Working on a food processing plant account here in Boise and discovered what I thought was a significant transformer loss billing error. Idaho Power was billing them for losses at 2.8% when their tariff Schedule 9 clearly states customer-owned transformers should be billed at 1.5%. Calculated about $34k in overcharges going back 18 months. Submitted the claim feeling pretty confident about the tariff interpretation. Idaho Power came back explaining that this particular customer had two separate service points - one fed through utility-owned equipment at 2.8% losses, another through customer-owned at 1.5%. The higher loss charges were completely legitimate for that portion of their service. I had lumped everything together without understanding their electrical configuration. Anyone else get tripped up by multiple service points under one account?
Idaho Power transformer loss calculation - walked into that trap
PSE here in Seattle - similar situation with a retail chain that had both primary and secondary service at the same location. Thought PSE was applying the wrong transformer ownership code to half their demand charges. Spent days building spreadsheets to prove they owed the customer $67k. Turns out their older building addition was fed at secondary voltage through PSE transformers, while the main building was primary service with customer-owned gear. Two different loss factors were correct. The key lesson for me was getting the actual electrical one-line diagram before making any transformer loss claims. Most utilities will provide it if you ask nicely.
PSO territory - got burned on this exact issue with a manufacturing client in Tulsa. They had three separate electrical feeds under one billing account, each with different voltage levels and transformer ownership. I assumed all the loss calculations should be identical and built my entire analysis around that assumption. Wasted probably 40 hours before realizing each feed was correctly calculated per its specific configuration. Now I always request service records and transformer ownership documentation upfront. Saves a lot of headaches and false starts.
APS here in Phoenix - learned this lesson the hard way on a hospital account with six different service points. Each had different transformer configurations and loss factors. What made it worse was that APS had changed ownership on two of the transformers during our review period, so the loss factors actually changed mid-stream. I initially calculated $89k in overcharges because I was applying current loss factors to historical periods with different transformer ownership. The billing was correct throughout, just complex. Always verify transformer ownership history for the entire audit period, not just current status.