Understanding the electricity usage of your air conditioner or heat pump involves two key aspects:
- Electrical Power Usage: This indicates how fast the AC or heat pump consumes electricity, measured in Watts (W) or kiloWatts (kW). More precisely, it reflects the rate at which electrical energy is consumed.
- Electrical Energy Consumption: This represents the actual quantity of electricity the unit consumes during a specific time frame, measured in Watt-hours (Wh) or kiloWatt-hours (kWh).
Both of these aspects are important and serve distinct purposes.
For instance, when determining the size of equipment like inverters and generators, the Power Usage (Watts) of the unit is the primary consideration.
On the other hand, the Energy Consumption (kWh) of the air conditioner or heat pump is valuable for sizing solar panels and batteries. Additionally, it proves useful when estimating the operational costs of the unit.
Click here to learn more about the difference between Electrical Power (Watts) and Electrical Energy (kWh).
In this article, I will explore the both Power Usage (Watts) and Energy Consumption (kWh) of 4-ton (48,000 BTU) air conditioners and heat pumps. I’ll provide estimates and guide you on how to accurately determine these values.
Following that, I will discuss the operational costs related to these units. You’ll learn how to manually calculate estimates or have the option to use a calculator to quickly estimate these costs.
Let’s jump right in.
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How many watts does a 4-ton ac or heat pump use?
In general, a 4-ton (48,000 BTU) air conditioner or heat pump typically consumes between 4500 and 6000 Watts of power while running. However, this range represents the unit’s “Running” power usage or the power it consumes when in normal operation. The startup power requirements are significantly higher.
In fact, when a 4-ton unit starts up, it may briefly demand up to 30,000 Watts (30 kiloWatts) of power.
If you’re not planning on running the 4-ton unit on anything other than grid power, its starting power requirements shouldn’t be a concern. However, if you’re trying to size equipment, such as an inverter, or a generator, the startup wattage of the unit should be your number one consideration.
In any case, you can use the manufacturer’s electrical specifications to accurately determine both the running and starting power requirements of your 4-ton unit.
Let me break it down for you.
Your 4-ton air conditioner or heat pump consists of three main components that require power:
- The compressor.
- The condenser (outdoor) fan motor.
- The blower (indoor) fan motor.
You can calculate the power usage of each component using this formula:
Power Usage (Watts) = Amperage (Amps) x Voltage (Volts)
The “potential” running power usage of your 4-ton unit can then be calculated by summing up the power usage of these components:
Potential Running Wattage (Watts) = Compressor’s Running Watts + Outdoor Fan’s Running Watts + Indoor Fan’s Running Watts
Likewise, the “potential” starting power usage of your 4-ton unit can be calculated as follows:
Potential Starting Wattage (Watts) = Compressor’s Starting Watts + Outdoor Fan’s Running Watts + Indoor Fan’s Running Watts
The compressor and condenser fan are located in the condenser (outdoor) unit. By referencing the electrical specifications on the condenser unit, you can determine their power usage.
To give you an example, let’s take a look at this nameplate on the condenser (outdoor) unit of a 4-ton (48,000 BTU) heat pump:
On the nameplate, the manufacturer specifies the following:
- A Voltage of 208/230 Volts: This indicates that the unit can operate on either a 3-phase 208 Volt circuit or a split-phase 230 Volt circuit, with residential systems typically using 230 Volts.
- A Compressor RLA of 24.2 Amps: RLA stands for Rated Load Amperage, representing the maximum amount of current (Amps) that the compressor is designed to draw during normal operation.
- A Compressor LRA of 117 Amps: LRA stands for Locked Rotor Amperage, representing the maximum amount of current that the compressor might require during the startup phase.
- An (outdoor) Fan Motor FLA of 1.7 Amps: FLA stands for Full Load Amperage, representing the maximum amount of current that the fan motor is designed to draw under full load.
Using the Voltage and RLA ratings, we can calculate the “Running” power usage of the compressor:
Compressor’s Running Watts = RLA (Amps) x Voltage (Volts)
Compressor’s Running Watts = 24.2 Amps x 230 Volts
Compressor’s Running Watts = 5566 Watts
Using the Voltage and LRA ratings, we calculate the “Starting” power usage of the compressor:
Compressor’s Starting Watts = LRA (Amps) x Voltage (Volts)
Compressor’s Starting Watts = 117 Amps x 230 Volts
Compressor’s Starting Watts = 26,910 Watts
Using the Voltage and FLA ratings, we can calculate the running power usage of the outdoor fan motor:
Outdoor Fan’s Running Watts = FLA (Amps) x Voltage (Volts)
Outdoor Fan’s Running Watts = 1.7 Amps x 230 Volts
Outdoor Fan’s Running Watts = 391 Watts
Now, let’s determine the running watts of the blower fan motor, and for that, we need to refer to the nameplate on the air handler (indoor) unit of the heat pump:
On the air handler’s nameplate, the manufacturer specifies that the indoor fan motor operates at 230 Volts, and may require up to 6 Amps of current.
