Solar System Air Conditioner

Any small household appliance can be powered by a solar panel due to them pulling a constant current.

These appliances tend to have their power ratings labeled on them or in the box they came in, so it won’t be an issue.

The difficulty comes in when powering bigger appliances like fridges and today’s topic, an air conditioner.

Larger appliances contain motors and compressors that draw high amounts of power that needs to be averaged

So, let’s see how we would go about running an air conditioner using a solar system. But first, we need to break down the parts that make up a solar system.

Elements of a Solar System

Before we can dive into the average residential solar system size needed to power an air conditioner, we need to determine what makes up a solar system.

Installers or DIY users need to know the size of the system and what exactly they want to use the system for. That way, they won’t charge you for a system that’s too big or too small.

The first element is a solar panel. This allows us to harness the sun’s energy and convert it into electricity.

The second element would be solar inverters. These allow the energy coming from the solar panels to be converted into usable AC electricity.

Component number 3 is the battery or solar generator. This stores any energy that isn’t being used, acting as a reservoir in times when the sun isn't shining bright.

The final component is the charge controller. This manages the energy flow from the solar panel and makes its way towards the battery.

Ensuring that you have these critical elements in your solar system can help you figure out your solar needs.

It helps you answer questions like how many solar panels you need for a 5kw system, or how many solar panels you need to power the lights in your home.

Can You Run an Air Conditioner Using Solar Power?

Solar-powered air conditioners are useful in areas that are exposed to humid conditions and exposure to the sun.

This is working on the assumption that we’re receiving an irradiance of 4 peak sun hours every day.

For the battery, we suggest a 100Ah battery per ton for each hour that the solar system is running.

The reason we work with the running time of the system is to allow the battery to do its job when solar irradiance is lower than expected.

This also creates a reservoir that’ll supply motor surge current. This is the quick, short-lived flow of current in the system that occurs in short pulses.

Solar systems designed to run air conditioning need a battery bank, otherwise, your solar panel’s wattage rating would need to be big enough to supply the power to the air conditioner’s motor.

Anything can be powered using a solar system, including air conditioners. However, you need to look at factors such as the power rating and your solar needs. 

Knowing this allows you to plan the design and size of your solar system.

How to Calculate Solar Needs for Your Air Conditioner

This measurement is best calculated using an online solar calculator, and no matter which one you choose, they all perform the same task. Calculating your solar needs.

It starts by sizing your battery bank and asking how many watt-hours per day are consumed in your household.

So, if we have a 1,000W air conditioner powering a small cabin and it's being used for 4 hours per day, the watt hours are 4,000.

The calculator then asks how many days your solar system will run without sun, as well as the effective capacity of your battery during low temperatures.

All these values are put into an equation that returns the battery bank’s capacity in amp hours.

The next step in sizing is the solar panel and charge controller. You need to enter the average sunlight your area receives by looking at a solar map.

Based on your total consumption from earlier as well as where you are in the world, the calculator will tell you how many watts or kilowatts your system needs.

The solar charge controller is calculated as soon as you have the values of your solar panel sizing. Everything is done automatically.

Now that you have the size of your system and know that it's good enough to supply power to your air conditioner, let’s look at power ratings.

Power Rating and Calculation

Knowing the power rating of an appliance can help you determine how many solar panels are needed in your system. This is either found on the appliance or it can be calculated.

All you need to do is multiply the voltage with the amps. For example, if a DC load has a 12V supply that pulls 12A, the power rating would be 144W.

However, when it comes to working with an AC load, it’s not that simple. We need to take both the voltage and current waveforms into account.

These waveforms constantly move from positive to negative, and if the volts and current are at a maximum then we can use the standard V x A calculation.

When these two measurements aren’t in phase, the equation won’t work.

The average air conditioner needs around 1,200W worth of solar panels for each ton of cooling capacity. A solar heating system is around the same wattage.

Every air conditioning unit has different energy efficiency ratings.

