Room AC Replacement Calculator

This calculator weighs keeping your room air conditioner against replacing it with a new one. Describe the old unit by picking it from the ENERGY STAR lists, by the year it was made, or from the rating on its label; pick the new one from the current ENERGY STAR list; and say how many hours a year it cools, or let your state set an estimate. It works out the cooling the room needs, each unit's yearly electricity and cost, the yearly saving, the net cost of the new unit, the simple and discounted payback, and the cost over the years you choose of keeping the old unit, replacing it now, or replacing it when it wears out.

Model and climate figures come from federal sources only: the ENERGY STAR lists (EPA), DOE efficiency standards and test procedures, NOAA climate normals and EIA electricity prices. You set the price of the new unit; the opening example and each worked example carry a round illustrative price, labelled as such.

Purpose and model boundary

This calculator compares keeping the room air conditioner you have with replacing it with a new one. It works out the cooling the room needs from the old unit's capacity and the hours it runs, the electricity each unit needs to deliver it, and the cost at your electricity price, and sets the yearly saving against what the new unit costs. Over the number of years you choose, it compares keeping the old unit, replacing it now and, when you say how many years the old unit has left, replacing it when it wears out.

Every figure on this page is computed by the spreadsheet; the page adds nothing to it. It covers cooling running cost and purchase cost only; the heating mode of a reverse-cycle unit is shown on the model card but not costed.

Inputs and units

• The old room air conditioner, window or through-the-wall, described in one of four ways: a model from the ENERGY STAR historical lists; a model from the current ENERGY STAR list, for a unit that is still certified; the year it was made and its DOE product class, for which the calculator uses the federal minimum; or manual entry of its rating from the label (5 to 25 Btu per watt-hour) and the basis of that rating: CEER (labels from mid-2014), EER (older labels) or Unknown. For the age and manual routes, also give its cooling capacity, 3,000 to 40,000 Btu/h.
• Type: window or through the wall, for each unit. For a listed model, choose the type first, then pick the model from that type's list.
• The new room air conditioner: a model from the current ENERGY STAR list, or its cooling capacity and CEER entered by hand, and its price, which is always yours to set (more than $0 and at most $5,000).
• Use: the hours the unit cools in a year (0 to 8,760). Leave it blank to use an estimate for your state; optionally give your own cooling degree days, which replace your state's figure.
• Price of electricity: the state, which sets the default price, and your own price in dollars per kWh (0.01 to 2.00), optional.
• Purchase and finance: sales tax; verified incentives; removal; the old unit's sale value; yearly upkeep of each unit; the years the old unit has left; the new unit's expected life; the yearly change in electricity prices; the discount rate; and the years to compare.

Heating and cooling needs are in million Btu (MMBtu) a year of heat delivered or removed. Electricity is in kWh, fuel in US gallons or therms, efficiency ratings in Btu per watt-hour (CEER, SEER2, HSPF2) or as a fraction (AFUE), and money in dollars.

Governing relationships

• Cooling need = the old unit's capacity (Btu/h) x the hours it cools. A blank number of hours uses DOE's test basis of 750 hours a year, scaled by your state's cooling degree days relative to the US figure; that scaling is this calculator's own, labelled approximation, not a federal figure.
• Electricity = cooling need in Btu / (CEER x 1000). This is the formula behind the ENERGY STAR list's yearly energy figure at 750 hours.
• Older ratings: an old EER (labels before mid-2014) or a rating of unknown basis is used as if it were CEER. EER leaves out standby power, so this understates the old unit's use and therefore the saving. No federal EER-to-CEER factor exists, and none is invented.
• Yearly cost = electricity x electricity price + upkeep; the yearly saving is the old cost minus the new cost. Payback and present value follow the rules shared with the other replacement calculators, with nothing counted twice.

Calculation sequence

The spreadsheet first checks the inputs and finds each unit's capacity and rating, the hours and the electricity price. It works out the cooling need once, shared by both units, reduces each unit to the electricity it uses per million Btu of cooling, and from those computes the yearly electricity, costs and saving; the purchase cost, the paybacks, the present values and the year-by-year cash flow follow. The sensitivity table uses the same per-MMBtu figures, so it cannot disagree with the main result. A consistency check that the discounted cash flow reaches the same net present value as the closed-form formula runs before the status is returned.

Outputs and interpretation

The results show the cooling hours and need used, and for each unit the rating used, the yearly electricity and the yearly energy and total cost; then the yearly saving in dollars and kWh, the net cost of the new unit, the simple and discounted payback, and the cost of each path. When your hours differ from the 750-hour label basis by more than a factor of 2, a note says that the label's small standby share is scaled with them.

