Small meter question

Re: Small meter question

Take a read through this thread, and then ask your question, please.

Probably the same manufacturer (or at least, the same issues)...

-Bill

PS: I am assuming you are referencing the 200 watt Grid Tied Inverter and not a "meter"...

Re: Small meter question

Sorry, here is the missing link...

I see the youtube video in the Ebay site (I turn off all of the flash stuff unless I am looking for Flash/video).

The meter you are looking at appears to be a "People" brand electric utility meter... You probably have a similar device on the electrical panel of your home.

I don't know the brand "People", it could be from anywhere in the world--but I would guess that it is a Main Land China utility meter (perhaps even "branded" with the name of a utility company).

If you are looking for a good meter for use at home, take a look at Kill-A-Watt series of meters (assuming you are in North America--120 VAC 15 amp 60 Hz branch service).

The only thing this Kill-A-Watt meter cannot do is reverse directions when the power is supplied from a GT Inverter--which you should not really be doing (safety and for legal reasons).

-Bill

Re: Small meter question

Search the web for kWh meters... You will find a lot of them out there...

The Kill-A-Watt will work well (it totalizes power use)--but, like many meters, cannot measure forward/reverse power--so if this is a requirement, you will have to ensure the meter you are purchasing does support "net metering".

-Bill

Re: Small meter question

Personally, I would still purchase a Kill-A-Watt meter. And measure the power draw when there is no sun (say 5 watts), and then subtract the number of hours of darkness per day per year (say your unit averages 10 hours of sun power then 14 hours per day 5 watts of standby losses then, on average, you can subtract:

14 hours * 5 watts = 70 Watt*hours per day of standby losses

The above would "add" to the kWhr meter reading--so you would simply subtract 70 watt*hours per day from your cumulative reading. Probably close enough for your needs... You will probably be off ~10-20 WH per day, but you will be generating ~1,000+ watt hours per day (on a good day with a 250 watt system)--that is within a 1-2% error--roughly the accuracy of most non-lab meters anyway.

Otherwise, you will need to go on the web and find a meter than meets your needs.

-Bill

Re: Small meter question

boisblancboy wrote: »

1. Would there be a way to stop the meter from reading the standby by wattage while no sun?

Depends on the meter... The Kill-A-Watt is a electronic consumer meter and is not configurable.

For meters with this type of function, it would probably be pretty expensive (have a programmable interface). And directional kWhr meters are not cheap anyway (kill-a-watt meters are about the cheapest and easiest to use--and was way safer than the expensive Watt / Watt Hour meter I used to use in my lab with open 120/240 VAC binding posts and exposed wires that would fall off if somebody tripped).

2. Is there a meter that I could install between the inverter and panel to record my power and therefore not having to worry about what I am losing because of standby?

You will need to worry about standby losses--if the GT inverter standby losses are low--that is a good thing, and may not even really matter when using the K-A-W meter (if, for example, your standby losses are just 1 watt, that is ~15 watt*hours in a day--less than 1% of the total power per day a well working unit would generate--so why waste the money on something else)

3. Any type or places should I look for a meter, your recommendations?[/quote]

Not really--just go on the web and/or Ebay.

If you are working with 120 VAC and 15 amps or less--the K-A-W is a great meter for the price. There is a battery backed K-A-W version if you have the occasional power failures and don't want the meter to reset back to zero.

On Ebay, you can get old electric utility billing meters. I have a very old one that is configured for 120 VAC. Most I have seen on Ebay are for 120/240 VAC and either need to be connected to 240 VAC (directly or with a small transformer for the other phase)--or run at 120 VAC and simply divide the kWhr readings by 1/2. The spinning "wheel" can be timed with a stop watch to let you see the current Watts being produced.

I just went to EBay and searched for "kWh meter" and found a bunch. Used utility meters for 4x for $40, $100-$200 electronic sub-meters (some with software for connecting to a computer), and $2,200+ lab systems.

It all depends on what you want.

Personally, I would go with the kill-a-watt meter until you understand more of the details and what you will need next. Also, the kill-a-watt meter can be used around your home and friends places to show them how much power their old fridge/freezer or entertainment system is costing them every month.

