Newbie question: accessing solar power when grid is down

Hi all, and thanks in advance for you patience with this question.

I have been doing quite a bit of research on solar power and do want a grid tie sytem. Makes the most sense for a number of reasons. I am not looking at 100% replacement of my current usage or anything that spectacular, just to augment with the option to grow later if it makes sense.

However, it has been a bit unclear what it would take to have access to that solar power in the event that the grid is down. Again, not 100% replacement but enough to:

1) access the power that is generated during the day
2) provide minimal battery backup overnight for a single medical device.

(For the record, loss of use of the medical device is not life threatening)

I guess my thought has been that if the grid is down and its sunny outside, why can't I access the power generated by the panels during the day?

So here are my questions:

1) I understand that it is not necessary to have a 1:1 match between the solar array output and the battery backup. Is this correct?

2) If I have a very small battery backup (lets say 2 midsized batteries...I only need a minimum of ~2 amps contnuous (200W device) overnight in an emergecy), and the solar array is much larger than required to charge these batteries, can I access that extra power during daylight hours? (This is the bit I am confused about)

Let me rephrase that question: If the grid is down and the sun is shining, am I drawing power from the batteries or the solar array? What limits the system during daylight, the battery capacity or the solar array output?

3) I have noted that the efficiency of a battery backup system is significanly less than a straight grid tie system. Is this still true if I am just keeping a very minimal battery backup? In other words, is the loss in efficiency due to the size of the battery charging or due to inherent losses in the MPPT charger system?

As noted above, I am not trying to have a uninterrupted power supply. The backup "circuits" would just be plugs I could access with extension cords. Frankly, its mostly a matter of having a bit of "emergency" power supply just in case.

I noted that the Outback FlexWare 500 has knockouts for a GFI outlet, which is what started my thinking on this. That outlet would meet my needs for "emergency" power and now its a question of what it would really take.

Now, if is going to cost thousands of dollars and a severe drop in efficiency, I guess I will drop it. It just seems odd that the current system designs don't seem to allow access to the power that is available. I assume this is due to regulations related to the intertie, but it would be cool to get access to the solar array in an emergency.

thanks in advance!

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Newbie question: accessing solar power when grid is down

    Well, your options are:

    1. Grid Tie, no solar backup power
    2. Off-Grid, no GT back to the grid
    3. Hybrid, Grid Tie with Off-Grid backup
    4. Home Brew:
    • a. Configurable wiring of solar panels to switch to battery charging
    • b. Connect "GT Inverter" to "Off-Grid Inverter"--GT will backfeed and charge batteries through Off-Grid Inverter.
    Referring to above:
    1. Cheapest and least maintenance costs. If you don't have many outages--do this, and get a generator (gas, natural gas, propane) for emergency backup
    2. Certainly less efficient--makes most sense if no grid available
    3. Hybrids are nice, should be more efficient than #2. Basically, a solar powered UPS with Grid Tie inverter.
    4. Hombrew:
    • a. can be done, switches and/or jack panel. Certainly easy to wire a part of your array (maybe 1/4 or so easily, more of the array requires more work and pre-planning). Issues with code and safety (depending on how you do it).
    • b. Also can be done--but at this time, I don't see any good (safe and reliable) way of integrating with a battery charge controller (complex system design issue). Go with #3 if you need a "full" sized GT / Off-Grid system.
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2
    System2 Posts: 6,290 admin
    Re: Newbie question: accessing solar power when grid is down

    Thanks for the reply....

    I guess I am a little confused. If I just put many thousands of dollars of PV panels on my roof, I don't understand why I should go out and get a generator! Your answer is consistent with everything I have read, so I am not really questioning it. I just don't understand what it is about this setup that makes it so difficult/expensive to allow me access to the power the system is generating!

    For instance, I have to assume that the inverter and associated control equipment is creating a nice, clean power output for the utility company when the sun is shining. Why can't I just have a "sunshine" plug that gives me access to this when the grid is down? I could plug a completely separate battery system into the array if the grid goes down....in my mind (small as it may be) this seems reasonable yet all the information says that this is either "impossible" or "expensive".

