In some areas it's as quick as three weeks. In other areas, it can take three months.
Most solar companies are ready to install your system the day after you say yes to getting it. The timeline has very little to do with the actual install company or the company who sold it to you. Most of the timeline is created by the utility companies, the jurisdictions that you live in, the city, and the County permitting. The timeline for when it gets installed is something you should definitely talk to your rep about because depending on the city you live in that's going to be different. Now once your install day comes, most installs that are under a 10 kilowatt system size take one day. It could be longer, it could be just six or seven hours, but for the most part, it's a day. Again, you should talk to your sales rep about this though. If they tell you it takes an hour, that's not real. But for the most part it's not going to be a three or four day process.