A Solar Energy System That Works At Night

Solar energy is power from the sun. But what about power during the night?

Here’s how it’s done:

Batteries! Solar energy is radiant energy collected from the sun. Not only can it be harnessed and converted immediately to household electricity, but it can also be harnessed and stored in special batteries to be used later (when the sun goes down).

While the technicalities of a solar energy power system may be somewhat complicated and require a certain level of “know-how” in the field of electro-mechanical & electronics, these systems can be professionally installed or you might even consider doing it yourself if you have the knowledge and abilities to DIY.

The key to a 24-hour (around the clock) solar energy system is battery storage.

Not only will battery storage capacity provide energy during the night, but even during the day you might encounter a period of cloudiness which will reduce energy output from PV (photo-voltaic) solar panels. Batteries (a battery bank) however will make up the difference when solar output is reduced or gone during the night.

The design of a battery storage system requires its own unique technical expertise while considering the specific battery type, size, charge/discharge parameters, load expectations, configuration and interconnection, and much more (which is not the thrust of this brief post).

FYI, My current battery bank at home consists of (24) Trojan 31-AGM deep-cycle batteries which provide enough stored energy to run the house without issue overnight (and then some…).

For those who may be interested in procuring your own solar energy system with sufficient power to run your essential systems at home (or more), or to install in your trailer, RV, or cabin, I found this battery which looks intriguing and is rated with excellent reviews:

Designed for Use with Pv Solar Panels, Smart chargers wind Turbine and Inverters

12 Volt 125Ah Group 31 AGM Deep Cycle Heavy Duty Battery
Military grade custom made plates
Float service life span of 8 to 10 years
Designed for no dangerous fumes or gases.

Vmaxtanks Vmaxslr125 AGM

Currently and apparently there is FREE SHIPPING with these batteries!

Here’s an interesting website with solar energy maps:
National Renewable Energy Laboratory

Solar Energy Books

Alternative energy sources are a great way to further your self-sufficiency and decrease your dependency on other external systems. I plan to write more articles about this in the future ;)


  1. For a moment there I thought you were talking about panels that charge from starlight. I believe that it could be done. We noted that our solar panels still produced on cloudy days, just not as much.

  2. For anyone that’s considering adding a “Solar Energy System” ya might be interested to know the Fed’s have extended the 30% federal Income Tax Credit on your income tax, this is 30% for the entire insulation Labor and Materials….

    If you get a very nice system like the Grid Connected (sell back), Battery Backup, full house system, with generator backup most companies will estimate the system will pay for itself totally within 5 years, AND your electrical bill (from the ‘man’) will be Zero. Make sure your electrical company will do a ‘buy-back’, mine does at 80% for per/kwh cost.

    AND a lot of suppliers/companies will do an install on Credit, yes I said that word, but something to think about…. After 5 years, free electricity, yes yes yes, there is ‘some’ maintenance cost, but still


    1. Im trying to figure out how to capture and utilize my methane emissions, the tank and collection apparatus looks oddly something like a politician, they are after all big gasbags, so far i have only been able to get a flame to burn for 25 seconds, last one left me with an odd scent

  3. @ NRP

    There are some legal issues to consider when installing solar power and when also connected to the grid.

    1. If a lineman or electric power company employee is ever injured/killed trying to repair their grid consider what happens then. Well, if your house sells electricity back to the electric company and the spouse has a lawyer that says sue the home owner(you) not the electric company since the home owner has fewer lawyer dollars. The spouse can expect their home owners insurance to quickly settle out of court and then drop their coverage of you. Or you may pay the whole suit. The lawyer knows that the suing the electric company takes years to collect even if you win.

    2. Any voltage spikes that come from the grid will destroy you solar inverter and charge controller. And you not the electric company will have to pay for your solar power system repair.

    3. Also, insurance on your solar power equipment is paid by you not the electric company and yet they sell your electric power at a higher price than what you get for your electrical power.

    4. Finally, in some states when you are connected to the grid the home owner has to pay a fee to the electric company for usage of the grid system when selling power back to the electric company.

    I was once caught up in all of the above issues.

    1. @ no joke

      Will not disagree with you on any points; hence one needs to hire a licensed, bonded and insured electrical contractor to do the install, second one must get all permits and have EVERYTHING signed off by electrical inspectors AND the Electrical Company, next you must buy/use equipment that is ‘UL’ listed and approved for the installation you have.

      The new ‘codes’ are very VERY specific to the use of ATS, sub-panels, disconnect switches and ‘anti-feedback’ equipment that must be installed. I would say that most, not all, but most homeowners the installation of a Grid Tied System is something they should not undertake.

      If one is going to install a system, ya had better know the ramifications of all you mentioned and build the system correctly not only to protect all as you mentioned, but not to fry all the electronics and house you have….

      As far as electrical ‘spikes’ I agree if the system is not installed with the proper ‘surge’ protection you may get your equipment fried. And the Electrical Company is ‘not responsible’.

