Off Grid Air Conditioning

Having grown up in the south, I have a unique appreciation for air conditioning that can only come from experience.  After working outdoors all day every summer in the humid heat, you learn to appreciate that cool air when trying to sleep at night.

Maybe that’s why I now live in a climate where we fire up the wood stove at least occasionally for 9-10 months out of the year :-).

But I do have compassion for those of you sweltering in the southern inferno.  And even in our northern mountain location, we typically experience weeks of weather in the 90’s.  Since it cools off nicely every night, a well insulated house with efficient ceiling fans can stay quite comfortable.

However, our recently acquired old home is not exactly well insulated.  LOL!  This is why I recently acquired an air conditioner to help keep things more comfortable.

"But, wait a minute" (I can hear you saying).  "I thought you were off the grid.  How can you use an air conditioner off the grid?"

Good question.  In the not too distant past, it was not feasible to run an air conditioner for any length of time.  But the cost of solar power has come down significantly, allowing us to build larger power systems; and now there are more efficient cooling options that were not available years ago.

So it is totally feasible to use air conditioning off the grid.  But, you need to be strategic about it and make good choices when purchasing and using an air conditioner.

In this article, you'll learn about the different options for air conditioning, what I recommend for different situations, and I'll also cover the things you can do to make your air conditioner even more efficient.

As I see it, there are 4 main types of air conditioners these days…

Forced Air A/C

This is the most common type, but also the least efficient.  I mean, it almost seems wrong to use the word efficient in the same sentence as forced air A/C!  We’re talking about massive amounts of power, not just for the compressor unit and all that, but also for the fan that forces the air through ducts in your home.  It is simply not feasible off the grid unless you have an enormous budget.

Split System (ductless)

This is a relatively new type of air conditioning system that is becoming increasingly popular—especially for folks who are trying to become as energy efficient as possible.  It consists of an outdoor unit (the compressor/condenser) which cools the refrigerant by dissipating the heat it has picked up inside the house.  The cooled refrigerant is then pumped back to the house to an inside unit which uses a fan to force air across an evaporator.  In the process, the air is cooled.  Instead of forcing air through an inefficient system of air ducts, the only thing that is transported is liquid refrigerant in small pipes.

Mini-split systems consist of one inside unit connected to one outside unit.  A muliei-split system can run multiple inside units with only one outside unit—thus providing cooling to multiple rooms.  And each room can be set independently for greater efficiency (i.e. higher temperature in an unused room).  This is called “zoning” since you can make each room or area of the home it’s own zone and regulate the temperature differently depending on what is needed.

While split systems are much more efficient than conventional forced air ducted A/C systems, they can still require a substantial amount of power.  But with the price of solar panels down as far as it is, it’s quite feasible to build a large enough off grid solar system to power a split system.  You’ll just need to take it into account when sizing your solar equipment, so you don’t end up with an undersized power system.  In my opinion, this is probably the best option for someone going off the grid in a climate that will require A/C for much of the year, or for someone with a larger home.  As always, don’t forget the basics that can save you tons of power (excessive insulation, efficient ceiling fans, don’t cool rooms that don’t need to be cooled, shades/blinds on windows with lots of direct sun coming in,  etc).

Expect to pay less than you would for a conventional forced air A/C system, but don’t expect it to be cheap.  And go with the most efficient unit you can find, especially if your climate is such that it will be running a lot.

Window or Wall A/C

This is the least expensive type of air conditioner.  We’re all familiar with them in hotels and small homes.  Window air conditioners are certainly not the most efficient cooling option out there, but surprisingly, they can be a viable option for folks who don’t run A/C very much or for folks with a small home that doesn’t need a lot of cooling power.

Here’s the deal.  In most areas, the time when you are most likely to need A/C is also the time when you are getting the most solar power (sunnier and longer days).  Since a properly designed system should be sized for the winter months, there will be an excess of power during the summer.  This excess power is what we will be using for most of our air conditioning.

If your climate is such that you don’t need A/C very often, then it probably isn’t worth the additional expense to install a split system.  Install just enough window A/C power to keep things fairly comfortable.  In many cases, you’ll have enough excess solar power to handle it.  And if not, you can use your backup power source (grid power or generator) for the rest since you don’t need A/C for long.

