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Photograph of  this unusual attic air conditioning system is an example of the range of human creativity observed during a career of building inspections Air Conditioner Costs &
Heat Pump Operating Cost
How to actually calculate HVAC operating costs

Air conditioner or heat pump operating cost guide: this article explains how to calculate the actual cost of operating an air conditioning system in easy to understand language

This article series answers most questions about air conditioning systems. We continue to add to and update this text as new details are provided.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

How Much Does It Actually Cost to Run An Air Conditioner or Heat Pump?

at SEER RATINGS & OTHER DEFINITIONS we explained SEER ratings that measure air conditioning system efficiency, and we explained how we can determine how much energy an air conditioner uses either by the hour of by the season of use. At the end of that section we knew how much energy our air conditioner used, either on an hourly basis or for use during the whole cooling season.

We were able to express the total air conditioning energy used in BTUs or in Kilowatts per hour or per season. Here we complete the process of translating air conditioner use into actual dollar costs.

How Much Will It Cost Per Year to Run An Air Conditioner?

In the United States for December 2007 the average retail price of electricity paid by residential consumers ranged from about $0.063 per kWh (Idaho) to $0.287 per kWh (Hawaii). Your electrical bill will indicate the current charge per kilowatt hour kWh of electricity you use.

How to use the air conditioning cost formula given just below

  • Plug in your actual Air Conditioner's Wh: Where we used 500, plug into the equation below the actual Watt Hours (Definition of WATT HOUR) Wh your air conditioner uses, by following the procedure at SEER RATINGS & OTHER DEFINITIONS.
  • One Wh = one Watt-hour.
  • One kWh = one kilowatt hour or 1000 watt-hours.
  • Plug in your electric bill kWh rate: Just plug in to the equation example below the cost per kWh of electricity from your electric bill where we've used $ 0.25.
  • Multiply these two numbers. Just below, we use an example of $ 0.25 or 25 cents per kWh cost from an electric utility company.[Electrical costs provided by the U.S. Department of Energy at eia.doe.gov/cneaf/electricity/ epm/table5_6_a.html]
  • 500 kWh used per season x $ 0.25 = $125.00 - that's your electricity cost to run the air conditioner for a season.

    How Much Does It Cost Per Hour to Run An Air Conditioning System

    This is an even simpler calculation. Using as an example information from our example air conditioner's data tag,

    ((5000 BTUH) / (10 SEER)) = 500 Wh

    500 Wh x $ 0.25 = $0.12 per hour to run our air conditioner. Twelve cents per hour is your hourly cooling cost to run your A/C.

    Paul Presson, R.A. notes: "Correct the cost per operating hour calculation - the $0.25/kwh needs to be divided by 1,000 to get the watt hour cost."

    Other Equations Using SEER Ratings

    We can also write the SEER equation shown above as:

    SEER = BTUs / Watt-hours
    where "watt-hours" = (number of hours of system operation) x (watts used per hour)

     




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    Reader Comments, Questions & Answers About The Article Above

    Below you will find questions and answers previously posted on this page at its page bottom reader comment box.

    Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

    Comments:

    (June 26, 2014) Paul A. Presson, R.A said:
    Appreciate the info. Need to correct your cost per operating hour calculation to note the $0.25/kwh needs to be divided by 1,000 to get the watt hour cost.

    Reply:

    Thanks so much, Paul.

    Question: How Can I Reduce the Operating Cost and Energy Consumption of my Air Conditioning & Heat Pump System?

    As we discussed at POST a QUESTION or COMMENT about the Energy Star Program's SEER and EER definitions and equipment ratings,

    Answer: List of Air Conditioning & Heat Pump System Steps or Installation Details that Save on Operating Cost

    According to SoCalEdison's "Comprehensive Packaged Air Conditioning Systems", Residential and commercial air conditioning is responsible for the largest share of peak demand in California, contributing approximately 33% of peak demand. < [3] [4]

    Saving money on central or even portable air conditioners and heat pumps starts by buying equipment with a high SEER (Seasonal Energy Efficiency Ratio (SEER)) rating. But as SoCalEd points out [4] , the purchase of high efficiency (high SEER) HVAC equipment captures only a small part of the total savings in air conditioning or heat pump costs that could be saved by other installation and maintenance steps that we outline here [quoted, paraphrased, and expanded from [4] ]:

    Proper Sizing of the Air Conditioner.

