
Site maintenance cost |
$/yr | 15 | 8 | 450 | 2,250 | 22,500 |
|
Maintenance cost allocation |
cents/kWh | 0.0 | 0.1 | 3.2 | 4.2 | 10.4 |
|
Cost per mile for EV @ 200 Wh/mi |
cents/mi | 2.0 | ||||
| Energy cost | ||||||
|
Electicity cost |
cents/kWh | 10.0 | ||||
|
Cost per mile for EV @ 200 Wh/mi |
cents/mi | 2.0 | ||||
| Vehicle equipment cost | ||||||
|
Onboard hardware cost |
$ | 300 | 1,500 | 300 | 300 | 300 |
|
Useful life |
miles | 100,000 | ||||
|
Vehicle hardware cost allocation |
cents/mi | 0.3 | 1.5 | 0.3 | 0.3 | 0.3 |
| Total charging cost | ||||||
|
Investment + maintenance + energy + vehicle equipment |
cents/mi | 2.4 | 3.6 | 4.6 | 5.3 | 7.5 |
A technology patented by AC Propulsion that reconfigures the motor windings and power switching devices in the motor controller so they can serve as a high-rate charger. This technique allows the vehicle to plug in to standard power outlets and charge at rates up to 20 kW.
| Vehicle | current sensors, input filters, conductive charge port |
| Charge site | outdoor 240V/30A up to 240V/80A outlet, card reader |
A conventional stand-alone charger packaged on the EV. The charger is typically limited to under 7 kW due to size and weight considerations. Because the charger shares no components, its cost in higher than the Reductive(tm) Charger. If properly designed, it can plug into standard outlets.
| Vehicle | complete charger and controls, conductive charge port |
| Charge site | outdoor 240V/30A outlet, card reader |
Inductive coupling is used to transfer power to the vehicle from a charger located at the charge site. This system limits charging to only locations where chargers are installed. The GM unit is rated at 6.6 kW.
| Vehicle | inductive charge port |
| Charge site | inductive charger, cable, water-cooled inductive paddle, controls, card reader |
A larger version of the offboard inductive charger that charges at 25 kW.
| Vehicle | inductive charge port |
| Charge site | inductive charger, cable, water-cooled inductive paddle, heat exchanger and coolant circulation system, controls, card reader |
The offboard charger converts line power to DC for conductive transfer to the vehicle at 100 kW. This allows substantial recharging in just ten minutes. The high current requirements require site specific electric utility grid connections, special connectors and charging cables.
| Vehicle | unique high current DC connectors and cabling with mechanisms to isolate battery from connector when not charging; a complete, entirely separate charging system for standard-rate charging |
| Charge site | dedicated substation to connect one or more quick chargers to the electric utility grid, controls for matching DC output to battery voltage and charging requirements, high current cable and connector, card reader |