How much battery power is needed to run a 5000 BTU air conditioner?

Air conditioners are generally big energy consumers, especially the ones with high capacity. So, it can be a little challenging to run them on batteries and solar.

Relatively speaking, a 5000 BTU unit doesn’t consume a crazy amount of energy. Running these air conditioners on batteries and solar panels is very doable.

In this article, I will discuss the energy requirements of 5000 BTU air conditioners, how long they would run on a battery, and based on your requirements and habits, how much battery power you’ll need to run yours.

How much energy does a 5000 BTU air conditioner use?

The energy consumption of a 5000 BTU air conditioner (or any other air conditioner for that matter), depends on many factors, such as:

• The age and efficiency of the unit
• How good the insulation is
• The outdoor temperature
• The usage time of the AC unit

However, as a general rule of thumb, a 5000 BTU air conditioner should be expected to consume between 300 and 400 Watt-hours of energy per hour (0.3 – 0.4 kWh/hour).

With bad insulation and temperatures exceeding 95°F, a 5k AC unit can consume as much as 500 Wh/hour. With good insulation and temperatures between 85°F-90°F, an efficient unit could consume as little as 250 Wh/hour.

Same as refrigerators, you can estimate the energy consumption of an air conditioner using its power usage (watts), usage time (hours), and an estimate of its duty cycle (%):

Energy Consumption (Wh) = Power Usage (W) x Usage Time (hours) x Duty cycle (%)

The power usage is usually provided by the manufacturer, and the usage time represents the amount of time (in hours) for which the AC is turned ON.

However, the duty cycle, which is the percentage of time for which the compressor of the AC is really running, would at best be a rough estimate. This means that the calculated energy consumption would also be a rough estimate.

So, how do you accurately measure the watt-hours that your 5k unit consumes?

The best and most accurate way to do this is to use an electricity monitoring device. These devices give you readings on the exact power usage, as well as the exact energy consumption of an appliance over time.

Click here to learn more about this topic.

How long would a 5000 BTU window ac run on a 12V-100Ah battery?

As mentioned above, a 5k BTU ac unit would on average consume between 300 and 400 Wh of energy per hour. At 12 Volts, this amount of energy consumption is equivalent to about 25-33 Ah (Amp-hours) of energy consumption per hour.

With the health of the battery taken into consideration, at this rate of energy usage, a 12V-100Ah lithium battery would be able to run a 5000 BTU unit for around 3 to 4 hours. A 12v-100Ah lead-acid battery, on the other hand, would only be able to run these air conditioners for 1.5 to 2 hours.

This is mainly because different battery chemistries have different recommended Depths of Discharge (DoD). This means that the usable capacity of a battery depends on its chemistry.

There are negative effects to depleting batteries, such as reduced lifespan and losses in capacity. However, some battery chemistries can be discharged deeper than others and can power bigger loads.

For example, a Lithium Iron Phosphate (LiFePO4) battery, can be repeatedly discharged to about 10-20% of its capacity (80-90% DoD) with no significant effects on its health. Even with a 100% depth of discharge, these batteries will have a thousand cycles left.

In other words, the usable capacity of a 12V-100Ah LiFePO4 battery is 80 to 100 Amp-hours (960 to 1200 Watt-hours). This means that one of these batteries can run your 5000 BTU air conditioner for 3 to 4 hours without sustaining damage.

On the other hand, a Flooded Lead Acid (FLA) battery, can only be repeatedly discharged to about 50% of its rated capacity (50% DoD). A 12V-100Ah FLA battery has a usable capacity of 50 Amp-hours, which is equivalent to 600 Watt-hours of energy.

A 5000 BTU unit would only be able to run on one of these batteries for 90 to 120 minutes before the battery starts degrading.

How much battery power is needed to run a 5000 BTU air conditioner?

As mentioned above, the amount of battery power that you’ll need to run these units does not only depend on the amount of energy that they’ll consume, but also on the type of battery you’ll be using.

For example, to run a 5000 BTU AC unit for 8 hours, you’d need 2 to 3 12V-100Ah LiFePO4 batteries. If you were to run one of these units on Sealed Lead-Acid batteries, you’d require 4 to 6 batteries.

To be as precise as possible, you’ll need the answer to answer 2 questions:

• How much energy will the AC consume?
• Which kind of batteries will you be using?

How much energy will the AC consume?

As mentioned above, there are many factors that influence the energy consumption of an air conditioner. The best way to determine this is to use an electricity monitoring device. For example, a Kill-A-Watt meter can calculate the energy consumption of your AC over time.

All you have to do is plug it into the power source, and plug the air conditioner into it. With a push of a button, the device will display how much energy has been consumed so far.

The problem is that if you don’t already have a setup in place, you can’t really use a Kill-A-Watt. In this case, the only option is to estimate.

But don’t worry, I’ve got you covered.

