What's wrong with something like this?

Thick8 · August 2018

https://theinverterstore.com/product/3000-watt-solar-10000-watt-pure-sine-power-inverter-charger/

It seems reasonably priced and a large majority of the reviews of the individual components are 5 star.

Free shipping and no sales tax. $3250 federal tax break. $500 a year for 7 years SC state tax break. Making a real cost of $4000 before any grid savings. With an average monthly electric bill of $150 this package would pay for itself in 2 years.

BB. · August 2018

Ignoring the actual system and costs for a moment... Just to take some generic back of the envelope calculations:

3,000 Watt array * 0.52 off grid system eff * 5 hours of sun per day = 7,800 Watt*Hours per day
7.8 kWH per day * $0.20 per kWH hour utility cost = $1.56 worth of utilty power per day
$1.56 per day * 30 days = $46.80 per month power costs (sunny months of the year)

Assume average usage is ~75% (or even as low as 65%) of generated power (you cannot use 100% of off grid energy per day--Some days more sun than you use, other days, you have to cut back or use utility/genset power when the weather is bad/winter).

$46.80 * 0.75 usage factor = $35.10 average energy usage per sunny month
$4,000 / $35.10 per sunny month = 114 months

That is almost 10 years (or more, if you assume that your average sun is is 4 hours or so for entire year).

Replace AGM batteries every 5-7 years. Repair/replace electronics (inverter, charge controller) every 10+ years.

Short answer--Off grid solar power is not going to save you any money. And to generate ~$150 per month of "useful" power, you would need ~5x larger array and battery bank (~15,000 Watt). More costs...

In general, if you want to save money on utility power, look at conservation (lots of insulation for summer cooling/winter heating), Energy Star rated appliances, possible Heat Pump HVAC system, etc. Look at appliances (fridge, freezer), home entertainment (older TVs, Radios, DVRs, etc. can take quite a bit of power, even on "standby").

-Bill

Thick8 · August 2018

I got more from this one response than I have from reading 10+ articles on the subject. Thank you .
I think that what I really want after delving into solar is a backup system. With solar to keep the batteries charged.
oh yea, I’ve already have energy efficiency appliances, insulated all around, doors and windows upgraded, encapsulated crawl space.

MrM1 · August 2018

I think you could do it for less with higher end gear.

Photowhit · August 2018

What is truly sad about the information, is that they say "... A more economical solution if your inverter doesn’t need a ETL/CSA to UL 458 listing." UL 458 is the standard for Mobile application! It's not even the standard for home installations, which is UL1741!!!

One of the hard things about off grid solar applications is that you need a system large enough to supply your needs year round to achieve even a 65% usage of the potential of the system your energy needs must closely match the amount of available energy.

So if you need solar energy in the summer to run an air conditioner and you reach the maximum percentage possible of about 75% since you will still have cloudy days and need to reach full charge a few times a week. But in the late fall, winter and early spring you don't need to run an air conditioner, that extra potential is lost. I live every close to the potential of my system. I doubt I use 65% of the available energy.

oil pan 4 · August 2018

3,000w worth of panels will only generate around $1 per day worth of power.
That's only if you consume every bit of that power, such as you use a grid tie inverter.

So if your power bill is $150 you are probably using 1,000 to 1,500 kwh per month. 3kw of panels is only going to generate 400 to 500 kwh per month.
To go off grid you shout be looking at getting more like 20kw worth of panels.

If you haven't you may want to switch all appliances to gas, mainly the water heater, stove and furnace.

If you want a power backup system get a generator or some grid charged batteries and an inverter. Then if you are really into backup power get batteries, inverter, generator and appropriate battery charger.
Then if money is no object a hybrid solar and generator.

Thick8 · August 2018

Ah, the 12kw one is UL1741. https://www.aimscorp.net/12000-Watt-Inverter-Charger-48-volt-120-240vac.html
This one is a 100a service that I could hook between my meter (100a) and breaker box. Throw a few thousand ah of batteries in the mix and I’m backed up for a while depending on the season. btw, I have gas heat and water.

