Download Free (.pdf)PVWatts
An NREL modeling tool used to calculate solar production output based on location, orientation, and system size.
PV Self-Consumption
A strategy that prioritizes using on-site solar generation by charging the battery when solar output exceeds load and discharging when solar production drops. This reduces grid imports and increases renewable energy use on-site. It is common in regions with low export compensation.
Non-Export Limitation
A requirement that prevents a system from sending power back to the utility grid. Controls ensure net site output stays at or below zero kilowatts at all times. These requirements are common in jurisdictions with strict protection rules or limited grid hosting capacity.
Net Billing/Net Billing Tariff
A rate structure where exported energy is compensated at a different (often lower) rate than imported energy.
Import Limit
The maximum power a facility is permitted to draw from the grid at any moment. Storage or on-site generation may be used to stay below this value. These limits help prevent overloading utility or facility infrastructure.
Grid Resilience
The ability of the electric grid to absorb, adapt to, and recover from disruptions such as extreme weather, equipment failures, or security threats.
Export Limit
A restriction on how much power a facility can send back to the utility grid. These limits protect upstream equipment and are common in non-export or partially exporting systems. Storage controls must ensure total site export remains within allowed values.
DC Rating
The total rated capacity of a solar array measured in DC watts under standardized test conditions.
Azimuth
The compass direction a solar array faces, measured in degrees (e.g., South = 180°).