The following table provides estimates of the energy consumption of a 5000 BTU AC in Watt-hours and Amp-hours:

Run time	Energy consumption in Watt-hours (Wh)	Energy consumption in Amp-hours (Ah) @ 12 Volts
1 hour	350 Wh – 450 Wh	30 Ah – 37.5 Ah
2 hours	550 Wh – 700 Wh	45 Ah – 58 Ah
3 hours	800 Wh – 1000 Wh	67 Ah – 84 Ah
4 hours	1050 Wh – 1250 Wh	87.5 Ah – 105 Ah
6 hours	1600 Wh – 1900 Wh	134 Ah- 160 Ah
8 hours	2200 Wh – 2600 Wh	185 Ah – 215 Ah
10 hour	2700 Wh – 3200 Wh	225 Ah – 270 Ah
12 hour	3200 Wh – 3800 Wh	270 Ah – 320 Ah
16 hour	4400 Wh – 5000 Wh	370 Ah – 420 Ah

Now that we at least have an estimate of the power consumption. We can determine how much battery power is needed to offset it.

Which kind of batteries will you be using?

Let’s assume that you have a 5000 BTU window air conditioner that you want to run for 8 hours a day. Let’s also assume that this AC consumes around 2400 Watt-hours of energy over these 8 hours, which is equivalent to 200 Amp-hours of energy at 12 volts.

If you go with Lead Acid batteries, it’ll cost you around $200 for every 12V-100Ah battery you buy. However, you’ll only be able to discharge them to 50% of their capacity (50% Depth of Discharge). At this depth of discharge, these batteries will last 1000 cycles.

If you want to run the AC for 8 hours a day on a lead-acid battery bank, you’ll need 4 batteries. A battery bank of this size will cost you around $800. At a cycle per day, this battery bank will last 3 years.

If you go with LiFePO4 batteries, it’ll cost you around $400 for every 12V – 100Ah battery you buy. However, the recommended depth of discharge for these batteries is 80%. At this depth of discharge, these batteries will last around 3000 cycles.

To run a 5000 BTU ac unit for 8 hours on a lithium battery bank, you’ll need 3 of these batteries. A lithium battery bank of this size (300Ah @ 12V) will cost $1000 to $1200 but can last up to 10 years.

However, premium choices such as Battle Born can cost up to $800-$900 for every 12V-100Ah battery.

In any case, the type of batteries you’ll be using will have a direct impact on the size and rating of the battery bank.

So, how much battery power will you need?

The following table provides the required battery capacity based on the run time of the air conditioner and the chemistry of the battery bank:

Run time	Avg. Energy Consumption in Amp-hours (Ah) @ 12V	Required Battery Capacity (in Ah) at 12V
		Lithium (LiFePO4/Li-Ion) (80% DOD)	Lead Acid (FLA/SLA/AGM) (50% DOD)
4 hours	100 Ah	125 Ah	200 Ah
8 hours	200 Ah	250 Ah	400 Ah
12 hours	300 Ah	375 Ah	600 Ah
16 hours	400 Ah	500 Ah	800 Ah

Please note that the values provided in the table are somewhat accurate, but are still estimates.

To calculate the battery bank rating that you’ll need to run a 5000 BTU air conditioner, you’ll need to divide the (daily) energy consumption of the AC (in Amp-hours) by the recommended depth of discharge for the battery type you’ll be using:

Battery Bank Capacity (Ah) = (Energy consumption (Wh) ÷ 12)  ÷ Depth of Discharge (%)

Battery Bank Capacity (Ah) = Energy consumption (Ah)  ÷ Depth of Discharge (%)

For example, let’s assume that I used a Kill-A-Watt meter to measure my 5k BTU unit’s energy consumption over 8 hours, and measured that the AC consumed 2200 Watt-hours of energy over these 8 hours. Let’s also assume that I’ll be using LiFePO4 batteries for my setup.

To get more cycles out of these batteries, and to maintain their capacity even longer, I’ll only be discharging these batteries down to 25% of their capacity. So instead of an 80% depth of discharge, I’ll be going for a 75% DOD.

The battery bank capacity is calculated using our formula:

Battery Bank Capacity (Ah) = (Energy consumption (Wh) ÷ 12)  ÷ Depth of Discharge (%)

Battery Bank Capacity (Ah) = (2200 Wh ÷ 12)  ÷ 75 %

Battery Bank Capacity (Ah) = 183.4 Ah  ÷ (75/100)

Battery Bank Capacity (Ah) = 244.5 Ah

According to these calculations, I’ll need a 12V battery bank that has at least 244.5 Amp-hours of capacity. A good and affordable choice would be 3 of these 12V-100Ah Ampere Time batteries.

With these batteries, the battery bank would be rated at 12V-300Ah. The extra 55 Amp-hours of energy will come in handy when the temperature is higher than usual, and/or if I’m using other small appliances as well.

Or, I could go for a higher depth of discharge (90-95% for example) and only use 2 of these batteries.

In any case, these batteries would require a sustainable supply of energy to refill them every day. And in terms of sustainability, the best option is solar power.

How many solar panels to run 5000 BTU AC?

The amount of solar panels that you need depends not only on the energy consumption of your AC unit but also on the amount of sunlight available to you.

However, as a general rule of thumb, you would need about 500 to 600 Watts of solar power to run a 5000 BTU air conditioner for 8 hours a day.

The solar panels would be connected to your battery bank through a solar charge controller, an inverter will then convert the DC (Direct Current) power from your batteries, into AC (Alternating Current) power that your air conditioner can use:

To learn more about these components and how to size them correctly, please refer to this page: How to run a 5000 BTU air conditioner on solar?