Estragon · August 2018

The inverter takes 200w just being on with no load. That's 4.8kwh/day. For 2 days autonomy, 400+ah bank just to keep the thing lit. A few thousand ah indeed!

oil pan 4 · August 2018

Better inverters have lower standby power draw.
To generate and store 5kw per day just to cover it being on would require about $2,000 to 3,000 worth of panels and around $1,000 to $2,000 worth of batteries. You are better off spending that money on a better inverter.

Thick8 · August 2018

No kidding! I saw the <25w standby but the 200w didn't register. Thanks for pointing that out.

oil pan 4 · August 2018

That inverter would be good for like a backup, or if you needed to turn it on for short bursts of power then turn it back off, it's not really good for being on all day.
But it's still a lot more efficient than running a generator all day.

MrM1 · August 2018

Besides the standby power draw being hi (as noted) You also have to keep in mind that in that Kit being offered there is no Balance of System (BOS) gear really to speak of. There are no breakers, no sub-panel for your solar circuits, no wiring to speak of (you need a lot more than what is included) AND if you must meet some kind of code inspection, while the kit might give you a UL 1741 inverter, in most jurisdictions in the US today if they are under NEC code for 2017 you also have to have a rapid shut down system for the panels and inverter and battery bank (if the bank is 48v). So depending on how you set it up and what might be required, there is a good bit of expense in the install you may not have considered. Just some things to think about.

As to savings: My system consists of 9 panels totaling 2565 watts with a 3400 watt inverter (see the link in my signature for my full set up) and a 435 Ah 24v battery bank. I knew going in the what the costs would be to install the system, and I also knew my intention was not to save money. It was being designed as a back up solar generator. I have the system set up to utilize almost as much power as the system can generate daily thru diversion loads heating water after the batteries are charged. I am capable of generating in excess of 12.5 kWhs per day. On most average weather days I generate 8-10 kWhs per day. I have generated just over 1.8 megawatts since Oct 2017. It sounds like a lot, but in reality it equates to about 20 a month off my electric bill on average the past 10 months. I knew this going in, and knowing that battery life is 3-5 years at a cost of $1300 ... my only hope in the savings I knew I would see was to save enough to merely replace the batteries every few years or so and possibly an upgrade or panel replacement as needed.

So please be aware that the savings you seek, may not pay off the system as quickly as you hope... and probably never will. So it really depends on what your goals are.

Thick8 · August 2018

I like your setup. I think that's sort of what I want. The essentials for power outages. I can run the A/C, dryer, sprinkler pump, under house de-humidifier, and pool pump on 1 of my current 100a circuits and half of the other 100a circuit Then put the rest of the house on a 50 amp circuit with battery backup. Once I take out those big power draws I don't use much electricity at all for day to day living.

So would it be better to have the batteries cycling or just set up for standby with solar hooked up to keep them floated with a little extra for minor outages?

oil pan 4 · August 2018

How many kwh are on your bill per month?

bill von novak · August 2018

Thick8 said:

https://theinverterstore.com/product/3000-watt-solar-10000-watt-pure-sine-power-inverter-charger/
It seems reasonably priced and a large majority of the reviews of the individual components are 5 star.
Free shipping and no sales tax. $3250 federal tax break. $500 a year for 7 years SC state tax break. Making a real cost of $4000 before any grid savings. With an average monthly electric bill of $150 this package would pay for itself in 2 years.

It's a terrible price and would likely never pay for itself. Problems:

1) The "10,000 watt inverter" isn't. 10,000 watts at 48 volts is 208 amps. 1/0 cables will not handle 208 amps and those batteries won't put out that much current.

2) Those batteries (12 of them) would need to be wired 4s3p, which guarantees rapid failure under heavy cycling. So you'd be looking at replacing them at ~300 cycles (i.e. once a year.)

3) It's just not a good price. Let's price it with solid conventional gear:
-3000 watts solar $1500
-3600 watt inverter $1700 (GVFX3648)
-80 amp charge controller $500 (FX80)
-24kwhr of batteries (Rolls-Surrette S550) $2700

So you are at $6400 with all the basics paid for. For another $2000 you add racking, wire and all the other BOS items - and you are at $8400 without labor.

