An energy utility needed a more reliable way to forecast its future customer base at tariff level so it could improve procurement planning, sales target setting, and pricing decisions. The challenge mattered because customer stock development depended on both active and passive churn, market-relative price positioning, and varying acquisition levels across segments. Additional complexity came from small tariff populations, tariff migrations, internal tariff switches, and the need to reflect crisis-related market effects without distorting a realistic planning baseline.