Residential renewable energy systems, both PV electric and Solar Water Heating, can reduce greenhouse gas emissions and air pollutants, but homeowner's decisions on selecting technology are ususally based on energy cost savings and system payback. Comparing Solar Water Heating to PV electric systems, we can summarize by comparing efficiency, installed cost, and resultant cost per KWH. Residential Solar water heating systems (two collector/80 gallon) typically offer collector efficiency of 50 -70%; system efficiency of 35-50%; installed cost of $8000.; and resultant energy generating cost of $0.09 per KWH. PV electric systems (grid tied-2 KW) offer module efficiency of 5-19%: system efficiency of 4-13%; installed cost of $20,000.; and resultant energy production cost of $ 0.27 per KWH.(three times more) You need to note federal and local rebates and incentives can decrease these costs, so actual resultant costs can vary. Bottom line is solar water heating remains your best renewable energy investment. Contact us to learn about the Velux system. . | 
