Here's the question we get more than almost any other in San Mateo and Santa Clara counties right now: "I want an EV charger, a heat pump for heating and cooling, a heat pump water heater, and an induction range. Do I need to upgrade my panel to 200 amps?" The honest answer is maybe — but often no. A lot of homeowners are told they need a $5,000 service upgrade before they've ever had a real load calculation done. Sometimes you do. Just as often, a proper calculation shows your existing 100-amp panel has more room than anyone guessed. This guide walks through how to actually figure it out instead of guessing.
Why Everyone Is Stacking Loads at Once
California's push toward electrification is real and it's accelerating. Between Title 24 energy code updates, CALGreen requirements pushing EV-ready and electric-ready construction, PG&E rate structures, and rebate programs, more Bay Area homeowners are pulling gas appliances out and replacing them with electric ones. The problem is that most homes here were wired for a very different era. A house built in the 1960s with a 100-amp panel was sized for a gas furnace, a gas range, a gas water heater, and maybe one window AC unit. Now we're asking that same panel to feed a Level 2 EV charger, a whole-home heat pump, a heat pump water heater, and an induction range — loads that simply didn't exist when the service was installed.
The instinct is to assume the panel can't handle it. Sometimes that's correct. But the only way to know is to add up the actual numbers.
What Each New Load Realistically Adds
These figures vary by model, climate zone, and how the equipment is wired, so treat them as typical ranges rather than fixed values. But they give you a feel for the scale of each appliance.
Level 2 EV Charger
Typically 32–48 amps at 240V. Most home Level 2 chargers are set up to draw 32–40 amps continuous and are wired on a 40–60 amp circuit (the circuit is sized larger than the draw because EV charging is a continuous load). A 48-amp charger on a 60-amp circuit is roughly 11.5 kW. The good news: nearly every modern EV charger is adjustable, so we can dial the amperage down to fit your available capacity without crippling overnight charging. For more on this, see our guide on EV charger installation cost in the Bay Area.
Heat Pump HVAC (Heating + Cooling)
Varies widely — roughly 15–40 amps at 240V depending on system size. This is the load that fluctuates the most between homes. A small ductless mini-split serving a few rooms might pull 15–20 amps, while a larger ducted heat pump sized for a whole house can land in the 30–40 amp range or higher. Sizing depends on your square footage, insulation, and climate zone, so this one genuinely has to be looked at per home.
Heat Pump Water Heater
Either roughly 30A at 240V, or as little as 15A at 120V on a plug-in model. This is one of the most overlooked tricks in the whole conversation. Many heat pump water heaters now come in a 120-volt plug-in version that runs on a standard 15-amp circuit. They heat more slowly than the 240V models, but for a lot of households that's a non-issue — and it can mean the difference between needing a panel upgrade and not.
Induction Range
Typically 30–50 amps at 240V. A full induction range is usually wired on a 40 or 50-amp circuit. There are also smaller induction cooktops and 120V plug-in single-burner units, but if you're replacing a full gas range with a full induction range, plan on a substantial 240V circuit.
How an Electrician Actually Runs a Load Calculation
This is the heart of the whole question, and it's where guessing gets replaced with the National Electrical Code. A licensed electrician doesn't just eyeball your panel and quote an upgrade. We run a load calculation under NEC Article 220.
The Standard Method
The standard calculation adds up the general lighting and receptacle load (based on square footage), the small-appliance and laundry circuits, and then the larger fixed appliances — range, water heater, HVAC, EV charger, dryer, and so on. The code allows certain demand factors, because in real life you're never running every appliance at full tilt simultaneously. The total is then compared against your service size. If the calculated load comes in under your panel's capacity with margin, you're fine. If it exceeds it, you need more service.
