Administration - Roof Effectiveness Score (RES) Parameters

Setting RES Threshold Values

SolarNexus' exclusive Roof Effectiveness Score (RES) feature provides you an objective measure of a given roof's effectiveness for a PV system installation.  Users with administrative permissions can set the threshold for what RES is considered an excellent lead and for what is considered the minimum acceptable RES for your company's leads.

These Roof Effectiveness Score limits are set at Administration > Lead and Job Data > Roof Effectiveness Score.  The initial values for an excellent RES threshold is set at 90.  As your company gains experience, you may wish to increase or decrease this value.  Likewise the minimum acceptable RES is initially set at 75.  These threshold values are reflected on all RES charts with colored ranges in the background,.

Setting RES Calculation Parameters

The SolarNexus algorithm considers both the solar production and the array layout when calculating the best configuration for PV arrays of different sizes.  First, a maximum array is created with modules populating all roof surfaces.  Then, the least effective 1 kW is removed, until the system size is at 2 kW, with RES values being calculated for every size.  Two RES parameters may be configured: the 'Keep Array Threshold' and 'Multi-Array Effectiveness De-Rate.'

Keep Array Threshold

The Keep Array Threshold is used by the algorithm to preferentially remove the last 1kW array from a roof even it would be more productive in kWh than removing a 1kW of modules from a larger array. A good way to think about this is to ask 'how much more productive would a 1 kW array need to be when compared to removing the same 1 kW of modules from a larger array?'  SolarNexus populates a default value of 1.5.  This value helps ensure that there will not be multiple 1kW arrays in the system, even if they could produce marginally more kWh than fewer, larger arrays.

Multi-Array Effectiveness De-Rate

The multi-array effectiveness de-rate value is used to quantify the additional cost and complexity of additional arrays.  A typical value is 0.04 (4%).  The larger the multi-array de-rate value, the greater the reduction in RES value when an additional array is added to make the system larger.  The first graph below was computed with a value of 0.02.  As the system size increases from four to five kWs, a second array is added and there is a drop in RES to account for the added cost.  At a value of 0.02, this drop is rather small.

If the multi-array effectiveness de-rate value is increased to 0.08, the RES value drop is much larger as a second array is added, as shown in the RES graph below.

Expected Behaviors when RES Parameters are Changed

• Changing RES Threshold values will immediately be reflected in all RES charts for individual jobs, but the scores will not be changed.
• Changing RES calculation parameters will effect all future RES calculations.  If you wish to recalculate RES values for an existing project, you must unconfirm and reconfirm the site location.