Working on a case where TVA claims a mechanical meter was under-registering by 12% over five years, resulting in a $23,000 adjustment for a small manufacturer in Huntsville. The meter passed its accuracy test when installed but apparently "drifted" over time. TVA's tariff allows adjustments for meter errors over 2%, but I'm questioning whether 12% drift is realistic for a properly maintained meter. What's been your experience with acceptable variance ranges for mechanical meters? Are we talking normal wear or possible tampering/damage?
Mechanical meter "creep" - how much variance is acceptable?
Albert, 12% seems excessive for normal mechanical meter drift. Idaho Power's standards typically consider anything over 4-5% as requiring investigation. We had a similar case where a client's meter showed 8% under-registration after seven years. Turned out the meter had been damaged during a facility renovation two years prior - a forklift had bumped the meter housing. The utility agreed to limit the adjustment to the period after the damage occurred. I'd request detailed maintenance records and ask if there were any incidents that could have affected meter accuracy.
Duke Energy Ohio's position is that mechanical meters can drift up to 2% per year under normal conditions, so 10% over five years wouldn't be unreasonable in their view. However, we successfully challenged a similar case by demonstrating that the meter's installation environment wasn't suitable - excessive vibration from nearby equipment was affecting the mechanical components. The key is getting an independent meter test and reviewing the installation conditions. If the meter was subject to unusual environmental factors, the utility should have monitored it more closely.
City Utilities here in Springfield has been pretty reasonable about meter variance issues. Their policy is to investigate any drift over 3% annually. In cases where environmental factors contributed to accelerated wear, they'll often split the adjustment with the customer. Albert, I'd also check if TVA performed any routine meter testing during that five-year period. If they had opportunities to catch the drift earlier and didn't, that strengthens your case for limiting the adjustment period.