Photovoltaic System Worksheet

Do you have ambitions of putting a Photovoltaic array on top of your house and disconnecting your electric company? Or, of staying attached to the grid and selling electricity back to them? This worksheet does a simple, "back of the envelope" calculation of PV system economics (Please do a more careful sizing before you buy something!), and can help you understand many of the tradeoffs that are involved in using this increasingly popular renewable energy technology.

Enter information about your electricity consumption, your cost of service, and your local sunshine, and this worksheet will help you investigate the relative cost of installing a photovoltaic system that meets your needs. You can click on the "?" button in any table entry for more explanation and help.

Electric Utility Photovoltaic System
Monthly Electricity Usage (KWH)
Average Daily Sunlight Hours
Percentage of energy from battery storage
Grid Attachment Cost
PV System Peak Wattage Requirement
Electricity Cost ($/KWH)
PV System cost per peak watt ($$)
PV System Yearly Expense
PV System Lifetime(years)
Displaced Grid Electricity Cost ($$)
PV System Cost ($$)

Two other things to consider: An increasing cost of electricity (at percent per year) will increase the present value of your future grid-supplied electric consumption, while the time value of money (at percent per year) decreases it, as well as the present value of yearly PV operating expenses.

Comparing the cost of the PV system to the displaced electricity cost, you will probably conclude that disconnecting the electric company won't save you money right now. On the other hand, it is feasible and not incredibly expensive, particularly if you live in an energy-efficient way. Also, note that if the electric grid isn't near, PV generated electricity may be the cheapest option.

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