And if you have a very small home, then a window A/C could also be a low cost option even in a warmer climate.  If you can get by with a single small window A/C unit, then it may very well be an option for you and would certainly be cheaper than a split system.  But as mentioned before, I do recommend going with a split system if you’ll be running it a lot.

Portable A/C - This is very similar to a window A/C except that the main body of the unit sits inside the house on wheels and a short hose pipes the heated air outside.  From my research, I found these unites to not generally be as efficient as some window A/C units, but there may be some exceptions.  For the most part, I would look at this type of A/C in the same way as I do a window unit except that the portable units are much easier to move around from room to room.  They are also a little more expensive than window A/C units.

What We Did

LG LW6017R

I sometimes hesitate to share what we did out of concern that others may follow suite without checking to see if what we did is the best option for them.  So please bear that in mind, do your own research, and choose what works for you.

Since our climate is such that an A/C would only be running for a few weeks out of the year (and only for 4 or 5 hours a day during that time), I felt that we would be better served by a less expensive window A/C.  In addition, our available solar power is truly amazing during the summer season, so I’m not overly concerned about efficiency in those months.

I settled on the LG LW6017R.  It is a 6,000 BTU unit with an EER efficiency rating of 11.5 (the higher the better).  It cruises at a little less than 500 watts when the compressor is running, and it has an energy saver mode that turns the fan off when the compressor is not running (yes, there are some models that run the fan all the time!).  It is thermostatically controlled and also has a 24 hour time that we can set to have it come on in X hours or to have it turn off in X hours.

On a hot day (in the 90’s) I turned the A/C on around the middle of the day and set it for 77°F.  By the end of the day, it had kept the temperature fairly consistent in the main part of the house and had used a little over 3 kWh.  It cycled on and off (with not much on time) during the middle of the day and late in the evening, with more and more on time during the heat of the day.  I have little doubt that it would have used less power if our home was better insulated.

One thing I found early on is that waiting until the house is already hot before turning on the A/C, is a losing strategy!  I believe you will find it to be more efficient to turn it on before your home is hot so it can maintain the current temperature rather than having to cool down the existing temperature.  Maintaining the current temp is a lot easier for a small unit to do than reducing the existing temp.

All in all, I’m pleased with the model we chose, especially considering that it cost roughly $180 and we won’t be using it much.  And with a 3,000 watt solar array that is properly sized, it’s not uncommon for the batteries to be fully charged by the middle of the day in summer months.  This means that a little over 1-2 hours of excess sun is all we would need to power that A/C on a day in the 90’s.  Not bad!

If we lived in a hotter climate that would require more A/C use or if our home was larger, then I would probably be inclined to go with a split system.  It really is a matter of balancing the level of comfort you want with your climate, home size & insulation, and perhaps most importantly your budget.

Remember, you can do almost anything you want off the grid, it boils down to your budget.  The more power you use, the larger and more expensive it will need to be.  Choose accordingly.

9 Comments

  • Avatar

    marc

    Reply Reply July 13, 2017

    please send me a link as to where i could buy one or 2 please

    • Nick Meissner

      Nick Meissner

      Reply Reply July 13, 2017

      Hi Marc, Here's the LG 6,000 BTU unit that I mentioned in the article and that we use.

      Hope that helps!

  • Avatar

    Wally

    Reply Reply July 13, 2017

    Why no mention of evaporative cooling? Uses very little power and water. In hot dry areas it works well.

    • Nick Meissner

      Nick Meissner

      Reply Reply July 13, 2017

      Good point. I didn't mention evaporative coolers (swamp coolers) because the article was focused on air conditioners for off grid use, but in retrospect, I should have. Will try and add that in when I get a chance. Thanks.

  • Avatar

    Wally

    Reply Reply July 13, 2017

    That is great because there are some very efficient swamp coolers being made now. Bon Aire out of Australia is one that comes to mind. Has a large fan w/small motor and uses CELdek cooler pads. Will be installing one in our off-grid house in a few months.

  • Avatar

    Kevin Fisher

    Reply Reply July 13, 2017

    I use a 17 seer mini-split AC unit that also heats in the winter, but at 9 seer efficiency. It is 110 volts, 1 ton unit (12000 btu) by Pioneer and is sold over Amazon. $700. This type of unit is more professional than a window Ac unit that is open to the outside and takes a larger opening to the outside. The condenser sits outside and the Freon is already in the copper line going to the air handler in the home. Easy to install. I have a 4800 watt solar power system with part of my home on the grid and part on solar. A separate breaker box for the solar circuits. MyHomesteadMarketplace.com helped me with it.

