# How many watts does a 3 ton AC or heat pump use? And how much does it cost to run one?

There are two key aspects to consider when it comes to the electricity usage of heat pumps and air conditioners:

1- Their Power Usage, measured in Watts (W) or kiloWatts (kW):

This indicates how quickly the unit consumes electricity, essentially measuring its energy consumption rate.

When you’re sizing equipment like an inverter, or a generator for your 3-ton unit, the power usage (wattage) is a crucial factor to consider.

2- Their Energy Consumption, measured in Watt-hours (Wh) or kiloWatt-hours (kWh):

This quantifies the actual amount of electricity used over a specific period.

When sizing equipment such as solar panels, or batteries, as well as estimating operational costs, understanding the energy consumption (kWh) of your 3-ton AC or heat pump is important.

In this article, I’ll discuss both the power usage (in Watts) and energy consumption (in kWh) of 3-ton air conditioners and heat pumps. I’ll provide estimates and guide you on accurate methods to determine these values.

Additionally, if you’re curious about operational costs, I’ve included a calculator to give you quick estimations.

Let’s dive in.

## How many watts does a 3-ton AC or heat pump use?

Typically, air conditioners and heat pumps with a 3-ton (36,000 BTUs) rating will use around 3000 to 4000 Watts of power while running. However, keep in mind that this power range reflects their normal operational wattage. When a 3-ton unit is starting up, it could potentially demand up to 25,000 Watts (25 kW) or more of power.

To accurately determine the running and starting power requirements of your unit, refer to the electrical specifications provided by the manufacturer on the unit’s nameplate.

These specifications include Amps (Current) and Volts (Voltage) ratings, which can be multiplied to calculate the Power Usage in Watts:

Power (Watts) = Current (Amps) x Voltage (Volts)

For example, let’s examine the nameplate on the condenser unit of a 3-ton heat pump:

The main power usage of an air conditioner or heat pump is attributed to its compressor. To determine the unit’s power usage, focus on understanding the compressor’s power requirements.

Check the nameplate for the compressor section, where you’ll find three key electrical specifications:

• Voltage (Volts): Look for the unit’s voltage specification, which is usually presented as 208/230 Volts. This indicates that the unit can operate on both 3-phase 208V and split-phase 230V circuits. Residential ACs and heat pumps usually run on 230 Volts.
• Compressor RLA (Amps): RLA stands for Rated (or Running) Load Amps, indicating the maximum current (in Amps) that the compressor draws during normal operation. For instance, if this unit has a Compressor RLA of 17.9 Amps.
• Compressor LRA (Amps): LRA stands for Locked Rotor Amps, indicating the maximum current that the compressor’s rotor might require to start rotating. This unit has a Compressor LRA of 112 Amps.

The Compressor RLA, coupled with its rated voltage, can be used to calculate the maximum power it consumes during normal operation. Specifically, the Running Wattage can be determined using this formula:

Compressor’s Running Wattage (Watts) = Compr. RLA (Amps) x Voltage (Volts)

Compressor’s Running Wattage (Watts) = 17.9 Amps x 230 Volts

Compressor’s Running Wattage (Watts) = 4117 Watts

On the other hand, the Compressor LRA (Locked Rotor Amperage) can be used to calculate the “Potential” Starting Wattage of the compressor:

Compressor’s Running Wattage (Watts) = Compr. LRA (Amps) x Voltage (Volts)

Compressor’s Running Wattage (Watts) = 112 Amps x 230 Volts

Compressor’s Running Wattage (Watts) = 25,760 Watts

In addition to the primary power consumption attributed to the compressor, air conditioners, and heat pumps have two more components that contribute to power usage and should not be overlooked:

1. The condenser fan, a.k.a “outdoor” fan.
2. The blower fan, a.k.a indoor fan.

To assess the energy usage of these fans, you can refer to their Full Load Amperage (FLA) ratings, which are also specified by the manufacturer on the outdoor and indoor units.

Fan Wattage (Watts) = FLA (Amps) x 230 Volts

However, as a convenient rule of thumb, when both fans are operational, the fans on 3-ton units are capable of consuming up to 1000 Watts.

