Yes, it’s possible to electrify a home on just 100 amps

It may require careful planning and efficient appliances like heat pumps, but 100-amp service can be enough to kick fossil fuels out of your home.
By Alison F. Takemura

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inside a 100-amp electrical panel. A graphic overlay says "Electrified Life."
A 100-amp electrical panel may be all you need to electrify your home. (Binh Nguyen/Canary Media; Square D)

Canary Media’s Electrified Life column shares real-world tales, tips and insights to demystify what individuals can do to shift their homes and lives to clean electric power.

In 2022, Wayne Szeto was psyched to electrify his home. But his electrical panel presented a potential hurdle: It was only powered with 100 amps of electrical service from the utility — an amount that’s often thought to be too small to fully electrify a home.

And Szeto, a 52-year-old Burlingame, California resident, had a lot of gas appliances to switch over: a furnace, water heater, stove and clothes dryer. He also planned to get solar and a battery. To his dismay, he was hearing from contractors and electricians that he’d need to upgrade his electrical service from 100 amps to 200 amps to accommodate the new power sources and appliances. The update would likely cost him $20,000, because of the labor needed to dig up and replace his service line — an expense that would’ve destroyed” the financial case of making his home all-electric.

Whether to upgrade electrical service is a question that an estimated 48 million U.S. homeowners who have panels below 200 amps could eventually face. And because service upgrades can cost anywhere from $2,000 to $30,000 and take two months to two years, according to California-based all-electric home developer Redwood Energy, they can snarl decarbonization budgets and timelines.

But a growing number of experts are encouraging homeowners and electricians to question the assumption that homes with less than 200 amps need electrical-service upgrades in order to fully electrify. Indeed, California utilities Pacific Gas & Electric, Sacramento Municipal Utility District and Peninsula Clean Energy have found that required service upgrades are often the exception, rather than the rule.

That turned out to be the case for Szeto. In March, he finished electrifying his whole 2,350-square-foot ranch home built in 1958. He has a heat-pump heater/​AC, heat-pump water heater, heat-pump clothes dryer, solar, battery, induction stove and EV charger — and he managed to fit it all on 100 amps. He had electrical work done, he said, but was able to avoid spending a ton of money” on a full service overhaul.

So if you’re looking to electrify your home and have just 100 amps, don’t rush to upgrade your service. By thinking ahead about your electrification strategy, you might find you already have all the amps you need.

Why 100-amp homes may not need a service upgrade

Many homes with 100 amps never get close to maxing out that limit, according to Blake Herrschaft, building electrification programs manager at Peninsula Clean Energy, a California provider of 100 percent carbon-free electricity.

Peninsula Clean Energy has found that across more than 100,000 single-family homes it analyzed in its service territory, 99 percent of both gas-using and all-electric homes never draw more than 100 amps of electric current all year. More than 80 percent of homes never pull more than 40 amps.

It’s almost impossible — even if you tried — to use every load in your house at once,” Herrschaft said. You’d need to turn the oven on full blast…run your dryer during the most intense part of the cycle and then go turn on all your showers so the hot water is going and blast your AC. It’s just very rare that all those happen” simultaneously.

Though much of the data comes from California’s relatively mild climate, electrifying without a service upgrade can also work in places that get extremely hot or cold, according to Sean Armstrong, managing principal of Redwood Energy. Additional insulation and efficiency investments can certainly help pull that off, as evidenced by a handful of whole-home electrification retrofits done on 100 amps by Passive House Alberta in Calgary, Canada.

Armstrong points out that technology advances in the last few years, from low-power 120-volt heat-pump water heaters to smart electrical panels that automatically flatten demand peaks by pausing nonessential loads, make 100-amp electrification eminently doable. That’s especially true for single-family homes that are under 2,500 square feet, Herrschaft said.

Running the numbers to electrify on 100 amps

Still, some electricians can be quick to suggest electrical service upgrades — even when calculations from the National Electrical Code show they’re unnecessary, Herrschaft said.

The NEC has two methods for calculating how much electrical service a home needs. One way (Code 220.83) is to add up all the power demands a home’s existing or to-be-installed electrified HVAC, lights and appliances require. The other way (Code 220.87) is to check with the utility about historical peak amp usage and add a 25 percent buffer for safety. That’s the number of amps needed to meet existing demand, and the rest is available for electrification. These are the by-the-book approaches to check whether a home has enough amps or needs a service upgrade.

