Start with your actual miles, not the worst case

Everyone shops for the commute they might have. Do the one you have. Round trip to Santa Rosa is short. To Petaluma, short. Marin depends where in Marin. San Francisco is the long one, and if you are doing that daily you already know it.

Convert that to a rough number. Most electric cars use somewhere in the neighborhood of a quarter to a third of a kilowatt-hour per mile in mixed driving, worse when it is cold or you drive fast, better in traffic. Take your daily round trip miles, multiply by three tenths, and you have a workable kilowatt-hour figure for the day.

Now compare that to what a given charger puts back in the hours your car is actually home. That is the whole calculation. Not battery size, not the manufacturer’s peak charge rate, not a marketing number.

When Level 1 genuinely suffices

Level 1 means the cord that came with the car, plugged into a regular 120 volt outlet. It typically delivers somewhere around one to one and a half kilowatts. Over twelve hours parked, that is roughly twelve to eighteen kilowatt-hours, which for a lot of cars lands somewhere near forty to fifty miles of range added overnight.

If your round trip is under about thirty miles and the car sits home all night, Level 1 covers you and you will never think about it. Santa Rosa commuters especially. We have told plenty of people to try the cord for a month before spending anything, and a fair number never called back, which is the correct outcome.

Two conditions, though. It should be a dedicated circuit, not shared with the freezer and the garage door and a workbench. And it should be a properly terminated outlet in good condition. Level 1 charging pulls near-continuous current for many hours, which is a real duty cycle for a receptacle that was installed in 1972 and has had a shop vacuum in it ever since. Warm plug means stop and call somebody.

When Level 2 is the right call

Level 2 runs at 240 volts on a dedicated circuit. A common residential setup is a 40 amp charger on a 50 amp circuit, delivering somewhere near seven and a half to nine and a half kilowatts, which puts back roughly twenty-five to thirty-five miles of range per hour depending on the car.

The cases where it earns its keep: a real Marin or San Francisco commute, two electric cars in one household, a car that is not reliably home all night, or a household that just does not want to think about it. Also anybody planning to lean on off-peak rates, because a narrow overnight window needs the speed to fill in the time available.

Most people who install Level 2 do not regret it. That is a fair thing to say. It is also fair to say a good share of them did not strictly need it, and that both of those can be true at once.

Garage circuit realities in a tract house

Here is what we usually find in these garages. One or two general purpose circuits doing everything, shared with the laundry more often than you would like. The panel on the exterior wall or in the garage itself, which is genuinely convenient. And a short, clean run from the panel to wherever the car parks, which is the part that makes these houses good candidates.

That short run matters. On a lot of Rohnert Park tract homes the charger ends up ten or fifteen feet of conduit from the panel, and that is a straightforward day. Where it gets longer is a raised ranch or a split-level where the panel is on the opposite side of the house from the garage, or a detached garage, or the car parks in a driveway that was never wired for anything.

The other thing worth planning around: where the car actually parks, not where you imagine it does. Cord length is finite, the port is on a different corner depending on the car, and moving a charger after the fact is a second permit and a second day.

The load calculation against a 1970s service

This is the part that determines everything, and it is not something you can eyeball. A load calculation adds up the house’s general lighting and receptacle load, the fixed appliances, the range, the dryer, the heating and cooling, and the new charger, and it applies the demand factors the code allows, and it tells you whether your service can carry it.

Two houses on the same street with the same 100 amp service can land on opposite sides of that line. Gas range, gas dryer, gas furnace, no air conditioning: usually plenty of room. Induction range, electric dryer, heat pump: often not, and then a second car makes it definitely not.

There is also a spaces question separate from the amps. Even if the service has capacity, you need two adjacent slots for a 240 volt breaker, and a lot of these panels are already full with tandems doubled in. Capacity and room are different problems and you can have one without the other.

Load management, which most people have not heard of

If the calculation says you are short, replacing the service is not the only answer. There is a whole category of load-management approaches, and on an older Rohnert Park house they are frequently the better move.

Simplest version: dial the charger down. Most Level 2 units let you set the maximum current at commissioning. A charger set to 24 amps instead of 40 still adds meaningful range overnight and asks a lot less of the service. For a commuter who parks at six and leaves at seven, the slower rate is invisible.

Next: a load-management device that watches the total draw and reduces or pauses the charger when the house is busy. The car is charging at two in the morning when nothing else is running anyway, so it rarely notices. Some chargers include this natively and some need a separate device with a current sensor at the service.

Then there are smart panels, which handle this at the panel level along with a lot else. We install Span, and they are a good fit for some households and overkill for others. The honest version is that a dialed-back charger solves a majority of the cases we see, and it costs the least of anything on this list.

PSPS, and what a charger does not do for you

Worth being direct about this one since it comes up here every fall. A Level 2 charger does nothing for you during a Public Safety Power Shutoff. It is a load, not a source. When PG&E de-energizes, your charger is as dark as everything else.

What actually helps is keeping the car reasonably charged going into red flag weather, which is a habit rather than an install. If you want real backup, that is a battery or a generator conversation, and it is a different project with a different budget.

Some newer vehicles can feed a house through the right equipment, and that is genuinely promising, but it depends heavily on your specific car and a compatible system. Ask before you assume yours does it.

Permits, and how the sequence runs here

A dedicated 240 volt circuit for an EV charger is permitted work in California. Anybody who offers to skip that is telling you something about how they work. It gets inspected, and the inspection is quick when the work is right.

If the load calculation says the service needs to grow, Rohnert Park adds a step worth knowing about. A residential main service replacement here requires a written serviceability inspection from a certified licensed electrician, provided to the City for the permanent permit record. And if the existing panel is found serviceable, the project can proceed without replacing it. So an old panel is not an automatic upgrade even when you are adding a charger.

Practical order: we do the load calculation, we look at the panel, we tell you which of the three paths you are on, straight install, install with load management, or install plus service work. Then we pull the permit and schedule.

Tell us your daily round trip, what car you are getting, where it parks, and send a photo of your panel label. That is enough for a real answer about which path you are on before anybody comes out. Reach us through the contact page or call (707) 684-0024. Details on the install are on our Rohnert Park EV charger page.