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EC Pro - I receive "free" KWH from a roof-mounted solar arrays. How do I track this? Does it affect cost avoidance?
Posted by Joel Brickell, Last modified by Joel Brickell on 29 December 2016 09:27 AM

I receive "free" KWH from a roof-mounted solar arrays. How do I track this?  Does it affect cost avoidance?

Assumptions:

* The solar system provides electricity to the host building first.  Any excess electricity is either stored or directed back to the grid.

* The solar system will never provide 100% of the host building's monthly KWH.  The building will also be served by conventional metered electric power.

* When energy management initiatives result in reduced usage of KWH, the reduction comes from the conventional power and not from the solar.  The solar KWH is the base load that is always fully consumed. The conventional grid power meets the variable load on top of that.  When KWH is avoided due to energy management, only conventional power usage is avoided, never solar.

* It would be foolish to avoid free solar KWH, so in the event that the array is sized so large that the building cannot use all of it, the excess is stored, used in an adjacent building, or sold back to the grid.  In this way, energy management will never cause avoided solar KWH.

Because avoided KWH in buildings that host solar arrays is always conventional power, the cost avoidance should be calculated using the prevailing average unit cost of conventional power and not a lower value that includes the impact of solar credits or free KWH.  So, a CAP Adjustment must be created for this meter to set the desired unit cost.  Use the Cost Avoidance = Avoided Use x Unit Cost option, specifying the unit cost in the Amount field.  (The second last CAP Adjust option)  To determine the unit cost, look at the average unit cost of similar non-solar buildings, or use an actual bill and calculate the unit cost of the conventional power.

A new feature in Pro 2011 (2Q11) allows you to track green energy credits in bill details. These green energy credits are then taken into account on the carbon footprint reports (CAP 15, 15A, 15B, 19).  The solar KWH, but not the conventional power, is green energy.

 

Created by Steve Heinz (07/20/2010) EnergyCAP Professional version 2009 SP1

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