Wanting to be Off Grid

DMJACDMJAC Registered Users Posts: 6
I live very rural and would like to put my house off grid ( and my electric bill behind me ). per my current utility bill I am using approx. 4500kw per month. I have put together so for a 3kw 115 volt inverter with 6 -115 AH batteries wired in parallel maintaining a 12 volt system. I have 4 - 100 watt panels going through a 30 amp charge controller. I know this isn't enough to power my home yet, but I'm stuck, how many of what do I need? I have tried solar calculators that show me anywhere from 400 batteries and 200 panels to 18 batteries and 12 panels - where does the truth lie in this?

Comments

  • zonebluezoneblue Solar Expert Posts: 1,218 ✭✭✭✭
    Re: Wanting to be Off Grid

    Hi and welcome to the forum. Theres a couple of very active mods here who will chip in shortly no doubt. In the mean time i suggest you spend some time reading the last couple of weeks posts. Almost all of your questions have been answered in that time period.

    One thing i learned about DIY solar, is that masses of reading is very much unavoidable!

    DMJAC wrote: »
    I live very rural and would like to put my house off grid ( and my electric bill behind me ). per my current utility bill I am using approx. 4500kw per month. I have put together so for a 3kw 115 volt inverter with 6 -115 AH batteries wired in parallel maintaining a 12 volt system. I have 4 - 100 watt panels going through a 30 amp charge controller. I know this isn't enough to power my home yet, but I'm stuck, how many of what do I need? I have tried solar calculators that show me anywhere from 400 batteries and 200 panels to 18 batteries and 12 panels - where does the truth lie in this?
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • BB.BB. Super Moderators, Administrators Posts: 30,055 admin
    Re: Wanting to be Off Grid

    What is your $/kWH cost ofpower?

    More or less, I would be telling you to reduce your power usage to around 450 kWH per month--then look at going off grid.

    Off grid power is very expensive. About 10x the cost of a typical utility connection.

    If you have reasons/needs to be off grid, we can help. But a system this large could cost $500,000 or even much more.

    Conservation is almost always the first/best first step.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Wanting to be Off Grid

    WOW!!! 4500 kwh/month! That's hanging around 150 kwh per day!
    Unless you do a VERY SERIOUS look at where you're using this power, when you're using that power and why, if it's necessary, and then cut WAY back on your usage, I would suggest you immediately start buying lottery tickets and Pray for a win, because you're looking at a HUGE and extremely expensive system that is virtually guaranteed to end up costing you far more than your present grid power. The #1 rule of living off grid is: Conserve, Conserve, Conserve. It's far cheaper to cut a wasted KWH than to build a system to produce that wasted KWH. Your present usage is roughly 6.25 Kwh per every single hour, and who knows what your momentary peak consumption is. Many/most off grid homes don't use that much in a whole 24 hour day. In fact many use a lot less than that.
    As Zoneblue said, start doing a LOT of reading and learning before you proceed. To be honest, with your present consumption, the items you've purchased so far are all but totally useless.
    In the meantime, the utility company that supplies your power must really love you! :D
  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭
    Re: Wanting to be Off Grid

    Grid tied is the most efficient form of producing raw electrical energy.
    Feed in Tarrifs help increase the Return On Investment.
    I highly suggest you do your homework.

    Off grid systems cost roughly $5.20 per watt and are generally 2/3 larger to scale than grid tied photovoltaics.
    Grid tied can be had for under $3.50 per watt and are much smaller in size and the utility companies are forced to pay feed in tariffs for distribution through a process called NET metering.

    If you are on grid, it is foolish to try and live off grid, its impractical by any means.
  • bill von novakbill von novak Solar Expert Posts: 891 ✭✭✭✭
    Re: Wanting to be Off Grid
    DMJAC wrote: »
    I have tried solar calculators that show me anywhere from 400 batteries and 200 panels to 18 batteries and 12 panels - where does the truth lie in this?

