Solar Generators - Trash or Treasure?

Portable solar system

In the last several years, the market has been flooded with many so-called "solar generators".  They are basically tiny, portable solar systems and are often touted as your key to energy independence or security.

But do the facts bear out these claims?

Are "solar generators" ever useful for anything?  In other words, are they trash...or a treasure?

In this article I'll help you determine if a solar generator is for you and make sure you are getting your money's worth.

 

What Do You Need Solar Power For Anyway?

The first step is to determine what your goals are for this power system.

Are you needing it to power your entire home indefinitely while maintaining a normal lifestyle?  Or are you just wanting to charge your cell phone and power a light or two during camping trips or short emergency blackouts?

If the first option describes you, then you are MUCH better off sticking with a conventional solar system (as the numbers below prove).  And if the second option sounds like you, then a portable "solar generator" is definitely the way to go.  But the folks who are most likely to get confused are those who find themselves in the gray area in between these two extremes.  You are who I am really writing this article for.  You'll need to ask some questions in order to find the best fit for you.

Do you need the unit to be readily portable?

What appliances are you needing to run?  And for how long?  In other words, how much power do you need to produce and store?

These are the most important questions that will help you know.

Let's take a look at your power needs and I think you'll be shocked at what we find...

Do The Math!

How much power will you need?  First off, don't go by a "solar generator" company's description of what you can power with their system.  You really should do the simple calculations yourself so you know what can be powered with the unit.

Here's how...
Let's say you want to charge your laptop and power 2 lights for a few hours each day.  Many latops use 25 watts and take 2-3 hours to charge.  So 25 watts X 3 hours = 75 watt hours.  A 14 watt CFL light bulb running for 2 hours requires 28 watt hours.  So 75 + 28 = 103 watt hours.  This would be your daily power need.

Battery preliminaries
One would think that you could just look for a system with a battery that holds at least 103 watt hours, but it isn't that simple.  Depending on the type of battery, you may not want to discharge it all the way.  This is especially true with lead acid batteries, but holds true with many other types to a lesser extent.  For deep cycle lead acid batteries being used continuously, discharging no more than 50% is a good idea.  If this will only be used during short emergencies, then discharging all the way down to 30% could be acceptable.

So if you decided to discharge to 50%, that means you will only be able to access half of the battery's capacity, which means your battery would need to be twice as large.  So now we are up to 206 watt hours.  If the battery type is such that complete discharge is acceptable, then you can skip this step.

Battery Sizing
Having enough battery capacity to last one day is great, but what happens after that?  The theory is that your solar panel(s) charge the battery each day, but this is only going to happen if the solar system is appropriately sized and the weather cooperates (i.e. the sun shines).  Ideally, you would like to have enough battery capacity to get you through cloudy days, but with a portable micro system such as what we are discussing here, this is probably not going to be so feasible.

But it is important to have at least a couple days worth of power stored in your batteries, and more like 3-5 days would be recommended if you want to have a fairly reliable power system for longer periods of time.  For our example, we'll go with 3 days of battery power which would be at least 618 watt hours (206 watt hours X 3 days).

Solar
The final step involves solar.  I mentioned earlier having enough solar power to charge your batteries.  Determining how much solar power it will take is a more involved process than I'm able to teach in this short article, but since we are discussing very small portable systems and brevity is important, I'll give you a greatly simplified version.  It is for the sake of giving you a way to compare two systems ONLY!

Check out this map and determine how many peak sun hours you can expect each day on average.  Bear in mind that during the summer, you may get more and during the winter you will likely get less.  So play it conservative if you want a more reliable system (the lower the number of peak sun hours you figure on, the more conservative you are, since you are planning on receiving less sun).  For our example, we'll say 4.2 hours.

Now we'll take our daily power usage (103 watt hours) and divide that by the number of peak sun hours (4.2) which equals 25 watts of solar required.  But please realize that there are numerous inefficiencies at play here (for instance, the solar panels seldom put out their full rated power output), so I would tack on an extra 25% or more to this number.  In the current example, since we are dealing with a very small system, I would bump it up to 50 watts of solar, but when dealing with larger systems, such a large increase may not be warranted.

Once again, please don't use this rough method of sizing for any larger or home-sized off grid system.  It is just a quick and dirty way to get you in the ballpark for a small backup system.