    My question is in earnest. If there is a technical reason, I would really like to know it. It just makes little sense to me that I can't tap into that output when the grid is down without the expense and complexity of adding a battery backup in the middle.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Newbie question: accessing solar power when grid is down

    Yes, there is a reason why the "average" GT Inverter turns off when the utility power is down...

    Basically, a GT Inverter is the exact opposite vs an Off-Grid Inverter...

    The OG Inverter, outputs exactly 120 VAC @ 60Hz (Regulated Output). The DC input to the OG Inverter is variable current (and voltage to a degree) that the OG Inverter just takes, what it needs to supply its AC output.

    The GT Inverter, on the other hand, more or less regulates on the DC input. And the output voltage & frequency is set by the utility (think of the utility as being a giant "AC Battery" for all intents and purposes).

    The GT Inverter, monitors the input voltage and available current from the solar panels using the equation P=I*V (power = current * voltage). What it does, is it looks for Pmax based on Imax and Vmax, many times a second--and transfers as much power as possible (and legal) to the AC Utility lines.

    If you tried to run a GT Inverter without an AC voltage for it to follow--it will assume the AC Mains have a problem and will shut down for safety (prevent electricution of utility workers and such).

    There are other issues too... One is that a GT Inverter, typically requires 200-600 VDC for operation. The Solar Charge Controllers, which power the battery bank and OG Inverters, typically use Vbatt+a few volts to ~140 VDC maximum... So you cannot just "swap" the panels from a GT Inverter to a Solar Charge Controller.

    Another is that to be able to switch between AC Mains + GT Inverter to OG Inverter only--there needs to be an AC Transfer Switch (extra parts and money).

    If you want a true hybrid system... The Xantrex XW series is a really nice system. But, it will cost a lot more to install vs the standard GT Inverter.

    Got to go now--please feel free to ask more questions for when I return.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Newbie question: accessing solar power when grid is down

    if the only thing you are worried about is a noncritical piece of medical equipment to be backed up, then go with a full gt system and place a battery and charger into it to run a inverter that will power that medical device for times when the power isn't available. all other methods and ways, as few as there are, would be overkill for that one thing to be powered. this sounds like it might be a cpap machine. we have had some conversation on that subject.
  • System2
    System2 Posts: 6,290 admin
    Re: Newbie question: accessing solar power when grid is down
    BB. wrote: »
    Well, your options are:

    1. Grid Tie, no solar backup power
    2. Off-Grid, no GT back to the grid
    3. Hybrid, Grid Tie with Off-Grid backup
    4. Home Brew:
    • a. Configurable wiring of solar panels to switch to battery charging
    • b. Connect "GT Inverter" to "Off-Grid Inverter"--GT will backfeed and charge batteries through Off-Grid Inverter.
    Referring to above:


    1. Cheapest and least maintenance costs. If you don't have many outages--do this, and get a generator (gas, natural gas, propane) for emergency backup
    2. Certainly less efficient--makes most sense if no grid available
    3. Hybrids are nice, should be more efficient than #2. Basically, a solar powered UPS with Grid Tie inverter.
    4. Hombrew:
    • a. can be done, switches and/or jack panel. Certainly easy to wire a part of your array (maybe 1/4 or so easily, more of the array requires more work and pre-planning). Issues with code and safety (depending on how you do it).
    • b. Also can be done--but at this time, I don't see any good (safe and reliable) way of integrating with a battery charge controller (complex system design issue). Go with #3 if you need a "full" sized GT / Off-Grid system.
    -Bill

    Bill, can you please explain how the Homebrew option would be done using switches and or jack panel. I want to do something similar and would love to be able to switch a string of my panels from Series to Parallel on the fly with a switch, so I could have lower voltage to charge the battery bank on my golf cart as a emergency backup power solution. I can then put an inverter on the golf cart batteries to power my freezer and fridge ... emergency lighting... renewable emergency energy.

    I have a similar Grid-tied system 5.1Kw.

    Thanks,
    Cabinman
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Newbie question: accessing solar power when grid is down

    Cabinman,

    I will make a suggestion on "how I would do it"... However, there is real danger if you follow my instructions (or not). So, this is just to give you an idea of the basics. The details will be up to you.

    As an example... Say you have a two strings of panels. Each panel has a Vmp of 18 volts, there are 10 panels in each string, for a Vmp on your GT inverter of ~360 volts. And each string is 5 amps, for a total of 10 amps to the GT.

