For the same kVAR, a delta-connected bank needs one third the capacitance of a star one — because reactive power scales with the square of the voltage each capacitor sees.
Q = 2πfCV². In delta each capacitor sits across the full line voltage; in star it sits at line/√3, so its V² is three times smaller and it takes three times the capacitance to deliver the same correction. That is why delta is the default. The trade is voltage rating: every delta capacitor must withstand full line voltage. Quoting a kVAR figure without saying which connection it assumes is how the wrong part gets ordered.
Estimate with the rule, then check it against the calculator that models it properly.
Open Power Factor Calculator →For the same kVAR, a delta-connected bank needs one third the capacitance of a star one — because reactive power scales with the square of the voltage each capacitor sees. Q = 2πfCV².