Reality Check - Cost & Quality Comparison

So now you know what it would take to power a few lite loads for a few hours.  What if you are needing something more substantial that you could actually live with for a period of time.  Well, I think it's important to do a reality check before you get sucked into a rather unpromising "deal".  You see, while "solar generators" do have a place, especially for someone needing portability or needing only a tiny amount of power, they are often a really bad investment when your needs are larger.  You'll likely need to step up to something more sizable (and expensive) and will end up flushing all the money you spent on a "solar generator" down the drain.

Recently a friend contacted me asking my opinion of a portable solar system she was considering.  So I did a simple comparison of the specs for her prospective portable system versus what it would cost to replace my stationary off grid power system.  Here we go:

PORTABLE SYSTEM:
12 volt system (very limiting for future expansion but appropriate for a tiny system like this)
300 watts of solar
2,160 watt hours of battery capacity (super expensive lithium ion batteries)
1,800 watt inverter (mediocre quality)
Excellent charge controller

OUR POWER SYSTEM (capable of powering our entire home and office 24/7):
24 volt system (good choice for powering a home)
1,800 watts of solar (excellent quality)
19,296 watt hours of battery capacity (with 15+ year lifespan in continuous use)
4,000 watt inverter (excellent quality)
Excellent charge controller

So you may be wondering much much extra it would cost to go with my far superior stationary system over the portable one, right?  Would it surprise you to know that the cost of the core components for my system listed above is actually LESS than the cost of the portable system?  The portable system costs over $9,000 dollars with shipping.  Last time I checked, the core components of my system listed above come up to around $7,000 plus misc. items like wiring, breakers, solar panel mounts, DC disconnect, etc.  So even if we tack on another $1,000 or $1,500 for all that, the cost is still less.

Did you notice the huge disparity in solar system size, inverter, and battery bank?  Our power system is WAY larger and better quality in almost every way, but it costs less than the portable system!  The two advantages of the portable system are that it is already assembled and it is portable.  But the size would be very inadequate for doing much beyond running a few things like a computer and some lights.

Conclusion

So really, it depends on your specific requirements.  If you need something that can easily be moved or you just need emergency backup power for a few small loads, then you may be better off with a small "solar generator".  But if you are looking for something substantial that will actually power a home, do yourself a big favor and set up a REAL power system.  You are almost always going to pay way more and receive way less when you go with a power system that is pre-assembled and portable.

25 Comments

  • Avatar

    Robert Taylor

    Reply Reply June 29, 2015

    Buyer be ware your system is a lot better good info

  • Avatar

    Denis Miron

    Reply Reply June 30, 2015

    Very good info, thank you.

    So if the core materials cost around $6800 + $1500= 8300.
    So for those who can not put this together what would be the ballpark figure for assembling all of it?
    Also are the same components available in Canada? And I image the costs would probably be slightly higher.

  • Avatar

    Eugene F (Gene) Augustin

    Reply Reply June 30, 2015

    Nick,

    Thanks so much for 'running the numbers' on the two systems. It sure looks like a no-brainer to me. I can't imagine a situation where I would want to spend $ 9K on something that might give me enough power to run a computer and a couple of small lights.

    Very well done, my friend. Good information and well put together.

    Blessings.

    Gene

  • Avatar

    Donna

    Reply Reply July 2, 2015

    Nick,

    Thank you for sharing this excellent information.

    I am also interested in finding someone who can assist our family in assembling a system capable of powering a home [at least essential components for survival, i.e., well pump, perhaps freezer and other items] for a fee.

    Blessings and Thanks,

    Donna

  • Avatar

    Century22

    Reply Reply May 15, 2017

    They are all trash !
    Overpriced, Underpowered, mismatch, an Mis-Named !

  • Avatar

    GARY H

    Reply Reply May 15, 2017

    The "solar generators" I've seen are also sold with pressure, touting that they will run your house fridge when the power goes out. When I was at an expo booth quizzing the sales staff on their (well known) system and components, within 10 minutes they were walking away when I would point out the shortcomings of their system and proving to them that their claims had no merit when I began showing them the real numbers. I laugh when I see these same systems at garage sales and neighborhood classified ads trying to get rid of these worthless systems trying to recoup whatever they can after finding out they don't hold up to the claims...

