How We Got, What We Got
1. The Array: 6.86 kW STC, (28)Trina TSM-245PA05.08 Modules, (1) SMA SB 7.0-1SP-US-40-240V, Ground Mount,Tilt Angle of 35°, Location St. Louis ,Mo, Lat 38.6270° N.
Modeled using Sunny Design 3 software.
Performance Ratio: 87.3%
Beginning annual energy yield of 10, 232.2 kWh.
Assumed output decrease of 0.7%/yr., 80% power output by year 25. (Typical power warranty)
Output of 8,244.6 kWh in year 25.
25 year yield = 231,748 kWh.
(2)The Array: 7kW STC, (26) Jinko Solar JKM270M-60B Modules, SMA SB 7.7-1SP-US-40-240V,
Roof Mount 23° (5in 12 roof pitch, shingled), Location Springfield, IL, Lat. 39.7817° N.
Modeled using OnGrid
Beginning annual solar production of 9,687 kWh
Inverter replacement @ year 15, $1,400.
System Maintenance 0.15% of gross cost.
Annual module degradation of 0.5%.
System Efficiency of 78.8%.
Installed cost of $1.95/watt, $13,689 (yr. 2018)
30% Federal Tax Credit included.
Sources:
U.S Residential Electricity Price- EIA


7% Investment

After Tax Inv - Electric Bill w/o Solar
7% Investment w/Solar


The Cost of Doing Nothing
Assuming a 2%/year increase in electricity rates.
897 kWh per month usage.
Solar Savings
Assuming a 2%/year increase in electricity rates.
897 kWh per month usage.
Module degradation of .5% per year,
Inverter replacement @ year 15.($1,400)