How Many Solar Panels To Run 5 Ton AC Unit?

Air conditioners, like fridges and freezers, are a bit special because they contain compressor motors.

This means that the power rating changes depending on the cooling cycle and a motor that starts and stops periodically, so you need to use average energy consumed in calculations.

How Many Solar Panels To Run 5 Ton AC Unit?

A 5 Ton AC unit requires 6000 watts of solar panels, assuming irradiance of 4 peak-sun-hours per day. 500Ah of battery energy storage will also be needed per Ton for each hour of running time when the sun doesn’t shine. For daytime running a 200Ah battery is sufficient to ensure surge currents are supplied.

You need to consider these factors before sizing solar panels to run an AC unit:

• Why are AC units rated in tons?
• What the actual AC power rating in kW?
• What is compressor motor inrush current?
• How long will you run the AC unit?
• Do you need batteries to run your AC?
• Which batteries are best for storing solar energy?
• How much power can solar panels produce?
• What size solar panel you intend to use
• Why you need an inverter and how to size it

Video – Can you run a 5kW AC unit with solar panels?

Can solar panels run air conditioning?

For d.c. loads, power calculations are a piece of cake. Watts is calculated by multiplying volts and amps.

If a d.c. resistive device is supplied with 12 volt and it draws a current of 11 amps, the formula below can be used to calculate power in watts:

12 volts x 11 amperes = 132 watts

In alternating current (A.C.). circuits, voltage multiplied by current doesn’t necessarily equal power in watts (although it can do!) Let’s get into it …

In a.c. circuits V and I need to be ‘in phase’ for product to equal power in watts

Domestic appliances use alternating current, so the power calculation needs to be handled differently. Voltage and current waveforms change all the time in a sinusoidal shape.

Because of the inductive nature of motors, the current waveform can lag behind the volts and change the power calculation.

If volts and current are at a maximum at the same instant in time, they are ‘in phase’ – in this case volts x amps really does equal watts.

If volts and amps are out of phase, then the equation isn’t strictly true and in general more solar power is needed for the extra current.

How much electricity does an air conditioning unit use?

Why air conditioners are rated in tons?

An air conditioning unit is rated according to efficiency. They are all different, so if we used electrical kw rating to compare them, it might not be a true comparison of their cooling capacity.

Basically, two AC units rated at 5kW will probably not have the same cooling capacity – it depends on their efficiency.

So how do we define a ton of ac cooling power? It is the amount cooling capacity needed to melt 2000 lbs of ice in 24 hours. It’s known as a short ton.

The higher ac tonnage, the bigger the volume of air can be cooled per hour. One ton is also equivalent to 12,000 BTU/hour (British Thermal Units/hour), which is the same as 3.5 kW.

A 1 Ton ac unit has a cooling capacity of:

(12000 x 1055)/3600 = 3516 Joules/sec = 3516 Watts

What is EER rating in AC?

EER stands for ‘energy efficiency ratio’ and it’s a measure of how well an ac unit cools. If you divide an air conditioner’s BTU value by it’s power rating in Watts , then that ratio is an indication of efficiency.

A very efficient ac unit might have an EER ratio of 12, for instance. AC units with higher EER ratings, more than 10, are mostly recommended for hot humid climates..

The EER rating system uses a standard outdoor temperature of 95°F, inside temperature of 80°F, and humidity of 50%.

The SEER rating is used more and more today, because it uses an ac’s cooling power over a range of outdoor temperatures. The ‘S’ stands for ‘seasonal’. 

The table underneath the text indicates the SEER/EER for some common home air conditioning units.

Lennox are improving their designs with solar panel support and it seems this will become an industry-standard for future technology.

Table – SEER and EER ratings comparison

How much does it cost per hour to run an aircon?

This depends on several factors – see below:

• the efficiency of the AC unit
• how often will the ac run?
• how long will the AC unit run during the day
• what is the outside temperature
• the cost of your electricity per kWh

As you might imagine, it gets a bit complicated but is all this detail worth it? Let’s see which factors are the most important.

