Understanding Renewable Energy.
How many solar batteries can run an Air Conditioner.?
The job of the batteries in a solar installation is to store all the energy generated by the solar panels and make that energy available for use at all times. In other words, the battery bank should be large enough to store and supply the energy demands of the air conditioner.
In general, the battery bank would consist of multiple batteries, and each battery would have voltage (V: Volts) and charge (Ah: Amp-hours) ratings. For example, a 4800 Watt-hour battery bank would consist of 4 12V-100Ah batteries (4 x 12 x 100 = 4800). The more batteries, the higher the capacity of the battery bank.
If the manufacturer recommends a DoD of 80%, the battery should be discharged to 20% of its capacity.
If the recommended Depth of Discharge is repeatedly exceeded, the battery would lose big chunks of its capacity quicker than it should. This damage would be irreversible.
What you should know is that there are 2 types of batteries that you would usually find on the market:
- Lead-Acid batteries: These batteries are cheaper but generally have a DoD of 50% and fewer charge/discharge cycles.
- Lithium batteries: These batteries are more expensive but generally have a recommended DoD of 80% (up to 100%) and 3 to 5 times the charge/discharge cycles of a lead-acid battery.
The fact that lithium batteries can be discharged deeper (up to 100% DoD), means that you would need fewer lithium batteries than lead-acid batteries to provide the same amount of energy and they are light in weight.
Air Con. Capacity | Est. Energy Consumption over 8 hours | Required Lithium Battery Capacity (in AH @ 12V) | Required Lead-Acid Battery Capacity (in AH @ 12V) |
| 5000 BTUs | 2500 Wh (2.5 kWh) | 260 Ah | 420 Ah |
8000 BTUs | 4500 Wh (4.5 kWh) | 470 Ah | 750 Ah |
12000 BTUs (1 ton) | 7000 Wh (7 kWh) | 730 Ah | 1160 Ah |
18000 BTUs (1.5 tons) | 10000 Wh (10 kWh) | 1050 Ah | 1700 Ah |
24000 BTUs (2 tons) | 14000 Wh (14 kWh) | 1500 Ah | 2300 Ah |
36000 BTUs (3 tons) | 20000 Wh (20 kWh) | 2100 Ah | 3400 Ah |
Estimated lithium and lead-acid battery capacity required to run different air conditioners for 8 hours.
To determine the battery needed to run your air conditioner, simply divide the daily energy consumption of your AC unit, by the recommended Depth of Discharge of the batteries you’ll be using.
Required Battery Capacity (Watt-hours) = Air conditioner’s daily energy consumption (Watt-hours) ÷ Depth of Discharge (%)
This will give you the battery capacity in Watt-hours. Since most solar batteries are rated at 12 Volts, simply divide those watt-hours by 12 and you’ll have calculated the battery capacity in Amp-hours (at 12V).
Required Battery Capacity (Amp-hours) = Required Battery Capacity (Watt-hours) ÷ 12 (Volts)
For example, if our air conditioner consumes 5000 Wh per day, and we use lithium batteries (80% DOD) to run it, the required battery capacity to run our air conditioner is:
Required Battery Capacity (Watt-hours) = Air conditioner’s daily energy consumption (Watt-hours) ÷ Depth of Discharge (%)
Required Battery Capacity (Watt-hours) = 5000 Watt-hours ÷ 80%
Required Battery Capacity (Watt-hours) = 5000 Watt-hours ÷ 0.8
Required Battery Capacity (Watt-hours) = 6250 Watt-hours
Now let’s assume that we’ll be using 12V-100Ah lithium batteries:
Required Battery Capacity (Amp-hours) = Required Battery Capacity (Watt-hours) ÷ 12 (Volts)
Required Battery Capacity (Amp-hours) = 6250 Watt-hours ÷ 12 Volts
Required Battery Capacity (Amp-hours) = 520 Amp-hours
According to these calculations, we would need (at least) 520 Amp-hours of battery capacity (at 12 Volts).
An affordable choice for this setup would be 12 of Universal 12v-100ah AGM Lead-Acid Batteries.
A more premium choice would be 6 of 12v-100ah Renogy lithium batteries:
How many solar panels needed to run an air conditioner?
The amount of solar power or the number of solar panels that you need to run your air conditioner would mainly depend on 2 factors:
- The daily energy consumption of your air conditioner.
- The average amount of sunlight that your solar panels would receive on a daily basis.
In other words, the higher the energy consumption of your air conditioner, the more solar panels you would need. Also, the less sunlight you get, the more solar power you would need.