    Not to repeat what others have said, but you are going to need a massive system. If you really use that much power you'll need about 40kw of PV (~200 panels) and the whole thing will run you on the order of $200,000. Assuming you are in a good area for solar. To put it another way your system now is about 1% of what you need.
  • DMJACDMJAC Registered Users Posts: 6
    Re: Wanting to be Off Grid

    ok - added an extra 0 in my original post, sorry. it was a slip of the finger. as for as reading, been doing that for almost 2 years - the math doesn't make sense to me - sorry. I understand ohms law.
    but in the back and forth between usage and requirements in a/c and supply in DC throw adequate charge to batteries in with the mix and its more than my little brain can handle.
  • offgrid meoffgrid me Solar Expert Posts: 119 ✭✭
    Re: Wanting to be Off Grid

    Quick math
    15kwh per day, so 7500 watts of panels, 2 80amp charge controllers, and around 1200amp hour of battery at 48 volts call it $35000 for system. This is just very loose starting point calcs without knowing where you live and how much sun you get. No way to choose an inverter without knowing how large your loads are.
  • DMJACDMJAC Registered Users Posts: 6
    Re: Wanting to be Off Grid

    ok - I have put together so for a 3kw 115 volt inverter with 6 -115 AH batteries wired in parallel maintaining a 12 volt system. I have 4 - 100 watt panels going through a 30 amp charge controller.

    I have just checked my meter and I have used 48 ( call it 50 ) kwh in 24 hrs again, I am using a 12 volt system not a 48. based on the math I am using 1500 kwh per 30 day period anybody know what I need to add to my current system to get me to where I need to be? BTW I also have a 400w wind gen connected to my battery bank - daylight hours here is on average 10 to 12 no shade

    I also don't know if I am reading the meter correctly today 71460 yesterday 71412 multiplier is 1000
  • jcheiljcheil Solar Expert Posts: 722 ✭✭✭
    Re: Wanting to be Off Grid

    What kind of loads do you have that consume THAT much power?

    And you would need to be on a 48v system period. Don't waste any more money on 12v stuff. And 10-12hours of sun doesn't mean you get 10-12hours of power. If you let us know your city, we can lookup the exact number of "solar" hours for your area. Generally it averages out to only around 5.

    Like everyone said, you are wasting your time and money if you think you are goign to get this current system you have to work.
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
  • DMJACDMJAC Registered Users Posts: 6
    Re: Wanting to be Off Grid

    that load is with a refrigerator water heater and a well pump, using open blinds for light and 1 laptop and 1 desktop computer my current system is running my spare refrigerator and 19cu ft chest freezer since jan 15th cost to date on existing system including wind gen is 1100 - family of 5 city is Florien, La
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Wanting to be Off Grid

    You can do it , but it comes at a Price. The best is to put in a Grid Tie system and let the Grid be your batteries, use, store and sell your excess. Take what you have now and use it as your backup. Not that 450KWH per month is something that is not doable, it's all you have to spend and change to make it work.
  • DMJACDMJAC Registered Users Posts: 6
    Re: Wanting to be Off Grid

    not a very helpful answer I'm afraid, LOL I think that my biggest issue is not understanding the math a/c vs D/C vs kwh's . I know I can't keep paying almost $400/mth to the utility company, I have the money to put a system together, I understand I will need to take some power from the grid in certain instances to keep charged, but peak solar days I want to be able to provide my own power. most of what I'm seeing here and other places on the web is no one seems to agree on an actual formula for all of the above. I suppose I will just put together multiple systems like the one I currently have since I seem to be able with just the sun and some wind to keep the freezer and refrigerator running with it which equate to approx. 20 amp of use for 20 mins per hour. the 3kw inverter is able to provide just at 26 amps with double that for a surge. by my calculations 3 such systems and a step up transformer should run my house, if you disagree please provide actual verifiable math ( formula ) to back it up.
  • mike95490mike95490 Solar Expert Posts: 8,614 ✭✭✭✭✭
    Re: Wanting to be Off Grid
    DMJAC wrote: »
    ....I have just checked my meter and I have used 48 ( call it 50 ) kwh in 24 hrs ....