Air conditioning installers use rule-of-thumb guides for sizing ac units and solar support. A common rules states that an ac unit draws about 7 amps for a Ton of cooling power rating.

This doesn’t stay constant but changes as the Tonnage changes.

• 2 ton draws 15 amps
• 3 ton draws 18 amps
• 4 ton draws 21 amps

For general sizing and installing systems, this is a good rule. For me, when designing a solar panel system, I like to know exactly what’s happening electrically!

The value RLA (Rated Load Amps) is another value that can lead to confusion – it’s found on the ac conditioning label – see below:

Making sense of ac current ratings

The RLA value of current is not the normal AC current – it’s the maximum current the compressor motor draws while the AC unit is cooling.

It can be confused with the LRA value, which stands for Locked Rotor Amps. This can happen when a motor is stalled or locked, it can’t turn and draws maximum current to try to rotate.

This value is about same as the surge current drawn when compressor motor starts up from cold. The average running current is dependent on other factors.

Resource: https://www.energy.gov/eere/buildings/appliance-and-equipment-standards-program

What is meant by AC inrush current?

When any motor starts up from cold it draws much more current than when running continuously.

The value of the running current in amps will be depend on the size of the load, but the surge or inrush current will be the highest current the motor normally draws.

Installation wiring sized is calculated on maximum running current plus 10%. Inrush currents last for just a few seconds and the heating effect is negligible.

Circuit breakers and fuses need to be sized correctly, so that they can pass the inrush surge without tripping.

This also has some implications for a solar panel array built to run ac.

If running in the the daytime without a battery energy storage bank, the solar panels power needs to be increased to supply this extra motor inrush current.

A solar panel system designed for domestic appliances needs to use a device called an inverter to convert the d.c. voltage generated by solar panels into the a.c. needed for domestic use.

Solar panels need an inverter to convert dc power to ac for home appliances

How many solar panels to run ac unit?

Now you know what happens in an ac unit as the load, let’s take a look at solar panels can be used to supply this kind of load.

Test of the post will be based on using fixed solar panels with 300 watt rating, as bigger panels are better buy in terms of dollars per watt.

How much power can a 300 watt solar panel produce?

The output power of any solar panel depends on several factors:

• solar panel efficiency (between 20% and 22%)
• how big is the solar panel area in square meters
• irradiance (kWh/m2/day) (the sun’s energy, by location)
• orientation (solar panel direction and angle)
• fixed or auto-tracking for the solar panel array

A 300 watt solar panel will generate about 1.2kW/h per day with average peak-sun-hours of 4.

How does a solar inverter work? The basics

Solar panels generate direct current (d.c.) but domestic appliances use alternating current (a.c.), and this is why you need an inverter for the d.c. to a.c. conversion.

An inverter reshapes d.c. power electronically into a smooth sinusoidal waveform, which is identical to the power fed to your house by utility companies.

How much solar energy to run 5 ton ac unit? Calculation

Air conditioning is really needed when it’s very hot, which tends to be the four hours either side of 12 noon in most geographic locations.

This is fortunate, as this is mostly when the sun’s energy is at its maximum, solar panel output watts is also maximum.

1 Ton of AC cooling capacity is rated at 1.2kW of electrical power, so 4 hours running time would consume 4.8kWh of energy.

A 5 Ton AC unit will therefore consume:

1.2kW x 4 x 5 = 24kWh

A 300 watt solar panel generates 1.2kWh/day (in full sunshine). An easy formula for calculating how many solar panels are required run a 5 ton ac unit is as follows:

AC energy consumed (24kWh)/energy generated by 300W panel (1.2kWh) = 20 solar panels

20 solar panels rated at 300 watts = 6000 watts

A 5 Ton AC unit gives quite a bit of cooling, but it needs plenty of solar and battery backup to work properly.

For example, if a 5 Ton AC unit was going to run in the night when the sun doesn’t shine, it would need 500Ah of battery storage for each hour that it runs, which is huge and not really practical.

If it just runs in the daytime, then a 200Ah battery would be sufficient to support the extra surge currents and also compensate a little for reduction in solar output when clouds pass over the panels.