Consequently, the potential running wattage of a 3-ton heat pump can be calculated as follows:

Potential Running Wattage (Watts) = Compressor’s Running Wattage (Watts) + 1000 Watts

Potential Running Wattage (Watts) = 4117 Watts + 1000 Watts

Potential Running Wattage (Watts) = 5117 Watts

Potential Running Wattage (kW) = 5.1 kiloWatts

Similarly, you can determine the “potential” starting wattage by accounting for the power draw of both the condenser fan and blower fan:

Potential Starting Wattage (Watts) = Compressor’s Starting Wattage (Watts) + 1000 Watts

Potential Starting Wattage (Watts) = 25,760 Watts + 1000 Watts

Potential Starting Wattage (Watts) = 26,760 Watts

Potential Starting Wattage (Watts) = 26.76 kiloWatts

Based on our calculations, this particular unit could potentially demand as much as 26,760 Watts (26.76 kW) of power during startup. However, it’s important to note that this is a theoretical maximum and not a typical scenario.

Under normal conditions, the starting current of the unit will usually be lower than the Locked Rotor Amperage (LRA) of the compressor, meaning that the heat pump won’t consistently require the full 26.7 kW of power for startup.

Nonetheless, in the event that the compressor’s rotor becomes “locked”, the unit would indeed demand the entire 112 Amps to initiate, leading to a potential startup wattage of 26.7 kiloWatts.

It’s worth emphasizing that when sizing an inverter or generator for your 3-ton AC/heat pump, the equipment’s capacity should be sufficient to handle the highest power usage of your unit, which includes potential startup scenarios.

Now that we have an idea of the “rate” at which your unit consumes electricity, and how to calculate it, let’s move on to discussing the actual amount of electricity (quantity) used by a 3-ton air conditioner or heat pump.

## How much electricity (kWh) does a 3-ton AC or heat pump unit use?

The amount of electricity, or more accurately, the energy used by a heat pump or an air conditioner over a certain timeframe depends on a few factors, such as:

• The outdoor temperature
• The indoor temperature setting
• The quality of your home’s insulation
• Whether the unit is cooling or heating
• The efficiency of the unit

As a general guideline, a 3-ton (36,000 BTU) air conditioner or heat pump typically consumes around 1.8 to 2.8 kWh (kiloWatt-hours) of energy per hour during cooling seasons. Assuming a daily usage of 12 hours, this translates to approximately 20 kWh to 35 kWh per day, or about 650 kWh to 1000 kWh per month.

During heating seasons, a 3-ton heat pump uses around 3 kWh to 4.5 kWh per hour. With a daily operation of 12 hours, this amounts to roughly 35 kWh to 55 kWh per day, or approximately 1100 kWh to 1700 kWh per month.

Using the energy efficiency rating of your 3-ton unit, you can estimate its hourly energy consumption in kWh/hour (kiloWatt-hours per hour), and combine that with your regular daily usage to estimate its daily energy consumption (kWh/day), or monthly energy consumption (kWh/month).

Let me explain.

Air conditioners and heat pumps are assigned what we refer to as Energy Efficiency Ratios or Factors, which measure the efficiency of the unit at cooling or heating the air inside your home.

See, the 3-ton rating on your unit, equivalent to 36,000 BTUs, represents the capacity of the unit, or in other words, the amount of heat exchange that your air conditioner or heat pump is capable of performing in an hour of operation.

The Electrical Energy, measured in Watt-hours (Wh) or kiloWatt-hours (kWh), that the AC/heat pump uses to perform this degree of heat exchange, depends on its efficiency:

Energy Consumption (Watt-hours/hour) = Unit’s Capacity (BTUs) ÷ Efficiency Factor

Manufacturers calculate this efficiency for each model and express it through:

• SEER, which stands for Seasonal Energy Efficiency Ratio, and measures the efficiency of air conditioners or heat pumps during the cooling season.
• HSPF, which stands for Heating Seasonal Performance Factor, and measures the efficiency of heat pumps during the heating season.

