Grid-Tied with Backup - available inverters?

[WantsItAll]

I am considering retrofitting my 1982 home with a grid-tied with battery backup solar PV system. I understand that there are a limited number of appropriate hybrid inverters available, but don't know what models they are. At the Xantrax site, I couldn't even figure out which, if any, of there devices were appropriate. From one forum message I ran across, the Xantrax XW6048 has been replaced with a different model, but the writer did not identify the new model number.

I would appreciate anyone pointing me to model numbers (any manufacturer) appropriate for my application. I can then look up the specifications and prices and try to make sense of it all.

Thanks.

[greenHouse]

The Xantrex XWs' should still be available -- I've not heard they were discontinued.

However, the "Gold Standard" for battery-backed, off-grid inverters are OutBack. They don't have all the modern whistles and bells, but they are fairly bulletproof.

[Sunking]

What was Xantrex is now Schneider-Electric.

Here is there offerings:

But take my advice do not use battery backup. Much less expensive to use a stadby generator, and you do not have to put up with the limitations of battery power.

[greenHouse]

But take my advice do not use battery backup. Much less expensive to use a stadby generator, and you do not have to put up with the limitations of battery power.

That's absolutely miserable advice since it means living with a generator during an entire power outage, and living without power at all during generator refueling and maintenance.

For reasonably sized systems, battery backup adds about $1 per watt DC to the installed cost. For larger systems the costs improve, though some of that is economies of scale.

[WantsItAll]

Battery backup vs generator

It should be obvious that, if you have enough batteries and sufficient PV panel and inverter capacity, you can cover any arbitrary load set. It is also obvious that fuel costs and solar energy doesn't. So it is really a matter of (1) can I afford what I want to do and (2) which meets my individual requirements and desires, not all of which are economic.

Battery backup costs extra and adds nothing economically to simpler grid-tie solar, IF everything stays stable, i.e. if fossil fuel prices don't go through the roof and if a terrorist event or natural disaster does not disrupt the grid. But if the grid is disrupted for a long period of time -- weeks or months -- then folks like greenHouse will be way ahead.

I am at the stage of thinking about how to meet our power needs, and I can afford a reasonable amount to do so. So there are difficult decisions ahead. I appreciate your perspectives on them!

[Sunking]

That's absolutely miserable advice since it means living with a generator during an entire power outage, and living without power at all during generator refueling and maintenance.

For reasonably sized systems, battery backup adds about $1 per watt DC to the installed cost. For larger systems the costs improve, though some of that is economies of scale.

Oh I do not know about that. With a standby generator you do not have to do without things like Air Conditioning and heating, electric cooking appliances, water pumps for those on wells, ect.

At my home we use LPG for cooking, hot water, and heat so we have have an 1100 gallon tank. Personally I have never had to run the generator more than a day during outages, and that only happens on average every other year.

For those with NG at their home there is an endless supply of cheap fuel available.

As for cost, well do not think battery is any less expensive as it requires a much more expensive grid tied inverter, and with most systems they use a generator to keep the batteries topped off. So I guess I fail to see the gains you are speaking of.

[Sunking]

It should be obvious that, if you have enough batteries and sufficient PV panel and inverter capacity, you can cover any arbitrary load set.

OK so put a number on it. How much energy do you need each and every day? Depending on location of where you live, you will pay $3000 to $5000 for each kilowatt hour you consume per day. $1000 of that is just in battery cost that need replaced every 5 or so years. So if you can live like a hermit on 10 Kwh per day, you are looking at $30,000 in equipment cost, and $10K recurring cost every 5 or so years to replace the batteries. For less than $10K you can install a generator to supply you with 50 Kwh per day like nothing ever happened. Fuel cost per year based on two weeks per year operation $150.

[greenHouse]

Oh I do not know about that. With a standby generator you do not have to do without things like Air Conditioning and heating, electric cooking appliances, water pumps for those on wells, ect.

Having read a number of your posts I'm left with one major question.

Do you really design solar power systems? Because I have clients who run all those things off solar and aren't paying the kinds of outrageous amounts of money you assert have to be paid. Nor are they seeing maintenance costs where you claim they are. Or living like hermits.

