EV Charging at Home

Key concepts

• Level 1 charging: Uses a standard 120 V outlet. No special equipment beyond the cord that came with the vehicle. Slow—adds only a few miles per hour—but convenient for overnight top-ups or low daily mileage.
• Level 2 charging: Uses 240 V and a dedicated circuit and EVSE (charging unit). Delivers more power and can fully recharge most EVs overnight. Requires a licensed electrician and often a panel check.
• Amperage and circuit size: Level 2 units are typically rated in amps (e.g., 32 A, 40 A). The circuit must be sized for the unit’s draw; continuous loads usually require the circuit to be sized at 125% of the load. A 32 A EVSE often needs a 40 A circuit.
• Panel capacity: Your main panel has a total amperage (e.g., 100 A or 200 A). Existing loads (AC, heat, water heater, appliances) plus the new EV circuit must not exceed the panel’s capacity. A load calculation confirms whether you have room or need an upgrade.
• Time-of-use (TOU) rates: Many utilities charge more for electricity during peak hours. Charging during off-peak periods can cut charging cost. Some EVSEs and vehicles let you schedule charging to match these windows.

Step-by-step load and sizing framework

1. Know your panel size. Check the main breaker or label on the panel for the service amperage (e.g., 100 A, 200 A).
2. List existing large loads. Note the amp rating of big circuits: HVAC, water heater, range, dryer, etc. If you don’t have a recent load calc, an electrician can do one. Sum the loads that can run together (often with a diversity factor).
3. Add the EV circuit. A typical Level 2 EVSE might need 32–48 A continuous, so a 40 A or 60 A circuit. That load is significant; if the panel is already near capacity, you may need a service or panel upgrade.
4. Consider TOU and scheduling. If your utility offers TOU rates, charging in off-peak windows reduces cost and can ease peak demand on your panel and the grid.

Common mistakes

• Plugging a Level 1 cord into an old or shared circuit that can’t handle continuous draw, leading to tripped breakers or overheating.
• Installing a Level 2 EVSE without a panel load calculation, which can overload the panel or require an expensive upgrade later.
• Ignoring TOU rates and charging during peak hours when electricity is most expensive.
• Assuming the EV can charge at full speed on any 240 V outlet; the circuit and EVSE must match the vehicle’s maximum accepted rate.

Cost drivers (general)

Cost depends on the EVSE unit, circuit length and complexity, and whether the panel or service needs an upgrade. Permits and inspection may be required. Incentives for EVSE or panel upgrades exist in some areas. Get quotes from licensed electricians and confirm what’s included.

Safety and permitting

EV charging circuits must be installed per local electrical code. Dedicated circuits, correct wire size, and proper grounding are required. Permits and inspection are common. Use a licensed electrician; do not use extension cords or unapproved adapters for Level 2 charging.

FAQ