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Energy monitors?

PostPosted: Thu Mar 03, 2011 4:12 pm
by davidriley
Hey guys,

I am looking at some electricity monitors and narrowed it down to a couple... basically the Efergy E2 ( and the OWL Micro CM130 Wireless. Both look pretty good, but I figured I should ask around, see what other people think of them.

Anybody here been using any of these, or other?

Cheers mates.

Re: Energy monitors?

PostPosted: Mon Mar 07, 2011 7:13 am
by zzsstt
I use a Wattson for "whole house" consumption measuring, there is a review in another thread.

For individual devices I use a 15amp PowerMate, which I find to be just about the perfect device. It will tell me power consumption and cost (per period of time from hour to year), and also maximum current draw and various other numbers. It is useful for investigating "truths" about devices, such as power factor (which impacts the distribution grid), and maximum and minimum voltages which is useful for checking what impact motor startup has on your power. It does not connect to a PC, or have any download capability (I'm not sure if they've updated it, mine is a couple of years old) but for single appliance measurement it gives everything you will ever need.

As Tracker points out in the Wattson review thread, "whole house" measurement via current clamps is a touch hit-or-miss, but I believe it gives a good indication of how the house is run. Individual appliance monitoring is far more valuable to detect whih devices are creating the long term problems - a kettle will spin the meter (and the whole house monitor) but a device drawing a constant 50W will cost $100/year, and you may not even know it's doing it. And such a device is hard to track down with a whole house meter!

Re: Energy monitors?

PostPosted: Fri Mar 11, 2011 4:34 pm
by witzl
i'd argue that with a whole house monitor it IS possible to track down an appliance using 50-100W continuously - so long as you have one that is fast enough.

I have a Watts Clever wireless power monitor, which updates around every 4-5 seconds (pretty quickly). With the display being battery powered, i just walked around the house with it in my hand, and started turning appliances on and off and seeing what effect they had to base-line power consumption.
I was able to get my "base" power consumption down from around 400W to 250W - i found my hifi receiver was pulling 100W on standby, and a couple of other appliances werent helping either.

I could see that pretty instantly with teh Watts Clever unit. Even if i turned on the energy saver lights in the bedroom (3x 11W energy savers), i was able to see the power drop pretty close to 35W.

Re: Energy monitors?

PostPosted: Sat Mar 12, 2011 9:19 am
by zzsstt
witzl wrote:I could see that pretty instantly with teh Watts Clever unit. Even if i turned on the energy saver lights in the bedroom (3x 11W energy savers), i was able to see the power drop pretty close to 35W.

In the three buildings that I have tried using whole house monitors, there was a constant variation in power consumption of 50W to 100W. If the house was unoccupied and everything could be switched off, I have no doubt that a whole house unit could give a reasonable estimate of the instantaneous consumption of an appliance. However this is often not possible, and in any case it is only an instantaneous reading which may not be particularly relevant as many appliances are very variable in their consumption.

For example, with nothing else switched on;

a light will have a fairly constant power usage
a motor will have a very variable usage, depending on load
a "dumb" electronic device (amplifier) will vary the usage with load (louder=more usage!)
an "intelligent" electronic device will vary usage with "task"

Most appliances will have varying power usages. Those involving motors or heating elements will vary wildly. To attempt to track down the source of a small power draw against such a background is very difficult. To make matters worse, many devices have a variable load through the start-up cycle, and many do not take kindly to being switched on and off repeatedly! For example, we have a combined DVD player and hard disk recorder on the kids TV. It takes perhaps 30 seconds to power up or down, during which time it spins up its hard drive and has very variable power usage. I would be hesitant to repeatedly switch it off and on, and because of all it's "energy saving" features, any instantaneous readings through that process would be worthless. Yet because it is powered up 24/7 it contributes to our background use - but by how much? The only way to know is to measure it's actual consumption over a week or two, using a single appliance monitor.

Using the Wattson on my desk, I can instantly see when the power consumption is above "normal" background use. I can also see that my desk light pulls about 20W, but only by repeatedly switching it on and off and seeing how the mid-point of the normal fluctuation moves. Even then, if anything else changes it will confuse the issue, so I would need to switch off any variable loads before testing if I want any degree of accuracy or confidence in the result.

For removing gross loads (like your receiver) this is not too cumbersome. However in the buildings that I have investigated, there are very few gross background loads (the notable exception being airconditioners), and most background loading is comprised of a large number of far smaller devices (mostly plug in power pack/transformers). Each of these often draws only a few watts - in my last post I used 50W as an example, but most are much less, and are simply lost in the "noise" on a whole house monitor. The problem is that whole house monitor cannot tell you if the instantaneous reading of 400W is comprised of two 200W loads or twenty 20W loads. Moreover it cannot tell you if (for example) the circulator pump on your solar water heater is running 24/7 or just when the sun is shining!