What can't be done is ignore that the power is out, has been out, and will be out for an extended duration. But if that happens, you've got bigger problems than "I have no AC". I spent days on end in New Orleans after Katrina and we went =weeks= (and months ...) without electricity (and gas and water) and the problems were difficulty getting food and gasoline, a lack of stores to buy durable goods, a lack of medical facilities, etc. A standby generator (and I worked on a few of them as well) is a nice gadget, but in that scenario, fuel is the problem, unless you have a large tank, and I don't see that cost factored in. Or the lack of NG when the pipe line compressors all stopped working after the gas lines were full of water ...

That's the real world.

Solar works because the sun persists in coming up. Standby generators don't because there's no law of nature that makes the gasoline, natural gas or LPG keep showing up. And the price you quoted doesn't cover days or weeks of fuel storage and the infrastructure costs of same.

[WantsItAll]

Sunking: I'm with greenHouse on this one. Not only do you not walk the walk (a generator and no solar at home), but you don't even talk the talk. Though you obviously have some knowledge about power systems, you definitely don't live up to "Solar Fanatic"! I'm guessing that you may install grid-tie batteryless systems, but after reading your posts, I certainly wouldn't use your services.

Nevertheless, skepticism is a good thing to keep one grounded and realistic, so thank you for that! I'm just glad there are enthusiasts to balance your skepticism. And from what I can tell, greenHouse walks the walk and can speak from real-world experience.

Having read a number of your posts I'm left with one major question.

Do you really design solar power systems?
...
Solar works because the sun persists in coming up. Standby generators don't because there's no law of nature that makes the gasoline, natural gas or LPG keep showing up. And the price you quoted doesn't cover days or weeks of fuel storage and the infrastructure costs of same.

[Sunking]

Having read a number of your posts I'm left with one major question.

Do you really design solar power systems? Because I have clients who run all those things off solar and aren't paying the kinds of outrageous amounts of money you assert have to be paid. Nor are they seeing maintenance costs where you claim they are. Or living like hermits.

You need to stick with facts, I am not talking about Stand Alone OFF GRID Battery Systems, I am talking about Grid Tied with Emergency Stand By Back Up power.

People with Stand Alone Off Grid Battery Systems do not get luxuries like air conditioning, electric hot water, and electric cooking as the cost would be enormous and prohibitive to provide with solar. Off-Griders are folks who live very modest life styles in remote areas where commercial power is not available to them.

[Sunking]

Sunking: I'm with greenHouse on this one. Not only do you not walk the walk (a generator and no solar at home), but you don't even talk the talk.

Well I can understand your POV, as you seem to think a RE forum should only pitch the very narrow view of RE approach only. Unlike Greenhouse I do not represent any one narrow segment of the electric power generation market. This forum does not sugar coat the RE world. It is honest and presents the broad view and offers the user choices by informing them of all options and cost so they can make a informed decesion. If you want a narrow RE only POV I suggest you go to a vendor forum who only pitches the RE answer only.

I have worked for and with electric utility companies in generation and distribution, telephone and high tech companies as a power protection and distribution engineer up to around 2001 when the bubble broke in the telecom industry. At which point I started my own architectural engineering design/build firm where we now do work for utilities, telecom, commercial, and industrial sectors.

On the solar side 90% of our solar work is on the telecom side with wireless carriers cellular towers. All that is strictly remote cell tower sites where no commercial power is available at any cost. Only option is off-grid stand alone battery systems. On the grid interactive side most of that is on consulting bases with Electrical and Roofing contractors. These two industries do the residential grid tied systems. A typical residential electrical or roofing contractor usually offer a very narrow product line cookie cutter designs. They use use to stamp the pre-designed cookie cutter systems. There is very little money in residential work.

On the commercial side we have done quite a few grid interactive systems here and there with the largest being a 500 Kw system for a Walmart.

The point of all this soap box speech is I work all the segments of electrical power, not just a small segment. My job is to inform the client with all the options and associated cost and risk involved so the client can then make an informed decision. Once they make the decision, I could careless which route they go as I do not represent anyone segment.

[Sou]

I would appreciate anyone pointing me to model numbers (any manufacturer) appropriate for my application. I can then look up the specifications and prices and try to make sense of it all.

Thanks.

Sunny Backup is another option that might be available to you. It's designed to work with SMA sunny boy inverters I believe. Depends how much reserve capacity you want/need and what you're prepared to pay for it.

http://www.sma.de/en/products/backup-systems.html

[greenHouse]

You need to stick with facts, I am not talking about Stand Alone OFF GRID Battery Systems, I am talking about Grid Tied with Emergency Stand By Back Up power.

