I really enjoyed presenting the Photovoltaic Workshop for the NKCDC but wanted to show the math I started. Hopefully a few attendees read this and benefit from it. Promised Links are at end of post.
A 16′x16′ patch of roof is equivalent to 23m, the sun produces 1Kw/meter/day but common modules produce at ~17%. This leaves you with 170 watts per square meter or 3900 watts total. If you consider various inefficiencies you will produce approx 3500 watts AC from that system.
3500 Watts at $7/watt installed is going to cost you $24,500.00. In PA you will only receive the 30% federal rebate and various minor incentives leaving you with approximately $16,000 overall cost. If you pay this over 5yrs compound interest at %8/yr your monthly payment will be ~$330/mo. The modules you install have a GUARANTEED lifespan of 25 yrs and Inverters generally have a 10-15yr lifespan. So after the five years of slightly higher than average payments the modules will be nearly free. They do need to be cleaned once in a while and inverters do occasionally go bad.
The more time you invest in and understand your system the cheaper and more effective it will be. If you have any questions don’t hesitate to email or call me. Good Luck!
Design and Analysis Software
- Sketchup (free 3D design software from Trimble)
- ResCheck (free residential energy compliance software)
- PV WATTS (NREL)
- Appropedia (Appropriate Technology Wikipedia) software links
Do it Yourself (DIY) Alternative Energy
Documents and Articles