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Contractor glossary

Permission to operate (PTO)

Updated

Definition

Permission to operate (PTO) is a utility's written approval to turn on a grid-tied solar system. It's the last step of the utility's interconnection process, separate from the building department's inspection, and the system should stay off until it arrives.

Also called: PTO, Interconnection approval

Two approvals from two different offices

A grid-tied system has to clear two separate gates, and passing one doesn't mean passing the other:

Approval Who gives it What it covers
Final inspection The local building department The installation meets the codes that jurisdiction enforces
Permission to operate The utility The system may connect to and run on the utility's grid

A passed inspection means the work is approved. It doesn't mean the system can be switched on.

How a job gets to PTO

Each utility runs its own interconnection process, so learn the steps in every territory you sell in before you promise a date. On many jobs the path looks like this:

  1. Interconnection application. Find out whether the utility has to approve it before you install or reviews it afterward.
  2. Installation and final inspection by the building department.
  3. Completion paperwork to the utility, which may include the inspection approval, a final diagram and equipment details.
  4. A meter change or site visit, if the utility requires one.
  5. PTO, the notice that the system can run.

Keep a copy in the job file and in the customer's closeout package; a lender, an incentive program or a future buyer of the house may ask for it.

Planning around the wait

The wait between a passed inspection and PTO is mostly out of your hands and can vary by utility and by month. Three habits help:

  • Track it. Log the inspection date and the PTO date on every job, by utility.
  • Put it in writing. Your proposal and contract should say the system stays off until PTO, with a realistic range taken from your own records.
  • Size what waits on it. If your final payment, or a lender's last funding, is due at PTO, keep that amount small enough to carry through your slowest utility's wait.

Example: Your last six jobs in one utility's territory took 9, 12, 14, 15, 21 and 30 days from passed inspection to PTO. Tell customers to expect two to four weeks, and plan your cash for the long end. If $3,000 of each job is due at PTO and you finish four jobs a month, up to $12,000 can be waiting on that utility at any time. The numbers are made up for illustration.

Common mistakes

  • Letting the customer switch it on early. Panels on the roof look finished. Show the customer how the system is shut off, tell them in writing to leave it that way, and let the utility's approval decide when it runs.
  • Treating PTO as the end of the job. Finish monitoring setup, warranty registration, the closeout package and your final invoice the day PTO arrives, if they aren't done already.
  • Assuming PTO covers later changes. Adding modules or a battery, or swapping in a different inverter, can need a new utility review. Ask the utility before you change a system that's already approved.
  • Promising credits from day one. Explain when the customer's net metering or export credits begin, the way their utility describes it, so the first bill after PTO isn't a surprise.

How it connects

PTO can be the last milestone in a solar progress billing schedule, and until it's paid, that balance sits in your accounts receivable. The building department's side of the job runs through the building permit. From PTO on, the customer judges the system by the kilowatt-hours it produces against your estimate. How to invoice solar installations covers choosing inspection or PTO as the trigger for your final payment, and how to start a solar installation business covers mapping each utility's interconnection steps.

Go deeper

Solar guideHow to Invoice Solar InstallationsHow solar installers bill in milestones: deposits, equipment and install payments, PTO, lender funding, panel upgrade change orders, lien waivers and serials.Solar guideHow to Start a Solar Installation BusinessStarting a solar installation business in 2026: state licensing, NABCEP credentials, permits and SolarAPP+, utility interconnection and the end of 25D.Solar guideHow to Write a Solar ProposalBuild a solar proposal from 12 months of usage: production assumptions, equipment and warranties, price per watt, financing, incentives and honest savings.Solar guideHow to Get More Solar CustomersHow solar installers win customers in 2026: honest pitches without the federal credit, lawful door knocking and texting, referrals, trade partners and follow-up.
Net meteringNet metering is a utility billing arrangement that credits customers with onsite generation, such as rooftop solar, for electricity they send to the grid, so it offsets power they buy at other times. Whether it's offered, and what an exported kilowatt-hour is worth, varies by state and utility.Building permitA building permit is written approval from the local building department to do regulated construction, plumbing, electrical or mechanical work. It comes with inspections at set stages, and the job isn't finished until the inspector signs off on the final.Progress billingProgress billing is invoicing a job in stages as the work is completed, instead of sending one invoice at the end. Each invoice bills the part of the contract earned so far, either for reaching agreed milestones or by percent complete against a schedule of values.Accounts receivableAccounts receivable (AR) is the total your customers owe you for work you've done and invoiced but haven't been paid for yet. It's money you've earned but can't spend, which is why a busy month can still leave you short on cash.Kilowatt-hour (kWh)A kilowatt-hour (kWh) is a unit of energy equal to 1,000 watts used for one hour. Utility bills charge for electricity by the kWh, and a solar system's output is estimated in kWh, while its size is rated in kilowatts (kW).

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