Can I install the panels before the permit is approved?

You should not. If the plan comes back requiring changes — a different inverter for rapid shutdown, different attachment spacing, a relocated disconnect — you will be undoing finished work, and some inspectors take a dim view of work that was clearly completed before approval. Wait for the permit.

How long after installation until I can actually use the system?

Typically three to eleven weeks: inspection scheduling, then the utility's interconnection processing, then Permission to Operate. This final wait is the one people find hardest because the array is finished and visibly doing nothing. Running your interconnection application in parallel with the permit shortens it more than anything else.

Is winter a bad time to install solar?

For the roof work, yes — cold, ice and short days make it slower and considerably more dangerous. For the paperwork, winter is ideal: building departments and utilities are less busy than in spring. A common approach is to do permitting and utility application over winter and the physical installation in early spring.

How Long Does a DIY Solar Installation Actually Take?

Two to four months from decision to switch-on, of which only about a week is physical work. Where the weeks actually go, and which delays you can compress.

People plan a DIY solar installation around the weekend they will be on the roof, and are then surprised that the project takes a season. The physical work is genuinely about a week. Everything else is waiting — for a plan set, for a permit, for an inspector, for a utility. Knowing where the weeks go lets you overlap them instead of running them in sequence.

The realistic timeline

Phase	Your hours	Elapsed time	Waiting on
Research, design, load analysis	10 – 20	1 – 3 weeks	You
Equipment selection and ordering	3 – 6	1 – 4 weeks	Shipping
Plan set and permit application	5 – 15	2 – 8 weeks	Building department
Physical installation	30 – 50	3 – 7 days	Weather, help
Electrician for service tie-in	1 – 2	1 – 2 weeks	Their schedule
Inspection	2 – 4	1 – 3 weeks	Inspector availability
Utility interconnection and PTO	2 – 4	2 – 8 weeks	The utility
Total	55 – 100	8 – 20 weeks

Note the ratio. Roughly 55-100 hours of your effort spread across two to five months, and the three longest waits — permitting, inspection scheduling and utility approval — are entirely outside your control.

The delays you can actually compress

Call the building department before you design. Finding out which NEC edition they enforce and whether a stamped plan is required takes one phone call and can save a full redesign cycle.
Buy a kit with a permit-ready plan set. This removes the single most common multi-week delay. If your vendor does not include one, budget for an engineer early rather than discovering the requirement at submission.
Start the utility interconnection application in parallel with the permit. Many utilities accept applications before installation. Running these in sequence rather than in parallel adds a month for nothing.
Book the electrician before you need them. Good ones are booked weeks out, and this is a small job they will fit around larger ones.
Get the plan set right the first time. Corrections rounds are the largest avoidable delay, and first-time applicants very often get at least one.

The delays you cannot

Inspector scheduling and utility processing run at their own pace and no amount of preparation changes them. Utility interconnection in particular varies from about two weeks to a couple of months depending on the utility's backlog, and it comes last, after everything else is finished — which means the most frustrating wait is the final one, staring at a complete array you are not allowed to switch on.

Seasonal load matters too. Building departments and utilities are busiest in spring and summer, which is also when everyone wants to install. Starting the paperwork in late winter for a spring installation is a genuine advantage.

Where first-timers lose the most time

Ordering equipment before the permit is approved, then discovering the plan needs changing — now you own the wrong inverter
Missing the rapid-shutdown requirement in the design, which changes the inverter and optimiser choice entirely
Failing inspection on labelling or grounding — both trivially avoidable, both common, and each failure costs another scheduling round
Losing a weekend to weather, which is why a three-day job becomes three weekends
Not lining up a second person for panel handling, since panels are unwieldy and unsafe to place alone

Is it worth 55-100 hours?

At $10,000-15,000 saved against a professional installation, that works out to roughly $130-250 an hour. For most people that is a strong return on time — but it is time spread over months, largely in administrative work rather than the satisfying part, and the failure mode is abandoning the project half-finished.

If a two-to-five-month timeline does not fit your circumstances, the honest options are a professional installation or a standalone off-grid project, which skips permitting, inspection and interconnection almost entirely and can genuinely be done in a weekend. The cost comparison for both paths is in DIY versus professional installation.