      As far as insurance, I have already checked my insurances, the entire system is covered under the Home-Owner clause, without any additional ‘tag-on’ riders…. They classify it as part of the ‘house’ electrical systems.

      With all that said, I know there of thousands and thousands of grid tied systems that are up and running in full capacity as we speak, I would have zero concern with a properly installed system.


  4. I thought a lot about solar energy if I move. When the cost has doubled in 4 years to have electricity, it cut into my budget, and it’s not based on power usage, it’s the cost of having it at the house. Now the kw rate went up, and it will keep going up to where I can’t afford it with retirement and Medicare costs in 5 years.

    Problem with power companies here if you disconnect, you still have to pay all the monthly fees and taxes for non-usage, which is more than what I paid 4 years ago for my total electric bill. Yet they use your land for their poles and power lines free of charge by law, destroy your short berry bushes off to the side, and track up the yard which I kept mowed like a golf course.

    The only way I can escape the power fees is build on wild land or buy a cabin with no power grid ever put on it. Solar and a generator would be the way I would have to go. I started planning for my retirement future, and I overlooked the cost of inflation and used the rate over the past 5 years. Scary! Thanks for the info Ken!

  5. to no joke: Pardon my asking but what state did this take place in? Thanks for the scary warning.

      1. Ken,
        earlier I saw you had replied to a post and listed some of the equipment you use as well as a question about venting lead acid batteries–I don’t see that post or your reply. I also had posted asking if anyone has any feed back on the Sol-Ark systems, which are supposedly hardened against EMP–I don’t see that post either?

        1. @T for Texas, I recall having listed my equipment in the comment section from a previous article titled, “The Four Essentials Of Off Grid Solar”.

          Also, any comment with a link may still be tied up in the moderation que – which I get to once in awhile. Being on the road I don’t always have time to weed through everything.

        2. Thanks. Hey, maybe I posted in the wrong forum!? Gettin’ old ain’t for sissies.

  6. Some questions. How much energy will your solar array have to produce above and beyond your consumption during the day to recharge the batteries you used for your overnight needs? remember some nights are longer than others. This will also vary seasonally if you are running your heating/cooling system in extreme heat or cold. If generation is significantly reduced by heavy overcast for several days how will that impact recharging? Could your system take a week of weak solar input and still meet all your needs? Just wondering.

    1. @ JustAnOldGuy

      Your questions
      1. Your will need to calculate the usage you have during the night, normally its considerably less that in the day
      2. Plus you will need to calculate your ‘day’ usage and add the differences, remembering that batteries will only hold about 60% of the power you will need, reasoning is that you do not want to drain batteries completely dead, usually to about 40%
      3. Also figure in the inefficiencies of the system, if you buy a 100Watt solar panel, you’re not really going to get 100 usable watts.
      4. Yes, a system could take a week of more to supply only one day of ‘power’ depending on how the system is set up, the usage, the solar intensity and so forth.

      There are a LOT of very good companies that can help you design a system to meet your needs. Most of the time they will do the preliminary design at no charge and get you an estimate. If you sign a contract to allow them to install the system, they will completely design it for you.

      BUT you will need to supply them with your demands…. FYI, running an AC unit, an electric Dryer and Electric Stove/Oven, will probably not work without a HUGE system…


    2. I found a website through Google that tells you how many hours of sun average per day is in your area across the US. Here in Northern Minnesota it is only 4 hours average, so compared to desert regions I would have to double the amount of solar cells to collect as much as an average of 8 hours of sun.

      You would have to check how many kws you use a night to see how much power you need. Your electric meter reader would be a good source, and check with a dealer to get a meter to measure the charge you have given the amount of power your batteries received. You would have to experiment for a while depending how many batteries you are charging.

      With my scant sunlight, I thought a large mirror reflecting light from under the panels could boost more power so I looked it up and sure enough, even on dull hazy days or spring or fall when sun is lower, it produces an output increase by 75% when conditions are not so good by reading a meter. Just can’t do it on bright summer days for it may cook the panels from too much heat, and it doesn’t work on cloudy overcast days.

  7. One thing to remember is that most solar systems (pun intended) sold commercially are designed so that if the power goes out your system goes down. When I was researching it the stock answer I got when I told them I wanted to be able to use the power if there’s no electricity was “get a separate generator.” These are the grid-tie buy-back systems. While there are ways to bypass that, you need to have a supplier who WILL, and who knows that it’s possible.

    1. @ Lauren

      Actually your talking about a system that only ‘sells’ back to the Grid without a Battery backup…

      Battery backup systems are very common any more, with a LOT of good companies out there. Anyone that tells you to “get a separate generator.” RUNNNNNN. They have NO idea what they are talking about…

      And yes the new ‘safety’ AST’s, lockout’s, subpanels and the ‘correct’ way to designing a system are far beyond the old days of yesteryear; much like comparing a 2017 Duramax Truck to a 1957 Chevy pick-um-up truck.


      PS the “commercial” industry is designed to only supplement the Grid, having square miles of panels is the .gov’s way of saving us all from ourselves…..