    Supporting proper sizing in residential and commercial units can yield savings. Contractors frequently install oversized systems to avoid potential comfort and call back risks. See CO

    OLING CAPACITY, RATED, and also, because an oversized air conditioner is likely to fail to adequately dehumidify building air, also

    see A/C Not Dehumidifying.

    [Air Conditioner & Heat Pump] Refrigerant Charge and [compressor/condenser] Airflow.

    Between half and three-quarters of all packaged air conditioning units suffer from incorrect charge and low airflow. For both new and existing equipment, ensuring the proper refrigerant charge and airflow can increase efficiency. [5]

    See REFRIGERANT GASES & PIPING and

    see REFRIGERANT LEAK DETECTION where we describe types of A/C refrigeration system leaks, where they occur, and how they damage the system.

    Also see REFRIGERANT LEAK REPAIR. [We {DF] speculate that this problem may be more severe for residential air conditioners and heat pumps than for those commercial units whose design includes a refrigerant receiver.]

    [HVAC Air] Duct Sealing.

    Ensuring tight ducts in residential and commercial installations yields 10- 18% energy savings.6 The peak load reduction can be higher, yielding a demand savings of 25%.[ 4< and citations therein]

    See our articles on air duct leaks:
      
    LEAKY DUCT CONNECTIONS

        
    Leaky or Missing Air Ducts

        Hidden Missing Air Conditioner Duct

        Duct Retrofit Leaks

        Rooftop Duct Leaks

        RETURN DUCT AIR LEAKS

        SUPPLY DUCT AIR LEAKS

    In our [DF] OPINION in addition to sealing duct leaks, better attention to balancing the quantity of return air available to the air handler with the supply duct and register system is needed at many buildings. See RETURN AIR, INCREASE

    In our [DF] OPINION, the most basic homeowner maintenance task that can reduce air conditioning and heat pump operating tasks is to be sure that air filters are in place, properly selected, sized, installed, not leaky, and that the filters are changed on a regular schedule.

    See DIRTY AIR FILTER PROBLEMS and

    see AIR FILTERS for HVAC SYSTEMS for details. Also see our suggestions

    at AIR FILTERING STRATEGIES.

    HVAC Economizers.

    Research shows that the majority of [HVAC] economizers do not function as intended. Use of the Whole Building Diagnostician tool in new and existing buildings in California has confirmed that problems with outside air economizers are endemic. The potential savings from fixing a malfunctioning economizer are approximately 10 – 15% of total packaged air conditioning load. In addition, enabling damper function is a prerequisite for further savings from demand controlled ventilation. [4 and accompanying citation]

    Definition of Economizer for HVAC systems:

    economizers are devices designed to reduce the operating cost (and energy used) in mechanical systems, principally by re-using heat (or cooling) already produced within the system. Examples of economizer designs in HVAC systems include details that may be found both at the ductwork / air handling system (this is the common use of "economizers on

    HVAC systems) and also right inside of the compressor/condenser unit (a technical use of HVAC economizer heat exchange theory):

    • Air-to-air heat exchangers 

      that heat incoming fresh air (makeup air) being introduced into the duct system during the heating season by using the heat from combustion exhaust or other sources.
    • Refrigerant tubing co-soldering 

      of the high pressure (high temperature or "high side") refrigerant piping alongside of low pressure (low temperature or "low side") tubing at certain locations in the air conditioning or heat pump system to improve system efficiency. We explain this A/C or heat pump refrigerant line soldering/brazing detail

      at REFRIGERANT PIPING INSTALLATION - at the

      subtopic: Technical Note on Refrigerant Piping: HVAC economizer detail
    • HVAC Controls.

      Appropriate controls which enable variable heating and cooling conditions based on occupancy are also critical. With a comprehensive program to address all of these opportunities, the savings per packaged air conditioning unit easily approach 20 percent. [4]

    ...

    Continue reading at SEER RATINGS & OTHER DEFINITIONS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

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    Suggested citation for this web page

    OPERATING COST, AIR CONDITIONER at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


    Or see this

    INDEX to RELATED ARTICLES: ARTICLE INDEX to AIR CONDITIONING & HEAT PUMPS

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