New to the profession and working on my first TOU audit with Green Mountain Power here in Vermont. Client is on Rate 6 (Large General Service TOU) and I'm having trouble reconciling their peak period definitions. The tariff mentions 'system peak periods' but doesn't clearly define the hours. It references ISO-NE peak periods but those seem to change seasonally. Anyone familiar with GMP's TOU structure? This is more complex than I expected for my first case.
Green Mountain Power TOU confusion in Vermont
Chester, welcome to the profession! Vermont utilities can be tricky because they often tie TOU periods to ISO New England operations rather than fixed clock times. You'll need to cross-reference the GMP tariff with ISO-NE peak period definitions for each month in question. The ISO publishes this data but it's not always easy to find. New Hampshire utilities do something similar and it took me months to figure out the pattern.
Thanks Yvonne! I found the ISO-NE data but you're right - it's not straightforward. Peak periods seem to shift based on system conditions and seasonal factors. For summer 2023 it looks like weekdays 1:00-5:00 PM, but winter was 6:00-9:00 AM and 5:00-7:00 PM. How do I verify that GMP is applying these correctly to customer bills?
You'll need to get the actual peak period notices that ISO-NE sends to utilities. Sometimes GMP publishes these on their website under 'tariffs' or 'rate schedules.' If not available online, call their commercial rates department and ask for the specific peak period definitions that were in effect during your audit period. Don't assume anything - get it in writing.
Chester, Yvonne is giving you solid advice. ISO-tied TOU rates are complex but that complexity also creates opportunities for billing errors. I've seen utilities misapply ISO peak periods, use outdated period definitions, or fail to update their billing systems when ISO changes the rules. Once you get the official peak period data from GMP, create a detailed timeline and check every month individually. The extra work usually pays off with findings. Welcome to the forum and don't hesitate to ask questions - we've all been where you are now.