Working on a large industrial audit for a TVA customer here in Chattanooga and the interval data isn't matching the monthly billing totals. The 15-minute intervals sum to 2,847 MWh for July but the bill shows 2,963 MWh. That's a 116 MWh difference or about $7,500 at their rate. The TOU breakdown also seems wrong - showing way more on-peak usage than the interval data supports. Has anyone seen TVA interval data accuracy issues lately?
TVA interval data analysis - something's not adding up
Lorraine, I've seen this before with TVA. Sometimes their interval data export doesn't include all channels or there's a transformer multiplier error. Check if they're billing CT and PT ratios correctly. Also verify the interval data covers the full billing period including any partial days. What's the account voltage level?
Terry - it's a 46kV industrial account with CT ratio 2000:5 and PT ratio 480:1. I double-checked the multipliers and they seem right. The interval data does cover the full billing cycle. I'm wondering if TVA is applying load factor adjustments that aren't reflected in the raw interval data. Their tariff has some complex demand ratchet provisions.
Check for power factor corrections too. Gulf Power down here in Pensacola has similar issues where the interval data shows kWh but doesn't account for reactive power adjustments that affect the final billing. TVA might be applying kVAr penalties that don't show up in the standard interval export.
Nadine's right about power factor. Also check if TVA is using a different averaging method for demand calculations. Some utilities use rolling 15-minute averages while others use block intervals. The difference can be significant for industrial loads with high variability.
Great suggestions everyone. I found part of the problem - TVA was including transmission losses in the billed amount but not in the interval data. That accounts for about 65 MWh of the difference. Still tracking down the remaining 51 MWh discrepancy. Frank, you're right about the demand averaging method. I need to verify which calculation they're using.
Lorraine, transmission losses are usually around 2-3% for industrial accounts. If you're still missing 51 MWh, check for any billing adjustments or estimated reads during the period. Sometimes utilities apply corrections retroactively that don't show up in the interval data timestamps.
Elmer - that was exactly it! TVA made a mid-month meter reading adjustment that added 52 MWh to the bill but the interval data export didn't include the adjustment period. Mystery solved. Thanks everyone for the troubleshooting help. This is why I love this forum.
Great detective work, Lorraine. Alabama Power has similar billing adjustment issues. I always request a detailed billing analysis report along with the interval data to catch these types of mid-cycle corrections. Saves a lot of head-scratching later.
This thread should be required reading for anyone doing interval data analysis. The transmission loss and billing adjustment issues come up constantly. PG&E has the same problems out here in California. Always verify the interval data scope matches the billing period exactly.
Dan's absolutely right. I'm going to start including a data validation checklist in all my interval audits: CT/PT ratios, power factor adjustments, transmission losses, billing period coverage, and mid-cycle corrections. Would save everyone time upfront.