Home charging is easy to underestimate because the car is quiet. Level 2 chargers often deliver 6–11 kW (about 6,000–11,000 watts) for hours. The cost is kWh into the car times your rate — the same math as any other load, just larger.
A 30-mile commute might need on the order of 8–12 kWh to put back, depending on the car and weather. That can be cheaper than a gallon of gasoline even when electricity is not cheap. It is still a real line on the electric bill, and it can trip a main panel if everything else is already near the limit. Whatt estimates cost, not panel capacity or NEC load calcs.
Level 1 (a regular 120-volt outlet) is a much smaller wattage and a much longer night. Overnight “set and forget” is hours × that lower wattage.
Set the charger level and hours. Fine-tune watts to the circuit you actually use (for example 7,200 watts on a 240-volt 30-amp circuit at typical charge rate).
At 18.8¢ per kWh, 7,200 watts for 3 hours is 21.6 kWh — about 4.06 that session. Ten kWh to replace a short-day commute is about 1.88. Your car’s trip meter in kWh is the better input when you have it.
Not a panel calc
Whatt does not size a feeder or apply NEC demand factors. It prices the session you set. The car’s trip kWh is the best input when you have it.
Related
Usage estimate only — not a utility bill, load calc, or advice.