    Take string "A" and 5 panels in (at the mid point). Break the string and bring two wires down (+ and -), from the "+" of the "left" string, and from the "-" of the "right" string ("left" string, left end is "-" or "ground".

    Install three switches (wire switch box near your GT/Solar Charge Controller):
    • "I" at the "-" connection to the "A" panel (GT to string)
    • "II" at the "+" connection to the "A" Panel Split to DC Solar Charge Controller (5 of 10 panels)
    • "III" between the "+" and "-" split terminals.
    For normal GT operation... I is closed, II is open, and III is closed. Should be the same as normal GT connections with the current taking a loop down to the switch box and back up... Extra wiring will cost you some power--especially if the runs are long with too small of wire.

    Next install:
    • switch IV between "-" of A panel to the "-" DC Solar Charge Controller. Connect other end of switch II to "+" of DC Solar Charge Controller.
    For normal GT operation, switch "IV" will be open.

    So, with switches set as above--power flows through string A as normal.

    To switch to DC backup charge controller.
    1. Open all switches (I-IV).
    2. Then Close Switch IV. (negative connection to solar controller)
    3. Then Close Switch III. (positive connection to solar controller)
    The above setup will give you 1/4 of your array's rated output (only 5 of 20 panels are connected to your string.

    To switch back GT Inverter:
    1. Open all switches (I-IV).
    2. Close Switch I ("-" to GT inverter)
    3. Close Switch II (left and right string back together)
    Connections not wired correctly, and/or changing switches in the wrong order will probably ruin one or more pieces of equipment.

    Larger arrays will probably have fuses--so you will have to take those into account.

    If the above does not make sense, I can try my long rusty drawing skills.

    The switches may be real switches, or done with jumpers (and appropriate panel/plugs).

    Having emergency solar is a strong draw--but there are serious issues with safety and electrical codes if done wrong (and even if done "right").

    Perhaps Solar Guppy can chime in here... He has built exactly this sort of system (using breakers and jumpers?) because he needs to be able to reconfigure his arrays for his various test beds. But--remember--was a very experienced electrical design Solar/RE engineer when he built (and uses) his system.

    I know he made a post before with some pictures... But, alas, I did not find it.

    Here is one of Solar Guppy's posts describing his "back driving" a True Sine Wave off-grid capable inverter with a GT Inverter (option 4.b from my post (actually works well--but major issues with safety).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Newbie question: accessing solar power when grid is down

    It requires that the solar panels for the high voltage sting be home-run'ed every 48V ( Nominal ). So for example if you have 10 24V panels in a string, then you would have 5 sets of wires from the panels to the switch bank. where high voltage would only require a single pair.

    The Switchs need to be DPDT , center off. The PV ( plus and minus must both be switched! ) enter on the center commons, the one pole connects to the next and previous switch for series and the other pole connects the + to a breaker and - to a common ground

    It works well, but unless you have monster 600V DC rated switchs, care must be taken to only change the configuration when there is no load on the panels, otherwise, they will arc and destory the contacts.

    It is very handy, but literally 6X the wiring ( copper isn't cheap ). I only have this setup on two of my 4 arrays for test and design support. To run in an emergency, I'd use the GT inverters to back feed the XW .. much simpler and better efficiency
  • System2
    System2 Posts: 6,290 admin
    Re: Newbie question: accessing solar power when grid is down

    Thanks guys. Let me think this one through and get back to you ....

    Cabinman
  • System2
    System2 Posts: 6,290 admin
    Re: Newbie question: accessing solar power when grid is down

    Thanks again guys for your responses. I can visualize the jumper / switch solution .. and can see what you mean by safety issues. The XW solution seems good on the surface, but the XW is only rated for 50.4 nominal VDC, which is way too low for even one string of my Sharp 170w panels (about 10 per string). I would be nice to have a controller that was rated for high voltage, low amp, for the design of the off-grid solutions.

    I ran this problem by an old electrician I know and he told me that he was not a DC expert, but said I should look at rheostat(s) to see if there might be a fit there. It seems to me that this would be a large business opportunity for the Inverter Folks or some motivated small start-up group. I have blogged a few folks and it seems that there are lots of folks out there looking for backup solutions to their already installed Grid-tied inverters….. want to make a million :-)

    Thanks,
    Cabinman
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Newbie question: accessing solar power when grid is down

    Actually, backfeeding from a GT inverter to a TSW inverter (sharing the AC loads and to pump AC energy back into the off grid TSW inverter and charging the battery bank) work very well.