    I use 7KWh daily, in a very efficient house, 2 fridges, washer, gas dryer, microwave, gas for hot water & cooking. When you get your daily loads down to 20KWh, then you can run from solar, but if you are running air conditioning, or electric heating gear, it will be very tough. You will have to upgrade appliances, and then re-size your solar.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • mike95490mike95490 Solar Expert Posts: 8,614 ✭✭✭✭✭
    Re: Wanting to be Off Grid
    DMJAC wrote: »
    ....the 3kw inverter is able to provide just at 26 amps with double that for a surge. by my calculations 3 such systems and a step up transformer should run my house, if you disagree please provide actual verifiable math ( formula ) to back it up.
    Sounds like you have it all nailed down.

    the math:
    ____ daily KWh x 2 = _____ required harvest for one day usage & recharge of batteries

    Harvest depends on your local sun hours (Insolation) and array configuration/alignment:
    (___ sun hours x PV ) x .8 [use .7 if you are in a very warm area] typically, 4.5 hours, 3KW pv = 13.5 x .8 = 10.8kwh harvest

    ____ daily KWh x 3 = _____ KWh of battery bank (your bank WILL have to be 48V for your loads)

    This can be "fudged" a bit, if you are strict and load shift loads to the solar hours, so you run from the sun, not batteries.

    you can get more complicated and detailed in the math, but this should get you at least 80% accuracy. EACH install is going to be a little bit different.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • DMJACDMJAC Registered Users Posts: 6
    Re: Wanting to be Off Grid

    why 48 volt? at my current configuration 4 - 100 watt panels @ 12 volt gives me 33.33 amps charge to battery bank at 48 volts the same 4- 100 watt panels would only give 8.33 amps charge to the battery bank - causing me to spend more money on panels to get the same charge - not understanding the logic I am already using a 12 volt input 3kw inverter and to replace that to a 48 volt input inverter would be at least twice the money that I have spent,
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Wanting to be Off Grid
    DMJAC wrote: »
    why 48 volt? at my current configuration 4 - 100 watt panels @ 12 volt gives me 33.33 amps charge to battery bank at 48 volts the same 4- 100 watt panels would only give 8.33 amps charge to the battery bank - causing me to spend more money on panels to get the same charge - not understanding the logic I am already using a 12 volt input 3kw inverter and to replace that to a 48 volt input inverter would be at least twice the money that I have spent,

    Okay it's power, right?
    First, a 100 Watt 12 Volt panel even on an MPPT circuit provides 5.7 Amps to 6.4 Amps. At most four of them would provide 25.6 Amps, not 33.33. I don't know how you arrived at that number but there must be an error in it.
    12 Volts @ 25.6 Amps is 307 Watts. On 48 Volts this would be 6.4 Amps.
    Volts goes up, Amps goes down, power remains the same.
    With the exception that the 48 Volt system provides that power more as Voltage than current, and as such is more efficient because current = heat = lost power.

    On the other side a 3kW 12 Volt inverter would draw up to 300 Amps from the battery bank. Same amount of power on a 48 Volt system draws 75 Amps. Not only current = heat = lost power but also smaller wire sizes, fuses, fewer connections, less to go wrong.

    If it hasn't been clearly expressed before, off-grid is not desirable from a financial POV. Even in places where the utility rates are high the cost per kW hour is 2X more, and around here it's 10X more.

    A full off-grid system with all the power going in to and coming out of the batteries is 52% efficient end-to-end. That's lousy. It can be improved somewhat with opportunity loads but it isn't going to get close to the low cost of grid power. Trust me on this; I've repaired and designed more systems than most people ever see.

    Spend the money on conservation.
  • BB.BB. Super Moderators, Administrators Posts: 30,055 admin
    Re: Wanting to be Off Grid

    Let me try answering a different way... First, this is just simply a rough number that will help you choose a direction. Your actual costs could be 50% of what I said or even 2x as much--But from an engineering point of view, it is a "good enough" number to understand the problem and figure out what to do next.

    Very roughly, an off grid system is about 10x the cost ($/kWH) of utility power for the "average" home. So, your $400 per month electric bill would cost you around $4,000 per month in actual money out of your pocket (total cost over 20 years divide by total kWH used/generated over 20 years).

