Weekly digest #164: solar industry shifts

Where the solar market actually stands

Residential solar installs have flattened in 2026 after the 2025 ITC step-down and higher financing costs. Commercial and utility-scale work is up, especially battery-paired systems. If your shop only does roof PV, the pipeline is tighter. Crews chasing storage retrofits and microgrid tie-ins are still booked out.

Module pricing keeps drifting down, but balance-of-system costs (racking, conductors, switchgear) are flat or up. That changes how bids pencil. Labor is now the swing factor on most jobs, not panel count.

Watch for tariff-driven inverter shortages on certain SKUs. Lead times on three-phase string inverters above 50 kW have stretched past 14 weeks at some distributors. Spec alternates in your submittals.

Code refresh: 690 and 705 still bite

Most failed inspections this quarter trace back to the same handful of articles. NEC 690.12 rapid shutdown labeling and initiation device location, NEC 705.12 interconnection point and busbar calculations, and NEC 690.31 conductor methods on rooftops. None of these are new. Inspectors are just looking harder.

For the 120% rule under NEC 705.12(B)(3)(2), confirm the busbar rating before you size the backfed breaker. A 200A panel with a 200A main can take a 40A PV breaker at the opposite end of the bus. Anything bigger needs a supply-side connection or a load-side derate.

• NEC 690.12: rapid shutdown initiation within 10 ft of the service or at a readily accessible location.
• NEC 690.13: PV system disconnect grouped and labeled, max six operations to de-energize.
• NEC 690.31(D): conductors inside buildings need metallic raceway or MC cable until the first readily accessible disconnect.
• NEC 705.12(B)(2)(3): sum of breaker ratings cannot exceed 120% of busbar rating for opposite-end backfeed.
• NEC 705.11: supply-side connections must comply with conductor and OCPD requirements at the service.

Battery storage is where the work is

ESS retrofits on existing PV systems are driving most of the residential margin right now. Homeowners want backup, utilities want export control, and incentives in several states still favor paired systems. NEC 706 governs the install, and Article 480 covers the battery system itself.

Watch the working space. NEC 706.10(B) and 110.26 still apply, and a 9 kWh wall-mount unit needs the same 36 inches of clearance as a panelboard. Garage installs that looked fine on paper get rejected when the water heater or a shelving unit lands inside the working space.

Field tip: before you commit to a wall location for an ESS, tape out the 36 inch by 30 inch working space on the floor and the 78 inch headroom. If anything permanent intrudes, pick a new wall. Cheaper than a re-inspect.

Grounding and bonding: the inspection magnet

PV grounding still trips crews who came up on legacy systems. NEC 690.41 through 690.47 cover the system grounding, equipment grounding, and EGC sizing. Most modern inverters are functionally grounded (not solidly grounded), which changes how you treat the DC conductors and the GEC.

For module frames, the listed WEEB clip or grounding lug must match the rail and module combination on the listing. Mixing manufacturers voids the listing every time. Inspectors are pulling spec sheets on site now, so keep the cut sheets in the job folder.

• NEC 690.43: equipment grounding for all exposed non-current-carrying metal parts.
• NEC 690.45: EGC sized per 250.122, no upsize required for voltage drop unless the ungrounded conductors are upsized.
• NEC 690.47(B): the GEC connection point and sizing depend on whether the system is functionally grounded or solidly grounded.
• NEC 250.166: DC system grounding electrode conductor sizing if you have a solidly grounded DC system, which is rare on new work.

Conductor sizing in real conditions

Rooftop conduit runs get hot. NEC 310.15(B)(3)(c) is gone in the 2023 and 2026 cycles, replaced by Table 310.15(B)(2) ambient temperature adders based on height above the roof. If your conduit is less than 7/8 inch above the roof surface, add 33 degrees C to the ambient. That moves a lot of #10 THWN-2 runs into #8 territory.

Run the math both ways. Voltage drop on a 400 ft homerun from the array combiner to the inverter often drives the size before ampacity does. Three percent drop is the working target, two percent if the AHJ is strict.

Field tip: spec free-air conductors (USE-2 or PV wire) for the array-to-combiner runs and switch to THWN-2 in conduit at the combiner. You get the better ampacity table for the exposed sections and avoid raceway derates where it matters most.

What to bid this quarter

The shops winning right now are the ones cross-trained on PV, ESS, and EV. A single service call can pull all three. Pricing the service upgrade as the anchor (200A to 400A, or a 200A meter-main with through-lugs) gets you in the door for the storage and charger work that follows.

Keep an eye on utility interconnection queues. Some IOUs in California, Hawaii, and parts of the Northeast are pushing 90 to 180 day approvals on residential PV+ESS. Build that into your customer expectations and your draw schedule, or you eat the float.

1. Lead with the load calc per NEC 220 and the existing service capacity. Most retrofits stall here.
2. Confirm the busbar rating and main breaker before promising a backfed PV or ESS breaker.
3. Verify utility interconnection rules for export limits, anti-islanding, and meter configuration.
4. Pull the AHJ checklist for PV and ESS before the rough-in, not after.
5. Document rapid shutdown initiator location, labels, and the placard at the service.