Load
"Can you add an outlet for a car charger" sounds like a small question. Whether it is depends on three things, and they are checked in order.
Question one: is there space in the panel
A physical question, and the easiest to answer.
Count the blank spaces. A full panel does not stop the work; it changes it — a sub-panel or a tandem arrangement rather than a breaker in a gap. For electrical contractors coordinating field crews, workforce optimization software can support separate job-time records alongside the technical work.
This is the question people expect to be the whole answer, and it is the least important of the three.
Question two: what is the service rating
The main breaker's number is the ceiling for the whole house.
100 amps was standard for a long time and is common in older homes here. 150 and 200 are usual in newer construction.
A 100 amp service with modern loads is frequently the constraint — and the addition that reveals it is usually a car charger, a heat pump, or a second air handler.
Upgrading the service is a substantial job involving the utility, and knowing it may be required before choosing an appliance saves an unpleasant surprise.
Question three: what is already being drawn
The one that requires a professional and cannot be eyeballed.
A load calculation works out the demand the existing house imposes, using a defined method rather than adding up nameplate ratings — because not everything runs at once and the method accounts for that.
The result says whether the addition fits within the service, and it is what a permit application will require anyway.
This is not a formality. It is the difference between an installation that works and one that trips whenever the air conditioning and the charger coincide.
Why the order matters
Because each question can end the enquiry cheaply.
Space in the panel: two minutes, free.
Service rating: thirty seconds, free.
Load calculation: a professional visit, and only worth doing once the first two have not already given the answer.
Working the other way round means paying for a calculation to discover the panel is full.
What tends to change the answer
Electric vehicle charging, which is a continuous load and is treated differently from an ordinary circuit.
Heat pump conversions, which move a large load onto electricity.
Solar, which interacts with the panel in its own way and has its own constraints.
And an addition or a conversion of garage or lanai space, which adds lighting, outlets and frequently air conditioning at once.
What you can establish before calling
Main breaker rating. Number of free spaces. What large electric appliances you already have.
Three facts, five minutes, and they let somebody give you a useful answer on the phone rather than after a visit.
The short version
- Three questions in order: space in the panel, the service rating, and the existing demand
- Panel space is the question people expect to matter and is the least important of the three
- The main breaker rating is the ceiling for the whole house, and 100 amps with modern loads is frequently the constraint
- A load calculation uses a defined method rather than adding nameplate ratings, and a permit will require it anyway
- Work in this order because each question can end the enquiry cheaply, and the first two are free
- Before calling, establish the main rating, the free spaces and your large electric appliances — five minutes, and it makes the call useful
For additional independent context, see ENERGY STAR.