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.