What size electrical service does a custom home need in Arizona?

A 200-amp electrical service is the standard size builders run for a typical new home in the Phoenix and Scottsdale metro, and it covers most Arizona custom homes without issue. A large all-electric home is a different story. Once you stack an EV charger, a sauna, a car lift, a pool, and a big multi-zone air conditioning system onto one panel, the calculated demand often pushes you to a 400-amp service. The size is not decided by square footage or by a rule of thumb. It is decided by a load calculation run under NEC Article 220, which adds up every electrical load in your specific house and tells your electrician the real number.

Here is how the calculation works, what pushes a desert home from 200 amps to 400, and why getting this right before drywall saves you a five-figure fix later.

200 amps is the standard, 400 is for big all-electric homes

A 200-amp service handles most Arizona custom homes, and a 400-amp service is reserved for large homes with heavy electric loads. The service size is the maximum amount of power your home can pull from the utility at one time, measured in amps. A 200-amp panel at 240 volts can deliver roughly 48,000 watts, which covers a normal home with central air, an electric or gas range, a water heater, and standard outlets and lighting with room to spare.

ENERGY STAR notes that "most newer homes are outfitted with a 200A breaker box, which is sufficient to accommodate the addition of new electric appliances." For a single-story or modest two-story custom home with one or two HVAC systems and gas heat, 200 amps is usually plenty.

A 400-amp service is two 200-amp panels fed by a larger meter and main, and it exists for homes that simply pull more power. Think 6,000 square feet and up, all-electric, with multiple air conditioning systems, a pool, a workshop, and a garage full of equipment. In the desert, where air conditioning is the single biggest load and runs hard from April into October, the cooling demand alone can be large enough to tip a big home toward 400 amps.

What pushes an Arizona custom home to 400 amps

A custom home crosses from 200 amps to 400 amps when it combines several large, simultaneous electric loads. No single item forces the upgrade. It is the stack of them. The loads that move the needle most in a high-end desert home are:

• EV charging. A Level 2 charger draws a continuous 7.2 kilowatts or more, and a home with two EVs charging at once doubles that. The U.S. Department of Energy notes Level 2 home equipment runs on 240-volt service, and NEC Article 625 requires the circuit be sized for that continuous draw. Two chargers can eat a big slice of a 200-amp panel by themselves.
• A sauna. An electric sauna heater is commonly a 6 to 9 kilowatt continuous load on a dedicated 240-volt circuit.
• A car lift. A two-post or four-post lift adds a dedicated 240-volt motor circuit in the garage.
• A pool. A pool pump, heater, and any water features add steady load, and an electric pool heat pump is large.
• Big or multi-zone HVAC. A large custom home often runs two, three, or more air conditioning systems. In Arizona that cooling load is the heaviest draw in the house and it runs for months.

Add an electric range, an electric water heater, a heat-pump dryer, and a steam shower on top, and the math adds up fast. Industry guidance puts it plainly: a home that adds a heat pump, a Level 2 EV charger, a heat-pump water heater, and modern appliances can try to push 15 or more kilowatts through a service that older homes sized for 10. When that total clears what 200 amps can safely carry, you go to 400.

The load calculation under NEC Article 220 sets the real number

The correct service size comes from a load calculation done under NEC Article 220, not from a guess. Your electrician runs the numbers two ways under the National Electrical Code. The standard method adds up every fixed load in the house, then applies demand factors that account for the fact that not everything runs at once. The optional method for a single-family dwelling combines the general loads, applies 100 percent to the first 10,000 volt-amps and 40 percent to the rest, then adds heating or cooling. Either method produces a total demand in amps, and that total tells you whether 200 amps is enough or whether you need 400.

This is the step that separates a sized service from a hopeful one. An electrician who knows your plan list, your appliance schedule, and your future EV and pool loads can calculate the demand before the meter is set. Demand factors matter because they reflect real use. Your sauna, dryer, and oven rarely peak at the same instant, so the code does not require you to add every nameplate watt at full value. The calculation captures that. A licensed electrician or the design engineer on your custom build should hand you this calculation as part of the electrical plan.

Plan the service before drywall, and leave headroom

Decide your service size during design, because upsizing later is expensive and disruptive. Going from 200 to 400 amps after the home is finished means a new meter, a new main panel or a second panel, heavier service conductors, and utility coordination. Doing the same work while the home is framed and the trench is open costs a fraction of that.

The smart move on a custom home is to size for how you will actually live in the house, then leave room to grow. If you know two EVs, a pool, and a casita are coming, calculate for them now even if they install in phase two. If you are undecided on solar and battery, a 400-amp service or a panel with open breaker space keeps your options open. A smart electrical panel can also stretch a 200-amp service further by managing loads so the EV charger backs off when the air conditioning spikes, which sometimes avoids a 400-amp upgrade entirely. You can read how that works on our smart electrical panel page.

For an Arizona custom home, the practical path is simple. Ask your builder for the NEC 220 load calculation in writing, list every big load including the ones coming later, and let the number decide between 200 and 400 amps. A 400-amp service costs more in copper, conduit, a larger meter, and sometimes a utility transformer upgrade, but it is far cheaper installed during the build than retrofitted into a finished home. If you are close to the line, ask your electrician whether load management or a phased panel layout lets a 200-amp service carry your plan safely.

Cost and capacity figures here move with copper prices, utility fees, and equipment, so confirm current pricing and your final load calculation with your builder and licensed electrician at the time of your bid (figures noted as of June 2026). For interlocking decisions, see how cooling load drives equipment on our Arizona HVAC system page and how to leave a clean path for panels on our solar and automation pre-wire page.

Where Jematell Homes comes in

We build for the Sonoran Desert, not a generic climate. Reach out and we will talk through how this applies to your specific lot and plan.

Sources

• ENERGY STAR: Make Your Home Electric Ready
• U.S. DOE Alternative Fuels Data Center: Charging Electric Vehicles at Home (NEC Article 625)
• U.S. Department of Energy, Energy Saver: Home Upgrades