You seem to be in Texas, so a Kill-A-Watt should be appropriate for your needs. That and a decent DMM (digital multi-meter) will get you about 99% of what you need.

Many of the other meters (used utility meters and such) are designed for much larger loads than a small GT inverter... So, many times, the kWhr reading is in xx,xxx kWhrs... The K-A-W goes down to 0.xx kWhrs -- much more accurate for your needs. Also the K-A-W can measure freqency, VA, PF, current Watts too. Hard to beat for less than $30.

-Bill

Re: Small meter question

No, that is a standard k-a-w meter... I would guess that it will not read consuming or generating power any differently (i.e., count down when generating, counting up when consuming).


I could take mine and cut an extension cord to check (reverse the male/female connections) and put current backwards through the meter to check--but it is not worth it (to me) to cut up a couple of perfectly good cords.

This is the meter we recommend around here to measure appliance loads and kWhr use (whether for conservation, or for planning the AC usage for an off-grid system).

Just get the k-a-w meter and experiment... You are not going to find any other meter that is as easy to use and as cheap to purchase for the job.

Figure out the error from your standby current (may be very small--I have no clue)--and well below the overall accuracy of your meter anyway.

In general, your daily output, even on clear days, will vary by 10% (temperature, wind, water vapor, dust, pollution, etc.) anyway... Don't get pulled in trying to measure you accuracy to 1.0% or 0.1%...

A 250 watt GT inverter will generate around 1kWhr per day--that is $0.10-$0.15 a day worth of power... You are, potentially, worrying about $0.001 or $0.0001 worth of electricity per day. It would take years to even add up to $1.00 worth of error. And centuries to pay for a more sophisticated metering setup.

-Bill

Re: Small meter question

Depends on what you want the panels for...

I tend to stay away from amorphous panels. Typically, they degrade in the first six months about 20% or so... In theory, they don't degrade much more after that--but because many are "budget" panels, they don't last as long as the mono/poly crystalline panels (perhaps 10 years at best, vs the 20-25+ years for crystalline panels from good vendors).

In general, take the price of the panel and divide by the wattage.

Smaller panels tend to be around $10 per watt, and larger panels down towards $5 per watt (or less)...

Also, you need to look at the costs of shipping and insurance. Shipping costs are not cheap and the panels are fragile (thin glass).

I recommend you decide on your load requirements first, then look for the panels you will need... Depending on what you are looking at (off-grid, grid tie, PWM or MPPT controllers, etc.), your options will be different.

Also, if you can get reasonably priced panels in a larger wattage--I like those because there are fewer electrical connections and mounting points required (i.e., I would prefer 1x 150 watt panel vs 10x 15 watt panels).

I would start with our host's store--look at their product, pricing, and shipping costs first. You can always search the Internet for better deals (and I would suggest) nearer your location (once shipping and taxes are taken into account).

You will probably find it difficult to get a "good deal" for one 200 watt panel--once shipping/insurance costs are taken into account unless you can find it local (check with installers in your area and see if they have any "extras" or can add a couple panels to their next purchase).

If you are playing around and getting an education, a dozen amorphous panels and a 250 watt (illegal) grid tied inverters are not the worst place to start. With Enphase now offering UL Listed 175-250 watt grid tied "micro" inverters--you might look at getting one of them instead... However, they are only for 240 VAC split phase power (for your 120/240 VAC home power, but require a 240 VAC hardwired connection)--and, legally, require a building permit and utility approval for installation... Also, Enphase are safer and more reliable than the 120 VAC Ebay inverter specials.

If you expect this installation to function for more than a few months or years--then look for good products (new or used--used crystalline panels from good vendors produce about the same amount of power as new--with very little, if any, degradation over time). Anything less is just tossing your money away.

-Bill

Re: Small meter question

The problem is that with Grid Tied--you can not have "plug and play" and have a safe and legal system.

You need a dedicated branch circuit (plus other requirements) so as not to create a wiring hazard (15 amp service, with 15 amp breaker + 15 amp GT inverter = 30 amps on wire available for a short circuit/overload if sharing outlets).