So whilst it may be possible, under certain conditions, to identify fairly large and constant background loads with a whole house monitor, to accurately determine the real world consumption of an appliance requires a single appliance monitor.

Re: Energy monitors?

PostPosted: Wed Mar 23, 2011 10:29 pm
by rebeccaasmit
Thanks for posting this !! Good Info..

Electric Heater

Re: Energy monitors?

PostPosted: Tue Mar 29, 2011 2:07 pm
by karlajensen
I have a few and the answer depends on what you want to do with it.

If you need to log the data to a computer the ENVI is the go
Not logging anything I found the TREC almost useless for my purposes.

if you dont need PC logging but like to see some history of use then the Efergy is a far easier device to use.
and has some handy stuff like temp and humidity, can also set grid voltage!
This is an important feature if your grid voltage is high (the ENVI is non adjustable 230V) like 250-260V then it will be more accurate.

ENVI pros and cons
eats batteries solved with re-chargeables.
adj voltages
multiple tarrifs
temp and humidity
on-board logging and history, cheap and easy to install.
only displays one thing use or generation not both.

uploads to google power
displays use and generation (not simultaneously)
only logs one channel to google power which sucks
have to upload data or run it plugged into computer 24/7 (crazy unless you are already doing so as power use from computer use is large)

Result -
If I had my time again, it would be two effergys one for the solar generation and one for house use
They are at times wildly innacurate I might add as TL inverters have a phantom reading when supposedly "off"

Re: Energy monitors?

PostPosted: Tue Mar 29, 2011 2:09 pm
by karlajensen
Update -now that I've seen the link you provided thats the go.
get one or even two of those
one for import the other export

Quote :
Measuring electricity 'exporting' back into the grid:
This product is attached to your main electricity cable and measures the electricity flowing through it.

It cannot determine the direction of the electricity (Whether it is going back to the grid or importing into your premises).

It is therefore not designed to provide accurate readings if you are sending power back to the grid on the same line that you import electricity.

Re: Energy monitors?

PostPosted: Tue Mar 29, 2011 4:56 pm
by zzsstt
karlajensen wrote:Update -now that I've seen the link you provided thats the go.
get one or even two of those
one for import the other export

On a gross FIT, two of them will give the right figures if the clamps are put in the right places.

On a net FIT it won't work. One device will not know which way the power is flowing so it will have to be connected on the "house" side of the PV input and measure only usage. The other will be connected to the PV cable and measure generation. Whilst this will give two totals, one for used and one for generated, it won't actually tell you what you exported, because the feed-in is an instantaneous subtraction of "generated" minus "used" at any point in time. It is possible on a given day to use 15kwh and generate 15kwh and export anywhere between 0 and the full 15kwh, and this unit will not have any idea of what happened.

If you need to measure the power exported under net metering, you need a unit designed to do so.

Also note that this unit is supplied with a single clamp, and therefore is only suitable for single phase. Many houses have two or three phases, in which case you will need to purchase another clamp for each additional phase.

Re: Energy monitors?

PostPosted: Thu Mar 31, 2011 12:13 am
by karlajensen
zzsstt wrote:
If you need to measure the power exported under net metering, you need a unit designed to do so.

Haha - its called an EM1000

I believe they are only $100 but most of us have got one supplied by our retailer

it would be nice to get some software for it :D

Re: Energy monitors?

PostPosted: Thu Mar 31, 2011 7:09 am
by zzsstt
I doubt you could buy one of those for $100..........or even $1000!!

I was talking about a homeowner who wants to be able to monitor their own power export, rather than get numbers from their power retailer. With a suitable unit (the Wattson has a PV clamp but I've never investigated how well it works because my array is 400m from my house), you should be able to look not only at the total power exported (which your retailer will provide) but also at how that happens through the day.

That may be important. In a net FIT scheme, any usage that can be moved from peak generating hours to somewhere else will result in more power being exported. From a "climate change" perspective that doesn't matter, but if the net FIT is higher than the retail price (in NSW this is no longer true!) the financial returns are worthwhile.

In NSW under the new FIT, where the FIT is less than the charge, the best option is net metering and arranging as much usage as possible to be on self generated power. The only exception to this is where an off peak rate is available, and costs less than the FIT.

However on a net FIT higher than the cost price, the best option is to use as little power as possible during generating hours to maximise the FIT.

On a gross FIT that is lower than the cost price, the best option is to move to a net FIT!!!

To monitor the above, you need an energy monitor that has usage and generation measurement, i.e. a PV clamp and 3 (for 3-phase) usage clamps, and can record generation and usage separately.