In this article, I break down the process of sizing an inverter that can run a 5000 BTU air conditioner efficiently. In doing so, I will talk about things like the wattage of these air conditioners, their surge power, and the efficiency of inverters.
I will also answer a couple of frequently asked questions about the battery capacity that is needed to run these units.
Will a 3000 watt inverter run a 5000 BTU ac?
A 3000 Watt inverter can definitely run a 5000 BTU air conditioner. However, if the AC unit is the only appliance running on the inverter, you should expect 15 to 30% losses, depending on the inverter. Meaning that the inverter would draw 15-30% more power than your AC is actually using.
Let me explain this further.
Electronic devices are never 100% efficient, meaning that the input, will always be higher than the output in some way.
Since the job of an inverter is to convert DC power into usable AC power, their efficiency is calculated by dividing the output AC power by the input DC power:
Inverter Efficiency (%) = AC Power (Watts) ÷ DC Power (Watts)
When you’re shopping for an inverter, and you’re looking at some of the high-quality ones, you’ll probably see manufacturers specifying a nominal efficiency for the inverter (ex. >90%) or a peak efficiency (ex. 98%).
However, the actual efficiency of the inverter is not constant. The efficiency provided by the manufacturer is either the highest efficiency that the inverter is capable of achieving, or is calculated through one of 2 formulas that predict how efficient the inverter will be on average. Click here to learn more.
The actual efficiency of an inverter depends on what percentage of its capacity is used. In other words, inverter efficiency depends on the load.
For example, while a 1000W inverter might be 95% efficient when powering a 500W load (50% load), it might only be 70% efficient when powering a 100W load (10% load).
The relationship between inverter efficiency and load percentage, itself, depends on the type of the inverter. For example, while high-frequency inverters are most efficient at 100% of their capacity, low-frequency inverters are most efficient at 20% to 50% of their capacity.
However, as a general rule of thumb, if the load will only make use of 15% or less of the inverter’s capacity, the inverter will be highly inefficient. In this particular case, the 5000 BTU air conditioner’s power usage, will only make use of about 13 to 15% of the inverter’s capacity.
So, unless the 3000W inverter is running other appliances as well, you should probably go with a smaller inverter.
In the next sections, I explain how to properly size an inverter that could efficiently run your 5000 BTU air conditioner, plus other small appliances.
What size inverter for 5000 BTU air conditioner?
In general, you would need a 1500 Watt inverter to run a 5000 BTU air conditioner. An inverter of this size can easily and efficiently run the air conditioner, and can also handle the starting wattage of the AC.
When it comes to air conditioners, there are 4 main specifications to look for in the inverter:
- Continuous Power
- Surge Power
- Input voltage
The Continuous Power or Wattage on an inverter represents the amount of power that the inverter can output continuously. This rating is the first rating you’ll see on the inverter. For example, a 1000W inverter can continuously output 1000 Watts of power. If the load is over 1000 Watts, the inverter will likely shut off.
Most manufacturers specify this rating in W (Watts), which refers to the Real Power. However, some models will have a VA (Volt-Amperes) rating, which refers to Apparent Power.
If you’re looking at an inverter with a VA rating, as a rule of thumb, simply multiply that value by 0.8 to get the rating in Watts.
So, what should the continuous power rating of the inverter be to run a 5000 BTU unit?
A 5000 BTU air conditioner uses 400 to 500 Watts of power, and some older units use up to 600 Watts. This means that the inverter that could run these units, should be rated at more than 600 Watts.
However, the continuous power rating is not the only specification that matters here. For example, a 700W inverter might be able to run a 5k BTU ac unit, but will probably not be able to start it.
Let’s see what this means.
The surge power rating on an inverter represents the maximum amount of power that the inverter can output for a short time. This rating is typically double the continuous power rating of the inverter.
For example, a 1000W inverter will typically have a surge power rating of 2000 Watts. Meaning that if necessary, this inverter can briefly output 2000 Watts of power.
This rating is especially helpful when the inverter is used to run appliances with electric motors. Appliances such as air conditioners, refrigerators, and pumps, require a relatively high amount of power to start.
This starting wattage only lasts for a couple of seconds but should be considered when sizing an inverter.
The starting wattage of 5000 BTU air conditioner is usually around 2000 Watts, however, it can be as high as 3000 Watts. This means that an inverter that could run these units, should have a surge power rating of at least 3000 Watts.
