100A from the utility is plenty when you add a second power supply on-site
Homeowners adding solar, batteries, EV chargers, or heat pumps are routinely told they must first upgrade their utility electrical service from 100A (or 125A) to 200A. In almost every residential case, that is flatly untrue—and paying PG&E for a service upgrade is a rip-off.
Real-world smart-meter studies from Pecan Street, Peninsula Clean Energy, and SPUR show that even fully electrified Bay Area homes (running heat pump HVAC, heat pump water heaters, induction ranges, and Level 2 EV charging) rarely peak above 40A to 60A (9.6 to 14.4 kW) in actual draw—well below the 24 kW capacity of a 100A service. Worse, if your utility service feed runs underground, upsizing to 200A requires PG&E engineering review, sidewalk and street permits, and trenching across driveways or landscaping, easily costing $10,000 to $30,000+ and stalling your project for 6 to 12+ months.
Spending $10,000 to $30,000 on a thicker utility wire lowers your PG&E bill by $0 and gives you zero backup power during an outage. Investing that same capital in a second on-site supply of electricity—rooftop solar paired with an EG4 FlexBOSS21 hybrid inverter and battery bank—adds up to 16 to 21 kW (66A to 87A) of local power capacity right at your home while slashing your utility bill and keeping the house running during blackouts. With two supplies feeding your home, 100A or 125A from the street is plenty.
Why everyone keeps pushing you toward a service upgrade
If 100A is plenty, why do utilities, contractors, and smart-panel ads keep insisting on an upgrade? Follow the incentives and outdated playbooks:
- Utilities are financially incentivized to build capital upgrades: Under California cost-of-service regulation overseen by the CPUC, investor-owned utilities like PG&E earn a guaranteed regulated return on equity (~10%+) on physical capital added to their rate base (transformers, trenches, and heavy service conductors)—not on software load management that avoids grid hardware.
- Many electricians want the $5,000–$15,000 panel-upgrade job (or default to old habits): For a traditional electrical contractor, a main panel and service upgrade is a lucrative standalone job. Many electricians either want that scope of work or still rely on pre-2023 rules of thumb, adding up breaker numbers on paper rather than using modern load management.
- Plan reviewers and inspectors often apply outdated static math: Traditional NEC Article 220 worksheets assume your EV charger, dryer, oven, and heat pump all run at 100% power at the exact same second, overlooking the 2025 California Electrical Code (CEC Sections 220.70, 705.13, and 750.30) rules that explicitly let software-controlled Energy Management Systems cap service and busbar load calculations.
- Full smart-panel vendors (like SPAN) use the $20,000 trenching scare to sell a $5,000+ box: Companies like SPAN have published scores of articles explaining why 100A service upgrades are unnecessary—because their pitch is to sell you a $4,500 to $7,000 installed proprietary smart panel instead. They are right that you should not trench the street, but you do not need to replace your entire breaker box just to pause one or two heavy 240V circuits.
The smarter solution: Eaton smart breakers and code-backed pushback
Instead of a $10,000–$30,000 utility service upgrade or a $6,000 proprietary smart panel replacement, Potrero solves 100A and 125A constraints using open, code-approved hardware and software:
| Dimension | Potrero: On-site battery + Eaton smart breakers | 100A → 200A utility service upgrade (or full SPAN panel) |
|---|---|---|
| Typical cost | $0 for inverter PCS limiting, or a modest add-on for a few Eaton AbleEdge smart breakers (+$2,900 only if an unsafe Zinsco/FPE box needs a like-for-like swap). | $5,000–$10,000 for overhead utility upgrades, $10,000–$30,000+ for underground utility trenching, or $4,500–$7,000+ for a full SPAN smart panel swap. |
| Schedule impact | Zero PG&E service-upgrade delay; permitted alongside your solar and battery. | 6 to 12+ months of PG&E engineering, trenching, and disconnect scheduling. |
| Bill savings & outage backup | Adds a second on-site supply of electricity (16–21 kW) that cuts your PG&E bill and powers your home during outages. | $0 in electricity bill savings and 0 kWh of backup power from a thicker street wire or standalone smart panel. |
- Inverter current limiting & managed EV charging (2025 CEC Section 705.13): Our hybrid inverter and whole-home backup switch use UL 1741 Power Control System (PCS) current sensors to continuously cap busbar and service current, while dynamic EV charger control throttles EV charging only during the rare minutes your oven, dryer, and heat pump peak simultaneously.
- Modular Eaton AbleEdge smart breakers (2025 CEC Section 220.70 & Article 750): When a city plan checker requires automatic hardware load shedding for specific 240V circuits (such as an EV charger, electric dryer, or water heater), we can install a few modular Eaton AbleEdge smart breakers as a simple add-on in our scope of work—or show your electrician how to configure them. They drop directly into standard Eaton breaker spaces and pause non-essential 240V loads only when total home draw approaches your main breaker limit.
- Told you must upgrade? Share their reasoning with us: If an electrician, plan reviewer, or inspector tells you that you need a 200A utility upgrade, forward us their load calculation or comments so we can push back on your behalf. The only time a breaker box itself needs to be replaced is if the physical enclosure is a recalled fire hazard (such as a Zinsco or Federal Pacific panel) or corroded—and even then, we swap the enclosure like-for-like at your existing amperage (+$2,900) without touching your PG&E service.