People with Stand Alone Off Grid Battery Systems do not get luxuries like air conditioning, electric hot water, and electric cooking as the cost would be enormous and prohibitive to provide with solar. Off-Griders are folks who live very modest life styles in remote areas where commercial power is not available to them.

That's where you're just plain wrong, and I have more than a few clients who defy your assertions.

One of my clients, out in Hill Country (Mason County, since you're in Texas) has air conditioning, and they aren't filthy rich. Many others lead far less than "modest" lives, they simply don't waste electricity like they are some kind of drunken sailor on a three day liberty. I'm doing a bit of software testing and my nice little three bedroom in Austin is spending some time off-grid so I can verify parts of the software that are geared towards off-grid people. And while we're having a bit of miserable weather at present, my far-less-than-$10K battery bank will carry me for a few days while I wait for the weather to improve (you can look at the real-time array performance here -- http://data.digitalgnomon.com:8080/?port=3&array=y), or not. I need the batteries closer to 47 volts than 49 volts and may just recharge my electric motorcycle to get them there. FWIW, my motorcycle draws more than my A/C when running. It also runs for several hours at a go.

Point being that living with a hybrid system isn't goom-and-doom, and many scenarios where backup power is needed don't work with generators. I worked with these people -- http://dianelent.com/common1.htm -- for 18 months, off and on, and my life would have been =much= better if we'd had solar, because we couldn't always get gasoline, and we couldn't always keep generators running, and the noise just plain got OLD after a while.

The other point is that why the heck did I spend $19K (my original system cost minus the original batteries) if several times a year I lose power? The $2K for the original batteries -- which were sized small because I knew I was going to add more -- meant the difference between hot-transfer from grid to batteries and =zero= outages, except the ones I schedule, for more than 3 years. ZERO. With a generator, that would have cost more than $2K, I'd have experienced all the outages my neighbors experienced, just for 10 to 30 seconds at a time, and I'd have routine generator runs to exercise the generator, plus annual service calls to check up on the generator, plus ... and those add up.

For the most part, your posts read like someone who just doesn't understand solar, or else who has an agenda of selling generators and grid-tie-only systems. You seem like a smart guy, so I'm going with "has an agenda", but that's just my opinion.

[greenHouse]

The point of all this soap box speech is I work all the segments of electrical power, not just a small segment. My job is to inform the client with all the options and associated cost and risk involved so the client can then make an informed decision. Once they make the decision, I could careless which route they go as I do not represent anyone segment.

I think that if you actually stuck with actual facts I'd have fewer problems with your posts. What you seem to do is present the absolute worst case scenario for whatever you're disagreeing with, and then paint an unrealistically rosy picture for whatever you're advocating.

Battery back-up is, based on all the clients I work with (most of my clients are installers), about a $1 to $1.50 "surcharge" over straight grid-tie. Tell me the array size in DC watts, and the cost of making it a hybrid system -- hybrid, not stand-alone -- is about that many extra dollars, to perhaps 1.5 times that many extra dollars. For what it costs to add batteries to a 3KW residential system -- fairly typical in many parts of the country -- you can't even get an automatic start standby generator installed, along with the rest of the work associated. A bottom of the line Generac is $2,000 just for the hardware. That's no installation, site prep, gas service changes, etc. AND, you still get all the power outages, they just are limited to 10 to 30 seconds.

[Sunking]

One of my clients, out in Hill Country (Mason County, since you're in Texas) has air conditioning, and they aren't filthy rich.

Prove it, show me your calculations. My guess if true they live in a very small home built like a refrigerator and use a 1 ton or less cooling system, and they live on a coop system with extremely high electric rates and monthly service connection charges. No one in their right mind would choose to pay more than $1 per Kwh if there were other options. Which brings me to my point, show all the options. How many Hurricanes does Tx Hill Country experience in the last 100 years?

FWIW I learned the solar design practices from John Wiles of NMSU and Sandia National Labs back in 1997 to 2001 while setting on the NEC code panels. If you do not know who John Wiles is or read any of his suggested design practices, then you are the one who still wet behind the ears and lacking experience. My guess is you are right out of UT or TAMU lacking real world experience.

It is really this simple if solar were the most economical and reliable solution out there, industry would use it. Fact is they do not unless there is no other option. Investigate any industry with mission critical application, you will not find a single solar panel. What you will find is battery plants and UPS systems, all backed up with diesel generators in the event of a commercial power outages.