The Utility-to-Utility Gap, in Real Numbers
Permission to Operate, often shortened to PTO, is the utility’s formal sign-off that lets a completed solar system actually turn on and start generating. Aurora Solar’s own glossary defines interconnection as the process of connecting a system to the grid, ending in that PTO approval, and defines PTO itself as the utility’s go-ahead.
How long that review takes depends entirely on which utility is reviewing it. EnergySage’s own installation-timeline research puts Duke Energy’s typical PTO review at around 14 days, while some California utilities take 30 or more days for the same step, on a system that is, in every other respect, identical. Nothing about the panels, the installer, or the paperwork explains that gap. The utility does.
Where Interconnection Sits in the Full Timeline
Interconnection is the last of four stages between a signed contract and a system going live. Scheduling and design typically takes 1 to 2 weeks. Permitting, reviewed by the local Authority Having Jurisdiction rather than the utility, typically runs 2 to 4 weeks. Physical installation itself takes 1 to 3 days of work, though crew-scheduling can add another 1 to 2 weeks before that work even starts. Inspections and utility interconnection close out the process, typically 1 to 4 weeks.
Added together, industry experts put the full signed-contract-to-operating window at roughly 60 to 90 days. Interconnection sits at the very end of that chain, which means a slow utility does not just add its own delay, it adds that delay on top of every stage that already ran before it.
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Book a Solar CallWhy the Utility Step Specifically Runs So Unevenly
The research behind this guide does not break out exactly why one utility’s queue clears in two weeks while another’s runs past a month; the available data documents the gap itself, Duke Energy near 14 days against some California utilities past 30, without publishing the internal reasons behind it. What the pattern does show clearly is that interconnection runs through the utility’s own internal review process, a separate system entirely from the local permitting office that handles the AHJ stage earlier in the timeline.
That separation matters for how a sales team should talk about it. A fast permit does not predict a fast interconnection, and a slow interconnection in one utility’s territory says nothing about how that same utility handles permitting, because different offices, on different systems, are running each stage.
What a Sales Team Should Set Expectations Around
Do not quote one universal Permission to Operate timeline across every market a team sells in. Ask which utility territory a specific address falls under, and treat the 60-to-90-day full-process window as an industry-typical range rather than a guarantee, particularly in California, where PTO review specifically runs slower than the roughly 14-day pace documented at Duke Energy.
A homeowner who hears “about two to three months, and it can run longer depending on our utility” at signing is far less likely to call in frustrated at week six than one who was told a specific date nobody actually controlled.
What this means for you
- Utility Permission to Operate review alone ranges from about 14 days at Duke Energy to 30 or more days at some California utilities, for an identical system.
- Interconnection is the last of four stages in a roughly 60-to-90-day signed-contract-to-operating timeline, so a slow utility adds delay on top of everything before it.
- A fast local permit does not predict a fast utility interconnection; the two run through entirely separate review processes.
Sources
The external data in this guide draws on the sources below. Figures described in the text as estimates or industry triangulations are directional and are not attributed to a single dataset.