In addition to that, it is also important to note that if you are trying to build an off-grid system, your solar system would consist of the following:
- Solar panels
- A battery bank
- An inverter
The answers to these 2 questions are quantifiable and can be used to determine the amount of solar power that you need to run your air conditioner. But before we get into that, to give you an idea, the following table below estimates the amount of solar power that would be needed to run different air conditioners for 8 hours a day:
| Air Con. Capacity | Est. Energy Consumption over 8 hours | Est. Solar Panels Needed (Watts) |
| 5000 BTUs | 2500 Wh (2.5 kWh) | 500 Watts |
| 8000 BTUs | 4500 Wh (4.5 kWh) | 900 Watts |
| 12000 BTUs (1 ton) | 7000 Wh (7 kWh) | 1400 Watts |
| 18000 BTUs (1.5 tons) | 10000 Wh (10 kWh) | 2000 Watts |
| 24000 BTUs (2 tons) | 14000 Wh (14 kWh) | 2800 Watts |
| 36000 BTUs (3 tons) | 20000 Wh (20 kWh) | 4000 Watts |
| 48000 BTUs (4 tons) | 28000 Wh (28 kWh) | 5500 Watts |
| 60000 BTUs (5 tons) | 35000 Wh (35 kWh) | 7000 Watts |
Please note that the values provided in the table are rough estimates and their purpose is to give you an idea of what to expect.
As mentioned above, to estimate the amount of solar power that you need more accurately, you’ll have to estimate (or measure) the amount of energy that your AC unit consumes on a daily basis, and determine the average amount of sunlight that your receive (Peak Sun Hours) each day.
Let’s begin with: the energy consumption of your air conditioner.
How much energy does your air conditioner consumes?
The energy consumption of an air conditioner depends on the following factors:
Air conditioner capacity: this is measured in BTUs (British Thermal Units) or tons, the higher the capacity, the more energy is required to run the air conditioner.
Run-time: This is the amount of time the air conditioner is left on (8 hours a day for example).
The efficiency of the air conditioner: The efficiency of an air conditioner is specified using an Energy Efficiency Ratio (EER, SEER, or CEER). In general, newer AC units will be more efficient than older ones.
Temperature: This is the outdoor temperature vs the indoor temperature setpoint. The higher the difference, the more energy the AC unit will have to consume (longer run time or higher power draw).
Insulation: This represents the overall quality of your insulation, which includes the insulation of your home or business, and the condition of your ductwork (for ducted systems)
If the recommended Depth of Discharge is repeatedly exceeded, the battery would lose big chunks of its capacity quicker than it should. This damage would be irreversible.
What you should know is that there are 2 types of batteries that you would usually find on the market:
- Lead-Acid batteries: These batteries are cheaper but generally have a DoD of 50% and fewer charge/discharge cycles.
- Lithium batteries: These batteries are more expensive but generally have a recommended DoD of 80% (up to 100%) and 3 to 5 times the charge/discharge cycles of a lead-acid battery.
The fact that lithium batteries can be discharged deeper (up to 100% DoD), means that you would need fewer lithium batteries than lead-acid batteries to provide the same amount of energy.
Air Con. Capacity | Est. Energy Consumption over 8 hours required | Required Lithium Battery Capacity (in AH @ 12V) | Required Lead-Acid Battery Capacity (in AH @ 12V) |
5000 BTUs | 2500 Wh (2.5 kWh) | 260 Ah | 420 Ah |
8000 BTUs | 4500 Wh (4.5 kWh) | 470 Ah | 750 Ah |
12000 BTUs (1 ton) | 7000 Wh (7 kWh) | 730 Ah | 1160 Ah |
18000 BTUs (1.5 tons) | 10000 Wh (10 kWh) | 1050 Ah | 1700 Ah |
24000 BTUs (2 tons) | 14000 Wh (14 kWh) | 1500 Ah | 2300 Ah |
36000 BTUs (3 tons) | 20000 Wh (20 kWh) | 2100 Ah | 3400 Ah |
To determine the battery needed to run your air conditioner, simply divide the daily energy consumption of your AC unit, by the recommended Depth of Discharge of the batteries you’ll be using.
Required Battery Capacity (Watt-hours) = Air conditioner’s daily energy consumption (Watt-hours) ÷ Depth of Discharge (%)
This will give you the battery capacity in Watt-hours. Since most solar batteries are rated at 12 Volts, simply divide those watt-hours by 12 and you’ll have calculated the battery capacity in Amp-hours (at 12V).
Required Battery Capacity (Amp-hours) = Required Battery Capacity (Watt-hours) ÷ 12 (Volts)
For example, if our air conditioner consumes 5000 Wh per day, and we use lithium batteries (80% DOD) to run it, the required battery capacity to run our air conditioner is:
Required Battery Capacity (Watt-hours) = Air conditioner’s daily energy consumption (Watt-hours) ÷ Depth of Discharge (%)
Required Battery Capacity (Watt-hours) = 5000 Watt-hours ÷ 80%
Required Battery Capacity (Watt-hours) = 5000 Watt-hours ÷ 0.8
Required Battery Capacity (Watt-hours) = 6250 Watt-hours
Now let’s assume that we’ll be using 12V-100Ah lithium batteries:
Required Battery Capacity (Amp-hours) = Required Battery Capacity (Watt-hours) ÷ 12 (Volts)
Required Battery Capacity (Amp-hours) = 6250 Watt-hours ÷ 12 Volts
Required Battery Capacity (Amp-hours) = 520 Amp-hours
According to these calculations, we would need (at least) 520 Amp-hours of battery capacity (at 12 Volts). An affordable choice for this example would be 12 of Universal 12v-100ah AGM Lead-Acid Batteries. A more premium choice would be 6 of Renogy lithium batteries. Now you know.
