Quick Answer
Many older Marin homes still run 100-amp service sized for a pre-EV era. If breakers trip often, the panel feels warm, or you’re adding an EV charger, induction range, or heat pump, it may be time to upgrade — usually to 200-amp service. A licensed electrician runs a load calculation, pulls the permit, coordinates with PG&E, and installs a clean, labeled panel. If your panel is fine, a good electrician will tell you so.
Key Takeaways
- A median Novato home was built around 1974, so much of Marin’s housing stock runs electrical service designed for a very different era of demand.
- Frequent breaker trips, a warm or buzzing panel, dimming lights, and heavy reliance on power strips are the everyday signs worth an honest assessment.
- 200-amp service is today’s residential standard; 400-amp is for larger or all-electric homes — and the right size comes from a load calculation, not a rule of thumb.
- A proper upgrade is permitted, coordinated with PG&E, inspected by your local Marin jurisdiction, and left clean and fully labeled.
- Not every 100-amp panel needs replacing today; the decision turns on your home’s real electrical demand, not its age alone.
A panel upgrade is the replacement of your home’s main electrical service equipment with a higher-capacity panel — most often moving from 100-amp to 200-amp service — so the home can safely power modern electrical loads. That definition matters in Marin because a median Novato home was built around 1974, which means a 50-year-old house is often asking a 50-year-old electrical service to do things its designers never imagined: charge a car overnight, run an induction cooktop, power a heat pump, and keep two home offices online at once. Most of the time the panel just quietly struggles. Occasionally, it warns you.
What does an electrical panel actually do?
Your electrical panel is the central hub that distributes power from the utility to every circuit in your home and protects each one with a breaker. When a circuit draws more current than it should, the breaker trips and cuts power before the wiring can overheat — that is the safety promise of the whole system. The panel’s amperage rating is the ceiling on how much power your home can draw at one time. When that ceiling is set for a 1970s household and you keep adding modern loads, you eventually run out of room, and the symptoms below start to appear.
Amperage (amps) is a measure of how much electrical current a home can safely draw at once; older homes often have 100-amp service, while modern homes with EVs and electric appliances typically need 200 amps or more.
Why Marin's housing stock makes this a local issue
Marin’s homes skew older than most of California’s, and older homes mean older service. Historic houses in Old Town Novato, mid-century homes across Mill Valley’s hillsides, and long-owned properties in San Anselmo and Fairfax were frequently built with 100-amp service — perfectly adequate for their era. The same homes are now the ones adding EV chargers and electrifying their kitchens and heating. That combination — old service, new demand — is exactly why panel work is the most common upgrade we’re asked about across the county. When we walk an older home, the panel is almost always the first thing we look at, because everything else — the EV charger, the induction range, the heat pump — depends on it having room to grow.
A load calculation is the code-defined method under the National Electrical Code (Article 220) of adding up a home’s total electrical demand to size the service correctly — the difference between a guess and an engineered answer.
What are the signs an electrical panel needs upgrading?
The clearest signs a panel needs upgrading are breakers that trip frequently, a panel that feels warm or buzzes, lights that dim when large appliances start, and a home that relies on power strips in every room. None of these guarantees an upgrade on its own, but together they signal a service that’s stretched past its comfortable limit. A single tripped breaker is a breaker doing its job; a pattern of trips is the home telling you it’s being asked for more than it was built to give. If you’re weighing a specific new load, our guide to a panel upgrade for EV charging walks through that decision in detail.
The warning signs that deserve a same-week call
Some symptoms are about capacity; a few are about safety. A panel that is warm to the touch, that buzzes, or that shows any scorching or discoloration around a breaker is not a “watch it” situation — it’s a reason to call promptly. The same is true of a persistent burning smell near the panel or repeated trips on the same circuit that get harder to reset. These don’t always mean a full upgrade is required, but they do mean a licensed electrician should look before you keep loading the system further.
A panel rarely fails all at once. It sends signals first — the job is to read them before they turn into a bigger problem.— Towery Electric
What's the difference between 100, 200, and 400 amp service?