The Measured-Load (Existing Dwelling) Method
Here's the part homeowners almost never hear about. NEC also permits a calculation method for existing homes that uses the actual measured peak demand of your home over a period of time, rather than the conservative assumptions of the standard method. PG&E can often provide your historical usage data, or we can install a metering device for a period. Because the standard method tends to be cautious, the measured-load approach frequently reveals real available capacity that the worst-case math hides. We've seen homes that "needed" a 200-amp upgrade on paper turn out to have plenty of headroom once the actual demand was measured. This single step has saved homeowners thousands of dollars.
When 100 Amps Is Genuinely Enough — and When You Need 200
100-amp service is often enough when: you're not adding every electric load at once, you choose a 120V plug-in heat pump water heater, your heat pump HVAC is modestly sized, you're willing to set your EV charger to a lower amperage, or a measured-load calculation shows real available capacity. Plenty of Bay Area homes run an EV charger plus one or two other electric appliances on 100 amps without issue.
You genuinely need 200-amp service when: the load calculation actually exceeds your existing capacity even after demand factors, you're electrifying the entire home all at once with full 240V appliances across the board, you have a large house with a big ducted heat pump, or your existing 100-amp panel is also old, obsolete, or has no open breaker spaces and needs replacing anyway. If the numbers say upgrade, upgrade — an overloaded service is a real fire and reliability risk, not a theoretical one. We walk through the full decision in our electrical panel upgrade guide.
The Alternatives Nobody Tells You About
This is where an honest electrician earns their keep. A full panel upgrade is the default recommendation, but it is not the only path. Before you commit to one, consider these.
Smart Panels and Load-Management Devices
Smart panels and automatic load-management devices monitor your home's real-time usage and prevent two big loads from peaking at the same instant. For example, the device can pause EV charging for a few minutes if the heat pump and oven both kick on, then resume automatically. To the NEC, a listed load-management device can let you add a major load without increasing your service size, because the loads are managed so they never exceed capacity together. A load-management device is frequently a few hundred to roughly a thousand-plus dollars installed — often dramatically cheaper than a full service upgrade.
Circuit-Sharing Splitters for EV Charging
If your dryer and EV charger are near each other, a listed circuit-sharing device can let them share one 240V circuit, switching power between them so they never run at once. For a household that charges the car overnight and runs the dryer during the day, this can eliminate the need for a brand-new circuit entirely.
120V Plug-In Appliances
As mentioned, a 120V heat pump water heater sidesteps a whole 30-amp 240V circuit. Pairing that choice with a modestly sized heat pump can keep the total load well under what a panel upgrade would otherwise require.
Staging and Prioritizing Loads
You don't have to electrify everything in one weekend. If you add the EV charger now and the heat pump next year, the staged approach gives you room to choose efficient equipment, take advantage of load management, and avoid a knee-jerk upgrade. We can wire the home today so that future loads drop in cleanly.
What This Costs — and Why Honesty Matters
For transparency: a 200-amp panel upgrade in the Bay Area typically runs roughly $3,000–$6,000 or more, depending on the condition of your existing service, the meter, the panel location, permit fees, and whether PG&E has to upgrade the service drop or do utility-side work. That utility coordination is often what drives both the cost and the timeline. You can read our detailed breakdown in our panel upgrade cost guide. By contrast, a smart load-management device is frequently a fraction of that. When we run your load calculation, we'll tell you straight: if the numbers say upgrade, we'll explain exactly why; if a load-management device or a smarter appliance choice does the job, we'll tell you that too — even though it's the smaller invoice. That's the difference between an electrician and an upsell.
Call Fox Electric
Fox Electric is a licensed C-10 electrical contractor serving homeowners across San Mateo and Santa Clara counties. Whether you're planning a full home electrification or just adding your first EV charger, we'll run a real NEC load calculation, look at the measured-load option, and lay out every path — panel upgrade, smart load management, or a smarter appliance choice — so you only pay for what you actually need. Explore our panel upgrade service and EV charger installation service to learn more.
Call (650) 550-0719 to schedule a load assessment and get an honest answer about your panel.
