100-Amp vs 200-Amp Service: Which Does Your Marin Home Need?

For a smaller home with gas heat and cooking and modest electrical demand, 100-amp service can still be adequate — it ran homes reliably for decades. Where it falls short is the modern, electrifying home: add an EV charger, a heat pump, and induction cooking, and the simultaneous demand can exceed what 100 amps can safely supply. So “enough” depends entirely on your loads. If you’re not adding major appliances and aren’t tripping breakers, 100 amps may serve you fine; if you’re electrifying, it often becomes the bottleneck.

It’s less about any single device and more about running high-draw loads simultaneously. A 200-amp service comfortably supports an EV charger, a heat pump, an induction range, and your everyday household loads all at once, whereas 100 amps runs out of headroom when you stack those. Individually, a 100-amp service might handle one new big load with careful management; the problem is the combination. 200 amps roughly doubles the ceiling, which is why it’s the practical baseline for a home that’s electrifying or planning to.

With a load calculation, not a guess. An electrician uses the code-defined method to total your home’s existing loads plus everything you plan to add, then compares that to your service capacity. That’s the honest, specific answer to whether your 100-amp service can carry your plans or whether you need to upgrade. Reading the panel label tells you what you have, but only the calculation tells you whether it’s enough for where you’re headed — and it’s inexpensive relative to the cost of guessing wrong.

Sometimes, yes — it depends on your home’s other loads and whether there’s spare capacity, which a load calculation determines. If the numbers are tight, a load-management device can let the charger draw only when other big loads aren’t, avoiding an upgrade. But if you’re also planning a heat pump or induction range, stacking them on 100-amp service usually isn’t viable, and upgrading to 200 amps once for everything is cleaner and cheaper than managing load repeatedly or upgrading twice.

It’s more involved than a same-size panel swap because you’re increasing the actual service capacity, which brings in new metering equipment and PG&E coordination for the disconnect and reconnect, on top of the new panel. That makes it a bigger project in both cost and timeline than simply replacing a panel at the same amperage. It’s still a routine, well-understood upgrade for a licensed electrician, but it’s worth planning — and doing once for your full electrification picture rather than piecemeal.

It rarely shows as a dollar-for-dollar appraisal line, but like other electrical upgrades it removes friction and signals readiness. A 200-amp service tells buyers the home can handle EVs, heat pumps, and modern electric living without a follow-on project, and it takes an undersized-service objection off the table at sale. In an increasingly electrified market like Marin, that readiness matters. As with any upgrade, keeping the permit and inspection records is what lets a buyer’s agent and inspector rely on the work you did.