[EVDL List]

Re: [EVDL] Current Cost energy meter

I've used their previous version, and it worked pretty well and was easy to
install, but does not measure voltage -- which means it cannot measure power
factor. It does an assumed power factor of about 0.85 from what I could
tell. This means that on a lower power factor load, it will underestimate
energy use, and on a unity power factor load, will overestimate use. There
will also be a little error if your utility is running the voltage different
than 240 .. alot of them run it a bit high. If more accuracy is of
concern, the TED is a better unit, as it measures voltage and can account
for power factor of the load. But, it also costs a bit more for the one
that can interface with the google power meter.

Z

<[email protected]> wrote:

> Has anybody used this? What do you think about this device?
> http://www.currentcost.net/buynowmain.html
>
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[EVDL List]

Re: [EVDL] Current Cost energy meter

I haven't used that particular meter, but I have used a current meter which
was very similar. The USB and Network connectivity is a nice feature I
didn't have before!

The problem with meters like this is that they show you the overall usage of
the house, but don't necessarily help you understand what exactly is using
the power inside the house. Which circuit and which device is using the
majority of the power? Knowing when the usage spikes in real-time can help
you walk around and see what's active at that time, but there are more
direct ways to do that.

They don't mention it in the installation instructions, but a current sensor
like that should be usable on a branch circuit. I don't know if this one is
or not. If it is, this can be handy because you can put the sensor around
individual wires and measure circuit usage. However, this can be difficult,
because you can't put it around a multi-conductor cable, it has to be around
each, separate wire, after they are broken out of the cable. I was able to
find a few places in my box to do this around a few circuits, such as water
heaters and the clothes dryer. (The feed wires they're placing the sensors
on in the box are individual feed cables from the meter.)

If you were to consistently do this on every circuit, I am willing to bet
there would be surprises. I was running my furnace blower full time to
circulate the air. It wasn't the largest consumer of power instantaneously,
but because it was running 24x7, it was one of the most expensive devices.

For individual devices on a 120v circuit, a Kill-A-Watt is really hard to
beat. For 220V devices, I used the current meter to understand their
instantaneous draw and then a 220v hour meter to find out how often/long
they were running. Luckily, most of those big devices (water heaters,
furnaces, etc.) run pretty much all on or all off. Once you know their
draw, you can calculate their power usage by knowing how long they run
(hours running per month * amps * 220V / 1000 = kWH/month). It's not
elegant, but it works.

Mike

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of [email protected]
Sent: Wednesday, September 01, 2010 8:18 AM
To: Electric Vehicle Discussion List
Subject: [EVDL] Current Cost energy meter

Has anybody used this? What do you think about this device?
http://www.currentcost.net/buynowmain.html

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[EVDL List]

Re: [EVDL] Current Cost energy meter

Can either of these measure which direction the power is flowing?

I recently installed a solar array so sometimes the power flows out to the
grid instead of in.

> If more accuracy is of
> concern, the TED is a better unit, as it measures voltage and can account
> for power factor of the load.
-snip-
>> Has anybody used this? What do you think about this device?
>> http://www.currentcost.net/buynowmain.html

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[EVDL List]

Re: [EVDL] Current Cost energy meter

The old ted's do not.... they just assume it's always positive, so if you
have a PV system, you need to make sure that it feeds in upstream of the
measurement (easy with some sorts of interconnections, but not for a backfed
breaker in the main panel, which is probably the most common type). I had
two of them on my house... one measuring just PV production, and one
measuring the main loads panel, as my PV was connected with a line side tap
upstream of the breaker panel (but still downstream of the utility meter, of
course). TED now claims to have a PV compatible one, but I think it just
uses two sets of CT's.

Yes, kill-a-watts only measure current in the nuetral leg, and multiply it
by line to nuetral voltage (with power factor taken into account), and
assume it's always positive power. I've used them to measure 220vac as well
by running one hot leg through the nuetral, one around the meter entirely,
and the nuetral through the meter's hot leg... it works, but I'd never do it
outside of my own house (experiment station...).

Z

Lee Hart <[email protected]> wrote:

> On 9/2/2010 4:07 PM, [email protected] wrote:
> > Can either of these measure which direction the power is flowing?
>
> I don't know about these, but the popular Kill-A-Watt does *not*
> correctly sense direction of power flow. I have a grid tie inverter, and
> the Kill-A-Watt displays positive power no matter which way it's
> flowing. It appears to just take volts x amps.
>
> Its power factor conversion also assumes sinusoidal current, so it reads
> high for things like switching power supplies or non-PFC battery chargers.
>
> --
> Lee A. Hart | Ring the bells that still can ring
> 814 8th Ave N | Forget the perfect offering
> Sartell MN 56377 | There is a crack in everything
> leeahart earthlink.net | That's how the light gets in -- Leonard Cohen
>
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