Or go with a 3000 watt grid tie system for $5000 without labor. Much cheaper.

oil pan 4 · August 2018

Traditionally going grid tie means you can't use your solar power at all when the power goes out.
But now we have the sunny boy SPS which gives you up to 1,600 watts while the sun is directly on the panels.

MrM1 · August 2018

Thick8 said:

I like your setup. I think that's sort of what I want. The essentials for power outages. I can run the A/C, dryer, sprinkler pump, under house de-humidifier, and pool pump on 1 of my current 100a circuits and half of the other 100a circuit Then put the rest of the house on a 50 amp circuit with battery backup. Once I take out those big power draws I don't use much electricity at all for day to day living.
So would it be better to have the batteries cycling or just set up for standby with solar hooked up to keep them floated with a little extra for minor outages?

What bill von novak said above is what I was trying to say at post #4 when I said you could do it for less with better gear (I did not have time to write it out - bill said it better)

What are you thinking your loads would be once you separated out the "essential" loads?

Thick8 · August 2018

Maxed out I’m just over 6000w. But that’s with both gaming computers at full power and 2 laptops, 2 iPads, and 4 phones charging. As well as the fridge and a bunch of lights and a couple of ceiling fans. Realistically I’ll probably be drawing about 2000 watts at any given time with jumps to about 3500-4000 occasionally. I will probable run down to Lowe’s for a 5000 btu window unit if the power is going out in the summer. Figure in another 500 Watts for that and I’m looking at about 4500 Watts. Add some for loss and stuff I didn’t think about and this looks like the inverter. https://www.solar-electric.com/sma-sunny-island-6048-us-inverter.html

MrM1 · August 2018

But if you are trying to plan a battery bank size and solar charging system, you will also need to know with a pretty good degree of certainty, what your Daily WATT HOURS are. Not just your watts at any given time. You might be surprised. You might want to start with a note book and a Kill-a-Watt meter. Let it run on appliances like fridge for 2-3 days and then average the total out to a 24 hour period. do this for everything you got / possibly can. It will take about a week to 10 days, but will give you a really good idea of how much power you need per day.

mcgivor · August 2018

For a backup system this is extremely large, generally the essential loads are what the capacity is based on, not a whole house no conservation calculation, depending upon how long the outages are, the battery capacity would be enormous. The costs associated with something that only gets used on occasion would probably exceed that of a standby generator, remembering that batteries need replacement wether used or not, they die of old age. Then again if money is no object anything is possible.

Thick8 · August 2018

MrM1 said:

But if you are trying to plan a battery bank size and solar charging system, you will also need to know with a pretty good degree of certainty, what your Daily WATT HOURS are. Not just your watts at any given time. You might be surprised. You might want to start with a note book and a Kill-a-Watt meter. Let it run on appliances like fridge for 2-3 days and then average the total out to a 24 hour period. do this for everything you got / possibly can. It will take about a week to 10 days, but will give you a really good idea of how much power you need per day.

I used a kill-a-watts on everything that would be needed in the event of a power outage. Then plugged the numbers into an Excel spreadsheet that I made based on wholesalesolar's calculator. I only checked each component for a couple of minutes. Other than the fridge I know how long each of the components are plugged in each day (mostly).

With the 1.5x for the DC/AC conversion and 20% loss factored in I ended up at 9098 watts per day. That's with the fridge running 6 hours per day. If I'm in emergency power saving mode then I can cut that number way down.

BB. · August 2018

Just to be be clear about the math (10,000 WH or 10 kWH per day is ~300 kWH per month--A relatively low amount of energy usage for a normal grid tied home in North America--That is good). For example:

LED lighting: 3 bulbs * 13 Watts each * 5 hours per day = 195 WH per day
Laptop computer: 30 Watts * 5 hours per day = 150 WH per day
Refrigerator: 120 Watts * 6 hours per day (or 120 Watts * 25% duty cycle * 24 hours per day) = 720 WH per day
Total = 1,065 WH per day

An example of how to use average Watts (measured for a few minutes) to estimate daily energy usage.