    And the cost to build such a system... Around 1/2 of that 20 year cost has to be paid for "up front" to buy the components and install the system:
    • $400 per month * 10 off grid cost * 12 months per year * 10 years = $480,000 up front cost
    Just to do some very rough math--Assume you pay around $0.10 per kWH, that is 4,000 kWH per month. Designing a nominal off grid system (the numbers I would be recommending as a starting point) would look like this:
    • 4,000 kHW per month * 1/30 days per month = 133 kHW per day
    • 133,000 WH per day * 1/0.85 inverter eff * 1/48 volt battery bank * 2 days of storage * 1/0.50 max discharge = 13,039 AH @ 48 volt battery bank
    • 13,039 AH * 48 volts * 1/(6 volt * 220 AH golf cart battery) = 474 "golf cart" batteries
    Obviously, I would not tell you to buy GC batteries--Just to give you a scale of something that you would be familiar with. If this was done with ForkLift batteries, it would look something like:

    Crown Industrial Battery - 24 Volts, 1875 Amp-hoursPrice: $7,180.66
    • 13,039 AH * 1/1,875 AH batteries * 2 (two batteries in series for 48 volt) = 13.9 = 14 fork lift batteries
    • 14 * $7,180.66 per battery = $100,529 battery bank
    Next, solar array... If you have a minimum of 4 hours per day of sun (typical US average minimum sun for ~9 months a year):
    • 133,000 WH per day * 1/0.52 over all system efficiency * 1/4 hours of sun per day = 63,942 Watt Array minimum
    And a fork lift battery typically needs a minimum of 10% rate of charge:
    • 13,039 AH * 59 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 99,909 Watt array minimum (based on battery needs)
    So--The "nice" sized array would be around 100,000 Watt... To purchase and install such an array would be in the range of $2 per watt (panels+racking+Wiring)
    • 100,000 watt array * $2 per Watt = $200,000 for the solar array
    Need charge controllers--The typical large MPPT controller is ~80 amps of output current:
    • 99,909 watt array * 1/59 volts charging * 0.77 panel+controller eff * 1/80 amps per charge controller = 16.3 = 17 charge controllers
    • 17 charge controllers * $610 each = 10,370 each
    By the way, the batteries will last ~15 years (if you take good care of them, and most people around here have "killed" the first battery bank by accident, so it may not even last 5 years)--So you will need to purchase at least one more battery bank in the next 5-15 years. Your electronics (charge controllers, AC inverters, backup battery chargers, etc.) will last around 10+ years--So there is another $100,000 expense for batteries (plus inflation which is getting really bad right now). Plus another $20,000 or more for electronics at ~10 years.

    Plus a genset (call it a 100 kVA genset) and maybe 10 gallons of diesel per hour every time you fire it up. Plus a few thousand gallons of diesel on property for long term storage/emergency use (another $50-$100,000 expense).

    As I said, we can "fine tune" the requirements--But this gives a good idea of how much it would cost to replace a $400 per month utility bill with a full off grid power station. And we have not even included the 10-30% incidentals (wiring, permits, taxes, engineering, labor if you do not do it yourself, etc).

    So, if you could justify spending $240,000 (1/2 of the cost of a solar power system) on your home to reduce power usage by 1/2--Could you think of anything that you would do to replace your bill?

    Lots (and lots) of insulation (lots of ceiling insulation), triple pane widows, awnings over windows, energy conseration appliances, a super efficient A/C / Heat pump system. Get your hot water/electric heating from a heat pump system. Reduce inside electrical usage (lights, TV, laptop computers vs desk top servers, etc.)--Less heat you bring into the home, the less you pay for A/C to move the heat back outside again. Etc....

    Don't get two wrapped up in AC vs DC kWH--From a math point of view, there is no difference. From a practical point of view off grid power is typically at 48 volts DC and your large appliances (electric stove, electric water heater, A/C, etc.) all run at 240 VAC.

    Say your peak load is 60,000 watts (just a wild guess):
    • 60,000 watts * 1/240 VAC = 250 Amp Utility Service
    • 60,000 Watts * 1/48 VDC * 1/0.85 inverter eff = 1,471 Amp "DC Service"
    You need ~6x heavier wiring/larger circuit breakers/etc. just to run the "DC side" of your home's power system... Plus you still need the AC 240 VAC wiring side too.

