What is permission to operate (PTO) for a solar array?

Are you waiting to turn on your home solar panels? Here's how the process for getting PTO works.

Question mark (photo illustration)
Credit: Towfiqu Barbhuiya/Unsplash

If you are having a home solar system installed, in almost all cases it will be interconnected with the grid.

This means that you will still have service from a utility company, and there will be times when you buy electricity from the utility and sell excess solar electricity to them. The process of obtaining this type of two-way connection between your solar home and the grid is called grid interconnection.

For a homeowner, the final step to completing interconnection is getting permission to operate (PTO) from the utility company. In most cases this process is quick, but once in awhile there can be delays. While it’s understandable that interconnection is a regulated process, for the homeowner who just had solar panels installed and is waiting to turn them on, the wait can be frustrating.

Getting PTO for residential installations usually takes days or months, which can be a frustrating delay when the system is ready to go. There often isn’t much you can do but wait.

This article will help explain what permission to operate means, and why delays can happen.

What is permission to operate?

Even after the work of installing solar panels on your home is done, you can’t turn them on until the utility company has granted you permission to do so. This means that the power cutoff switch for the system will be in the “off” position until the utility has notified your installer that permission to operate (PTO) has been granted.

This might be confusing because one of the first steps in the installation process is to apply for interconnection with the utility. If you have a permit, shouldn’t you be able to turn the system on?

Not quite. The interconnection application only gives you the go-ahead to start the project. PTO is granted after the final inspections have been done, which might involve your city’s electrical inspections and other permits. In other words, you can only have permission to operate once your system has passed all its final inspections.

Once the permits and inspections done, the installer can finally apply for PTO with the utility company. This is the last bureaucratic hurdle you need to clear in your home solar project.

How long do you need to wait for PTO?

In 2015, the National Renewable Energy Laboratory (NREL) released a study (PDF) showing that the median time between applying for PTO and receiving approval varies widely across the country. At the time of that study, the median wait was 10 days. However, it also showed that the wait time differs between states, and delays can add weeks even in states that have shorter wait times.

This study was based on data between 2012 and 2014, but newer data is available. The NREL has a tool called SolarTRACE that allows you to look up the median amount of time it takes for your city or state to issue permits, perform inspections, and grant PTO. At the time of writing, the last set of data was from 2021.

Use SolarTRACE to find out PTO times in your area

To use the tool, navigate to the tool and scroll down to the section titled “START USING SOLAR TRACE”. Enter your location.

Once you do that, you’ll see a chart and table with data on median wait times. Here are the results I got for Sacramento, CA:

Screenshot of SolarTRACE

If you point your mouse at each of the bars in the graph, you’ll get more detail. (Unfortunately, the page isn’t mobile-friendly, so it won’t be very usable on your phone.) In this example, you can see that the median time it takes the City of Sacramento to approve permits is 3 days. “Pre-Install IX” refers to the interconnection permit you need before installation can proceed, and it varies by utility company, which is why there are two bars for Sacramento - one for Pacific Gas & Electric, and another for Sacramento Municipal Utility District.

The next bar is the median time it takes the City of Sacramento to complete inspections, and the final pair of bars is “Post-Install IX”, which is median time for the utility companies to grant permission to operate.

If you scroll the page a little further down, the same data is also presented in a table. It includes a little extra data not shown in the graph, such as the number of business days that the utility company is required to respond to applications by.

Median installation, permitting, interconnection, and total project times by state

The SolarTRACE tool also reports on the median times for the various stages of residential solar installation projects by state. You can see this data when do you a search for your location - the state-level data will be at the bottom of the page.

Here’s the data for some of the largest states for home solar:

StateAHJ Permit TimePre-Install Interconnection TimeInstall TimeInspection TimePost-Install Interconnection TimeTotal PII Cycle Time
New Jersey156112210100
New York82108473
New Mexico82614128103


AHJ Permit time: The Authority Having Jurisdiction is the local agency responsible for issuing permits for your project. This is usually a city government, but rules vary across the country. You can look up the AHJ for your address using this tool created by SunSpec.

Pre-Install Interconnection Time is the time is takes for interconnection permits before installation starts. Not all jurisdictions will have this, which why some states have zero times.

Install is the time it takes for installers to complete their work. This is the median for all installers in the area, and you can expect this to vary widely by installer.

Inspection Time is the post-installation inspection by the AHJ.

Post-Install Interconnection Time is the time it takes the utility to grant permission to operate.

Total PII Cycle Time is the total amount of time taken by the project from contract signing to PTO. Note that this is longer than the sum of other times in the table because not every stage is tracked by this tool.

Reasons why PTO can be delayed

As you can see in the SolarTRACE data, in most states the median wait time for PTO is a couple weeks at most. If your project is taking much longer than that, here are some possible reasons.

One is that the office responsible for processing permits can get swamped at times. Holidays and busy seasons for solar installation can result in a paperwork backlog. For example, as the deadline for California’s net metering change approaches, you can probably expect permitting delays.

Another possible reason is a failed inspection. Remember that PTO is granted once all final paperwork is filed, the work is done to code, and permits are granted. If your project failed to pass inspection, that can be a reason why PTO hasn’t been granted. Installers might not always be upfront about this and blame the utility for permitting delays, but the process exists to ensure that your project is installed safely and up to code.

To be clear, most installers will be transparent and honest about the process along the way, but unfortunately some of the biggest solar installers in the nation have records of poor workmanship and questionable business practices, leading some of them to go bankrupt. This underscores the need to get multiple quotes and ask the installers plenty of questions before you hire one for your solar installation.

#Installation Process

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