String count vs. module count: which one proves construction progress?

A draw request lands with a percent-complete number attached to it, and nobody on the lender side asks which count sits underneath it. That's a gap worth closing before the next milestone is certified, because string count and module count answer two different questions, and only one of them usually matches what the loan agreement asks for.

What each number counts

A string is a series of modules wired together into one DC circuit feeding a combiner box or an inverter input. Counting strings tells you how much electrical termination work is done. It does not tell you how many physical panels are sitting on the racking. A string can show complete in a commissioning log before every module in that string has been torqued down, and the opposite happens too: whole rows get mechanically installed and sit untouched for weeks before an electrical crew comes through to terminate them.

Module count is the simpler of the two. It's a physical tally of panels installed on the racking, table by table, regardless of whether the wiring behind them is finished. Module count cares only whether the panel is bolted to the array, independent of combiner boxes or inverter inputs further downstream.

Why the gap matters for a draw schedule

Interconnection schedules and drawdown milestones are almost always written against physical installation, something like "90% of modules mounted," not against electrical completion. An EPC reporting string completion as a stand-in for module completion will overstate progress on any site where the electrical trade is running behind the racking and procurement crews, which happens constantly when a GC is pushing mechanical install hard to hit a weather window. It also runs the other way on sites where strings get pre-terminated in staging ahead of full-row torque-down, understating the true mechanical count if that's all a lender is looking at.

Neither number is wrong on its own terms. String count tells you something real about readiness for interconnection testing. Module count tells you whether the construction milestone written into the loan agreement has actually been met in the field. The trouble starts when a monthly report quotes a single percent-installed figure without saying which of the two it's drawn from, and a lender finds out only after the draw has already closed.

Which one belongs in the draw certification

If the milestone language says "installed modules," the number certifying that milestone needs to be a module count taken from the array itself, counted independent of any wiring percentage quoted in a weekly progress report. String count can legitimately run ahead of or behind the physical module count depending on how an EPC sequences its crews, which makes it a poor substitute whenever the specific thing being financed is the array buildout, not the electrical commissioning.

This is also where self-reported progress tends to get soft. A contractor under schedule pressure has an obvious incentive to round the array count up to match a healthier-looking string number, or to quote whichever figure is higher that week. None of that requires bad faith. It just means the two numbers get blended in a way that's hard to untangle from a spreadsheet alone.

An independently counted module inventory pulled from site imagery each quarter sidesteps that blending. It counts physical panels in place against what the interconnection schedule or drawdown milestone specifies, without routing through the EPC's own wiring logs or progress estimates.

If the next draw hinges on a module count, it's worth having one that didn't come from the EPC's own report.