Safety first. If charging is slow and the plug, outlet, cable or charger feels hot, looks discolored or smells like burning, stop charging and call an electrician. Several chargers slow down on purpose when they sense heat. Do not open the panel, remove covers or take the charger apart.
How fast should my Level 2 charger be?
Multiply volts by amps. At 240 volts, 32 amps is about 7.7 kW, 40 amps about 9.6 kW and 48 amps about 11.5 kW. Your car charges at the lowest of three limits: the charger's setting, the circuit it is on, and the car's onboard charger. Find the lowest one first.
| Charger output | Breaker | Power at 240 V |
|---|---|---|
| 16 A | 20 A | about 3.8 kW |
| 32 A | 40 A | about 7.7 kW |
| 40 A | 50 A | about 9.6 kW |
| 48 A | 60 A | about 11.5 kW |
The charger runs at 80 percent of the breaker because EV charging is a continuous load. See what size breaker for an EV charger.
Tesla's Mobile Connector manual gives a quick time estimate: divide the battery size in kWh by the power in kW.
Why is my EV charger charging slowly?
The usual reasons are a charger set below its circuit's capacity, a car whose onboard charger accepts less than the charger offers, a reduced current setting in the car, a cold or hot battery, load management sharing power, or a charger cutting current because it senses heat. Only the last one is a safety concern.
The charger's amp setting is low
Some chargers ship at a low setting until someone raises it. ChargePoint says a licensed electrician can set the Home Flex amperage "from the default 16A" over Bluetooth. A Tesla Wall Connector's output follows the breaker size entered at setup: 60 amps gives 48, 40 gives 32, 20 gives 16. If the setting is lower than the circuit allows, the fix is a settings change, done to match the breaker.
The car's onboard charger is the limit
The charger offers power; the car decides how much to take. Tesla's onboard charger table lists "Model 3 Rear-Wheel Drive: 7.7 kW (32 amp)" while its 48 amp group gets 11.5 kW. Tesla's tip: "Tap the lightning bolt icon on the touchscreen to view the max amperage of your vehicle."
A plug-in charger is capped
Tesla's Mobile Connector on a 14-50 adapter delivers 32 amps, 7.6 kW. ChargePoint limits NEMA plug-in Home Flex models to 32 or 40 amps. Getting 48 amps means hardwiring; see hardwired vs NEMA 14-50.
The car's current setting is reduced
Tesla cars let you lower "Charge current at this location," and the car remembers it for that spot. A setting lowered once for a weak outlet can stay low at home. Check your car's manual for an equivalent setting.
Battery temperature
Tesla's manual says charge time "depends on ambient temperature and the vehicle's Battery temperature," and that the car "heats or cools the Battery before or during charging" when needed. On a cold Ogden morning, longer sessions are normal. EV charging in Utah winters covers it in more detail.
Load management or power sharing
Emporia's PowerSmart "automatically adjusts charge rate based on total home energy use," and linked Tesla Wall Connectors split power between cars. See EV charger load management.
The charger is cutting current for heat
This is the one to take seriously. Tesla's Mobile Connector shows a code for "Charging current is reduced due to high temperature detected in the wall plug." The Wall Connector's three red blinks mean "High temperature detected; charging limited or disabled," and Tesla has an electrician check wire size and terminal torque. If you see a heat code, read NEMA 14-50 outlet getting hot.
What can I safely check myself?
Check the charger's amp setting in its app against the breaker's printed rating, look up your car's maximum charging rate, check the car's current setting, note the outside temperature, and look for heat codes or a warm plug without touching anything inside. Changing the circuit or breaker is electrician work.
- Read the charger's amp setting in its app or display.
- Read the number on the charger's breaker handle. The setting can be up to 80 percent of it.
- Find your car's maximum AC charging rate in its manual or charging screen.
- Check the car's current setting for home.
- Look for heat codes, and check the plug and outlet for discoloration without touching anything inside.
When should I call an electrician?
Call an electrician if the charger reports high temperature, if the plug or outlet is warm or discolored, if you want more speed than the circuit allows, or if the charger's setting should be raised but nobody has confirmed the breaker and wire can carry it. Raising amps without checking the circuit is how breakers trip and terminals overheat.
Our EV charger repair page covers circuit checks. If the car and charger are matched and the circuit is the bottleneck, EV charger circuit installation explains upgrading it.
Slow charging questions
How fast should a Level 2 charger be?
Multiply volts by amps. A charger delivering 32 amps at 240 volts gives about 7.7 kW; 48 amps gives about 11.5 kW. The car takes the lower of what the charger offers and what its onboard charger accepts. The Department of Energy puts typical Level 2 at about 25 miles of range per hour.
Will a bigger charger make my car charge faster?
Only if the car can accept more. A car with a 32 amp onboard charger will not charge faster on a 48 amp charger. Tesla's own table lists Model 3 Rear-Wheel Drive at 7.7 kW (32 amp) and its 48 amp group at 11.5 kW. Check your car's limit first.
Is slow charging ever a safety problem?
It can be. Some chargers cut current when they sense heat. Tesla's Mobile Connector reduces charging when it detects high temperature in the wall plug, and the Wall Connector's three red blinks mean high temperature with charging limited. Heat at a plug or outlet needs an electrician.
Charging slower than it should? Tell us the charger, its setting, the breaker size and your car.
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