How many batteries to run RV AC?

Air conditioners have a huge power draw and need to run for hours, which makes them the most energy-consuming appliance in your RV. This means it won’t be cheap to run yours on battery power. However, with a little bit of optimization, it is doable.

In this article, and using a few examples, I’ll explain in detail how you can estimate the size of the battery bank required to run your RV air conditioner. But first of all, how doable is it?

Can you run your RV AC on batteries?

The answer is yes, you can run your RV AC on batteries. However, if you’re planning on running the air conditioner for several hours, you would need a very large battery bank. You would also need a large inverter to convert the batteries’ DC power to AC (Alternating Current) power.

If you’re planning on running it on batteries every day, you would need an energy source (such as solar power) to refill these batteries.

The size of a battery bank that could run your air conditioner depends on things like the capacity of your AC, its usage, the chemistry of the batteries you’ll be using, the temperature, etc…

Let’s see how these factors come into play and how you can estimate the size of the battery bank required to run your AC.

How many batteries to run an RV air conditioner?

The average RV air conditioner is rated at 13500 or 15000 BTUs, air conditioners of this size consume between 1300 and 1600 Watts when running.

On average, to run an RV air conditioner, you would need anywhere from 90 to 130 Ah (amp-hours) of battery energy for every hour of use. This much energy can be provided by either 2-3 100AH Lead-Acid batteries or by 1-2 Lithium batteries.

In other words, for every hour of usage, you would need 1-3 12V batteries depending on which type of battery you’re going with. Mainly because different battery chemistries have different acceptable depths of discharge. (more on this below)

The following table provides the amount of battery energy required to run different AC sizes:

BTU rating Avg. Hourly Energy Consumption (Ah/hour @ 12V)  Required Battery Capacity per hour of usage (in Ah) at 12V
Lithium (LiFePO4/Li-Ion) Lead Acid (FLA/SLA/AGM)
12000 BTUs 80 Ah/hour 100 Ah 160 Ah
13500 BTUs 90 Ah/hour 110 Ah 180 Ah
15000 BTUs 100 Ah/hour 125 Ah 200 Ah
27000 BTUs 180 Ah/hour 225 Ah 360 Ah
30000 BTUs 200 Ah/hour 250 Ah 400 Ah
Battery capacity needed to run RV air conditioners.

To understand the figures in the table, we must first under how energy is measured.

Electrical energy is measured in Wh (Watt-hours) or in Ah (Amp-hours) at a certain voltage. It can be expressed through these formulas:

Energy (Wh) = Power (Watts)  x Time (hours)

or:

Energy @ 12 Volts (Ah) = Amperage @ 12 Volts (Amps)  x Time (hours)

So, to calculate the energy requirements of an appliance, you’ll need their wattage and their run time.

Built-in RV air conditioners are typically the non-inverter type, which means they run at maximum power when turned on, and turn off automatically when the set temperature is reached. They then keep turning ON and OFF to maintain this temperature.

The percentage of time for which the AC stays ON is called a duty cycle. For example, a duty cycle of 50% means that for every hour, the AC is only ON for 30 minutes.

For example, assuming the air conditioner draws 1500 Watts when ON, we can estimate the energy that the AC consumes over 5 hours as such:

Energy Consumption over 2 hours (Wh) = Power Usage (Watts)  x Run time (hours) x Duty cycle (%)

Energy Consumption over 2 hours (Wh) = 1500 Watts  x 5 hours x 50%

Energy Consumption over 2 hours (Wh) = 3750 Watt-hours

Learn more about your RV air conditioners’ power usage and energy consumption here: how much power does an RV AC use?

To translate this amount of energy into Amp-hours, simply divide by 12 (battery voltage).

Please note that the higher the temperature, the higher the duty cycle, and the more energy is needed to run the AC. Usually, the duty cycle is 70-90% at temperatures between 80 and 95°F.

