Score the eight systems — kratky, DWC, NFT, ebb & flow, drip, vertical tower, RDWC, aeroponics — with experience ×1.5, crop ×1.5 and budget ×1.25 weights, then normalize into the 40–95% band and read the top-two gap as confidence.

Size the kratky arm: tanks = target yield ÷ 2.5 kg per tank. On the 10 m² beginner case that is 50 kg ÷ 2.5 = 20 passive tanks.

Set the NFT arm on the slope rule — slope % = drop ÷ run length × 100 — 12 ft at 2.5% means a 3.6 in drop, then count channels from 20 kg per channel: 200 kg ÷ 20 = 10 channels.

Count vertical towers from the 20 kg per tower budget: 500 kg on 5 m headroom → 25 towers, stepped at 30–42 in centers.

Cost the build — base + units × unit cost — and solve payback against monthly revenue minus the photoperiod operating cost.

Read the last three arms: water at 10 L/kg/day, lighting energy at system watts × 18 h ÷ 1000 (kratky at 0 W), and the safety band from experience × system × build cost — green for a beginner kratky, red for expert tower/raceway scale.