Using the Voltage and FLA ratings, we can calculate the running power usage of the indoor fan motor as follows:
Indoor Fan’s Running Watts = FLA (Amps) x Voltage (Volts)
Indoor Fan’s Running Watts = 6 Amps x 230 Volts
Indoor Fan’s Running Watts = 1380 Watts
Now that we know the running/starting watts of the compressor and the running wattages of the outdoor fan motor and the indoor fan motor, we can calculate the potential running wattage of our 4-ton heat pump as follows:
Potential Running Wattage (Watts) = Compressor’s Running Watts + Outdoor Fan’s Running Watts + Indoor Fan’s Running Watts
Potential Running Wattage (Watts) = 5,566 Watts + 391 Watts + 1,380 Watts
Potential Running Wattage (Watts) = 7,337 Watts
On the other hand, the starting power requirement of the unit is the sum of the compressor’s starting power, the outdoor fan’s running power, and the indoor fan’s running power:
Potential Starting Wattage (Watts) = Compressor’s Starting Watts + Outdoor Fan’s Running Watts + Indoor Fan’s Running Watts
Potential Starting Wattage (Watts) = 26,910 Watts + 391 Watts + 1,380 Watts
Potential Starting Wattage (Watts) = 28,681 Watts
Now, it is worth clarifying that the keyword here is “potential”, and both the running and starting wattages that we’ve calculated represent the maximum amount of power that this particular 4-ton heat pump is capable of using. A worst-case scenario if you will.
This particular 4-ton heat pump will usually only require around 15,000 – 18,000 Watts when starting up, and will likely only use around 4500 – 6000 Watts when it’s in operation.
However, if you’re sizing equipment that can run the unit, it should be done based on these maximums. An inverter or a generator that can run your 4-ton unit should be able to do so even in the worst-case scenarios.
Alright, let’s shift our focus to the actual amount of electricity these units consume, known as their energy consumption in kilowatt-hours (kWh).
How much electricity (kWh) does a 4-ton ac or heat pump use?
As a rule of thumb, a 4-ton (48,000 BTU) air conditioner or heat pump will typically consume 2.4 to 3.6 kWh of energy per hour during the cooling season. If we assume a daily usage of 12 hours, this means it would use around 30 to 45 kWh each day, totaling approximately 900 to 1400 kWh per month.
However, during the heating season, a 4-ton heat pump will generally consume between 4 to 6 kWh of energy per hour. With a daily runtime of 12 hours, this translates to roughly 50 to 70 kWh per day and 1500 to 2100 kWh per month.
The exact energy consumption of a heat pump or an air conditioner will depend on various factors, including:
- Outdoor temperature.
- Indoor temperature settings.
- The quality of insulation in your home.
- The condition of the unit.
- The efficiency of the unit.
- And your usage patterns, such as daily usage duration, etc…
But if you put most of these factors aside, you can use your 4-ton unit’s efficiency rating to estimate its hourly energy consumption rate. Combining this with your typical daily usage will help you estimate the unit’s daily and monthly energy consumption.
Let me explain.
Air conditioners and heat pumps are assigned Energy Efficiency ratios or factors, which gauge the energy efficiency at which the unit produces warm or cool air.
You see, the 4-ton or 48,000 BTU rating on your air conditioner or heat pump represents the capacity of the unit, or in other words, the amount of heat exchange that it can perform within an hour of operation.
The energy efficiency of the unit will determine how much energy it will consume to perform this degree of heat exchange.
In fact, the relationship between the energy consumption of your 4-ton unit and its energy efficiency is as follows:
Hourly Energy Consumption (Watt-hours/hour) = 48,000 BTUs ÷ Energy Efficiency Ratio
Hourly Energy Consumption (kWh/hour) = (48,000 BTUs ÷ Energy Efficiency Ratio) ÷ 1000
For each model, manufacturers estimate these energy efficiency ratios/factors and express them as follows:
- A SEER (Seasonal Energy Efficiency Ratio) rating: This rating is given to both air conditioners and heat pumps, and it measures their energy efficiency during the cooling season.
- An HSPF (Heating Seasonal Performance Factor) rating: This rating is given to heat pumps, and it measures their energy efficiency during the heating season.
