[RE-wrenches] How can I calculate ROI when the kWh rate varies through the day?

[Mick Abraham]

Hello, Mechanix~

A client requested a pure grid tie PV quote and of course I wish to help
him project ROI return on investment. PV Watts only allows a single value
to be keyed for the cents per kilowatt-hour, but my customer is on a TOU
"time of use" billing program, so from 1 P.M. to 5 P.M. the value of his
generated power is ~50% of the value during all other sunny hours.

Is there a more sophisticated ROI calculation tool that allows $0.xx per
kilowatt hour for one time interval then $0.yy in for a different time
interval? This particular situation then also needs $0.zz for a third
interval to get an accurate projection. The rooftop is skewed to the east
so that skews the power delivery to benefit those hours before the value
per kilowatt hour drops, so the ideal ROI tool would factor in that non-180
degree azimuth orientation, roof pitch etc.

If I can think of any way to make this question more complicated, I'll post
a follow up (!)

Thanks in advance. The Wrench List is da bomb!

Mick Abraham, Proprietor
www.abrahamsolar.com

Voice: 970-731-4675
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