The difference between 100, 200, and 400 amp service is simply how much electricity your home can draw at one time — think of it as the width of the pipe feeding the house. 100-amp service was standard for decades and still suits some smaller homes with gas appliances. 200-amp service is today’s residential standard and the right target for most Marin homes adding EVs, electric cooking, or climate equipment. 400-amp service is reserved for larger homes, all-electric properties, or estates running multiple EV chargers. For a deeper look at what a specific upgrade runs, see our guide to what a 200A service upgrade really costs in Marin.
Which one is right for your home isn’t a guess and shouldn’t be sold as one. A licensed electrician runs a load calculation — the method defined in the National Electrical Code — to size the service to your actual home rather than a generic assumption. The chart below shows why the trend line runs toward 200 amps: each major electric load takes a meaningful bite out of a 100-amp budget.
| Service size | Typically fits | Common limitation |
|---|---|---|
| 100 amps | Smaller homes with gas appliances and modest loads | Little headroom for EVs, induction, or heat pumps |
| 200 amps | Most modern Marin homes; the current standard | Sufficient for typical electrification with room to spare |
| 400 amps | Large or all-electric homes; multi-EV estates | Higher cost; warranted only when a load calc confirms it |
How does a panel upgrade actually work?
A panel upgrade is a coordinated, permitted process that a licensed electrician typically completes in a single working day, with power off for part of that day. It starts with an assessment and a load calculation, moves through permitting and utility coordination, and ends with an inspection before the new service is energized for good. It’s more coordination than chaos, and knowing the sequence up front takes the mystery out of it. If you’re adding capacity in stages, our guide to sub-panel installation covers when a second panel is the better answer.
- Assessment & load calculation. We measure your current loads and what you plan to add, then calculate the service size your home actually needs.
- Permit & PG&E coordination. We pull the permit and schedule the utility disconnect and reconnect required to swap the service.
- Installation. The new panel goes in with clean terminations, organized circuits, and a fully labeled directory.
- Inspection. Your local Marin jurisdiction inspects the work before it’s permanently energized — proof it was done to code.
After the inspection passes, you’re left with a panel that has real headroom — capacity for the EV charger, the induction range, or the heat pump that prompted the upgrade, plus room for whatever comes next. What you should expect from a good electrician is a clear timeline before the work starts, a planned power-off window, and a clean, labeled panel at the end that you could read at a glance.
Not sure whether your panel is ready for the way you live now?
Request Your EstimateWhen should you upgrade — and when can you wait?
You should upgrade when you’re adding a major electric load or seeing capacity and safety warning signs; you can often wait when your 100-amp service is healthy and your loads are modest. This is where honesty matters more than urgency. If your panel is in good condition, your home runs on mostly gas appliances, and you’re not planning to electrify, a 100-amp service may have years of safe life left — and a trustworthy electrician will say so rather than manufacture a reason to sell you a new panel.
The moment the math changes
The upgrade becomes clearly worth it when demand shifts: you’re adding an EV charger, converting to electric cooking or heating, running out of circuits, or seeing the warning signs above. In those cases, upgrading first is almost always cleaner and cheaper than bolting new loads onto a panel that can’t support them — and it prevents the frustrating scenario of buying equipment you then can’t safely connect. If you expect to electrify further over the next few years, upgrading once to 200-amp service usually beats working around a full panel twice.
What are the most common mistakes with panel upgrades?
The most common mistake homeowners make is treating a panel upgrade as a commodity — choosing on price alone, skipping the permit, or letting an unlicensed handyman do the work. Electrical service work is the most safety-critical wiring in the house, and the U.S. Consumer Product Safety Commission and fire-safety authorities like the Electrical Safety Foundation International consistently tie home electrical fires to improper installation and overloaded, outdated equipment. Unpermitted panel work can also create insurance problems and headaches when you sell — a hidden cost that dwarfs whatever the shortcut saved.
How to avoid them
Avoid these pitfalls by hiring a licensed C-10 contractor who runs a real load calculation, pulls the permit, and has the work inspected — and by being skeptical of any quote that’s cheap because it skips those steps. If a known-hazardous brand like Zinsco or Federal Pacific is involved, the fix is replacement, not a patch; our guide on Zinsco and Federal Pacific panels explains why. The right partner treats the permit and inspection as features, not friction.