The SEER rating of your air conditioner or heat pump can be used to estimate the hourly energy consumption of the unit during the cooling months:
Hourly Energy Consumption (Watt-hours/hour) = 48,000 BTUs ÷ SEER
Hourly Energy Consumption (kWh/hour) = (48,000 BTUs ÷ SEER) ÷ 1000
And the HSPF of your heat pump can be used to estimate its hourly energy consumption during the heating season:
Hourly Energy Consumption (Watt-hours/hour) = 48,000 BTUs ÷ HSPF
Hourly Energy Consumption (kWh/hour) = (48,000 BTUs ÷ HSPF) ÷ 1000
The SEER and HSPF ratings of your AC or heat pump are typically provided on the EnergyGuide (yellow) label that came with the unit.
To illustrate this, let’s take a look at this EnergyGuide label from a 4-ton (48,000 BTU) heat pump:
The label provides the following ratings:
- A SEER of at least 20.5.
- An HSPF of at least 10.4.
A conservative estimate of the hourly energy consumption of this unit during the cooling season can then be calculated as follows:
Hourly Energy Consumption in the Cooling Months (Watt-hours/hour) = 48,000 BTUs ÷ SEER
Hourly Energy Consumption in the Cooling Months (Watt-hours/hour) = 48,000 BTUs ÷ 20.5
Hourly Energy Consumption in the Cooling Months (Watt-hours/hour) = 2341 Wh/hour
Hourly Energy Consumption in the Cooling Months (kiloWatt-hours/hour) = 2.34 kWh/hour
Similarly, for the heating season, the hourly energy consumption of this 4-ton unit can be calculated as follows:
Hourly Energy Consumption in the Heating Months (Watt-hours/hour) = 48,000 BTUs ÷ HSPF
Hourly Energy Consumption in the Heating Months (Watt-hours/hour) = 48,000 BTUs ÷ 10.4
Hourly Energy Consumption in the Heating Months (Watt-hours/hour) = 4615 Wh/hour
Hourly Energy Consumption in the Heating Months (kiloWatt-hours/hour) = 4.61 kWh/hour
Now, with these hourly energy consumption estimates and your typical daily usage, you can calculate both the daily and monthly energy consumption of your unit in the corresponding season:
Daily Energy Consumption (kWh/day) = Hourly Energy Consumption (kWh/hour) x Daily Usage (hours/day)
The daily energy consumption of your air conditioner or heat pump is going to be especially helpful if you’re trying to size equipment that’ll run the unit, such as solar panels, or batteries.
If, on the other hand, you’re trying to figure out the monthly expenses associated with operating the unit, the first step would be to estimate its monthly energy consumption:
Daily Energy Consumption (kWh/month) = Daily Energy Consumption (kWh/day) x 30
Speaking of expenses, let’s see how much these units cost to operate.
How much does it cost to run a 4-ton AC or heat pump?
The cost of running your 4-ton air conditioner or heat pump not only depends on its exact energy consumption but also on the cost of electricity in your area.
For instance, using the U.S. national average electricity cost of approximately 16 cents per kWh, a 4-ton air conditioner or heat pump would cost roughly $0.5 (50 cents) for each hour of operation during the cooling season.
During the heating season, a 4-ton heat pump would consume about $0.8 (80 cents) worth of electricity per hour of operation.
However, it’s important to note that while the U.S. national average cost per kWh is 16 cents, the actual cost per kWh can vary across the country and may range from 10 to 30 cents per kWh.
For a more accurate estimate of the operating cost of your 4-ton unit, you should multiply the unit’s energy consumption by the actual cost per kWh in your area:
Cost ($/Timeframe) = Energy Consumption (kWh/Timeframe) x Cost per kWh ($/kWh)
For example, let’s assume you have a 4-ton heat pump, and you’ve estimated its energy consumption to be:
- 900 kWh of energy per month during the cooling season.
- 1600 kWh of energy per month during the heating season.
Now, let us assume that you live in the state of Pennsylvania, where, according to the Energy Information Administration (EIA), the average cost per kWh is around 18 cents ($0.18/kWh).
The average monthly cost of running the heat pump in the cooling season would be calculated as:
Cost ($/month) = Energy Consumption (kWh/month) x Cost per kWh ($/kWh)
Cost ($/month) = 900 kWh/month x $0.18/kWh
Cost ($/month) = $162/month
Similarly, the average monthly cost of operating the heat pump during the heating months would be:
Cost ($/month) = Energy Consumption (kWh/month) x Cost per kWh ($/kWh)
Cost ($/month) = 1600 kWh/month x $0.18/kWh
Cost ($/month) = $288/month
To save you time, I’ve designed a calculator that estimates the daily and monthly average operating costs of your 4-ton air conditioner or heat pump. The calculator will factor in whether the unit is in cooling or heating mode, your daily usage duration, and your location:
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