Yes, you can often install a Level 2 EV charger on a 100 amp service. Sometimes you cannot, at least not at full power. A lot of South Florida homes built between the 1950s and the 1980s still have the 100 amp service they started with, and whether one of them has room for a charger depends almost entirely on what else the house runs. This guide works through three illustrative houses, with the arithmetic shown, so you can see where the line falls and what the options are on each side of it.
The houses and their numbers are made up to be typical, not taken from real jobs. Your house needs its own calculation.
The rules the arithmetic follows
Florida's electrical code today is the 2020 National Electrical Code, adopted through the Florida Building Code 8th Edition (floridabuilding.org). For an existing home it offers two ways to check a service:
- The existing-dwelling calculation: general lighting at 3 VA per square foot, 1,500 VA for each kitchen small-appliance circuit and the laundry circuit, and the nameplate ratings of fixed appliances. The first 8,000 VA counts at 100 percent and the remainder at 40 percent. Air conditioning or heat is then added at full rating (EC&M, dwelling unit load calculations).
- Measured demand: a year of maximum-demand readings for the service, taken at 125 percent, plus the new load (UpCodes, determining existing loads).
The charger's breaker must be at least 125 percent of its output because EV charging is a continuous load (Mike Holt, NEC Article 625 summary). At 240 volts, a charger set to 32 amps is 7,680 VA; at 48 amps it is 11,520 VA.
House A: all-electric ranch with a pool
1,600 square feet, 100 amp service, electric range, electric tank water heater, electric dryer, dishwasher, pool pump and a central A/C of about 5,280 VA (larger than its heat strips).
| Item | VA |
|---|---|
| General lighting (1,600 sq ft x 3) | 4,800 |
| Two kitchen circuits + laundry | 4,500 |
| Range | 12,000 |
| Water heater | 4,500 |
| Dryer | 5,000 |
| Dishwasher | 1,200 |
| Pool pump | 2,000 |
| General loads total | 34,000 |
| First 8,000 at 100% + 26,000 at 40% | 18,400 |
| Plus A/C at 100% | 5,280 |
| Calculated load today | 23,680 VA = about 99 A |
House A is already at its limit before a car arrives. Adding a charger set to 32 amps puts 40 percent of 7,680 VA into the general loads and brings the total to about 26,750 VA, or 111 amps. Even a charger turned down to 16 amps lands at about 105 amps. On paper, this house does not have room for a Level 2 charger without either load management or a larger service.
House B: smaller, with gas cooking and gas hot water
1,300 square feet, 100 amp service, gas range and gas water heater, electric dryer, dishwasher, disposal, no pool, A/C of about 4,800 VA.
| Item | VA |
|---|---|
| General lighting (1,300 sq ft x 3) | 3,900 |
| Two kitchen circuits + laundry | 4,500 |
| Dryer | 5,000 |
| Dishwasher + disposal | 2,000 |
| General loads total | 15,400 |
| First 8,000 at 100% + 7,400 at 40% | 10,960 |
| Plus A/C at 100% | 4,800 |
| Calculated load today | 15,760 VA = about 66 A |
With a 32 amp charger added in the general loads, the total is about 18,830 VA, or 78 amps. A 48 amp charger reaches about 20,370 VA, or 85 amps. House B has room.
There is a catch worth knowing about. Some building departments want the EV load counted at its full rating rather than inside the 40 percent. Counted that way, the 32 amp charger brings House B to about 23,440 VA, or 98 amps: technically inside 100, with nothing left over. The 48 amp charger would put it at about 114 amps, over the line. That is why we confirm the building department's approach before recommending a charger size.
House C: measured demand instead of a calculation
A 1980s townhouse where a year of demand readings is available for the account. Suppose the highest reading all year was 12,000 watts, in August, with the A/C running hard. At 125 percent that is 15,000 VA. Add a 32 amp charger at 7,680 VA and the result is 22,680 VA, or about 95 amps: it fits. A 48 amp charger (11,520 VA) would reach about 111 amps and would not.
Measured demand can help a house that looks tight on paper, because real homes rarely run everything at once. It depends on the data existing for your account; ask your utility whether it does before planning around it.
The options when a 100 amp house is tight
| Option | What it means | Good fit when |
|---|---|---|
| Turn the charger down | Set an adjustable charger to 16, 24 or 32 amps on a matching breaker | Daily driving is modest and the house is close but not far over |
| Level 1 | Charge from 120 volts, about 5 miles of range per hour | Very short commutes, or a plug-in hybrid |
| Load management | A device that reduces or pauses charging when the house is busy | The house is over on paper but rarely busy overnight |
| Service upgrade | A larger service, usually 150 or 200 amps | The house is well over, the equipment is old, or more loads are coming |
The Level 1 figure is from the Alternative Fuels Data Center, which puts Level 1 at about 1.9 kW and roughly 5 miles of range per hour, against about 25 miles per hour for a typical 7.2 kW Level 2 charger.
On turning the charger down: many chargers can be set below their maximum, and on fixed equipment whose setting is protected (a tool-required cover, a lock or password-protected software) the adjusted setting may be used as the charger's rating (NEC 625.42 text). For example, Tesla's Gen 3 Wall Connector is set to 32 amps on a 40 amp breaker and 24 amps on a 30 amp breaker (Tesla installation manual, breaker settings).
On load management: one example is the RVE DCC-12, which cuts power to the charger when the panel's load exceeds 80 percent of the main breaker rating and restores it after 15 minutes below that level (RVE DCC-12 specification sheet). How a building department credits a device like this under the 2020 code is its decision, and we confirm before anything is ordered. We compare the approaches in EV load management vs a panel upgrade.
What to ask your electrician about a 100 amp house
- Which calculation method are you using, and are you counting the charger at its full rating or in the demand factor?
- What is the calculated load today, before the charger?
- What is the highest charger setting that fits, and how many miles per night does it give my car?
- Is the existing panel and meter equipment in good enough condition to keep, or should it be replaced anyway?
- If I add a second EV or a pool heater later, does this plan still work?
Questions homeowners ask
Is a 100 amp service too small for any EV?
No. Plenty of 100 amp homes have room for a Level 2 charger, especially smaller houses with gas appliances. The calculation decides it, not the service size alone.
My A/C runs all day in summer. Does that count?
Yes. Air conditioning is added at its full rating in the calculation, and in South Florida it is usually the largest single load in the house. It is the main reason many all-electric homes here are tighter than similar homes elsewhere.
Will charging at night get around the problem?
Overnight charging helps in practice, since the range and dryer are usually off. It does not change the calculation, because the code assumes loads can overlap. Load management is the way to rely on that timing formally.
If I upgrade, should I go to 200 amps?
Often, but not always. The right size depends on the calculated load with the charger and what you expect to add. Our post on when an EV needs a bigger electric service covers how that is decided.
More on the panel side is in panel upgrades for EV chargers, and the whole series is in the Florida Home EV Charging Guide. When you are ready, KRW Electric (EC13012832) runs the calculation, pulls the permit and does the EV charger installation across Miami-Dade, Broward and Palm Beach. Send us photos of your panel and main breaker or call (305) 359-7312.
Reviewed by Kyle White, KRW Electric Company LLC — licensed electrical contractor EC13012832.