Key Terms
- Electrical panel (breaker box)
- The central hub that distributes power to a home's circuits and protects each one with a breaker.
- Service upgrade
- Increasing a home's electrical capacity — for example, from 100A to 200A — to support modern demands.
- Load calculation
- A code-defined tally of a home's total electrical demand, used to size the service and circuits correctly.
- Amperage (amps)
- A measure of how much current a home can safely draw at once; the ceiling set by the panel's rating.
About the Author
Founder of Healthcare Marketing Group and author of The Ultimate Guide to Digital Marketing. Previously led a digital marketing company with 8,000+ clients. Writes on local-service SEO and E-E-A-T content strategy.
Reviewed By
Alex founded Towery Electric in Novato in 2014 and has upgraded services across Marin’s older neighborhoods. Reviewed this article for technical accuracy on Aug 5, 2026, 2026.
“On an older Marin home, I’d rather spend twenty minutes on a load calculation and tell someone their panel is fine than sell them a service they don’t need. The trust is worth more than the job.”
— Alex Towery, Licensed Electrical Contractor
How We Ensure Accuracy
Sources
- California Contractors State License Board. “License Detail — Towery Electric, Inc. (#989290).” cslb.ca.gov
- National Fire Protection Association. “NFPA 70 — National Electrical Code.” nfpa.org
- U.S. Department of Energy. “Charging at Home — Alternative Fuels Data Center.” afdc.energy.gov
- Electrical Safety Foundation International. “Home Electrical Fires and Safety.” esfi.org
- California Energy Commission. “Building Energy Efficiency Standards (Title 24).” energy.ca.gov
Frequently Asked Questions
How do I know if my electrical panel needs upgrading?
Look for a pattern, not a single event: breakers that trip often, a warm or buzzing panel, lights that dim when large appliances start, and heavy reliance on power strips. Age matters too — a home over about 25 years old still on original 100-amp service may be undersized. The reliable way to know is a load calculation from a licensed electrician, who measures your real demand against the panel’s capacity.
What's the difference between 100, 200, and 400 amp service?
It’s how much power your home can draw at once. Many older Marin homes have 100-amp service, which struggles with EVs and induction ranges. 200-amp service is today’s standard and fits most homes adding those loads. 400-amp service is for large or all-electric homes and multi-EV estates. The correct size comes from a code-defined load calculation, not a rule of thumb.
How long does a panel upgrade take?
Most residential panel upgrades are completed in a single working day, with power off for part of that day while the old panel is swapped for the new one. What can add calendar time around the install is the permit and inspection process and coordinating the PG&E disconnect and reconnect. A good electrician handles all of that and gives you the timeline before starting so you can plan around the power-off window.
Do I need a permit for a panel upgrade?
Yes. In California, upgrading your electrical service requires a permit and an inspection by your local jurisdiction. That’s what confirms the work was done to code and keeps it from becoming a problem when you sell or file an insurance claim. A licensed C-10 contractor pulls the permit and has the work inspected. If someone offers to skip the permit, treat it as a warning sign rather than a shortcut.
Is it safe to keep using an old 100-amp panel?
Sometimes, yes. A healthy 100-amp panel serving a home with modest, mostly gas-powered loads can be safe and have years of life left. The concern isn’t age alone — it’s demand, plus physical warning signs like heat, corrosion, or a known-hazardous brand. A licensed electrician can tell you which situation you’re in. A trustworthy one would rather confirm your panel is fine than sell you an upgrade you don’t need.
Editor’s Summary
A panel upgrade isn’t about fear — it’s about capacity. Marin’s older homes were built for a lighter electrical era, and adding EVs, induction, or heat pumps can outgrow a 100-amp service. The right move is a load calculation from a licensed C-10 electrician, an honest answer about whether an upgrade is warranted, and — if it is — a clean, permitted, inspected 200-amp panel built for how you actually live.