In other words, you can estimate the hourly energy consumption of an air conditioner or a heat pump in the cooling season as follows:

Energy Consumption (Watt-hours/hour) = Unit’s Capacity (BTUs) ÷ SEER

Energy Consumption (kiloWatt-hours/hour) = (Unit’s Capacity (BTUs) ÷ SEER) ÷ 1000

And you can estimate the hourly energy consumption of a heat pump in the heating seasons as follows:

Energy Consumption (Watt-hours/hour) = Unit’s Capacity (BTUs) ÷ HSPF

Energy Consumption (kiloWatt-hours/hour) = (Unit’s Capacity (BTUs) ÷ HSPF) ÷ 1000

You’ll typically find these SEER and HSPF ratings on the EnergyGuide label that comes with the unit. For instance, consider this EnergyGuide label from a 3-ton (36,000 BTU) heat pump:

During the cooling seasons, the average hourly energy consumption of this 3-ton (36,000 BTU) heat pump is:

Energy Consumption (Watt-hours/hour) = Unit’s Capacity (BTUs) ÷ SEER

Energy Consumption (Watt-hours/hour) = 36000 BTUs ÷ 18

Energy Consumption (Watt-hours/hour) = 2000 Wh/hour

Energy Consumption (kiloWatt-hours/hour) = 2 kWh/hour

And during the heating months, the average hourly energy consumption is:

Energy Consumption (Watt-hours/hour) = Unit’s Capacity (BTUs) ÷ HSPF

Energy Consumption (Watt-hours/hour) = 36000 BTUs ÷ 8.2

Energy Consumption (Watt-hours/hour) = 4390 Wh/hour

Energy Consumption (kiloWatt-hours/hour) = 4.39 kWh/hour

Using the typical daily operation of the unit, we can also estimate its daily and monthly energy consumption for the corresponding season:

Daily Energy Consumption (kWh/day) = Hourly Energy Consumption (kWh/hour) x Daily Operation (hours/day)

If you’re planning on running your 3-ton unit on solar panels or on batteries, the daily energy consumption of the unit will be the number one metric to take into consideration.

If you’re trying to figure out the monthly cost of running the unit, the first step is calculating the monthly energy consumption of the unit:

Monthly Energy Consumption (kWh/month) = Daily Energy Consumption (kWh/day) x 30 days

Speaking of which, let’s see how much these units cost to run.

## How much does it cost to run a 3-ton AC or heat pump?

The cost of running a 3-ton AC or heat pump will depend on the energy consumption of the unit, as well as the electricity prices in your area:

Cost (\$/timeframe) = Energy Consumption (kWh/timeframe) x Cost per kWh (\$/kWh)

For instance, considering the U.S. national average cost per kWh, a 3-ton air conditioner or heat pump will consume roughly \$0.4 (40 cents) worth of electricity per hour of operation during the cooling season. If you assume 12 hours of daily operation, this results in approximately \$5 per day or \$150 per month.

In the heating seasons, a 3-ton heat pump’s hourly operation cost is around \$0.65 (65 cents). Assuming 12 hours of daily use, the daily cost amounts to \$8, which translates to a monthly operational cost of \$240.

However, these estimates are based on the U.S. national average cost per kWh of about 16 cents a kWh. The actual cost per kWh you’re being charged will vary depending on your location and may range from 10 to 30 cents per kWh of energy.

A more precise approach to determining the cost of operating your 3-ton unit over a specific period is to multiply its energy consumption for that duration by your local cost per kWh (\$/kWh).

For example, let’s say you have a 3-ton heat pump, and using the method explained in the previous section of this article, you’ve estimated that the unit consumes around 700 kWh of energy per month during the cooling season and around 1200 kWh per month during the heating season.

Now, let’s also assume that you live somewhere in the state of New Jersey, which according to the U.S. Energy Information Administration (EIA), has an average cost per kWh of about 17 cents/kWh (\$0.17/kWh).

Using these pieces of information, the average monthly cost to run your 3-ton heat pump in the summer is calculated as follows:

Cost (\$/month) = Energy Consumption (kWh/month) x Cost per kWh (\$/kWh)

Cost (\$/month) = 700 kWh/month x \$0.17/kWh

Cost (\$/month) = \$119/month

Likewise, the average monthly cost of running the unit in the winter is:

Cost (\$/month) = Energy Consumption (kWh/month) x Cost per kWh (\$/kWh)

Cost (\$/month) = 1200 kWh/month x \$0.17/kWh

Cost (\$/month) = \$204/month

To help you get quicker estimates, I made a calculator that estimates the daily and monthly cost of running your 3-ton air conditioner or heat pump during the cooling or heating seasons.

All you have to do is pick the season, input your typical daily usage, and select a location:

Related:

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How much electricity does a 5-ton heat pump use?