NREL has released a new version of PVWatts® on September 8th, 2014 that changes the results significantly to more accurately reflect PV performance outputs from current systems. Note that the results will typically increase 7 to 10 percent. This version updates the default derate/loss values, uses a modern inverter curve and adds several options. You can read more about this update here. You can still access the old versions of PVWatts V1 and PVWatts V2 until NREL is satisfied that your needs are met with the new version. At that point (within the next six months probably), all older versions of PVWatts will be retired.
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