  • Avatar

    Jeff

    Reply Reply May 15, 2017

    Just a quick question and a little background. It's easy to figure what the output of an inverter is. Just read the label and hope it's honest. I would like to know what the current draw is at the INPUT of an inverter. I know it varies with drain at the output but 45 years ago, I had what was called a brute force inverter. I know that most of the digital ones now a days work with modified square waves, digital frequency controls and frequency counting chips and small transformers and why. I also know that their idle, (no load), current is minuscule compared to a full load draw. The one I had was a 60 Hz sine wave oscillator with 2 huge power transistors that used a massive transformer in a flyback configuration. It weighed about 15 pounds and put out only 100 watts at 110 VAC. At full load, it drew 10 amps out of a car battery. It's idle current was almost 7 amps. I also know you don't get something for nothing but today's inverters that claim as high as 85% efficiency. If compared to my antique at 10% efficiency, (10 amps @ 12VDC to produce 1 amp @ 110VAC), this would almost sound like perpetual motion. Please guide me through my math confusion. I don't need a lot of math as much as maybe a simple, average ratio. Draw this much out / put this much in. Thanks for any help, Jeff M.

  • Avatar

    AngelaW

    Reply Reply May 15, 2017

    I'm am looking for an honest local solar panel set up and installer in Priest River, Newport Wa area.

    • Avatar

      Alex

      Reply Reply May 15, 2017

      Hello,
      I live near that area and I would recommend going to Albeni Falls building supply and asking the people at the lumber counter about Bierwagen Construction.
      Good luck!

  • Avatar

    Virginia

    Reply Reply May 15, 2017

    I have only had to use my solar generator once which I purchased several years ago from Solutions from Science. I have never hooked it up and charged it thru the 2 portable panels but I did plug it in and charged it and it worked just fine keeping my frig going a year ago when the power was out for a while. I believe it is 7000 watts.

  • Avatar

    Jim Higgins

    Reply Reply May 15, 2017

    Nick,
    I have enjoyed many of your articles in the past. You have shown your knowledge about solar system sizing, etc. But I have to say that this article, while true about many small systems, your generalities are so misleading and grossly inaccurate that I feel compelled to add some comments.
    The quality and sizing of each component is critical, as you say. However, your complete failure to explain anything about the ability to recharge any system is not only determined by the amount of daily sunlight but also the size of the solar panels and their ability to capture as much of the available sunlight as possible and convert that into usable electricity.
    Realizing that the figures I am using below are greatly rounded to the lesser value so as not to decieve, it should make it plain that the recharge rate is just as important as the storage amount. We'll use just one 100 amp battery for this example. A 100 amp battery will store approximately 1000 watt hours of energy. If you are using an AGM battery you can only access about 500 of those watt hours before having to recharge the battery. Using your example of 103 watt hours a day you might conceivably get almost five days (103x5=515 watt hours) of use without recharging your battery.
    Using three 15 watt solar panels from Harbor Freight (approximately $150) could provide up to 45 watts of energy every hour or 180 watts of recharge power in four hours. In order to replace all 500 watt hours consumed would require approximately three good days of at least four hours of sunlight each day before your one battery would be fully recharged.
    If instead you you spent say $250 for one 200 watt solar panel you could replace all 500 watts of used power in only two and a half hours of sunlight in one day. The point being that you must have more than enough battery power and more than enough solar panel recharge power for any system to realistically provide for your needs. If someone is being at all realistic about power failures they are going to be worried about a lot more than a laptop and a light for a couple of hours each night. Systems really do exist that will meet real long term needs. I am an authorized reseller of such systems. But to keep my name and my business out of this, may I suggest you go to the source and get real figures and true information to see the difference and what a quality system can actually do. Go to before you make such generalized statements again.

    • Nick Meissner

      Nick Meissner

      Reply Reply May 16, 2017

      Hi Jim,

      Thanks for your comment. I can't help but think that either you didn't make it through the whole article or else we are having a miscommunication. Let me try and clear this up...

      1 - If I am guilty of "generalities [that] are so misleading and grossly inaccurate" then you have my apologies and I'd appreciate it if you'd set me straight. That's some pretty strong language, but in reading your comment, I don't see any "misleading and grossly inaccurate" generalities that were pointed out.

      2 - "...your complete failure to explain anything about the ability to recharge any system is not only determined by the amount of daily sunlight but also the size of the solar panels and their ability to capture as much of the available sunlight as possible and convert that into usable electricity". Hummm...perhaps I'm not understanding what you are saying. Maybe take a look at the section in the article titled "Solar" and the section called "Reality Check – Cost & Quality Comparison". In those sections I refer to the overall size of the solar array rather than the individual size or quantity of solar panels. There are so many different sizes out there that unless I'm talking with a specific person about specific panels, it is easier and less confusing (at least for me) to refer to the overall size of the solar array (i.e. 300 watts in the portable example and 1,800 watts in the stationary example). However I still stand by the statement that you must take into account the amount of solar resource you have available (# of hours of noontime equivalent peak sun).