    Part of your confusion may be about the "XW" hardware... There are several major components... One is a 48 volt input inverter that is both Grid Tied (Utility Interactive) capable and off-grid capable (includes a "transfer switch" to allow AC mains and generator AC power too). Roughly 3-6kW range of inverters available.

    Another "XW" component is a Solar DC Charge Controller to charge the battery bank from your solar PV panels. This unity (from what I have read) is very nice and very similar in basic functions to the Outback MX/FM family of controllers.

    With all of this equipment, you have several ways of connecting everything together.

    The first way, is how the XW system was designed. ~100 volts of solar panels connected to a 60 amp (or several) XW charge controller(s) to charge the battery bank. Then you attach the XW Hybrid Inverter to the battery and the AC Mains (through the transfer switch).

    The second way is the connect the solar panels to a standard Xantrex GT type Inverter--the standard type that is used for grid tied installations.

    The AC output is connected to the "protected" side of a XW Hybrid Inverter (which is connected to a DC battery bank).

    When the mains are up--the GT inverter simply back-feeds the AC house mains through the AC side of the XW hybrid inverter.

    If you have a power outage, the XW Hybrid goes Off Grid (just like a UPS)... But in this case, the GT Inverter is connected to the Off-Grid side of the XW Hybrid inverter. And, the XW TSW inverter (like some Outback Off-Grid Inverters) are really bi-directional with respect to their AC output... If the AC loads are less than the GT output, the XW Hybrid will make up for the "missing" power. If the GT is producing more power than the local AC loads, the AC power is pumped backwards through the XW TSW Inverter--and this energy ends up charging the battery bank.

    This "hidden" function available in Off-Grid inverters is used by at least once vendor to allow off-gird / battery backup to their GT product (in the case I am aware of--the SkyStream GT Wind turbine documents this option).

    A major issue, at this time, is that there is no regulation from the GT through the XW Hybrid to the battery bank... And you can end up severely overcharging your battery bank. You can either manual control the GT inverter (turn off the switch) or make up / connect some sort of battery charge controller that can either cycle the GT on and off, and/or place a "dump" load on the battery bank to use up the excess energy.

    The above GT/Hybrid system is not an impossible situation to convert to automatic control--but the details get very messy very quickly (there are multiple charger involved here--the normal XW Hybrid has an AC to DC charger, their may be a backup generator charger, there may be a XW Solar Charge Controller, and there is the backfeeding of the GT through the XW Hybrid charger. Especially if you want a multi-stage charge controller with backup if one of the "regulators" failed (required for dump type charge controllers by NEC for safety).

    Not something that I would blindly jump into (spending the money) without a lot of thought.

    But it is a very interesting project / solution waiting for vendor.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Newbie question: accessing solar power when grid is down

    All,

    I recently wrote an article for Solar Pro magazine titled "Grid Down, Power Up". The article describes the operational- and configuration differences between battery-less grid-tie systems and grid-tie systems with battery backup.

    The article is a 667 KB pdf, so I can't post it here on the forum. However, if you send a PM to me and include your e-mail address, I'll be happy to e-mail a copy of the article to you.

    HTH,
    Jim / crewzer
  • Brock
    Brock Solar Expert Posts: 639 ✭✭✭✭
    Re: Newbie question: accessing solar power when grid is down

    Jim if you want to shoot it to me, I can post it to a link for anyone to download if you like. Either way I would like a copy :)

    nevermab at uwgb.edu
    3kw solar PV, 4 LiFePO4 100a, xw 6048, Honda eu2000i, iota DLS-54-13, Tesla 3, Leaf, Volt, 4 ton horizontal geothermal, grid tied - Green Bay, WI
  • System2
    System2 Posts: 6,290 admin
    Re: Newbie question: accessing solar power when grid is down

    Jim,

    That was an excellent article. It helped answer some of my questions and confirmed other assumptions, nice work.

