Understand Your Home’s Power Before Adding an EV Charger
Most U.S. homes have 100A, 150A, or 200A electrical service. Your service size, existing electrical loads, and EV charging power all help determine how much charging capacity is available.
Adding an EV charger does not automatically mean you need to upgrade from 100A to 200A.
Check your power. Balance your load. Upgrade when needed.
How Do I Know My Home’s Service Size?
Start at your home’s main electrical panel and look for the main breaker, usually the largest breaker in the panel.
The number printed on the breaker is commonly:
100 → 100A main breaker
150 → 150A main breaker
200 → 200A main breaker
The main panel may be located in the garage, utility area, basement, or on an exterior wall.
If your home has multiple panels, a separate main disconnect, or older electrical equipment, ask a qualified electrician to confirm the actual service capacity.
100A vs. 200A
100A Service
Common in older and smaller homes. Many 100A homes can still support Level 2 EV charging depending on existing electrical loads and available capacity.
200A Service
Provides more capacity for EV charging and other large electrical loads such as air conditioning, electric cooking, heat pumps, water heaters, and additional EVs.
A 100A home does not automatically need a 200A upgrade just because an EV charger is added.
How Much Power Does an AC EV Charger Use?
Level 2 AC charging commonly ranges from 16A to 80A.
| Charging Current | Approx. Power at 240V | Typical Circuit |
|---|---|---|
| 16A | 3.8 kW | 20A |
| 24A | 5.8 kW | 30A |
| 32A | 7.7 kW | 40A |
| 40A | 9.6 kW | 50A |
| 48A | 11.5 kW | 60A |
| 64A | 15.4 kW | 80A |
| 80A | 19.2 kW | 100A |
Actual charging speed also depends on the vehicle’s onboard charger and the installed charging equipment.
Why Do You Often See the 80% Rule?
EV charging is considered a continuous electrical load.
For a typical EV charging circuit, continuous charging is commonly limited to 80% of the circuit rating.
For example:
60A circuit → 48A charging
50A circuit → 40A charging
40A circuit → 32A charging
This is why a 48A EV charger is typically installed on a 60A dedicated circuit.
Does a 100A Home Mean It Can Only Use 80A?
No.
The 80% rule for an EV charging circuit should not be interpreted as:
100A service = only 80A total home use
or
200A service = only 160A total home use
Available charging capacity depends on the home’s electrical loads and the applicable load calculation.
A qualified electrician should evaluate the service, panel, existing loads, and planned EV charging equipment.
Before Upgrading Your Panel, Check Available Power
Your home does not use every electrical load at maximum power all the time.
When household demand is low, more power may be available for EV charging. When large appliances are running, less power may be available.
This is where Power Balancing can help.
EVGREEN Power Balancing
Automatically adjust EV charging based on available electrical capacity.
The EVGREEN Dynamic Energy Meter monitors electrical usage. The charging system can then increase, reduce, or pause EV charging based on the available capacity and configured limits.
Home Power → Dynamic Energy Meter → EVGREEN Charger
This can help make better use of an existing electrical service before considering a larger panel upgrade.
When Might a 200A Upgrade Be Needed?
A 200A service upgrade may be appropriate when the home does not have enough capacity for planned electrical loads.
Common reasons include:
- Multiple EV chargers
- Additional major electric appliances
- Heat pumps or electric water heating
- Major home electrification projects
- Insufficient capacity based on the required load calculation
- Existing electrical equipment that needs replacement or modernization
A qualified electrician should make the final determination.
Check First. Upgrade Only When Needed.
Many homes may be able to add EV charging without automatically replacing a 100A service with 200A service. Understand your service. Choose the right charging power. Use power balancing when appropriate.
Important Installation Notice
Always follow local electrical codes and permit requirements. Consult a qualified electrician before upgrading, modifying, or adding circuits to your electrical panel.