      3 - "Using your example of 103 watt hours a day you might conceivably get almost five days (103×5=515 watt hours) of use without recharging your battery". I agree with you that it is best to not discharge a lead acid battery more than 50%. No disagreement there! However, I must say that in your example, a 100 amp battery tells us nothing unless we know the voltage. I'm assuming you were referring to a 12 volt battery. In that case, 12 volts x 100 amps = a minimum of 1,200 watt hours of capacity in the battery.

      4 - "The point being that you must have more than enough battery power and more than enough solar panel recharge power for any system to realistically provide for your needs." And I TOTALLY agree...that was part of the premise of this whole article--to try and encourage folks to look beyond these tiny portable systems and do the math and go with something that is large enough to really power what they need. If you came away from this article thinking I was trying to get folks to go with some tiny 15 watt cheapo panels from Harbor Freight, then I totally failed to express what was in my mind. The whole point was to get much higher quality and much more for your money by going with conventional components that are made for stationary systems rather than the cheap portable systems that are so prevalent these days. There are exceptions, however. You'll notice that in the one portable example I mentioned above, I stated that they include a high quality charge controller. That's great. But you also have to look at the inverter, solar panels, batteries and everything else. I have not looked at everything out there (there are a TON of them) but as far as I'm aware, I have yet to find one of these portable systems that includes what I consider to be a high quality inverter, and usually most of the components are inferior when compared to what we use in stationary systems. Even in the link you shared, the systems I looked at may have had a decent or good charge controller, but in all the examples I saw, it was a no-name inverter that doesn't even have a built in charger (hence the stand-alone charger). Also batteries and solar panels have no brand info that would help to determine the quality ("state of the art batteries, "commercial grade inverter", but no brand). Why a cheaper inverter? Perhaps one reason is because a quality inverter is HEAVY! To make a portable power system lightweight, they go with a cheaper inverter which is also much lighter. Also, the cost. A high quality inverter and batteries are expensive and there is more profit margin if a less expensive inverter and batteries are used. But what I fail to understand is why anyone would pay more money for a system that is much inferior in every way. It's beyond my understanding, unless the overriding feature needed was portability. Then I could possibly understand.

      5 - "If someone is being at all realistic about power failures they are going to be worried about a lot more than a laptop and a light for a couple of hours each night. Systems really do exist that will meet real long term needs." Once again, I couldn't agree more! That's the point of this article. Systems do exist which will power an entire home, and they are systems that are made for that purpose--not toy systems that you throw in the back of your car. But I felt it was important to realize that some folks may only need to power a few small things during an emergency. In that case, then these tiny portable systems may be the perfect fit for them (as long as they don't pay too much $). And that's why my system design example was for running a few small appliances. It was just an example to show HOW to do it for a tiny system. But I think that most folks would be far better off and get much more for their money if they invested in quality components and built their own stationary system of substantial size to power the things they need. In our case, we power our entire home 100% of the time with our off grid solar system.

      So I hope this has cleared things up and that perhaps we actually agree on many of these points. I'm sorry if my way of wording things caused any confusion for you. All the best,

      Nick

      • Avatar

        aj

        Reply Reply July 7, 2019

        I would like someone to contact me personally firca small sub station to run two appliances most if the day. I would like it to be affordable. I do not want a whole house system. I want several substations.

  • Avatar

    Michael

    Reply Reply May 16, 2017

    Thanks for the info, Nick. Always useful. As I understand it, these things are basically generators with a battery all covered by a small solar panel array. Is that correct? If so, the devices plugged into it are being keep running by the generator kicking on whenever there is not enough power from the sun. Or there may be more than one style of these.

    • Nick Meissner

      Nick Meissner

      Reply Reply May 16, 2017

      Hi Michael, There are a lot of variations out there, but the most common configuration that I see is basically 1 or more cheap solar panels, a cheap charge controller, a small battery bank, and a cheap inverter. It is rare to see a fuel powered generator included. It might have a separate charger that could be plugged into either a generator or grid power to charge up the batteries if needed (since these units don't usually have a high quality inverter which has a charger built in).

