The short version
- Signature to switch-on is commonly two to four months. The install itself is 1–3 days of it.
- Permitting and utility approval are the long poles, and neither is in your installer’s control.
- You cannot legally run the system until the utility grants permission to operate.
- Ask for the timeline in stages, not one number — it tells you whether they have done this locally before.
Where the time actually goes
Almost everyone underestimates this, because the visible part — a crew on the roof — is the shortest part. Here is the whole sequence with realistic ranges.
| Stage | Typical duration | Who controls it |
|---|---|---|
| Site survey & design | 1 – 3 weeks | Installer |
| Structural / electrical engineering review | 1 – 2 weeks | Installer |
| Permit application & approval | 2 – 8 weeks | Your city or county |
| Installation | 1 – 3 days | Installer |
| Inspection | 1 – 3 weeks | Local inspector |
| Permission to operate (PTO) | 2 – 6 weeks | Your utility |
Ranges overlap in practice — engineering often runs alongside permitting. Two to four months end to end is normal; six is not unusual in a slow jurisdiction.
Permitting is local, and that is the whole problem
There is no national solar permit. Your authority having jurisdiction — usually the city or county building department — sets its own requirements, queue and fees. Two houses twenty minutes apart can face completely different waits.
Some jurisdictions have adopted automated instant permitting for standard residential systems and turn approvals around in days. Others still require a full plan review with a multi-week backlog. Neither you nor your installer can change which one you live in.
What an installer can do is submit a complete, correct application the first time. Resubmissions after a rejection are the single most common avoidable delay, and they are a fair proxy for how often a company has worked in your area before.
Permission to operate: the step people forget
After the array is installed and inspected, it stays switched off until your utility grants permission to operate. This is not a formality you can skip: running an unapproved system that exports to the grid is a safety and tariff issue, and utilities do enforce it.
PTO involves the utility verifying the interconnection paperwork and, in many cases, swapping your meter for one that measures flow in both directions. The wait varies by utility rather than by state, and it is the stage where finished arrays most often sit idle for weeks. What the utility does after PTO — how it credits the power you export — is set at state level and covered in net metering explained and on the state pages.
Season matters more than you would think
- Spring and late summer are peak. Installer schedules fill and lead times stretch. Booking in the off-season often means an earlier date.
- Winter installs are normal in most of the country. Cold does not stop the work; heavy snow or ice on the roof does, and that is a day-by-day call.
- Incentive deadlines create surges. When a state programme is stepping down, everyone applies at once and every stage lengthens. Starting early is worth more than negotiating hard.
What to ask before you sign
- "What is your average permit turnaround in my jurisdiction?"A company that works your area regularly will answer with a number. A vague answer tells you something.
- "Who submits the interconnection application, and when?"It should be them, and it should be early — not after installation.
- "What happens to my price if this runs past the incentive deadline?"Get it in writing if a time-limited incentive is part of your maths.
- "What is the payment schedule against these stages?"Payment tied to milestones is normal. A large deposit with no milestones is a red flag.