How many solar panels to run an 8000 BTU air conditioner?

The amount of solar power needed to run an air conditioner will mainly depend on the energy consumption of the AC unit. This energy usage depends on the specific AC model, its cooling capacity, its efficiency, and other operating conditions such as outdoor temperature, indoor temperature setpoint, and daily usage.

The size of the solar system required to run your 8000 BTU air conditioner will also depend on the amount of sunlight that’ll be available for the solar panels to turn into electrical energy.

In this article, I’ll first discuss the electricity usage of 8000 BTU air conditioners, giving you some rough estimates and methods to measure it accurately. Then, I’ll talk about sunlight—how it’s measured, its availability in your area, and how to calculate the solar power you’ll need using it.

Once we’ve got that part covered, I’ll discuss the other components that you’ll need to complete your solar setup and guide you on sizing them correctly.

Let’s jump right in.

How many solar panels to run an 8000 BTU air conditioner?

In general, to run an 8000 BTU air conditioner, you would need around 100 watts of solar power for every hour of daily run time.

Assuming your 8000 BTU air conditioner runs for 8 hours a day, you would need between 700 and 900 watts of solar power to offset the air conditioner’s energy consumption.

To provide an initial reference, here’s a table estimating the energy consumption of 8000 BTU air conditioners and the required solar power based on their daily runtime:

Now, the figures in the table should give you a rough estimate of the amount of solar power that you would need.

However, it’s essential to emphasize that the actual solar power requirement depends on your AC unit’s exact energy consumption, and the daily sunlight available in your location, commonly referred to as “Peak Sun Hours”.

To size the system that you need, the first step is to determine the energy usage of your 8000 BTU AC.

How much energy does your 8000 BTU air conditioner use?

Air conditioners vary in efficiency, and even identical units can consume different amounts of energy due to operating factors like outdoor temperature, indoor setpoint, humidity, and insulation.

Some air conditioners are more efficient than others, and even 2 identical air conditioners can consume different amounts of energy depending on their operating factors, such as outdoor temperature, indoor temperature setpoint, humidity, and insulation.

The most accurate method to determine the energy consumption of your 8k BTU AC unit is to actually measure it. This can be done using an Electricity Monitoring device.

You can use a device like the Kill-A-Watt meter, or a similar one, by plugging it between your 8000 BTU AC and the electrical outlet.

The Kill-A-Watt meter provides essential information such as current (amps), Voltage (Volts), frequency (Hertz), and power usage (Watts) for your AC unit. Most importantly, it tracks and displays the Energy Consumption in kWh (kiloWatt-hours) of your air conditioner over time.

For instance, if your AC unit operates for 5 hours daily, you can plug it into the device and assess its energy consumption once you power it down. This would give you an accurate measurement of your AC’s daily energy usage.

If those measurements are in kiloWatt-hours (kWh), simply multiply by 1000 to determine the energy consumption of your AC unit in Watt-hours (Wh).

If you’re okay with rough estimates for now, there’s a quicker but slightly less precise way to gauge your air conditioner’s energy use. You can use its efficiency rating. Here’s how it works:

The 8000 BTU rating on your air conditioner tells you how much heat it can remove in an hour, and the exact amount of energy it needs to remove the 8000 BTUs of heat will directly depend on how efficient the AC is.

Manufacturers test this efficiency and provide it as an EER (Energy Efficiency Ratio) rating or, more recently, a CEER (Combined Energy Efficiency Ratio) rating.

Either way, you can use this efficiency rating to estimate the hourly energy usage of your 8000 BTU AC:

Hourly Energy Consumption (Watt-hours per hour) = 8000 BTUs ÷ Energy Efficiency (EER or CEER)

For example, let’s take a look at this EnergyGuide label on an 8000 BTU AC unit:

The label shows an EER rating of 12. With this rating, you can figure out the hourly energy usage of this unit like this:

Hourly Energy Usage (Watt-hours per hour) = 8000 BTUs ÷ EER

Hourly Energy Usage (Watt-hours per hour) = 667 Wh/hour

You can then multiply this hourly energy usage by the number of hours you use the unit each day to find out its daily energy consumption:

Daily Energy Consumption (Wh/day) = Hourly Energy Usage (Wh/hour) x Daily Usage (hours/day)

Now, if you intend to use additional appliances, it’s crucial to account for their energy consumption too.

To simplify the task of determining the energy usage of each appliance, I’ve developed an Appliance Energy Consumption Calculator that enables you to list your appliances and estimate their energy consumption.

