Panel upgrades on Oahu: what HECO and your inspector actually require
Older 100-amp panels struggle with AC, EV chargers, and solar backfeed — here is how to scope an upgrade without surprise delays.
If your home still runs on a 100-amp main, you are not alone — much of Oʻahu's housing stock was built before heat pumps, second fridges, and rooftop solar were part of the conversation. A panel upgrade is usually the first domino before HECO will approve new load or export.
Plan the panel before you plan the solar — reversing that order is how projects lose a month.
When an upgrade is non-negotiable
Adding a Level 2 EV charger, swapping gas for split AC, or installing battery backup typically pushes past what a legacy panel can safely carry. Your electrician should load-calc before quoting — not after the inspector shows up.
The usual sequence
- Load calculation & site visit
Document existing circuits, planned additions, and service entrance condition.
- Permit through DPP
Honolulu Department of Planning and Permitting — plan review timelines vary by district.
- HECO coordination
Service upgrade may require a meter pull and reconnect window — schedule early.
- Inspection & as-built
Passed inspection unlocks interconnect applications for solar or storage.
100A vs 200A service
| 100A (legacy) | 200A (typical upgrade) | |
|---|---|---|
| Central AC + EV | Often overloaded | Comfortable headroom |
| Solar backfeed | May block interconnect | Room for export |
| Future battery | Limited | Standard path |
Quick answers
- How long does a panel upgrade take on Oahu?
- Rough-in and swap often fit in 1–2 days; permits and HECO scheduling frequently set the overall timeline at 3–6 weeks.
- Can I add solar first and upgrade later?
- You can, but HECO may hold interconnect until service capacity is proven — upgrading first avoids rework.
