Net Metering - Billing Oddity - Looking For Advice

[jbumps]

All,

Our recent electric bill outlined the following:

Jun 22 KWH Reading (Actual) 41,797
May 20 KWH Reading (Actual) 40,346
Kilowatt Hours Metered 1,451

Jun 22 KWH Out (Actual) 20,007
May 20 KWH Out (Actual) 19,149
Kilowatt Hours Out 858

We were billed for 593KWH as the above data would suggest we should have been. The concern is that our solar meter (which we use to report production to the solar energy credit broker) reports a cumulative production figure of over 27,000 KWH, not the 20,007 the power company reports.

The meters have not been swapped since the installation of the array and a production report from the Enphase website very closely correlates with the solar meter on the house. Is there something wrong here?

I realize that some of the power produced by the array may be used instantaneously by our home, but the data from the power company would suggest that over 17% of the power produced by the array is used as it's generated. That figure strikes me as very, very high, given that we are not home to demand hot water, charge cars, etc... when production is at it's peak. FWIW - we run A/C 3-4 times per summer at most and our heat source is not a large electricity user.

Thanks in advance to anyone who can offer up some direction.

 

[BrettS]

You don’t say how long you’ve had the solar panels to figure out how many months that ‘missing’ 7000 kwh was used in. However, just looking at the numbers you have provided if we assume that you used 17% of the power your solar panels produced this month then based on the 853 kwh that was not used that would mean that you produced about 1026 kwh and used about 173 kwh. Your total metered consumption was 1451 kwh this month, plus the 173 kwh from the solor panels means that you used 1624 kwh this month and 173 kwh would only be about 11% of that.

Thinking about it another way, 173 kwh over 30 days would be just 5.7 kwh per day, compared to your total household consumption of 54 kwh per day.

This seems reasonable to me, but you can try to get an idea of how much power your house uses during the days by checking the meters in the morning, then checking again in the evening and subtracting.

 

[nwdiver]

I realize that some of the power produced by the array may be used instantaneously by our home, but the data from the power company would suggest that over 17% of the power produced by the array is used as it's generated. That figure strikes me as very, very high, given that we are not home to demand hot water, charge cars, etc... when production is at it's peak. FWIW - we run A/C 3-4 times per summer at most and our heat source is not a large electricity user.

Why does 17% seem high? According to my electric bill I self-consume ~20%.

 

[jbumps]

Thank you for the feedback. After changing the way I was viewing it, I suppose it doesn't seem all that out of line. I think I was hung up on the cumulative figure.

The array went live 1,458 days prior to the last bill. To consume the amount that would be required for the billing to be accurate, the house would need to consume 599.13 watts on average, over an 8 hour day (when the system is producing). Having played around with a friend's TED meter, that felt like a really high number. With some further thinking - we charge during the day on weekends often, are home doing laundry etc... as well. Giving consideration to those times when we'd be using 100% or a similarly large % of the arrays output, the average consumption rate on weekdays drops considerably. Summary - I just needed to spend 10 more minutes thinking about it, instead of being lazy and relying on a forum.

 

[TheTalkingMule]

It's a natural reaction that a lot of consumer would make. I found it interesting and work reading.

 

[dhrivnak]

I use about 30% of my production directly. I used to use less than 20% but then shifted charging my Roadster during the day and the gap narrowed.