    I do have a question for you, is there a technical reason why none of the companies like Outback produced a High-Voltage, Low AMP controller / inverter? It seems to me that being able to switch (bypass) your PV generated DC power from your Utility-interactive, grid-direct (UIGD) system, to a High-Voltage, Low Amp controller / inverter to charge some backup batteries for emergency power, would be a big seller. This little puppy could be added to existing systems, with-out re-wiring your existing PV strings and wire from the DC combiner box to the Inverter (smaller wires). Just trying to understand …..

    Thanks
    Marlon
    (Cabinman)
  • System2
    System2 Posts: 6,290 admin
    Re: Newbie question: accessing solar power when grid is down

    Bill,

    Thanks for the reply. I had to read your response about 4 times, but I think I finally understand. It seems very complex and expensive. Are you aware of any way to just regulate the DC power from High Voltage to Low Voltage? I am thinking along the lines of a reducer or step down device. Power loss (low efficiency) is not a concern, as I would be happy to just tap into 30% of the PV DC power in the case of an emergency. …. Once again the idea is to just switch the power from going into the Grid-tied inverter to a Off-grid controller, connected to a battery bank…… a separate inverter on the battery back can then produce my emergency AC power from batteries……
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Newbie question: accessing solar power when grid is down
    cabinman wrote: »
    Jim,

    That was an excellent article. It helped answer some of my questions and confirmed other assumptions, nice work.

    I do have a question for you, is there a technical reason why none of the companies like Outback produced a High-Voltage, Low AMP controller / inverter? It seems to me that being able to switch (bypass) your PV generated DC power from your Utility-interactive, grid-direct (UIGD) system, to a High-Voltage, Low Amp controller / inverter to charge some backup batteries for emergency power, would be a big seller. This little puppy could be added to existing systems, with-out re-wiring your existing PV strings and wire from the DC combiner box to the Inverter (smaller wires). Just trying to understand …..

    Thanks
    Marlon
    (Cabinman)


    The ones with Gridtie only did that for cost savings and have no hardware to back anything up, no stand-alone inverter, charge controllers, batteries ect. Add that stuff back in and then there is no reason for the GT only inverter and there is no real use for having both , well I do, but that work related.

    There is no equipment for what you seek as there is no market. Go tell A GT guy, hey we can install another inverter, battery bank, charger controller so for the once every 3 years power goes out you can use those solar panels that would be sitting idle and the cost is 6-9K for a starter backup system that could actual have some useful loads powered.

    OR

    get a 299 generator that can kick out 5kw for those few outages
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Newbie question: accessing solar power when grid is down

    Marlon,

    If it took only 4 times to read through my post--I did not make it obscure enough. :p

    I too would like a "black box" that I could just connect to my GT array and get 12-48 VDC out of it to charge/run an emergency set of batteries...

    A couple years ago, we had the exact same discussion with Solar Guppy when he asked for "ideas" about what consumers may want for new products that he may wish to design and sell.

    If I recall correctly, the end result was that the "high voltage" DC Converter/Charge controller (~200 VDC to 600 VDC input) would be quite an expensive animal to produce... And that the solution was just to take your normal GT inverter (that we already have) and back drive an Off-Grid AC inverter of equal or larger capacity (which would charge the batteries)--(GT/Off-Grid inverters from behind a automatic or manual AC Transfer Switch) .

    That is the simplest and cheapest way to go. And it does work (with the right equipment).

    For me, I had lots of questions about how one could safely regulator the charging of a battery bank for such a system.

    Conceptually, a simple method would be to configure two "dump" controller. One that would simply turn of the GT inverter (either using the DC inhibit switch that many have--or controlling a silicon relay in the AC output that would simply be turned off once the batteries were full). And a second "dump" controller that could be set as a backup to either turn on a dump load, or even control a second independent AC silicon relay to turn off the GT's output.

    While it sounds like a relatively straight forward concept--To figure out how to document a system for "everyone" with multiple vendors involved (Xantrex, Outback, GT inverter, Off-Grid Inverters, Hybrid Inverters, brand XYZ dump controllers, transfer switches, internal AC battery chargers, automatic generator, etc.)--it get pretty scary pretty quickly (from a safety and reliability point of view).

    No matter which way you take, it is going to be a bit of a pain to do (GT to off grid inverter, or bring down low voltage tapes from your array and switch/jumper to your DC Charge Controller.

