Charging your EV

Vehicle charging is an important part of owning an electric car. Here's where you can find out more about how charging works, potential electrical upgrades for level 2 charging, and the best times to charge your vehicle. 

Level 1 (120V/15A)

A typical outlet (120 volt) provides a level 1 charge. The cord has a standard three-prong household plug and a connector, which plugs in to the vehicle.

Level 2 (240V/30-70A)

This level offers charging through a 240-volt AC plug and requires installation of home charging equipment. Adding a 240-volt charger is similar to adding a large appliance (i.e. a clothes dryer). This might require upgrades to your electrical service.

DC Fast Charging

These charging stations can recharge an EV in less than an hour. This option is available along traffic corridors and at Rocky Mountain Power public stations in Utah and other areas. There are different types of connectors for charging: CHAdeMO, SAE J1772 or Tesla Supercharger.

Charging Type Voltage Time to Charge
(Battery EV)
Time to Charge
(Plug-in Hybrid EV)
Level 1 120 volts 8 to 15 hours 6 to 10 hours
Level 2 240 volts 3 to 6 hours 1 to 4 hours
DC Fast Charging 480 volts 20 to 40 minutes 5 to 15 minutes

Note: Charging time may vary based on vehicle make and model, battery size and state of charge.

Electrical upgrades may be necessary for home charging

Depending on the charging option, an upgrade to your home’s electrical system may be required. We can help guide you through this process.

Step 1: Check with the auto manufacturer or dealer on vehicle charging requirements.

Step 2: Determine if the vehicle requires an upgrade to your home's electrical panel and wiring.

Step 3: Contact a licensed electrician for consultation on your home's electrical needs and upgrades. Permits also may be required. (See the next tab for guidelines and specifications.)

Vehicle charging equipment installation costs can vary greatly depending on the configuration of your home's electrical circuits, local code requirements and the type of equipment installed. Permits may be required prior to installation or construction. If an electrical contractor is hired to perform the work, it is the homeowner’s responsibility to ensure the appropriate permits are obtained.

Step 4: If your electrician requires upgrades to your utility service, please contact us toll free at 1-888-221-7070 to request the service upgrade. If upgrades are needed to the infrastructure serving your home or neighborhood, we will upgrade your service as quickly and efficiently as possible. If permits or inspections are required, you are responsible for ensuring work is in compliance with federal, state and local codes.

Guidelines and specifications for electric vehicle charging home upgrades

Is an upgrade necessary? Uses a typical 120-volt household outlet so upgrades to your home's electrical panel may not be necessary. Charge requires 240 volts so this will likely require upgrades to your home's electrical panel and the addition of a new circuit similar to one for an air conditioner or electric dryer. Contact a licensed electrician to provide a cost estimate and perform the work.
National Electric Code requirements
  • 20-amp single-pole breaker
  • Ground fault circuit interrupter
  • Protected wall-mounted receptacle for 120-volt charging
  • 40-amp, two-pole breaker is required.
  • Charging equipment should be wired permanently to the electrical supply circuit.
  • Equipment may vary in design but must meet specifications set forth in the NEC. These specifications include equipment that is listed and labeled, ground fault protection, diagnostic capability to prohibit charging from taking place when the batteries or the vehicle is damaged or an unsafe condition exists; and an interlock that de-energizes the charging cable when the vehicle is disconnected from the charging equipment, or if excessive strain is placed on the cable/cord.

Best times for electric vehicle charging

As more drivers make the switch to EVs, it’s important to understand when to charge your vehicle to have less impact on the environment and the energy grid. As you can see from the charts below, energy prices are typically highest during the late afternoon and evening, which can result in increased electricity prices for everyone since electrical infrastructure must be built to provide power when energy use is highest. If possible, avoid charging during times when demand for electricity is highest.

Generally, the best times to charge your vehicle are during off-peak hours:

  • During the middle of the day from 10 a.m. to 2 p.m. when solar energy is abundant.
  • Overnight when the demand for electricity is lower – after 10 p.m. is best. 

Choices and recommendations for savings:

  • Choose our Utah EV Time of Use program to help save on your bills when you charge your car and use other home equipment during off-peak hours. 
  • Set your vehicle’s time scheduling function to charge your car during off-peak times. 

See the three charts below for more information on why charging during these times is best.