      But as I mentioned earlier, there are a LOT of variations out there, so the above is referring to what I most commonly see on the market.

      • Avatar

        Michael

        Reply Reply May 17, 2017

        Well, if they don't even have a generator, what a truly huge ripoff they are! $9000? Unbelievable! For that price you'd darn sure better get a generator for night time emergency use.

  • Avatar

    Mick

    Reply Reply May 16, 2017

    Thanks for the info! Good resource.

    • Nick Meissner

      Nick Meissner

      Reply Reply May 16, 2017

      You are welcome! Glad it helped.

  • Avatar

    Jim Higgins

    Reply Reply May 16, 2017

    Thanks for the reply, Nick.

    Actually we are on the same page and agree on most things. Last night late I was replying using a tablet on-screen keyboard and trying to be brief while providing enough detail. I obviously didn't do so well. Instead of rehashing other issues, please let me touch on just two points. If you looked at totalsolartechnologies.com then, based on your reply, you must have looked at the Ultra-portable systems. Roger only added those recently to make existing customers happy who wanted what I call backpack systems. They are numerous and can be found from many companies. Existing customers choose to buy from Roger because of his impeccable customer service. These units were wanted by some for off grid, overnight locations; not for real emergency grid replacement options.

    The units I was referring to as portable yet truly powerful and complete systems are the Solar Maxx systems. I am sure you would not call the Solar Maxx 6000 RV/CABIN portable system as one using cheaper, inferior components. There is absolutely nothing cheap or inferior about an AIMS Commercial/Marine grade 110/220vac split phase inverter, etc. Every component is industry rated top of the line and every system is 100% complete except for panel mounting hardware. My complaint, at least as I read your article, was my perception that you inferred there was no such thing as a worth while portable system, and I am not trying to sell TST systems. I was simply trying to show that "portable" doesn't have to mean a bad choice. If you expect to ever move or you are a prepper who expects to bug out to a long term alternate location with more then a 72 your backpack then "portable" can be a very wise decision.

    Thanks for all your info and efforts. I look forward to your continuing articles.

    • Nick Meissner

      Nick Meissner

      Reply Reply May 17, 2017

      Thanks for following up, Jim!

      I appreciate your input. Point well taken. I’m sure there are varying degrees of quality in the portable solar system business–some very poor and some that are good quality. My exposure must have been to those on the poorer quality end of the spectrum (which I think is the vast majority of the market), so I'll take your word for it that there are quality options out there that could realistically power a home (since I have yet to see them).

      You know, it just hit me. Perhaps our difference of understanding lies in the word "portable". When I use that word, I am thinking of something that could easily be transported by one person and would fit in the back of a hatchback car. But if you were to place under the "portable" umbrella any system with the typical stationary components as long as they are not permanently attached to the house, then I could certainly see the possibility of a portable system being quality and able to power a home. But it would be a "bear" to move around, as quality components are HEAVY :-).

      So I guess the moral of the story for everyone reading this is, do the math and the research ahead of time for yourself so you can ask the right questions and make an educated decision. Because in today’s market, buyers had better purchase with their eyes wide open.

      Thanks again for the feedback, Jim. It’s always healthy to hear differing perspectives :-).

  • Avatar

    BRUCE A STOCKBERGER

    Reply Reply November 13, 2017

    Nick. Are you planning on creating a directory of recommended solar related items that you approve of and links where your followers can read about these products? Have you thought of a "Request a Quote" program where your followers can "Fill in the blanks" and "Measurements" and submit them to you with their E-photos so you can quote your services and generalized prices for the job? Your abilities and knowledge of solar installations is much needed in these times. Bruce

  • Avatar

    Joseph Havard

    Reply Reply November 13, 2017

    $9,000?! I have less than $1,000 invested in 4 120W panels, 4 12V 135AH batteries, a great charge controller AND a 1000W inverter. I would never buy such a useless system as are offered in these survivalist ads. THX for the info, Nick!

  • Avatar

    LadySongbird

    Reply Reply November 14, 2017

    So what's a good option for people who don't own their own homes? And a couple of suggestions for quality products? Thanks

  • Avatar

    Craig Petroff

    Reply Reply November 27, 2017

    Thank you Nick, I have had an interest in the portable solar generator that I keep seeing on the internet.But kept asking how can it be true, it seems to small. Thank you for helping me think thru it better!

  • Avatar

    Richard Moore

    Reply Reply September 17, 2018

    Excellent,ty

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