But what we’re finding is a lot of these calculations are not happening,” Herrschaft said. Peninsula Clean Energy is encouraging electricians to do the math, rather than make assumptions. But until that approach gains widespread traction, homeowners can ask electricians directly to carry out these calculations.

Besides having the electrician on board, a homeowner will also have a much better chance of electrifying on 100 amps if they treat their amps like a maximum limit and budget accordingly. When electric appliances are added on a piecemeal basis, it’s all too easy to pick energy hogs.

That’s the philosophy behind the Watt Diet,” a concept popularized by Redwood Energy. By selecting lower-power, more efficient HVAC systems, appliances and EV charging equipment, people can get what they need without a service upgrade.

A table comparing non-planned electrification choices vs. planned or Watt-Dieting choices, like a low-power EV charger.
An unplanned home-electrification project can lead to equipment that together overshoots 100 amps. A Watt-Diet approach to electrification can keep power demands much lower. (Tom Kabat, developer of the Watt Diet)

Szeto followed this strategy with the help of local electrification consultants Tom Kabat and Josie Gaillard, who have championed the Watt Diet.

To help others across the country, Kabat has developed the Watt Diet calculator, a souped-up spreadsheet that homeowners and contractors can use to play the Tetris-like game of fitting everything into 100 amps. The tool takes information about a home’s heating needs (often the largest energy draw in a home), along with selected heat-pump HVAC and appliances, and tallies their expected loads to estimate the minimum panel size needed.

Ways to electrify on 100 amps

You can employ a number of tactics to electrify your home on a 100-amp (or 24,000-watt) budget.

You can get an EV charger that sips power instead of guzzling it. For example, you could stick with the low-and-slow 15-amp Level 1 charger that usually comes with an EV and delivers about 3 to 6 miles’ worth of charge per hour. Or you could buy a faster Level 2 charger that uses a 20-amp circuit instead of a 50-amp circuit. Some chargers, such as the Wallbox Pulsar, give you more flexibility by allowing you to adjust the amperage.

You can choose 120-volt appliances that run on 15 amps instead of 240-volt versions that need 30 amps. There are 120-volt heat-pump water heaters, heat-pump clothes dryers and forthcoming induction stoves. Armstrong loves combo appliances, which really save on amps: for instance, GE’s all-in-one washer-heat-pump-dryer.

You can get a right-sized, efficient variable-speed heat pump for your heating and cooling needs — without electric-resistance heat strips, which pull a lot of amps (see the chart below). That’s all the more feasible if your home is well sealed and insulated to keep temperatures comfortable.

Chart of watt values associated with different appliances and electrical equipment
Equipment that uses fewer watts — or even gives some back — helps homeowners electrify without a service upgrade. (Tom Kabat)

Another strategy is to use devices that control the power used by appliances so they can’t exceed the home’s supply.

One option is to deploy smart circuit-splitters or circuit-sharing plugs, also called load-sharing devices (such as Dryer Buddy, NeoCharge, SimpleSwitch or Splitvolt), which are simple to install and cheap: $400 to $700 each, according to pro-electrification nonprofit Rewiring America. These can pause one plugged-in load while feeding another, like putting EV charging on hold while the dryer’s going.

Another, albeit more expensive, approach is to get a smart panel or subpanel to prioritize certain loads over others (such as from Koben, Lumin or Span). These devices also allow homeowners to optimize their solar and battery-stored power. Per Rewiring America, these products cost about $3,000 to $5,000, not including installation.

To give you a visual, here’s an example of how all-electric appliances can fit on a 100-amp panel with the savvy use of circuit-sharing:

graphic of electrical panel with two automatic-sharing circuits, ductless mini-split heat pump, and heat-pump water heater
(Josie Galliard, Courtney Beyer, Tom Kabat; Redwood Energy)

For his part, Szeto had a SimpleSwitch installed to manage his family’s EV charging without tripping the 240-volt circuit breaker.

Szeto, his wife and two young kids have been absolutely loving their electrified home, he said. And his electrical service has been fine with the new loads. The highest we’ve pulled at any one time was 48 amps,” which was in April. We still have not come close to 100 amps at any point.”

For more on how to optimize the use of an electrical panel, check out New tools and tech to prep your electrical panel for an all-electric home” by Canary Media’s Jeff St. John, Rewiring America’s 100-amp electrification guide, Peninsula Clean Energy’s design guidelines for home electrification and Redwood Energy’s pocket guide to all-electric retrofits of single-family homes.

Alison F. Takemura is staff writer at Canary Media. She reports on home electrification, building decarbonization strategies and the clean energy workforce.