As for actual advice, you might save some by buying components yourself and getting quotes just for installation.

You can buy panels for around 60c/watt, inverters for 30c/watt, and the balance of components for a few thousand on top of that. If labor is about $50/hr, you'll get about 3 man-days of work per $1,000. Most residential install crews are 3-4 people, and they can do a system in 1 day. Double or even triple that and you're still in the $3k-$4k range for install labor. $1.50/watt all in is do-able. Minus solar credit, and perhaps local credits, $1.00/watt is not unheard of.

If you can get equivalent of 5x system capacity in kWh per day, on a 10kW system that's 50kWh per day. 8c/kWh price would be $4-5/day, $100+/month. $15k - 10kW ($10k with credits) system pays off in 100 months or less (8.3 yrs).

That's the math I am penciling out for my own home renovation and install later this year.

27kw system!?

Unless you live in a giant mansion, or in a warehouse, there is no way that much solar is going to fit on your roof.

Most houses will max out around 8-10kW, unless they are very large, or have their entire roof area optimally oriented in single large planes.

Even the most advanced panels these days make 20 watts per SF. To get 27,000 watts you would need almost 1,500-2,000 SF of roof area completely covered. Considering most roof profiles have 1/4 to 1/2 of their roof planes pointed away from the sun, you probably need a 4,000+ SF single story house (or 6-8k SF two-story).

Not to mention, a lot of utilities limit the size of residential solar. I've seen as low as 10-15kW limits if you're on a single-phase 240v service.

But if you can get away with it, more power to ya! With a system that size you could probably get bids from commercial contractors who may be a little more cost effective, and won't have to charge as much overhead to cover their army of door-knockers.