For example:

An RV air conditioner rated at 13500 BTUs, draws around 1350 Watts when it’s running. This is equivalent to about 110 Amps at 12 Volts. On a moderately hot summer day, where the temperature is around 90°F, the AC will typically have a duty cycle of about 80%.

In this scenario, the AC will consume around 1100 Wh per hour, which is equivalent to about 90 Ah per hour (at 12V). In other words, the air conditioner will need 90 Amp-hours of energy for every hour of run time.

As mentioned above, the capacity of the battery that can provide this amount of energy depends on the chemistry of the battery.

In general, manufacturers provide a recommended depth of discharge (DoD) for their batteries. Exceeding this depth of discharge can significantly reduce battery life and can result in permanent damage (fewer charge/discharge cycles, reduced capacity, etc..)

The following table provides the recommended DoD for different battery chemistries:

Battery Chemistry Recommended Depth of Discharge (DoD) Usable Battery Capacity of a 100AH battery
FLA (Flood Lead-Acid) 50% 50Ah
SLA (Sealed Lead-Acid) 50% 50Ah
AGM (Absorbent Glass Matt) 50% 50Ah
Li-Ion (Lithium Ion) 80% 80Ah
LiFePO4 (Lithium Iron Phosphate) 80% 80Ah
Different battery chemistries and their recommended Depths of Discharge

Following the previous example, on average, the AC requires 90Ah of energy for every hour of usage. To run this AC on battery, we would need a 110AH lithium battery, or a 180AH lead-acid battery.

Now let’s follow up on this example with a realistic assumption. Let’s assume that this air conditioner is left on for 7 hours at night, and 7 hours in the daytime. In this scenario, the A/C would be left on for 14 hours a day, which should ensure comfortability.

The temperature usually drops at night, so our average duty cycle (over 14 hours of using the AC) would be reduced to about 65-70%. With it, the average hourly energy consumption would also be reduced to about 75 Ah per hour.

However, the energy consumption of the AC over 14 hours would be around 1050Ah at 12V:

Energy Consumption over 14 hours (Ah) = Hourly Energy Consumption (Ah/hour)  x Run time (hours)

Energy Consumption over 14 hours (Ah) = 75 Ah/hour  x 14 hours

Energy Consumption over 14 hours (Ah) = 1050 Ah

To figure out battery size, the following formula is used:

Battery Capacity (AH) = Energy Consumption (Ah) ÷ Depth of Discharge

The depths of discharge (DoD) of different battery chemistries are provided by the previous table. For example, Lithium batteries have a DoD of 80%:

Lithium Battery Capacity (AH) = 1050 Ah ÷ 80% (or 0.8)

Lithium Battery Capacity (AH) = 1312.5 AH

To provide this amount of energy (1050 Ah) without damaging the battery, we would need around 1300AH of Lithium battery capacity or 2100AH of Lead-Acid battery capacity. And this is just for one day.

To maintain this kind of comfort for as many days as you want, you’ll need a sustainable source of energy that can compensate for the A/C’s energy consumption, which brings us to solar panels.

How many solar panels do I need to run my RV AC?

The number of solar panels you need to run your RV air conditioner depends on many factors, such as temperature, AC usage time, location of your RV, etc.

However, on average, you would need 200-300 Watts of solar panels for every hour of AC run time. This is equivalent to 2-3 100W RV solar panels.

For example, on average, you would need around 1500 Watts of solar power to your RV AC for 6 hours per day. This amount of solar power is equivalent to 12-15 RV solar panels, or 5 residential solar panels.

Learn more about solar panel sizes.

These Solar panels would be coupled with the batteries via a solar charge controller, and the terminals of the batteries would be connected to the AC via an inverter.

To learn more about the components required for this solar energy setup, feel free to refer to this article: A guide to running your RV air conditioner on solar

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Younes

Hi! My name is Younes. I'm an electrical engineer and a renewable energy enthusiast. I created renewablewise.com with a mission of delivering digestible content and information to the people who seek it.

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