    Does any of this help you to understand why this much power ($400 per month utility power) becomes such a huge off grid solar power system?

    Don't get me wrong, large systems are done all the time. It is just for the "average" home owner, off grid power does not save any money when compared with utility power.

    In some places (like California) where we can pay upwards of $0.50 per kWH, installing of Grid Tied solar power system with a good net metered time of use plan, we can actually save money. A GT power system can cost $0.15 per kWH or even a bit less for solar power--But this system has no batteries and cannot run if the utility power has failed (the utility is, for all the world, like a giant AC battery bank for GT solar).

    At this point, many areas GT solar can be a good deal (and 1/4 the cost of off grid solar)--However, there significant planning/building code issues, and many utilities are beginning to put major road blocks in front of new GT solar installs. (utility does not like GT solar as their other customers are significantly subsidizing the GT solar customer--another thread of discussion).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Wanting to be Off Grid

    BB (Bill) Are you telling me that if I stick a $300 solar panel on my roof, that all my energy problems won't be solved?
    Well that sucks! :cry:
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Wanting to be Off Grid

    Obviously there is no point in educated people trying to help someone who thinks they already know everything.

    For the attitude and profanity (deleted post) DMJAC can have three days off.
  • jcheiljcheil Solar Expert Posts: 722 ✭✭✭
    Re: Wanting to be Off Grid
    DMJAC wrote: »
    excuse me?!? Dude you have no idea about me nor will you, the money means nothing, I would rather put it toward my own use than someone elses, same reason I bought a home, not renting one. I was looking for some serious help/information - not to get into a pissing contest with you or anyone else on here - but as it were - don't mess with a redneck Louisiana boy

    Dude, you have 10+ people telling you that you are wrong (and proving it to you with DETAILED examples). Obviously you are one of those people that need 11 people to tell you before you believe them. And if "Money Means Nothing" to you, then you would not be complaining about a lousy $400/month electric bill. Good luck on your fantasy. We tried to help.
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
  • bill von novakbill von novak Solar Expert Posts: 891 ✭✭✭✭
    Re: Wanting to be Off Grid
    DMJAC wrote: »
    not a very helpful answer I'm afraid, LOL I think that my biggest issue is not understanding the math a/c vs D/C vs kwh's . I know I can't keep paying almost $400/mth to the utility company, I have the money to put a system together . . . . .

    Then take that money and put it towards efficiency.

    1) Get rid of any electric heat/cooking appliances. Go to natural gas, propane, oil or solar hot water.
    2) Go to all LED/CFL lighting.
    3) Replace older refrigerators/freezers with the most efficient ones you can get.
    4) Replace older A/C units with mini-splits, or at the very least the most efficient window or central compressor system you can find.
    5) Reduce phantom loads to a minimum (DVR's are a big hitter here.)
    6) Insulate everything
    7) Increase solar gain if you are heating; decrease it if you are cooling.

    This gives you far more bang for the buck. For every $1 you spend on efficiency, you can save ~$5 on the cost of your final solar system.

    THEN - once you have done all that and dropped your monthly bill to, say, $100 - THEN it will make more financial sense to go solar.
    most of what I'm seeing here and other places on the web is no one seems to agree on an actual formula for all of the above.

    You've seen several formulas for just that. We don't know all the details (your daily loads in kwhr, what you can reduce them to) so we can't give you exact numbers. But since a large number of us here have done precisely what you are intending to do, it might help you to learn from our mistakes.
    I suppose I will just put together multiple systems like the one I currently have . . . .

    That would probably be your first mistake. (I suspect this since I made a similar mistake ~15 years ago.) Such systems do not parallel well, and 12 volts is a poor choice for a DC voltage.
    if you disagree please provide actual verifiable math ( formula ) to back it up.

    Simple example:

    At 3kW your inverter will take 250 amps at 12 volts. If you need starting surges for things like compressors (most inverters will surge to 2x their nominal rating) that's 500 amps. 500 amps is VERY difficult to design for. Just try finding breakers for that current.

    At the same power, a 48 volt system will be running at 62 or 125 amps. That is much easier to design for - cheaper, lower loss, easier to get components.
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