  • Avatar

    Jeff McCrea

    Reply Reply July 13, 2017

    One thing that was popular in Florida back in the 70's for a split A/C system was to lay a grid field of PVC pipes, (copper is better but $$$ more), under about 2 or 3 feet of the yard, the deeper and larger, the better, and connect up a pump in a closed loop system that was similar but opposite to a circulated hot water solar heating system. In most split A/C systems, The outside condenser fan will suck air through the condenser into the box and out of the top. What they would do is run the pipes from the yard to the A/C condenser and place some sort of radiator outside and over the top of the condenser coil. The water that has been cooled under ground would cool the outside radiator pre cooling the air about to be drawn through the A/C condenser. The cooler the condenser, the cooler the refrigerant, the cooler the inside air and the less time the A/C would have to run to do the job. Air conditioners are kind of an oxymoron. They work most efficiently when it is cooler outside mostly when you don't need them. Anyway, they would wire the pump into the compressor motor circuit so it would come on with the A/C. If one has a heat pump, one would have to wire a cutoff switch as you wouldn't want to pre cool the condenser in the winter as it becomes the evaporator in the reverse cycle so as to draw outside heat inside. You could do this with a window unit too but you may have to wire the pump to some kind of thermostatic control that would sense the heat from the condenser. Otherwise, wiring inside the unit would void your warrantee. Also, don't make the pre cooler too dense as to restrict airflow as the blower on a window unit isn't exactly a hurricane maker. In Fla., you didn't need an antifreeze solution as it never got cold enough to freeze the system. You may need to run a 50 / 50 mix in your northern climate or drain the system every fall. Here in W.Va., people are using the outside boiler systems that pump an antifreeze solution into a radiator in the house central A/C unit that replaces the heat strips in a split A/C system They load wood into a double wall boiler that has a thermostatically controlled blower that air charges it like a forge up to a preset temperature. Then it shuts off. The heat is transferred to the 50 / 50 solution in the double wall boiler and pumped through insulated pipes into the house, into the radiator and the inside blower forces heated air throughout the duct work. People like it here because the fans and pump don't require a massive generator to heat the house if the power goes out. They can get away with 2Kw or less for the pump and fans. A 5th alternative for A/C is a natural gas A/C unit. They were popular here about 15 years ago and I'm told are still available. They heat the refrigerant with a gas flame like the old ammonia refrigerators did years ago to pressurize it and circulate it from there like a conventional A/C unit and wah lah. Cold air for the electrical power it takes to run the blower. They are especially popular here with people who have their own private gas well or get free gas in exchange for allowing a gas company to drill on their property. There is a renewed interest here in natural gas generators and A/C units since the discovery of the marcellas gas fields here in the east and similar deposits in the west. I know that's not exactly energy independence but it's good for a backup generator as you don't have to store and cycle out fuel before it gets old or worry about having gallons of explosive gasoline lying around and you don't have to go out on a winter night to gas up old Betsy in the middle of a blizzard. I apologize for the length of this but I had a lot of information on this subject. I hope you or someone can use it. Jeff M.

  • Avatar

    Ken Marsh

    Reply Reply July 14, 2017

    Good article Nick,

    Air conditioning and solar go hand in hand.
    When air conditioning is needed is also when the solar panels are at their maximum output.

    We are experimenting with solar heating.
    This is quite different.
    Non-the-less we are able to produce the majority of our heat, DHW and all AC with solar.

    In this case the key is a ground coupled heat pump.
    For every unit of energy produced by the solar panels,
    it draws three more units of heat out of the earth.
    and puts the sum of four units of heat into the house.

    There is no doubt in my mind that the future is solar.
    However at the moment, I do not know of any equipment being made specifically for this purpose.
    I built my own, or more precisely, modified a regular heat pump for the task.
    But the system works good.

    Ken Marsh

  • Avatar

    Ron

    Reply Reply September 25, 2017

    I'm thinking of building Under Ground. Cut down on Heating and Cooling!!!

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