Frank C. in Portland ME - we're primary metered at 34.5kV through CMP and just discovered the voltage transformer ratio has been wrong for over two years. The VTs are 200:1 but the meter was programmed for 400:1, so we've been underbilled by 50% on our Schedule LP rate. CMP wants to back-bill us for the full amount plus interest. Can they legally go back that far? This could be a six-figure adjustment.
VT ratio error on primary metered account - need help calculating adjustment
Frank C., this is a complex situation. In Maine, utilities can typically back-bill for up to 24 months when the error is in their favor, even if it was their equipment programming mistake. However, you may have grounds to negotiate the interest charges and payment terms. Document that this was purely a utility metering error - you had no way to detect VT ratio programming issues. Consider requesting a payment plan rather than a lump sum. Also verify their adjustment calculations independently before accepting.
Tom L. in Boise - Idaho Power tried to back-bill us three years when they found a similar VT error. We negotiated it down to 18 months and no interest by showing the error was entirely on their side. Get everything in writing and don't accept the first offer.
Theresa K. from Bozeman - NorthWestern Energy did this to us in 2015. The key is proving you had no reasonable way to detect the error. Primary metered accounts can't easily verify VT ratios like you can check CT nameplates. We got them to waive interest and spread payments over 12 months.
Thanks everyone. CMP agreed to 18 months back-billing with no interest and a 24-month payment plan. Randy D.'s advice about independent calculation was crucial - we found two months where their math was wrong and saved another $8,000. Final adjustment is $127,000 but at least it's manageable now.