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

[Mac Lewis]

Hi Mick,

There are many tools that would do this.  As far as free tools, NREL has a
program call the System Advisor Model (SAM) https://sam.nrel.gov/ that you
can download for free.  There is a learning curve with it for sure, but its
powerful.

If you are comfortable with spreadsheets, you can use PV watts to generate
hourly output and then apply time of use pricing to energy outputs.

I believe they are both built on the same computational engine, but PV
watts is much simpler.



On Wed, Apr 8, 2015 at 2:15 PM, Mick Abraham <mick at abrahamsolar.com> wrote:

> 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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-- 



Mac Lewis

*"Yo solo sé que no sé nada." -Sócrates*
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