What does service amperage actually mean?
Service amperage is the rating of the connection between the utility and your home, including the meter, service conductors and main breaker, and it limits how much power can flow into the panel at one moment. Think of it as the width of the pipe, not the amount of water flowing.
Your service is the connection between the utility and your home, including the meter, the service conductors and the main breaker. Its amperage rating limits how much power can flow into the panel at any one moment, no matter how many circuits the panel has. It is not the same as how much you use day to day. Think of it as the width of the pipe, not the amount of water flowing through it. If the pipe is too narrow for peak demand, you get tripped main breakers, dimming lights, or no room to add anything new.
Panels and services are related but not identical. A panel might be rated for more than the service feeding it, or the other way around, and the meter base and conductors each have their own ratings. The lowest-rated part sets the real limit, which is why inspection of the whole chain matters. Ask the electrician to point out each rating on site, so you can see which component limits the system.
Can 100 amps still be enough for a home?
Yes, 100 amps can still be enough for a smaller home with gas appliances, a modest air conditioner and no big electrical additions. If the panel is in good condition and the load calculation shows enough margin, there is no reason to replace it just because 200 amps is more common in new construction.
A smaller home with gas appliances, a modest air conditioner and no big electrical additions can run fine on 100 amps. Many original homes in Sun City and Sun City West were built with smaller services based on the loads of their time, and some still do the job. The key is that the loads are limited and nothing new is being added. If the panel is in good condition and the load calculation shows enough margin, there is no reason to replace it just because 200 amps is more common in newer construction.
Space in the panel is a separate question from capacity. A larger panel with more slots can be installed on an existing service when the calculation allows it, which solves a crowded-panel problem without changing the utility connection. An electrician can explain which of these you actually need. Many people are surprised to learn that a panel swap alone can solve a lack of circuit space.
What loads push a home toward 200 amps?
Large loads push a home toward 200 amps, including an electric range or dryer, electric water heater, pool pump, hot tub, EV charger or a second AC system. Arizona homes also run big air conditioning loads much of the year. Several together on a summer evening can exceed what a smaller service carries.
Arizona homes run big air conditioning loads for much of the year. Add an electric range or dryer, an electric water heater, a pool pump, a hot tub, an EV charger or a second AC system, and demand adds up quickly, particularly on a summer evening when everything is running. Plans for a mini split addition, a workshop, or an Arizona room also matter. Not every one of these runs at once, and the calculation accounts for that, but several together can exceed what a smaller service can safely carry without nuisance trips or overheated conductors.
Solar and batteries add another layer. If you are considering either, the service and panel affect how the system can be connected, and the rules around busbar ratings and main breaker sizing become important. Raise it early so any panel work is planned to fit the later addition. A clear plan up front also avoids having to redo breaker placement or conduit routes after the new equipment arrives.
How does an electrician decide between 100 and 200 amps?
An electrician performs a load calculation following the electrical code. It adds up square footage, major appliances and fixed loads, applies demand factors, and compares the result to your service rating. They also inspect the meter base, service conductors and panel, which replaces rules of thumb with a documented answer.
An electrician performs a load calculation following the electrical code. It adds up the square footage, the major appliances and the fixed loads, applies demand factors, and compares the result to your service rating. This replaces rules of thumb with a documented answer. They also inspect the condition of the meter base, the service conductors and the panel. Sometimes the limit is not the amperage but old equipment that should be replaced anyway. A written explanation of the calculation helps you understand why they recommend what they do.
Pay attention to what changes the calculation. Converting a gas furnace or water heater to electric, adding an Arizona room with its own cooling, or installing a larger pool pump can shift the numbers. Share your plans for the next few years, not just the current project, when you talk to an electrician. The sooner you share the full picture of your plans, the less likely you are to pay for work twice.
What does a service upgrade to 200 amps involve?
Going to 200 amps typically means a new panel, larger service conductors, a new meter base and possibly a new grounding system. The utility must disconnect and reconnect power, and the work needs a permit and inspection. It is licensed work only, and utility scheduling is often the longest part.
Going to 200 amps typically means a new panel, larger service conductors, a new meter base and possibly a new grounding system. The utility must disconnect and reconnect power, and the work needs a permit and an inspection before it is complete. This is licensed work only. The service conductors stay live until the utility disconnects them, which makes it among the most dangerous jobs in a home. Coordination between the contractor, the utility and the inspector affects how long the project takes more than the physical work does.
The utility sets some requirements too, such as meter location, clearances and equipment standards. A contractor who works with the local utility regularly can anticipate these. Ask about timing, since utility scheduling is often the longest part of the project, and plan accordingly if you have a firm deadline. Building in a buffer around utility timing keeps the rest of the project, such as a new AC, from sitting idle.
Why plan electrical capacity ahead instead of reacting?
Planning ahead is cheaper because sizing the service for the next decade is easier than opening walls and upgrading twice. If you expect an EV charger, a larger AC or gas-to-electric conversions, bring those plans to the estimate. An honest electrician will not push a bigger service than the calculation supports.
If you expect to add an EV charger, replace the AC with a larger system, or convert gas appliances to electric, plan the electrical capacity first. It is usually easier to size the service for the next decade than to open the walls and upgrade twice. Bring your plans to the estimate. An honest electrician will tell you if your current service is adequate, and will not push a bigger one than the calculation supports. Ask to see the load calculation, and confirm the license at roc.az.gov before you sign anything.
Documentation is worth asking for. Request a copy of the load calculation, the permit and the final inspection sign-off. These papers help if you later add equipment, sell the home or need to show an insurer that the electrical system was properly evaluated and upgraded. A tidy folder of these documents is one of the most useful things a homeowner can hand to the next owner.