Plus most (if not all) utilities require notification/permits/insurance from the GT system owner.

-Bill

Re: Small meter question

One is from Hong Kong, the other California... I don't do Ebay (my choice)--so I have nothing to add there.

The question still is "what are you going to do with them"... The listings do say if there are blocking diodes (or by pass diodes either) installed. Your application (grid tie, off grid, battery bank voltage, AA charger, whatever) will usually constrain which panels you can use for your application.

Not a big deal, but you might either need to add a small charge controller or a blocking diode to prevent discharging the battery at night/dark for the 2 Ebay panels listed.

If you just want to get some small panels in your hands, search Ebay for "VW Solar". You will find some 3-6 watt solar panels that VW puts in their cars for shipping overseas (to keep the battery charged). They are cheap and plentiful. And probably built pretty well. There are both crystalline and amorphous panels available--you will have to check the pictures/ask to get the crystalline panels (if that is what you want).

Or, you can look at NAWS' store--the larger panels even have 20 year warranties and are not much different in price than the Ebay ones. I don't know what the shipping costs NAWS would charge (I am not connected with their store in any way).

-Bill

Re: Small meter question

You would not need the blocking diode with a GT inverter.

But, how many panels are you thinking of getting/using? 20x 10 watt panels vs 1x 200+ watt panel?

10 or 20 watts of solar on a 250 watt GT inverter will, probably, just barely turn it on.

-Bill

Re: Small meter question

It depends on what use you want to put the panels to. For example, a small 5 watt panel to trickle charge a car battery without a charge controller--then you want the diode.

If you have a 100+ watt panel to charge a car sized storage battery, you will probably need a solar charge controller to prevent overcharging the battery (and then, a diode is not needed).

-Bill

Re: Small meter question

The first answer is, go ahead and just put a blocking diode on the solar panel, and a second one on the wind generator (if needed) and wire the two in parallel to the GT inverter.

The next level of detail... This is a terribly inefficient way of combining power... There are times when the wind generator will probably raise the input DC voltage above that of the solar panel (panel at 17 volts, generator at 24 volts). Practically speaking--it does not matter much. The solar panel is 1/10 the output of the wind generator--so would not add much when the turbine is running at speed. Also, unless you live in an area that has 12+ mph average winds most of the day (a very miserable place to live) and mount the wind turbine on a 30'+ high pole 300 feet away from any obstructions--the wind generator will rarely output any usable energy at all.

The third level of detail... A 20 watt panel on a 250 watt GT inverter is probably going to consume more energy than it uses...

For example (numbers are made up--but probably close enough for a guess), assume the GT inverter has 4 watts of standby power requirement (night light).

24 hours * 365 days/yr * 4 watts * 1kW/1,000W = 35 kWhrs per year standby losses

And lets assume you are somewhere near Fort Worth Texas. From the PV Calculator site, enter in 1 (1 kW of solar panels) and accept all the defaults.

For 1kW of solar panels, we find that a solar GT system will generate ~1,404 kWhrs a year of power. For 0.02 kW of solar panels:

1.404 kWhr/yr * 0.02 (your 20 watt panel) = 28.1 kWhrs per year

So, as configured (ignoring wind turbine), your 20 watt GT setup may end up costing you as much as 7kWhrs per year ($0.70 per year) to run and not generate any net usable energy for your home.

Even assuming zero watts standby, you are only going to generate about $2.80 per year worth of electricity (based on a $0.10 per kWhr energy rate).

Regarding the energy output from a 200 watt wind turbine--If you are in east Texas, you at best have only a class 1 or class 2 wind rating... As I understand, wind is not really practical unless you are in a class 3 or better area.

Again, if this is for your own education--go for it... If you are trying to do something "green" and practical--don't waste your money and spend it on conservation instead (more ceiling and wall insulation, wheather stripping, CFL lighting, timers, power strips to turn off unused loads, double pane windows, etc).

And use your brand new Kill-A-Watt meter on all of your electrical appliances too see which should be shut off with a power strip when not used, and which should be upgraded with Energy Star appliances.

-Bill