This calculator searches an actual catalog of 199 Grundfos pump models with published performance curves, instead of a generic power formula. Enter the required flow (Q) and head (H) - typically the output of a Pressure Loss or System Curve calculation - and every catalog pump's curve is interpolated to find its head at that flow. Pumps whose curve actually reaches or exceeds the required head are scored on distance from their Best Efficiency Point (BEP), whether the operating point falls in the manufacturer's recommended flow range, and overall efficiency. If no single pump covers the duty, parallel (flow-adding) or series (head-adding) multi-pump configurations are proposed automatically from the same catalog. Catalog coverage today is strong for Heating/Cooling/DHW circulation (61 pumps) and Pressure Boosting (up to 138 general-purpose pumps), but there are no dedicated Fire Fighting or Drainage/Submersible pumps yet - those searches will come back empty, reflecting a catalog gap rather than a search error.