It's 11pm. You're staring at a site plan you thought was done. The architect signed off, the client approved the parking layout, and then someone forwarded the PG&E service request comments. Now there's a red circle around the transformer location and a note that says "clearance conflict."

Welcome to the transformer pad problem. We deal with this on nearly every project that involves a pad-mount transformer, and it almost always comes from the same root cause: the 8 feet of front clearance nobody drew in at the start.

Let's fix that. Here's everything you need to know about transformer pad clearance requirements for PG&E service — dimensions, code basis, and how this intersects with your site plan before the concrete is poured.

What's a Transformer Pad, and Why Does It Need Clearance?

A pad-mount transformer is a ground-level, tamper-resistant transformer housed in a locked metal cabinet, mounted on a concrete pad. It's the green box you see in parking lots, apartment courtyards, and commercial loading areas. PG&E owns and maintains it; you provide the pad, the conduit stub-outs, and the real estate it sits on.

Clearances exist for two reasons: operational access and safety. PG&E crews need to pull up with a truck, open the cabinet doors, and work on energized equipment. That requires unobstructed swing room on the front face and enough working space to meet both PG&E's own standards (Green Book) and the National Electrical Code.

When either is compromised, PG&E won't energize the transformer. Full stop.

PG&E's Front Clearance Requirement: The 8-Foot Rule

The number that bites people most often is the 8-foot front clearance. PG&E's Electric Rule 16 and the Green Book (Electric Distribution Standards) require that the full face of the transformer cabinet — typically the high-voltage and low-voltage door panels — have 8 feet of unobstructed horizontal clearance measured from the pad edge on the access (door) side.

That 8 feet can't contain:

The practical implication: if your transformer is facing a parking stall, you need a minimum 8-foot setback from the stall line — not the wheel stop, not the curb, the stall line. Most parking stalls are 18 feet deep. Add 8 feet of clearance and you're looking at 26 feet of dead zone measured from the nearest wall or drive aisle edge.

On compact urban sites, that 8 feet can be the difference between the parking layout working or losing a stall you can't afford to lose.

Side and Rear Clearances

Front clearance gets all the attention, the sides and rear matter too.

Side clearances: PG&E typically requires a minimum of 2 feet on each non-access side of the transformer pad. This accommodates conduit entries, cable routing, and allows linemen to work around the unit without being pinned against a wall. If the transformer is recessed into a landscape pocket or wedged between structures, this 2-foot requirement will show up in your DRC comments.

Rear clearance: Minimum 2 feet from any wall, fence, or structure behind the unit. The rear of a pad-mount transformer typically contains the cable-entry compartment. PG&E needs access to pull and terminate the underground cables feeding the unit. If there's a retaining wall or building face within 2 feet of the rear, you'll hear about it.

Height clearance: Nothing overhead within 18 feet vertically above the pad, including canopies, tree branches, and building overhangs. If you're tucking a transformer under a carport or covered parking structure, that structure needs to be designed to accommodate this — or the transformer goes somewhere else.

What the NEC Says (And Why It Matters Separately)

PG&E's Green Book requirements are utility standards., the National Electrical Code (NEC) — specifically Article 110.26 — has its own working space requirements that apply to the customer's secondary service equipment. These aren't the same as PG&E's operational clearances, and both apply.

NEC 110.26 requires working space in front of electrical equipment:

For pad-mount transformers in California, the relevant working condition typically results in a 36-inch minimum working clearance from the secondary compartment. That's the minimum the inspector is looking at when he walks the site before meter release. It doesn't override the 8-foot PG&E requirement — both apply simultaneously.

The AHJ (Authority Having Jurisdiction, usually the city building department) enforces NEC on your side of the meter. PG&E enforces their own standards on their side. You need to satisfy both sets of clearances for the transformer to actually get energized and the building to get its Certificate of Occupancy.

How Clearance Zones Conflict With Your Site Plan

Here's where it gets expensive. The four most common clearance conflicts we see:

Conflict 1: Parking Stall Overhang

Parking stalls on a standard layout put the vehicle nose 18 inches beyond the wheel stop. If you position a transformer adjacent to a parking stall — even with the correct 8-foot line on paper — the actual vehicle overhang may encroach into the clearance zone. Design for the vehicle, not the stall line.

Conflict 2: Drive Aisle Fire Access Requirements

Fire departments in California require 20-foot clear drive aisle widths for apparatus access. If a transformer's 8-foot front clearance zone bleeds into a drive aisle, you've created a situation where meeting PG&E's requirements potentially narrows a fire lane below the minimum. On narrow sites, this is a real problem with no clean answer — it usually means moving the transformer.