      1. The way it was explained to me is that the current systems available are power-in power-out. If there’s no power in, you have no power flow from the cells. Yes, you can have a battery backup, but if it can’t be recharged because the cells themselves are designed not to work unless hooked up to the grid (and the grid is working!) it’s not going to do you any good in a long term grid-down situation. Two different types of solar cells, one designed for off-grid systems and one designed only for grid-tie systems. Yes, you can get systems that can stand alone, but the power company likely won’t approve the installation (they have to approve all installations that are grid-tie) and going off-grid in this area is currently illegal so none of the legitimate companies will touch it.

        I’ve spoken to several different companies in this area. Some knew about the difference in the cells and some didn’t, but all stated that if there’s no power in the grid, your power goes down as well. Two of them talked about battery backup. The others wouldn’t even discuss it.

        1. We are looking at an alternate system… a side by side with the current grid system. will have separate lighting running on solar, separate outlets to run necessary things in limited area… like kitchen, master bedroom, closet/living area/ maybe for fan/lights… will have to choose where most crucial needs are ahead..could also use large guage extention cord…one with # 6 wire. Still will need to caculate needs and use, but can use solar without grid tie. My husband has electrical training so he will do all independent of any existing wiring. Solar outlets will be color codes, probably red.

        2. We have our cabin and sheds wired like that. It has worked well for our needs. When I originally wired everything I also ran 12 volt wires for lighting, fans, TV and cigarette type plugs so we can power things without using an inverter. No power conversion loss that way.
          Also have power ports with 3,6,9,5 volt USB ports as well as 12 volt.

        3. @ Lauren

          I might suggest ya check out wholesalesolar.com, they have dozens of systems predesigned and any competent electro contractor ‘should’ be able to install them. They are a little pricy, but a good place for information on the industry.

          Please make sure to check out the “Grid-Tied Solar Power Systems with Battery Backup” page, it will explain the system in detail.


        4. Avoid grid-tie systems. People go for these with the idea of “selling” power to the utility company.

          I doubt you’ll get any of the freebies with an off-grid system. The utility companies and government want you on-grid.

  8. The Math in the KWH example is faulty. 450 Watts in 24 hours means 18.75 Watts per hour which is equivalent to 0.01875 KWH (and not 0.19 as stated).

    Regarding storing solar electricity in batteries, this is just too expensive due to a rather short life span of batteries. Even if properly maintained, it is difficult to achieve life spans of more than 10 years for batteries.

    A better idea is to have two systems: One grid tied solar system and and a second system which keeps batteries fully charged using grid energy. In the rare case where the grid fails for a limited number of hours, the batteries would take over the supply of electricity to the house.

    In general, as a society, we should invest into a better and more reliable grid. This is the cheaper option than to install individual battery banks in every house. There should be a solar system on every roof in the US. That system should be grid tied. The utility companies should employ large scale batteries in order to have a flexible buffer if excessive demand hits.

    Individuals should seek for ways to minimize electricity consumption. Better fridges, better and fewer lights, and fewer TV’s. That is the way to go. Insulate houses to minimize energy losses due to AC and heating.

  9. Ken,Thank you for the links and info. This is helping with planning in a few projects. The links and explanation just pushed the wife over in going LED now instead of gradually. The break down for $ savings sold it.

    1. @Rwt, Glad that it helped you out! Switching to LED light bulbs is a very significant cost savings over time. It’s incredible how much less energy they use compared to incandescent.

  10. Yes batteries can get expensive fast. But going cheap, and underestimated sizing. Well can get real expensive, and please stay away from flooded cell batteries. Life expectancy is short, and deep discharge will absolutely kill them.

    AGM batteries are a better choice and are safer from little to no off gassing.

    But even though you choose AGM type batteries, size the bank correctly. While they can take a deeper discharges, why take that chance? Stay above the 40% level and protect your investment.

    With the life expectancy of panels getting over 25 years, you will have to refresh the battery bank.

    The battery I use the most are Iron Edison, and can last the life of the solar panels.

    Expensive Yes, but how many times will you have to refresh your bank and how much will it cost each time?

    While most of the work I do is not grid tied, but has to be absolutely dependable!

    1. @Otarn, All good advice. My current battery bank consists of all AGM (so that I can keep them inside the house). My self-imposed discharge limit is only 30% (70% SOC state-of-charge). There is a significant difference in life expectation the less they are discharged every day. I hope to get at least 7 years, but we’ll see.

      Next time around I will be investigating other battery options, and maybe technology will have changed such that there will be something even better ;)

  11. Marine batteries are the best to use for this deep cycle application. IIRC they are around $250 each…
    I make notes on where solar panels are…. When the SHTF they will come down….

  12. Consider dumping excess power into your electric water heater instead of the grid. You can do this outside of your inverter loads straight from the solar panels during off solar window hours to take advantage of that un-usable power that your MPPT controller won’t use and after you battery is floating. The resistive load is not quality power sensitive and can handle the wide dc/ac variation your panels are putting out. The power is dumped into the heat sink and you get more than the pennies that the power company is paying you.

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