Solar PV Roof Mount  (photo voltaic) grid tied system, takes the sun's rays to create electricity. For every 100 square feet you can make 1,000 watts or 1kW. In Pennsylvania  the average solar exposure is 4 hrs a day all year round.

Pricing for roof mount solar PV systems
1.24kW : Time and Material $75 per guy (Small/Custom system)
3.1kW : $8,680
4kW $10,440
5kW $12,000
8kW $ 18,800
10kW $23,100
​50kW :  $111,000
-commercial is cheaper than residential, residential generally has dark hardware, rails & a skirt that help it integrate in with the roof structure
-Extra's Hidden conduit/ junction box fee
-Price to compare is $2.35 for roof mount solar PV systems. Updated 1/10/2022
*50kW is priced at $2.22 a watt
Pricing is a little different for ground mount installations due to more infrastructure, call to get a price for your solar PV system. Have a good day!

Break it down:
If you have a 4.5kW solar PV system, the formula goes like this, 4500 x .80 efficiency =3,600. Take 3,600 x 4 hrs =14,400 watts or 14.4kW hrs will be generated a day. Take 14,400 x 30 = 432kW hrs a month would be generated. So if your electric utility bill is $110 a month, and it cost $.14 a kW. Take 110 / .14 = 785.71kW . The 5kW solar pv system would cut your utility bill in half.  You'r utility bill would go from $110 to $50 a month. 26% Federal tax credit is good till the end of year 2022 and then will decrease to 25%. Estimated return on investment return would be 10 years.