Once you have measurements or estimates for the energy consumption of your AC unit and any additional appliances, the following step is to evaluate the amount of sunlight accessible for the solar panels to convert into electricity.

How many Peak Sun Hours do you get?

The energy output of a solar panel directly depends on the energy it receives from sunlight, which is measured in kWh/m2 (kiloWatt-hours per square meter). Each 1kWh/m2 is equivalent and referred to as 1 Peak Sun Hour.

For example, an area that – on average – receives 6kWh/m2 per day, could be said to receive 6 Peak Sun Hours per day.

The Peak Sun Hours that an area receives are obtained from historical data, but they can serve as a predictor for estimating the energy production potential of a solar installation in that specific location.

For example, if you install 200 Watts of solar panels in an area that, on average, gets 6 Peak Sun Hours daily, the solar panels would produce approximately 1.2 kWh of energy per day:

Daily Energy Production (Watt-hours) = Solar Power Rating (Watts) x Daily Peak Sun Hours

Daily Energy Production (Watt-hours) = 200 Watts x 6 Peak Sun Hours

Daily Energy Production (Watt-hours) = 1200 Wh

Reversibly, if you know the desired energy output and the number of Peak Sun Hours, you can calculate the required solar power:

Solar Power Rating (Watts) = Required Daily Energy Production (Watt-hours) ÷ Daily Peak Sun Hours

Nevertheless, because of inherent system imperfections, energy losses are bound to happen. In simpler terms, you won’t be able to fully utilize all the energy produced by your solar panels.

To accommodate for these inefficiencies and losses, it’s a good idea to use a multiplier of 1.25 when sizing your solar system:

Solar Power Rating (Watts) = (Required Daily Energy Production (Watt-hours) ÷ Daily Peak Sun Hours) x 1.25

This approach will lead to a somewhat larger system, but it will compensate for the typical 15 – 20% losses.

How do you determine your Peak Sun Hours?

You can do this easily, and for free using the PVWatts Calculator provided by the NREL (National Renewable Energy Laboratory).

Just input your address, and the tool will display the monthly and annual average Peak Sun Hours for each day.

For example, I used an address in Phoenix, Arizona, and in the Results section, the tool provided the following data:

At the bottom, you can see that on (annual) average, this particular location receives 6.57 Peak Sun Hours a day.

However, these results are based on the assumption that your solar panels will be directly facing south and tilted at a 20-degree angle. But you can still change these values in the System Info section of the tool:

Example

In this scenario, let’s consider an 8000 BTU air conditioner that runs for an average of 6 hours daily, consuming 3000 Watt-hours of energy during that period.

Additionally, you have other appliances like a refrigerator, a couple of laptop chargers, a TV, and a few lights, totaling approximately 1200 Watt-hours per day. This accumulates to a total daily energy consumption of 4200 Wh/day (3000 Wh + 1200 Wh).

Now, let’s assume your solar panels receive roughly 6.57 Peak Sun Hours each day.

Let’s now calculate the solar power required to cover this daily energy consumption using our formula:

Solar Power Needed (Watts) = (Required Daily Energy Production (Watt-hours) ÷ Daily Peak Sun Hours) x 1.25

Solar Power Needed (Watts) = (4200 Watt-hours ÷ 6.57 Peak Sun Hours) x 1.25

Solar Power Needed (Watts) = (639 Watts) x 1.25

Solar Power Needed (Watts) = 799 Watts

According to these calculations, you would require a minimum of approximately 800 Watts of solar power to operate the 8000 BTU air conditioner and the additional appliances. A suitable choice for this setup could be four 12V-200W Renogy Solar panels.

Until now, we’ve primarily focused on solar panels, which are just one element of the solar system you require. A complete solar setup consists of the following components:

1. Solar panels
2. A battery bank
3. A solar charge controller
4. An inverter
5. And, of course, the necessary wires and fuses or circuit breakers.

When these components are interconnected, your solar setup should look something like this:

Let’s start by discussing the amount of battery power that you’ll need for this setup.

What size battery bank do you need to run an 8000 BTU AC unit on solar?

The job of the battery bank is to store all the energy produced by the solar panels and make that energy accessible at all times.

Assuming your 8000 BTU air conditioner runs for 8 hours a day, you would need around 400 Ah of available battery capacity (at 12 Volts). This equates to about 5 12V-100Ah Lithium batteries (LiFePO4/Li-Ion) or 8 12V-100Ah Lead-Acid batteries (AGM/Sealed/Flooded).

The following table provides an estimation of the battery capacity (Lithium or Lead-Acid) required to power an 8000 BTU air conditioner using solar energy:

Related: How many 12V batteries to run an air conditioner?

