# Tool to measure real-time power consumption ?

#### Externet

Joined Nov 29, 2005
1,823
Hi.
What tool to use for measuring inductively the real-time power entering the breaker panel on a U.S. 120VAC + 120VAC (center tapped) utility supply ?

#### Irving

Joined Jan 30, 2016
2,562

#### Ian0

Joined Aug 7, 2020
4,904

#### LowQCab

Joined Nov 6, 2012
1,931
Read the number on your Utility-Meter on the side of the house,
it will provide the current Current demand, as well as the cumulative usage.

What is your definition of "real-time" ?
How much accuracy do You need ?
Is the "Power-Factor" important to You ?
Why do You need to know ?
Do You need to record the demand vs time ?
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#### Externet

Joined Nov 29, 2005
1,823
The utility meter does not read nor display power nor current, displays cumulative energy.

Real time is the power reading that moment I want to know the power being consumed by the dwelling.
Accuracy 1%
No power factor
To evaluate my solar generation into utility grid against dwelling consumption.
No recording.

Ideally, meter with two loops collaring each of the 'phases' summed and displayed.
Did not expect the Fluke to be that expensive, Perhaps the sum of two inexpensive 'hook' ammeters readings times the voltage will tell the power ?

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#### LowQCab

Joined Nov 6, 2012
1,931
"" Perhaps the sum of two inexpensive 'hook' ammeters readings times the voltage will tell the power ? ""

There ya go.
Now You just need to figure out a way to determine whether the Power is coming or going.
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#### Externet

Joined Nov 29, 2005
1,823
...You just need to figure out a way to determine whether the Power is coming or going.
Flipping the inverter breaker off reads consumption coming from utility.

#### Irving

Joined Jan 30, 2016
2,562
"" Perhaps the sum of two inexpensive 'hook' ammeters readings times the voltage will tell the power ? ""

There ya go.
Now You just need to figure out a way to determine whether the Power is coming or going.
.
.
.
That's easy, a simple current transformer over each incoming live wire (not over the live-neutral pair) and one over the solar feed from the inverter. The inverter takes almost nothing in so generally reads outgoing... works for mine... when the sun comes out you can see the incoming current drop as the solar takes over. I have one on the solar, one on the line and one on the feed to the consumer unit (breaker panel) after the junction of solar and utility line, so I can see current in all three legs and therefore deduce which is going which way...

#### John_TSTM

Joined Dec 23, 2019
4
The two current transformer method would be your best bet. You can find small cts that fit well in your panel and use a utility revenue grade meter (ANSI C12) such as a GE/Aclara kV2 or kV2C or similar, Form 3S or 4S, and a meter socket. Here is the catch: New meter lead times are presently 40-50 weeks, meter sockets about 40 weeks, cts about the same. Most utilities are holding on to their surplus/used equipment because of the lead times. Other businesses are charging up the wazoo for "reconditioned" equipment. The whole setup should cost you less than \$100. The kV2C meters can be programmed for delivered and received energy (kW, kVA, kVAR), real time energy (instantaneous voltage, current and power factor) and a host of other metrics. Why so cheap? Most utilities are implementing AMI and most of the early generation meters cannot host the selected modules but still are accurate within 100.00 +/- .15%. If you don't want to get to technical there are other ways.