Conflict 3: Landscaping and Planters

Architects love to hide transformers in landscape pockets. The instinct is good — nobody wants to look at a green box —, planters, hedges, and landscape berms count as obstructions. PG&E won't accept a transformer location where vegetation will eventually grow into the clearance zone. The landscape plan needs to show species with mature heights that don't conflict, or use hardscape that respects the clearances from day one.

Conflict 4: ADA Paths of Travel

An accessible route can't pass through an electrical clearance zone. This creates problems on sites where the transformer ends up adjacent to a walkway. You can't ask a person using a wheelchair to walk around a transformer's operational zone — that path needs to be rerouted, which sometimes triggers a cascade of accessible route redesign.

Pad-Mount vs. Subsurface Transformers: When Each Applies

Not every project gets a green box on a concrete slab. On constrained urban sites — think downtown Oakland or Honolulu multifamily towers — PG&E may offer or require a subsurface (vault) transformer. Here's the tradeoff:

Pad-mount transformers:

Subsurface vault transformers:

The decision isn't yours alone — PG&E has to agree to a vault installation. We initiate that conversation early in the dry utility coordination process, before the site plan gets locked. Waiting until DRC comments to discover you need a vault is a 6–8 week delay you don't want.

How the Civil Engineer Coordinates the Transformer Location

On a typical California commercial or multifamily project, here's how transformer location coordination actually flows:

  1. Preliminary site layout (30% CD): We identify the likely transformer location based on service entry point, load center, and available real estate. We sketch the clearance bubble — front 8 ft (access side), non-access sides 2 ft — directly on the site plan and flag conflicts.
  2. Architect coordination: If the clearance zone conflicts with parking, landscaping, or circulation, we work it out at this stage — not at plan check. Moving a transformer 8 feet to the left at 30% costs nothing. Moving it at 90% costs a redesign fee and a schedule slip.
  3. PG&E preliminary meeting or SCR (Service Coordination Request): We submit the site plan to PG&E for preliminary review. Their distribution planning group will confirm the transformer location, service entry direction, and required pad dimensions. This is where they tell you if a vault is needed.
  4. Site plan lockdown: Transformer location, pad dimensions, and clearances get dimensioned on the civil site plan and coordinated with the architectural floor plan and landscape plan.
  5. Construction: We confirm clearances are maintained in the field during construction administration. Contractors occasionally pour a curb or install a planter that wasn't on the final plan. Catch it before PG&E does.

Standard Pad Dimensions You Should Know

PG&E specifies pad dimensions based on transformer kVA rating. Common residential/light commercial sizes:

Add the clearance zones to those pad dimensions to get the total site area you need to reserve. For a 167 kVA unit with a 4'×4' pad, the total clearance envelope — 8' front (access side), 2' on non-access sides — works out to a roughly 10'×10' footprint minimum that's either paved accessible area or otherwise unobstructed. That's a real chunk of a tight site.

Exact pad dimensions are in PG&E Electric Rule 16 and the Green Book, and they do get updated. We pull the current standard detail directly from PG&E's distribution standards library at the start of each project rather than relying on what we used last time.

The "Final Site Plan" Problem

I've seen this scenario enough times that I'll just name it directly. The architect finalizes the site plan. The client approves it. Everyone celebrates. Then somebody submits for a PG&E service request and the distribution planner looks at the transformer location and asks a simple question: "Where's the 8-foot clearance?"

There isn't one. Because the transformer got pushed into a corner to maximize parking, and the parking layout was done without anyone drawing the clearance bubble first.

Now the "final" site plan isn't final. The parking count changes. The landscape plan changes. The architect is annoyed. The client is annoyed. And the project is 3–4 weeks behind schedule while everyone sorts it out.

This is exactly the kind of problem that integrated site planning with dry utility coordination is supposed to prevent. Transformer clearances aren't a PG&E formality you deal with at the end — they're a site planning constraint you bake in at the beginning.

Bottom Line

Transformer pad clearances aren't complicated, they're specific. PG&E requires 8 feet of unobstructed front clearance on the access side, 2 feet on non-access sides, and 18 feet of vertical clearance overhead. NEC Article 110.26 has its own working space requirements that layer on top of those. Both sets of requirements apply, and both will be checked before the transformer gets energized.

The fix is simple: draw the clearance bubble on the site plan at the same time you draw the pad. Don't wait for PG&E's DRC comments to find out there's a conflict. By then, the plan is "final" and fixing it's expensive.

If you're working through a transformer location issue on a current project, give us a call. That's what we do — and we'd rather solve it at 30% than at 11pm.

Learn more about our dry utility consulting services, or see how we integrate utility coordination into site planning from day one.