I've been working with Duke Energy Carolinas SGS (Small General Service) schedule for a 25 kW client in Charleston and the bills keep coming in higher than my tariff calculations. Base rate shows $11.89 customer charge and $8.46/kW demand but actual bills running about 15% higher. Are there additional riders or adjustments I'm missing in the tariff book?
Duke Energy Carolinas - Hidden riders in SGS schedule?
Flo N., Duke has several fuel and rider adjustments that aren't always obvious in the base schedule. Check for the fuel cost adjustment, transmission service charge, and the renewable energy portfolio standard cost recovery. These change quarterly and can add up significantly.
Thomas B. is on the right track. Duke Energy Carolinas has gotten particularly complex with riders over the past few years. Beyond the standard fuel adjustment, watch for the grid improvement plan rider, storm damage reserve rider, and the carbon plan cost recovery that just got approved. The PSC website should have the current rider values but they're often buried in supplemental filings. Also check if there's a gross receipts tax component - South Carolina adds about 1.5% to the total bill.
I'm in Tennessee with different Duke territory but we see similar rider creep. The carbon plan costs have been especially significant lately - adding almost $2/kW monthly on some schedules. Randy D. is right about gross receipts tax - easy to forget but it applies to the total bill including all riders.
Found the issue! It was the transmission service charge at $1.73/kW that I completely missed, plus the gross receipts tax Randy mentioned. Together they account for the 15% difference. The transmission charge wasn't listed in the main SGS schedule but buried in a separate rider tariff. Thanks for pointing me in the right direction.