Client has a 200 kW rooftop solar array on a warehouse in suburban Atlanta on Georgia Power. They're on Schedule NM-5 (Net Metering). The utility is crediting excess solar generation at the avoided cost rate — about $0.03/kWh. But the tariff says net metering customers under 250 kW receive credits at the full retail rate during the same billing period. Georgia Power was applying the avoided cost rate instead of the retail rate for same-period netting. The difference is about $0.08/kWh on all excess generation. Over 18 months, the undercredited amount was $24,200.
Net metering credits calculated wrong — $24K recovery
Net metering credit errors are becoming more common as solar installations grow. The tariffs are confusing because there are different credit rates for same-period excess (usually full retail), monthly rollover (sometimes retail, sometimes avoided cost), and annual true-up (often avoided cost). The utility billing system has to distinguish between these and it frequently gets the rate wrong. Good catch Greg.
Solar billing errors are a growing audit niche. The tariffs are new, the billing systems are being adapted, and the utility staff often don't fully understand the net metering provisions. Every client with solar should have their net metering credits verified against the tariff. The most common error is exactly what Greg found — applying the wrong credit rate. Also check whether the system is being credited for all generation, not just the net excess. Some billing systems fail to properly net the generation against consumption within each interval.
Georgia Power corrected the credits and issued a lump-sum payment of $24,200 within 45 days. Fastest resolution I've ever had — they knew they were wrong as soon as I cited the tariff section.