This page covers what FPE Stab-Lok and Zinsco/Sylvania panels are, what Tucson's own permit record shows about how many panels from that era have been documented as replaced, how to identify a panel by sight, and what a replacement involves here.
The short version: a panel from this era isn't something you can rule in or out from the street, and a permit on file is the strongest evidence one was ever addressed. The city's searchable permit statistics only start in January 2022, though, so an absent recent permit doesn't mean the work never happened — it may simply predate the record. The honest answer is to check the specific address.
What Federal Pacific and Zinsco panels are
Federal Pacific Electric (FPE) made the Stab-Lok panel line from the 1950s into the early 1980s, and it was one of the most common panels installed nationwide, Tucson included. Zinsco made a similar line through the same decades before being sold; later stock is sometimes labeled Sylvania or Sylvania-Zinsco. Both show up regularly in Southern Arizona homes built from the mid-1960s through the late 1980s.
The concern isn't age by itself. It's a documented pattern of breakers that fail to trip during an overcurrent or a short, tracing to how the breaker seats against the panel's bus bar rather than to any single breaker. Because the flaw sits in that connection, a new breaker of the same style does not correct it — the bus and stab design itself is what's in question (source).
Both brands carry a class-action history tied to these failure-to-trip claims, and many insurers now ask about panel brand on a new or renewed policy; some flag FPE or Zinsco for inspection, and some decline or non-renew coverage until the panel is replaced (source). It matters at resale too: Arizona sellers complete a Seller's Property Disclosure Statement and must disclose known material facts, and a seller who knowingly omits a documented panel issue can face a buyer's claim after closing (source).
What the Tucson numbers show
City of Tucson's assessor data lists a build year for 157,907 parcels. That field stops being populated after 2009, so it isn't a count of every home in the city — it's the group whose year built we can measure. Of those parcels, 99,861 were built between 1950 and 1989, the decades spanning fuse panels, aluminum branch wiring, and eventually FPE and Zinsco panels. Of that group, 33,546 were built specifically between 1974 and 1989 — the years when an FPE Stab-Lok or Zinsco panel was most often what went in new.
Since City of Tucson's GIS permit layer starts tracking data in January 2022, the city has issued 1,908 permits classified as a panel or service upgrade, residential and commercial combined. Set the two figures side by side and the ratio of homes built 1950–1989 to permitted upgrades since 2022 works out to roughly 52 to 1.
That is a documented-replacement gap, not a defect count. It says the number of panel or service-upgrade permits on file since 2022 is small relative to the number of era-appropriate homes — it does not say 52 out of every 53 of those homes still has an original panel, and it says nothing at all about any one specific address. The next section covers why.
Why the gap number needs a careful read
Three limits keep the 52-to-1 figure from being read as a defect count for any individual home.
- The GIS statistics window starts in January 2022. City of Tucson's own permit records reach further back — individual parcel files in PRO, the city's records system, commonly go back to 2006 or earlier — but the aggregate count above only totals permits issued from 2022 forward. A panel replaced in 1998 or 2015 is real work that simply isn't in the 1,908 figure.
- The citywide count isn't a parcel's own history. Looking up one address in PRO can surface an upgrade from any year on file for that parcel, even though the citywide statistic cannot reach back that far.
- Some electrical work happens without a permit. Arizona allows an owner-builder to pull a permit and perform their own electrical work on a primary residence, and they remain responsible for code compliance regardless (source) — but not everyone who does the work pulls the permit.
In practice, a permit on file is strong evidence — a dated record of a real job. An absent permit is weak evidence: consistent with an original panel, but just as consistent with pre-2022, unpermitted, or differently filed work.
How to identify a panel by sight
Short of removing the dead front and reading the label, a few things are worth checking — none of them conclusive on their own.
- The panel door or breaker faces are usually branded. FPE panels typically read "Federal Pacific Electric" or "FPE"; Zinsco panels often read "Zinsco," or on later stock, "Sylvania" or "Sylvania-Zinsco."
- Breaker style is a rough tell, not proof. FPE Stab-Lok breakers typically have a narrow, stab-in shape; Zinsco breakers often use a wider, colored toggle. Panels get mixed with replacement breakers over the years, so style alone can mislead.
- Build year narrows the odds without settling them. A home built in Tucson's FPE/Zinsco era, roughly 1965 through 1989, is more likely to have started with one of these panels — but plenty have already been replaced, and some homes from that era used other brands entirely.
Guidance like this is useful for deciding whether to look further. It isn't a substitute for a licensed electrician opening the panel, or for the permit record — the half of the picture a photo of the door can't give you.
Eras and typical wiring concerns
Panel brand is one piece of a broader pattern. Tucson's housing stock carries a handful of era-typical electrical concerns in addition to whatever is specific to any one house — typical, not diagnostic of any address.
| Built | Typically installed | What tends to matter |
|---|---|---|
| Before 1950 | Knob-and-tube wiring, fused service | 15,531 Tucson parcels fall here; knob-and-tube carries no ground wire and degrades where it contacts newer insulation. |
| 1950–1964 | 60–100A fused service | Usually undersized for a modern home's load; screw-in fuses invite someone eventually using the wrong amperage. |
| 1965–1973 | Solid aluminum branch-circuit wiring | 23,657 Tucson parcels fall here; needs connectors and devices rated for aluminum, or a copper pigtail — the failure mode is a loose, overheating joint, not the wire itself. |
| 1974–1989 | FPE Stab-Lok or Zinsco/Sylvania panels | 33,546 Tucson parcels fall here — see the sections above. |
Era mix varies block by block, not just decade by decade. The Tucson neighborhood permit data hub covers permit activity across a set of 12 Tucson neighborhoods. Whoever does the work should carry an active license — any Arizona contractor's license can be checked at roc.az.gov.
What a replacement involves in Tucson
If a panel does need replacing, in Tucson that is a defined process, not just a parts swap.
- A permit, typically issued quickly. The median time from application to issue for a panel or service-upgrade permit is 6 days, based on 1,281 issued permits — permitting itself is usually not the bottleneck.
- A TEP appointment. A panel or service upgrade starts with a New Service application to Tucson Electric Power, and larger jobs need an equipment-access appointment so TEP and the customer's electrician can reach TEP's equipment on site (source).
- A decision on service size. Whether the new panel stays at the existing amperage or moves up, commonly to 150A or 200A, comes down to what the home's current and planned load calls for, not just what's failing in the old panel.
- A load calculation. A proper replacement includes a load calc for the home's actual circuits rather than a like-for-like swap — see our residential load calculator for how that number gets built.
A licensed contractor pulling the permit also means the finished work lands in the same city record this page is built from, findable by the next owner, appraiser, or insurer.
See the permit history on file for your address
Enter any Pima County address below. We'll pull the parcel's year built (City of Tucson only), the full permit history — including any panel or service-upgrade permit on file — code cases, and a system-by-system read of what the record shows, free, no sign-up.