The table illustrates the fact that the required battery capacity depends not only on your air conditioner’s energy consumption but also on the type of batteries you’ll be using. This is due to something called Depth Of Discharge (DOD).

To put it simply, DOD signifies the percentage of the battery’s total capacity that can be utilized.

For instance, a 100Ah Lithium-Iron-Phosphate (LiFePO4) battery can provide 80 to 100% of its capacity, while a 100Ah AGM battery can only supply 50 Amp-hours before needing to be recharged or disconnected.

Even though lithium batteries come with a higher price tag, they can deliver double the energy output, effectively replacing two lead-acid batteries.

Typically, lithium batteries have a recommended DOD of 80%, while lead-acid batteries have a DOD of 50%.

Your daily energy consumption and the DOD of your chosen battery type are both key factors in determining the required battery capacity:

Battery Bank Capacity (Watt-hours) = Daily energy consumption (Watt-hours) ÷ Depth Of Discharge (%)

Since most batteries for these applications are rated at 12 Volts, the battery bank’s capacity in Amp-hours can be calculated as follows:

Battery Bank Capacity (Amp-hours) = (Daily energy consumption (Watt-hours) ÷ 12 Volts) ÷ Depth Of Discharge (%)

Following our previous example, the 8000 BTU AC unit and other appliances consume a total of 4500 Wh per day. Assuming I’ll be using a LiFePO4 battery bank, which can be 80% discharged, the capacity that I need is:

Battery Bank Capacity (Amp-hours) = (Daily energy consumption (Watt-hours) ÷ 12 Volts) ÷ Depth Of Discharge (%)

Battery Bank Capacity (Amp-hours) = (4500 Wh ÷ 12 Volts) ÷ 80%

Battery Bank Capacity (Amp-hours) = (375 Ah) ÷ 0.8

Battery Bank Capacity (Amp-hours) = 468.75 Amp-hours (@ 12 volts)

An affordable choice for this setup would be 5 or 6 of these 12V-100Ah Li-Time batteries. A more premium choice would be 5 or 6 of these 12V-100Ah Battle Born batteries.

Now, as I explain in this article, when sizing solar batteries, we also consider another critical factor: Autonomy days.

Autonomy days indicate how many consecutive cloudy days your battery should sustain as a backup. For instance, if we aim for 2 days of autonomy, we would multiply the previously calculated battery bank’s capacity by 2.

However, since batteries can be quite costly, a more budget-friendly alternative is to opt for a backup generator to rely on during periods of limited solar input. A generator like the WEN DF451i would be an excellent choice for an air conditioner of this size.

Related: What size generator to run an air conditioner?

In any case, the subsequent step involves selecting an appropriate solar charge controller.

What size solar charge controller do you need?

Solar charge controllers play a crucial role by connecting solar panels to the battery bank and ensuring the safety of both components. Learn more about solar charge controllers here.

The size of the solar charge controller required depends mainly on the scale of your solar array and battery bank, as well as their configuration.

Before delving into the sizing process, there are two types of solar charge controllers you need to know about:

1. PWM solar charge controllers: PWM stands for Pulse Width Modulation, and these are the more budget-friendly options but tend to be less efficient.
2. MPPT solar charge controllers: MPPT stands for Maximum Power Point Tracking. These controllers are pricier but offer greater efficiency, as they not only safeguard your system but also maximize your solar panel’s energy production. T

Given the long-term advantages of MPPT controllers, the focus will be on them for the remainder of this section. If you are looking for a cost-effective short-term solution, you can use our PWM solar charge controller calculator.

To simplify the process of sizing an MPPT controller for your system, I’ve developed an MPPT solar charge controller calculator that handles all the sizing details. All you need to do is provide some information about your system, and the calculator will do the rest.

Here are the key parameters you’ll need for the MPPT solar charge controller calculator:

1. Solar panel wattage: This is the power rating (in watts) for each of your solar panels.
2. Solar panel open-circuit voltage: You can typically find this value in the specification label on the back of your solar panels or by referencing the specific model’s documentation.
3. Battery bank’s nominal voltage: The voltage of each battery is typically labeled on the casing. If you have multiple batteries, the battery bank’s voltage is equivalent to the voltage from one string of batteries.
4. Lowest temperature during sunlight hours: Enter the lowest temperature you expect your solar panels to be exposed to during sunlight hours. This information helps the calculator estimate the highest expected voltage.
5. Number of strings: How many parallel strings make up your solar array?
6. Number of solar panels in each string: In each string, specify how many solar panels are wired in series.