Or, leave the meter plugged in for 24 hours (or longer) and use those numbers... For example:

2,400 WH * 1/36 hours of measurement time (1.5 days) * 24 hours per day = 1,600 Watt*Hours per day (24 hours)

-Bill

Thick8 · August 2018

Everything I have (except my gaming computers) is energy efficient or gas. So January thru May I'm in the 350kwh range. Come the summer though; with the 4-ton A/C keeping it 70ish in the house, the sprinkler running every other morning, the crawlspace dehumidifier maintaining a 65% level, and the pool running 8 hours a day I'm at 1450kwh last month. The next couple of months will probably be about the same. I have some of that roll out radiant barrier I started installing on the roof rafters but have yet to finish the job.

oil pan 4 · August 2018

1.5 mega watt hours of power is kind of huge.
What do you need to run?

Thick8 · August 2018

I want to have all the 120v household plug-ins to remain powered. That would keep all the LED lamps, small kitchen appliances and electronics going if there's just a power blip during a storm or an extended outage due to a STORM. I would want to run an 8000-12000 btu window unit in the case of the latter as well.

It also needs to be 240 volt capable to run the gas furnace portion of the central A/C unit in the event of a winter outage. Which is is what we've had the most of the past few years. That would be on a manual switch.

So really just the winter 12kwh daily use with a window unit thrown into the mix for long term summer outage.

mcgivor · August 2018

Excessive, massive, outrageous, exorbitant, extreme are a few words that come to mind, a big old diesel generator would be a far better choice to carry on living as though nothing happened in the event of an outage, battery backup is an extremely expensive choice, but hey, if one wants to burn cash in the fireplace to keep warm, who am I to judge.

BB. · August 2018

Do you have a large propane tank on the property (or available space for one)?

An alternative can be natural gas (if on property) to power a genset.

Generally larger "off grid" capable systems only make economic sense if they are used 9+ months of the year (full time off grid). And paying $1-$2+ per kWH is pretty common for full time off grid (the upfront costs of system, new batteries every 5-7 years, new chargers/inverters every 10+ years, etc.) usually is way more expensive than running a genset at ~$1 per kWH only when the utilty power has actually failed.

Off grid solar power system will cost you about the same whether you use it 24x7 or only for 1 week a year during outages.

Using laptops (with internal batteries) and/or small UPS (uninterruptible power supplies) for "critical loads" to ride through short outages until power returns, or a genset gets started, is usually a better solution for most people.

You can build a "hybrid" solar power system (does both Grid Tied and Off Grid/emergency backup power). May cost you closer to $0.50 per kWH--And your utility has to allow GT/Hybrid solar power systems (many smaller utilities may not allow and some larger utilities these days too).

-Bill

Thick8 · August 2018

I do have NG and could add a 250-500 gallon LP tank out of site somewhere just in case we loose NG. The 22,000 watt Generac with a pre-wired interconnect is only 5 grand. That may be the way to go. I really like the idea of solar but as mcgivor pointed out, that may be a bit extreme. Maybe when we put a house on our mountain property I can re-visit solar.

I plan to still play with the setup I have in the garage. Expand it some to make it more functional so I'll be around. Thank you all for your help and input. I have learned so much about renewable solar energy these last several weeks.

Till next time...

oil pan 4 · August 2018

A 22kw generator is probably going to suck down the better part of a gallon of gas per hour at light load, probably closer to a gallon near half load.

A more reasonable approach might be a smaller generator, battery bank with inverter and sizeable battery charger or chargers?

That way you can run all the big stuff for 4 to 6 hours, charge the batteries and run all the small stuff for the rest of the time?

BB. · August 2018

You are very welcome...

You can still do some solar... A 1 kWH per day system is enough to run lights, laptop, cell phone charging, and an RV water pump. Nice for "quiet times" (nights) and just run the genset during the day/evening when you needs more power.

A 3.3 kWH per day solar system will run the above plus a full size and an energy star refrigerator plus clothes washer (and possible solar friendly well pump). But even this is probably difficult to justify for a pure backup power system.

-Bill

What's wrong with something like this?

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