If we use the kilowatt rating as a comparison to how much power it needs or uses, it doesn’t reflect its overall cooling power.

When we speak about tons in the air conditioning power ratings, we refer to the amount of cooling needed to maintain 2,000 pounds of ice in a single day.

if the tonnage is large, you’ll have more air that can be cooled per hour. Numerically, a ton can also be represented as 12000BTU/h or 3.5KW here in the states (it’s different in countries that use metric measurements).

The Energy Efficiency Rating

Another common term you’ll see is the energy efficiency ratio. This is a measurement that tells you how well a specific air conditioner cools.

If you take the tonnage of an air conditioning unit and divide it by the electrical rating in watts, you are left with a ratio. This ratio is the EE rating.

An efficient air conditioning unit will have an EE rating of 11. If an air conditioner has an EE that’s greater than 11, it’s catered towards places with higher humidity.

This rating is based on an outdoor temperature of 95 degrees Fahrenheit, and an inside temperature of 80 degrees Fahrenheit.

Many have found that their solar systems for cabins that use air conditioning units prefer the Seasonal EE rating.

This rating considers the air conditioner’s cooling capacity over a range of outside temperatures.

How Much Does it Cost to Run an AC Using Solar Power?

Knowing how much it costs to run an AC gets complicated if you aren’t aware of some important factors.

Tonnage

Most installers of both solar systems and air conditioners have guides to sizing, giving you quotes before going ahead with anything.

One of the factors they take into consideration is that an air conditioning unit draws around 7A of power for every 1 ton of its cooling capacity rating.

However, this measurement is bound to change as the tonnage changes. The relationship between amps and tons changes as the cooling power of a unit increases.

For example, 2 tons need around 15A and 3 tons require 18A, with amperage increasing as the tonnage goes up.

When the air conditioner is powered on, it pulls several times more current than when it’s left to run continuously.

The operating current is dependent on the load, but the surge current is the highest that the motor will pull unless the motor is faulty.

The surge currents only last for a few seconds and the heating effect on the wires won’t be significant enough to cause an electrical fire.

However, we recommend using breakers and fuses that are sized accordingly to compensate for the surge without causing a trip.

What Are You Paying For?

At the end of the day, running an air conditioner through a solar system won’t cost you a cent if you’re living off-grid. Your local grid-tied power provider will charge you if you’re still living on the grid.

But if you are all to your lonesome, you don’t need to pay anything to use the sun’s energy to power your air conditioner.

The costs come into play during the purchasing of the components and installation of the system.

The average price installment as well as purchasing the system is around $16,000. 

In terms of an air conditioning unit, you’re looking at anywhere between $4,000 and $10,000 depending on the size of the unit.

Practical Example

Different solar panels would be used for different-sized air conditioners. 

The latter can be as big as a unit mounted on the ceiling or as small as one designed to be mounted on your room window.

Smaller Air Conditioners

If you have a small solar power system that contains a 200W solar panel, you can certainly power a smaller air conditioner unit that’s measured at 100W.

Also, if you already have or want to install an average-sized residential solar system, you will already have around 200W worth of solar power.

You always want to ensure that the total wattage of your air conditioning unit matches your solar system.

If it doesn’t and you find yourself 100W short, you can simply daisy chain the panels together and create a solar array.

But how do the bigger air conditioners fair with a smaller system? Unless their wattage is matched, they don’t fare too well.

Bigger Air Conditioners

These are the air conditioners that most American homes use to keep a large portion of the house at a cool temperature.

An air conditioner drawing around 5A measured at 115V gives us a wattage of around 575W per hour.

If this air conditioner is running on average for 8 hours per day, we’re looking at around 4600W which would need to be supplied by the solar system.

With these larger amounts, using a battery becomes detrimental as it will help store the excess energy that isn’t being used by the solar panels.

It also means that when the sun goes down, the batteries will kick into power your air conditioner during the night.

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