Most 1500 watt inverters can handle this amount of surge power.
The job of an inverter is to convert low voltage (12/24/48 Volts) DC power at its input, into a higher voltage (120/240 volts) AC power (Alternating Current). However, inverters are usually designed for a specific input voltage.
For example, a 1000W-12VDC inverter will only work with 12-volt solar/battery bank setups. If you have a 24V or a 48V battery bank setup, make sure the inverter is rated for that voltage.
DC sources such as solar panels and batteries provide Direct Current (DC), and the inverter converts it into the Alternating Current (AC) that appliances such as air conditioners can use:
The curve on the right shows what a perfectly alternating current should look like, a sine wave. However, the type of inverter you use will dictate how this output actually looks like. The closer the output of the inverter to this waveform, the better.
When shopping for an inverter, you’ll come across 2 types:
- Pure Sine Wave (PSW) inverters: these inverters are more expensive and the waveform of their output is closer to a sine wave.
- Modified Sine Wave (MSW) inverters: these inverters are cheaper, but their output is squarelike.
Air conditioners (and other motor-driven appliances) require a smooth alternating voltage to function properly and efficiently, which is why pure sine wave inverters are the go-to for these appliances.
An air conditioner running on a modified sine wave inverter will be much noisier, will consume more energy, and will inevitably be damaged.
For your 5000 BTU air conditioner to last longer and consume less energy, you’ll need the smoothest power you can get, which can only be provided by a PSW inverter.
With all of these specifications taken into consideration, here are the takeaways.
- To run your 5000 BTU AC unit, you’ll need 1500 Watts of inverter capacity (or more if you’re running additional appliances).
- The inverter should have a Surge Power rating of 3000 watts or more.
- Make sure the rated Input Voltage (Vdc) of the inverter matches the voltage of your battery setup.
- Make sure it’s a Pure Sine Wave inverter
Now that we have an idea about the size and type of inverter that could run these units, let’s talk about energy requirements.
How long can a battery and inverter run a 5000 BTU air conditioner?
As a rule of thumb, a 5000 BTU air conditioner consumes 300 to 400 Watt-hours per hour (Wh/hour). At 12 Volts, this amount of energy equates to 25-33 Amp-hours per hour (Ah/hour).
An inverter paired with a 12V-100Ah lithium battery can run a 5000 BTU unit for 3 to 4 hours until the battery is depleted. However, an inverter paired with a 12v-100Ah lead-acid battery can only run one of these units for up to 2 hours before the battery starts degrading.
But wait, both of these batteries have the same capacity, shouldn’t they run the air conditioner for the same amount of time?
The answer is no, different battery chemistries accept different Depths of Discharge (DOD).
A lithium battery can be fully discharged, its recommended depth of discharge is between 80% and 100%. For example, a 100Ah Lithium Iron Phosphate (LiFePO4) battery can deliver up to 100 Amp-hours of energy every time, and still maintain its capacity for years.
On the other hand, a Lead-Acid battery has a recommended depth of discharge of 50%. In other words, a 100Ah lead-acid battery can only deliver 50Ah of energy before it has to be recharged or disconnected.
The amount of battery power that you need to run 5000 BTU unit depends on 2 things:
- The energy consumption of the unit: This is the amount of energy that the batteries will need to offset.
- The type of batteries you’ll be using: This will determine the usable capacity of your battery bank
For example, let’s assume your 5000 BTU unit consumes – on average – 2400 Watt-hours of energy in 8 hours. At 12 volts, this amount of energy is equivalent to 200 Amp-hours.
If you use lithium batteries, you’ll need at least 2 12V-100Ah batteries to offset this energy consumption. If you use lead-acid batteries, you’ll need at least 4 12V-100Ah batteries.
The needed battery capacity can be calculated through these formulas:
Battery Bank Capacity (Ah) = (Energy consumption (Wh) ÷ 12) ÷ Depth of Discharge (%)
Battery Bank Capacity (Ah) = Energy consumption (Ah) ÷ Depth of Discharge (%)
The depth of discharge depends on the batteries you have or that you’ll be using, but the energy consumption depends on factors such as temperature, insulation, age of the unit, run time, etc…
To learn more about this particular topic, please refer to this article: Battery power needed to run a 5000 BTU AC