Question about net metering calculations (NEM2 in California)

[Velums]

I'm trying to use up "excess solar" generated during the day, to avoid those "non-bypassable charges" under NEM2 in California.

So, as I'm trying to optimize this, I have a question:

Does billing occur second-by-second? (i.e. if I send 0.1 kWh to the grid and consume 0.1 kWh from the grid a few seconds later, I'd have to pay NBCs on the 0.1 kWh?)

Or is it hour-by-hour? (i.e. if consume 1 kWh from the grid at 1:00-1:30 pm, I can avoid NBC's by exporting 1 kWh to the grid 1:30-2:00 pm, thereby zeroing out the usage for that hour?)

I realize that the meter is capable of reading the net consumption second-by-second, but I'm wondering whether the billing system uses all that granularity. (When I download my usage data from the PGE website, it only provides usage on an hourly level.)

 

[dailo]

As far as I know, it is based on hourly net energy consumption.

 

[RichardCullip]

For SDG&E billing I'm 98.6% positive that the time period for NBCs is 15 mins. When I download the 15 min Green Button data from SDG&E, I can match exactly the NBC amounts each bill period by adding up the Net Energy (consumption - generated) for each 15 min increment where the Net Energy is positive.

 

[miimura]

PG&E is also not consistent about the metering interval. At various times my SmartMeter has produced Green Button data that has 15 minute intervals or 1 hour intervals. I'm not sure what rhyme or reason PG&E uses to determine how your meter is configured.

When I had solar but no Powerwalls (~2012-2018) my account had 15 minute interval data. When I got Powerwalls I was put on the NEM-PS billing system and my account contained 1 hour interval data. They also "conveniently" wiped out all my historical Green Button Data from the prior period. The Solar Customer Service Department claimed it was not intentional, but since the Service ID was no longer attached to my account, there was now no way to access it. Not even directly through their back-end systems. Riiiight....

As to the OP's question - I am still on NEM 1, so I don't know if the positive interval data exactly equals the kWh quantity used for the NBC calculation like it did for the SDG&E customer above.

 

[Velums]

Thanks to all for your responses.

With this knowledge (especially the key terminology I was missing: "metering interval") I was able to find an official page with the answer.

According to the CPUC, here are the metering intervals for the calculation of NBCs:
1 hour for residential customers
15 minutes for commercial customers

Source: CPUC (scroll all the way to the bottom)

(But I'm still baffled by why there are reports of counterexamples - maybe some people's residential accounts are miscategorized as commercial?)

 

[miimura]

Thanks to all for your responses.

With this knowledge (especially the key terminology I was missing: "metering interval") I was able to find an official page with the answer.

According to the CPUC, here are the metering intervals for the calculation of NBCs:
1 hour for residential customers
15 minutes for commercial customers

Source: CPUC (scroll all the way to the bottom)

(But I'm still baffled by why there are reports of counterexamples - maybe some people's residential accounts are miscategorized as commercial?)

I was on NEM1 prior to the adoption of NEM2 when my residential meter was on 15 minute intervals. That rulemaking process may have solidified the 1 hour residential rule.

 

[Redhill_qik]

Thanks to all for your responses.

With this knowledge (especially the key terminology I was missing: "metering interval") I was able to find an official page with the answer.

According to the CPUC, here are the metering intervals for the calculation of NBCs:
1 hour for residential customers
15 minutes for commercial customers

Source: CPUC (scroll all the way to the bottom)

(But I'm still baffled by why there are reports of counterexamples - maybe some people's residential accounts are miscategorized as commercial?)

I never trust easy to read web pages, even when they are hosted on the CPUC website, and only trust the tariff rate documents. I went down this rabbit hole and could not find any formal definition of "metered interval". With PG&E it is absolutely 15 minutes based on my data from green button with the one hour interval and the PG&E NEMPS black bill detailed data. My NBC kWh range from 3-34 kWh higher than the hourly data each month with the smaller interval.

This really should not be much of an issue as with the current Minimum Daily Charge rate of $0.34810/day and NBC rate of $0.02666 you can import an average of 13.1 kWh over the year before you exceed the MDCs. Over the course of year the smaller interval added 106 kWh to my NBC total 2,647 kWh which is 4% or $2.83 more. Since on average I imported only 7.25 kWh/day and I am a net generator the MDCs where higher and I paid nothing extra at the annual true-up.

 

[RichardCullip]

Thanks to all for your responses.

With this knowledge (especially the key terminology I was missing: "metering interval") I was able to find an official page with the answer.

According to the CPUC, here are the metering intervals for the calculation of NBCs:
1 hour for residential customers
15 minutes for commercial customers

Source: CPUC (scroll all the way to the bottom)

(But I'm still baffled by why there are reports of counterexamples - maybe some people's residential accounts are miscategorized as commercial?)

I live firmly in the pay attention to what they do not what they say they do world.

I doubled checked my NBC math and confirmed that SDG&E tabulates NBC data on 15 min intervals. If I add up the NBCs based on hourly data I end up short of what SDG&E bills me for. If I add up the 15min data I match what is billed