Automation

Cobot ROI and Payback Period: Numbers Every Plant Manager Needs

AGV fleet size = total required moves per hour x (travel time + load/unload time) / target utilization. Here is how to calculate it and avoid both over-specifying and under-specifying your fleet.

AGV Fleet Size = (Total Required Moves per Hour x Average Cycle Time per Move) / Target Utilization. Average cycle time per move = travel time (loaded) + load/unload time + travel time (unloaded/repositioning). For a facility needing 30 moves per hour with average 6-minute loaded travel, 3-minute load/unload, and 4-minute repositioning = 13-minute cycle. At 75% utilization target: fleet size = (30 moves/hr x 13 min/move) / (60 min/hr x 0.75) = 390/45 = 8.7 vehicles, round up to 9.

Move frequency analysis requires mapping all material flows in the facility. Count: number of unique routes, frequency per route per shift, load sizes, and priority classes. The peak hour move requirement (not the average) is the correct sizing input. If average is 25 moves/hr but the peak hour is 40 moves/hr and you size for average, you will have a capacity shortfall 20% of the time. Size for 90th percentile peak unless you have explicit buffer inventory strategy.

Travel speed varies by AGV type and facility environment. Tow-behind AGVs: 0.5-1.5 m/s. Forklift AGVs: 0.8-1.0 m/s in aisles. Autonomous mobile robots (AMRs): 1.0-2.0 m/s in dynamic environments. Congestion at intersection points reduces effective average speed. In dense facilities with multiple AGV routes crossing, effective speed may be 50-60% of free-path speed due to queuing and path conflict avoidance.

Charging time must be factored into fleet size. If a vehicle needs 1 hour of charging per 4 hours of operation, 20% of the fleet is unavailable at any time for charging. To maintain 9 operational vehicles at all times, you need 11 vehicles total (9 operating + 2 charging in rotation). Opportunity charging (brief charges during natural load/unload stops) can reduce this overhead to 5-10%, requiring fewer total vehicles.

Fleet size has significant financial implications. AGV unit cost ranges from $25,000 for simple cart-type to $150,000+ for sophisticated forklift AGVs. A 9-vehicle AMR fleet at $50,000/unit = $450,000 capital cost. Compare this to direct labor replacement value and indirect labor (reduced forklift operator accidents, lower facility damage). Typical AMR ROI is 18-36 months when replacing dedicated material handling operators. The ROI calculation must use accurate total labor cost including burden, not just base wages.

Published 2026-05-28.