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Ok So I have just seen my Usage generate a neg. figure, my CT-1 is connected to the feed from the utility, this would mean that is the solar is generating more that hte house usage I'd see an neg. result. So to get actually household usage, I don't need to show the difference, but rather the sum of the 2

What is the update interval of the local emonCMS to emoncms.org site with a raspberry Pi ?

And how do I change it, and should I change it ?

Warlock,

The main method to do this is to create a feed that represents your total consumption and your total generation, and to take the difference between them as your net usage, which may be positive or negative based on your consumption. On my system here in the U.S.A, I have two feeds into the house, and a feed out of my solar inverter that will export on one of the two lines into my house. So, I have three CTs, one measuring my solar output, and the other two measuring the two lines coming into my house. My total consumption is the sum of all three outputs. If I am only generating a little power and am importing power from the grid as well, then my consumption is the amount I am importing plus all of my generation. If I am generating a lot and on my grid connected line I am exporting (the value is negative), my consumption is still the sum of all of those values, my solar plus the (negative) power on the grid line, with the resulting value being how much is being consumed inside the house. By logging that to a feed I can then have a net import/export feed which I show on a dial.

It appears on your second post that you figured this out. For my setup given I have two lines into the house I need to sum all three lines for my consumption. For your third post, I believe the update frequency is variable, but the default value is every 5 seconds. You can select a longer update interval if needed. For the standard sketch though, you are making a brief (~ 2 second long) measurement at each interval, assuming that the brief measurement represent the power over that entire sampling period. The longer you go between samples the less accurate your measurement will be. With the newer algorithms that integrate continously between reporting periods (EmonLibPro and the PV Router sketch), all power is logged and the average power is reported out at the sampling interval. So, you don't lose power information by going to longer sampling intervals, you just end up with a smoother graph.

I hope this information helps.

Dan

Thanks Dan

I found that when my Solar Array was producing more than what I was using the CT-1 sensor reported a neg. value, so basically ot get my actually house consumption I simply added the Solar CT-2 with CT-1

Thanks for all the information.