For a clearer understanding, let’s use the results from the previous sections as an example.

In the solar array sizing section, we determined that we needed at least 800 Watts of solar power to operate the 8000 BTU AC and additional appliances. As an example, we’ll use 8 12V-100W Renogy solar panels.

A suitable configuration for this system would be 4S2P, meaning we’ll have 2 parallel strings of panels, with each string consisting of 4 solar panels wired in series. This configuration will result in our solar array looking like this:

Based on our calculations, we’ve also established that we’ll require a minimum of 468.75 Amp-hours of battery capacity at 12 Volts.

A suitable choice would be to opt for 6 of these 12V-100Ah Battle Born batteries, providing us with a total of 600 Amp-hours of battery capacity at 12 Volts, which exceeds our needs.

An effective configuration for this battery bank would be 3S2P, where there are 2 parallel strings, each consisting of 3 batteries wired in series. This configuration results in a 36V battery bank:

Now that we know what our setup looks like, here are the values I’ll submit to our MPPT solar charge controller calculator:

1- Solar panel wattage: Each of the solar panels is rated at 100 Watts.

2- Solar panel open-circuit voltage: Each of these solar panels has an Open-Circuit Voltage (Voc) of 22.3 Volts.

3- Battery bank’s nominal voltage: Our battery bank has a nominal voltage of 36 Volts.

4- Lowest temperature during sunlight hours: For simplicity, I’ll assume the temperature does not go below 32°F (0°C).

5- Number of strings: Our setup Consists of 2 strings of solar panels.

6- Number of solar panels in each string: In each string, there are 4 solar panels connected in series.

I’ve submitted these details to the calculator, and here are the results:

According to our calculator, the solar charge controller required should be capable of handling 99 Volts on the PV side and delivering 20.4 Amps on the battery side.

For a premium option, the calculator recommends the 150V/35A MPPT from Victron. Alternatively, for a more budget-friendly choice, the 150V/50A MPPT from EPEVER is suggested.

Either of these options would allow for an additional 400 Watts to be added to the solar array or an extra 1000 Watts of solar (1.8kW total) if a battery is added to each string.

With this, we’ve covered the main components of the solar system, and the final step is to select the appropriate inverter for our setup.

What size inverter do you need to run an 8000 BTU air conditioner?

While the battery bank will provide DC (Direct Current) power, an 8000 BTU air conditioner requires AC (Alternating Current) power to run. The job of the inverter is to convert the relatively low voltage (12/24/36/48 V) DC power from the battery, into a higher voltage (usually 120 Volts) AC power.

In this article, I explain the specifications that should be considered, in both the AC unit and the power inverter. The inverter’s specifications to look at are:

• Waveform: The inverter you go with should be a Pure Sine Wave inverter. A Modified Sine Wave inverter can cause permanent damage to your AC unit.
• Continuous Power Rating: 8000 BTU AC units usually use 600-1000 Watts of power when running, which means the Continuous Power rating of the inverter should be higher than that.
• Surge Power Rating: 8000 BTU air conditioners can require up to 5000 Watts of power to kick off. A 3000W high-frequency inverter will usually have a surge wattage of 6000W, and a 3000W low-frequency inverter will usually have a surge wattage of 9000W.
• Input Voltage rating: Generally speaking, most inverters are designed to convert a specific DC voltage. For example, a 12VDC inverter will not be able to run on a 24V DC system.
• Output Voltage: Most power inverters in the U.S. market provide 120VAC, which should be compatible with your 8000 BTU unit. However, make sure to check the voltage of your air conditioner before choosing an inverter.

In general, to run an 8000 BTU air conditioner on solar, you would need a 2000 to 3000 watt Pure Sine Wave inverter, which can handle both the running and starting power of these air conditioners.

However, if you plan to operate extra appliances using the inverter, you might need a larger inverter with a higher continuous power rating, which depends on the power consumption of those appliances.

Inverter’s Continous Power (Watts) > AC’s Power Usage (Watts) + Combined Power Usage of the appliances (Watts)

Additionally, the input voltage rating of the inverter should also be compatible with your battery bank’s voltage.

Since the battery bank from our example is rated at 36 Volts nominal, a good choice would be this 3000W Pure Sine Wave inverter. It has a Surge Power rating of 6000 Watts and is designed to run on 36 Volts nominal.

Once you’ve sized your solar panels, the battery bank, the charge controller, and the inverter, the final step is to size the wires and over-current protection devices (fuses or circuit breakers) that connect these components. To ensure you do this correctly, please refer to these sizing guides: