How Much Power Do You Really Need? Sizing Your Panel for Modern Appliances

Most homes built before the 1990s have a 100-amp panel. That was plenty for a furnace, a dryer, and a few lights. It is not enough for a house with an EV charger, an electric range, a heat pump, and a whole-home generator. If you are adding any of those, plan on 150 to 200 amps of service. For larger homes or ones running a shop or well pump too, 200 amps is the safer target.

How to Tell Your Panel Is Too Small

You do not need an electrician to spot the early warning signs. Watch for these:

• Breakers trip often, especially when you run the microwave and a space heater at the same time.

• Lights flicker or dim when the AC or well pump kicks on.

• Your panel is rated 100 amps and you want to add an EV charger, generator, or hot tub.

• No room for new breakers. A full panel with no open slots means any new circuit requires a subpanel or upgrade.

Any one of these is worth a look. Two or more together usually means the panel is done.

What Actually Uses the Power

It helps to know what you are sizing for. Here is roughly what modern loads pull:

• Level 2 EV charger: 30 to 50 amps on its own circuit. One charger can eat a third of a 100-amp panel's capacity.

• Electric range or oven: 40 to 50 amps.

• Heat pump or electric furnace: 30 to 60 amps depending on size.

• Whole-home generator transfer equipment: needs its own connection point sized to match your panel, usually 100 to 200 amps.

• Hot tub: 40 to 60 amps.

Add two or three of these to a house that already runs a dryer, water heater, and kitchen circuits, and 100 amps runs out fast. That is why so many upgrade calls start with "we just bought an EV" or "we're putting in a generator."

What a Panel Upgrade Actually Costs

A straightforward upgrade from 100 to 200 amps runs in the low thousands of dollars in most cases. The final number depends on a few things:

• Service size. Jumping to 200 amps costs more than 150 amps, since the wire, breaker, and panel all cost more at higher ratings.

• Meter location. If the meter base needs to move or the utility has to reroute the service drop, that adds time and cost.

• Utility coordination. Avista or your local co-op has to disconnect and reconnect service. Scheduling that can add a few days to the timeline, though it rarely adds much to the price.

• Wall access. Open framing is cheap to work in. Finished walls with the panel far from the exterior wall mean more drywall repair and longer conduit runs.

• Permit and inspection. This is required for panel work and adds a modest fee, but it protects you if you ever sell the house. We wrote more about why skipping permits on a panel upgrade can cost you later, including insurance and resale issues.

Generators Add Another Layer

If a whole-home generator is part of the plan, budget separately for the transfer equipment. A generator inlet with a manual interlock is the cheapest option, often several hundred dollars installed. A full automatic transfer switch setup for a whole-home standby generator runs closer to one or two thousand dollars, on top of the generator itself. The right choice depends on whether you want manual switching during an outage or a system that kicks on automatically. If you already own a generator or are shopping for one, our guide on getting your North Idaho home generator ready for winter storms covers sizing and hookup basics in more detail.

Do You Need 150 or 200 Amps?

150 amps works for a mid-size home with normal appliances and maybe one EV charger. 200 amps is the better call if you have any of the following:

• An all-electric house with no natural gas backup for heat, cooking, or water heating.

• Two EVs or plans to add a second one.

• A shop, barn, or detached garage pulling power from the same service.

• A whole-home generator with automatic transfer.

Cabins and second homes are a different case. If you are only running lights, a fridge, and a small heater a few weekends a month, 100 amps might still be fine. But if you are adding a heat pump for shoulder-season comfort or planning to convert to a full-time residence, size for the future now. Redoing a panel twice costs more than doing it right once.

Getting an Accurate Number

The only way to know your real number is a load calculation, which adds up your existing circuits plus anything you plan to add in the next five to ten years. This is not guesswork. It follows a formula the local building department checks during permitting. An electrician can walk your panel, check your service size, and tell you within a few minutes whether you have room to grow or need a bigger box.

Sageland Electric has handled panel upgrades and generator hookups across Bonner and Kootenai counties for over 21 years, from cabins on the lake to full-time homes running EVs and heat pumps. You can see examples of past panel and service work in our project gallery, or reach out through our contact page to get a load calculation and a straight number for your home.