Reported wH Double Utility reporting


Well, I am back and feeling dumb by asking this question.

I have 240v US power and one CT on each main in. In IotaWatt I have the two mains added and sent to InfluxDB as “total_Wh”. I would post the uploader details, but I am at work and cannot access that right now.

I am summing and grouping by day to get kWh used per day. When I compare this to my utilities usage charts, it is almost exactly double.


Obviously, I am doing something wrong and could solve this by just dividing by 2, but it just seems wrong.

Do you have “double” checked on the mains CT setup by any chance?

1 Like

Man I wish it would have been as simple as that.

This is the watts and Wh I am sending to Influx from the mains. Is it the correct way to send usage?

And all my data points, just in case that is causing a problem.

Your mains CTs are configured as 200A, is it possible they are actually 100A?

1 Like

Well, there’s the problem! I knew it was something simple I had missed!

I have two 100A ct’s for 200A service.

I hope that is the correct CT amperage.

Usually, the cables for 200A service are too fat for a 100A CT (16mm). In any event, you have been uploading the combined mains amps to influx, so you can use the max() function in query to see if it ever exceeds 100A. With your old doubled data, you would need to check for 200A, but going forward after fixing the config, you can check for 100A.

To be thorough, you would upload the Amps for each leg individually and monitor each for >100A.

Very interesting… So my assumption that the presence of a 100A breaker in the main panel (to feed the interior sub-panel) would indicate 200A service, might be incorrect.

The highest point pre-config correction is 139A.

Panel pictures for good measure. This is directly connected to the utility meter/service entrance.

A 200A service has a 200A breaker for each leg (some have two 100A for each leg total 4). A 100A service has a 100A breaker on each leg.

I don’t know what that picture is. I see a 100A breaker, but I don’t see any breaker for the incoming lines. As you can see, a 100A CT could easily accommodate the wires coming from the 100A breaker. The incoming CTs on the incoming cables appear to be pretty snug. My sense is that those are sized for 200A service.

That said, and dividing the data by 2, it appears you drew a max of 70Amps over the last three weeks and typically are less than 50A. So if that is representative of your load over all four seasons, you may be OK for now (until you add an EV charger or other major load).

Long term, you might consider changing to 200A CTs.

I am learning so much right now! Thank you so much for being so responsive and willing to help educate people like me.

Here is the whole service entrance. The 100A CTs are snug. I measured the leads and they are 15.4mm OD cables insulation included. I was not about to try and measure the actual conductor size.
Looking at a site like this indicates the capacity of each conductor is around 200A. Again, I am assuming from the chart on the website the wire from the meter is 4/0.

I will order your 200A CTs soon. I can then move my 100A CTs down to that 100A breaker.