    For me--I took another route... Bought a Honda eu2000i for ~$900 and have 20+ gallons of fuel (metal 5 gallon cans + fuel stabilizer, plus siphon hose for car/pickup use)... Much cheaper, and much more portable than 20 solar panels and a couple thousand pounds of batteries.

    For us, the major natural disaster would probably be an Earthquake. Water, shelter, and food would be our major worries... Having electricity would be nice--but not a necessity. I look at my "emergency" situation more like camping...

    Flashlights/Headlamps with long lasting batteries (LED bulbs, Lithium and Alkaline AA's), camp stove that can also burn gasoline (everything has double duty), AA powered radio with solar panel and hand crank, etc. Enough Gas to run our fridge/freezer long enough to eat the fresh/frozen foods. Enough fuel to cook it.

    Every time I start thinking about off-grid emergency solar power, I keep coming back to the basics for survival. I.e., I will die if:

    3 minutes without air
    3 hours without shelter (harsh climates/weather)
    3 days without water
    3 weeks without food

    And every time I type up this list--I keep telling myself to haul my "behind" down to the hardware store and purchase a few covered 30 gallon garbage cans I can fill with water before the water mains fail (loss of power, loss of pressure). Have water filters and bleach to keep the water safe.

    For people that power outages more often (ice storms, hurricanes, line failures/brownouts, etc.)--something better than my generator option would probably make more sense.

    The Xantrex XW Hybrid GT/Off-Grid system really is designed for exactly this function. It was not available when I installed my GT system--but even now, I really cannot justify the batteries (which will need replacing every 5-10 years) when the last power failure that lasted more than a few hours was over 50 years ago in my area...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2
    System2 Posts: 6,290 admin
    Re: Newbie question: accessing solar power when grid is down

    Bill and Solar Guppy, thanks for the excellent feedback. I thought maybe I was just missing something here, but it sounds more and more like the emergency tap into the solar panels is just not economical. I will take your advice and look at the back-up generator option. Thanks again for your advice…..
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Newbie question: accessing solar power when grid is down

    Regarding the Generator... Run, do not walk past the average 5kW "noise makers" unless you live away from other homes. They are almost too loud to use in a neighborhood (unless everyone lost power and wants to plug into yours), and they consume 2-4x the amount of fuel vs the smaller (and more efficient) "inverter generators".

    The Honda eu1000i (900 Watt continuous) and the eu2000i (1,600 watt continuous) are very quiet and fuel efficient.

    My personal recommendation, the eu2000i will power just about anything you can plug into a 15 amp 120 VAC wall outlet.

    If you need to run something larger at times, you can get two eu2000i and parallel the AC outlets together and run a good sized room A/C unit. Or, you have two independent generators for backup.

    If you need larger loads, then a larger generator (perhaps diesel or natural gas) would be better...

    Another option, Tony/Icarus (if I recall correctly) said that used/working RV gensets (around 3-6kW) are cheap... They include auto-start/electric start and nice engines (sometimes with alternate fuel capability).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Newbie question: accessing solar power when grid is down

    Did I hear my name called in Vain?

    For occasional use I don't think there is anything out there as good or better than theEu line of Honda's. For quiet operation, fuel efficiency, ease of starting the EU wins hands down.

    Having said that, if you need a genny to run 24/7 for extended times, Onans are a great buy. Newer Emerald series can be had out of RV's for ~25% of new. I personally don't think these will have the longevity of the older series, but they are still pretty well built units.

    For my money, the older CCK series Onans have a bullet proof reputation. They came in many different configurations and wattages. These are 1800 rpm units that are quite quiet and fairly fuel efficient when run near full load. They will also run fully loaded (or even over loaded) for days on end. Onan also made a CCKB series that is essentially identical to the CCK except it was a 10kw unit that ran at 3600 rpm. These are not considered as good, but they too have pretty good reliability. (I have one, and while it runs great, it is a fuel hog, and it is quite noisy at 3600 rpm.

    All of these aircooled Onans are quite easy to service, and most spares, even for very old ones are still available.

    For those that are interested here is a pretty useful forum for Onan owners. http://www.smokstak.com/forum/forumdisplay.php?f=1

    Smokstak also has forums for Kohler, lister as well as other older gennies.

    Tony