The cash-flow table shows each year of the years compared: the cost of each path, the net benefit of replacing now, and its cumulative, discounted and cumulative discounted values. The sensitivity table shows the yearly saving with the cooling need scaled by 0.50, 0.75, 1.00, 1.25 and 1.50, at the same multiples of the electricity price used.

A model card beside each listed pick shows the unit's capacity, its CEER, its yearly energy on the label, its DOE product class and whether it also heats.

The first chart, “Cumulative net benefit of replacing now, by year”, shows Undiscounted and Discounted by year. The second chart, “Cost over the years compared”, shows Total and Present value by option. The third chart, “Running cost in year 1”, shows Cooling electricity and Upkeep by unit, stacked.

Validation and status logic

The workbook returns one status, chosen in this order: NOT VALID, then CHECK, then OK.

• NOT VALID names the first problem: an old-unit source or type that is not one of its options; a listed model that is not in its list or does not match the type chosen, or no federal minimum on file for that class and year made, in which case use the label rating; a manual rating missing or outside 5 to 25, or a basis that is not one of its options; an old capacity missing or outside 3,000 to 40,000 Btu/h; the same problems for the new unit; cooling hours outside 0 to 8,760; blank hours, so the state estimate is needed, in a state with no degree-day figure and none entered; no electricity price, or your own outside 0.01 to 2.00 dollars per kWh; a missing price for the new unit, or one outside its limits; a money amount, the years compared, the price change, the discount rate or a life in years outside its limits. NOT VALID is a refusal, not a numeric answer: every figure reads zero and is withheld.
• CHECK accompanies a computed result that needs the stated review: the old rating is the federal minimum for the year made; the old unit may be more efficient, so the saving may be overstated; the old rating's basis is Unknown and it is used as if it were CEER; an old EER rating is used as if it were CEER, which understates the old unit's use; the new unit's capacity is below 0.9 times the old unit's, so it may not keep the room as cool; zero cooling hours; no yearly saving, so there is no payback; the old unit's remaining life is shorter than the years compared, so read the end-of-life comparison.
• OK otherwise.

Assumptions and limitations

• The old unit sets the room's need. The cooling need is the old unit's capacity times its hours; the new unit runs as long as it needs to deliver the same cooling, so a bigger new unit does not raise the need.
• Standby is scaled with use. CEER includes standby power at the 750-hour basis; the calculator scales the whole figure with your hours, which moves only a few kWh a year.
• A federal minimum is a floor, not a measurement. An old unit described by the year it was made may be more efficient than the minimum, so the saving may be overstated. Where the minimum changed during a year, the newer, higher minimum is used, which keeps the saving on the low side. Wear with age is not modelled.
• Inputs with no federal source are your assumptions: the price of the new unit, and the hours when you enter them. The state scaling of the default hours is a design choice.
• Alaska, Hawaii and DC. NOAA publishes no statewide degree-day normals for any of the three. DC uses Maryland's figures; Alaska and Hawaii each use one NOAA station normal, at the Anchorage and Honolulu airports, labelled as a single station. Your own hours or degree days replace them.
• Prices. The price of the new unit is always your input; the workbook holds no price table. The opening example and each worked example carry a round illustrative price so that they compute, with the note: "Illustrative price for this example, not a quote or a current price. Prices vary: check current prices online or enter your own."
• The default electricity price is a state average. Your own price from your bill overrides it.

Data and vintage

• Current models: the ENERGY STAR certified room air conditioner list (EPA), window and through-the-wall units sold in the US; models sold only in Canada are left out, and where a model is listed more than once the most recent listing is used.
• Historical models: the archived ENERGY STAR room air conditioner lists for specification versions 2.1 and 3.1, whose ratings are EER or CEER as listed and are never converted.
• Federal minimum by year made and class: DOE energy conservation standards (10 CFR 430.32), with earlier editions of the Code of Federal Regulations (1997 and 2012) for the years before the current standard.
• Climate: NOAA NCEI statewide cooling degree-day normals for 1991-2020 (nClimDiv); the US figure covers the 48 contiguous states. NOAA calls these long-term averages rather than official normals, and its notes state neither the base temperature nor the weighting.
• Default price: EIA final 2025 average residential electricity prices by state (Form EIA-861).

Worked examples and prices

Prices are not part of the reference data: the price of the new unit is an input you set. The opening example and the five worked examples each use an illustrative price for the new unit, so that the example computes, and each says so: “Illustrative price for this example, not a quote or a current price. Prices vary: check current prices online or enter your own.”

Restrictions and non-computing states

The calculator enforces its numeric and choice limits before it accepts a result. A listed model that is not in its list or does not match the type chosen, a rating, capacity or number of hours outside its limits, a missing price for the new unit, and a missing electricity price are refused by the workbook.

Errors and warnings

A request rejected by the page's input limits is not a computed result. A transport or service failure, a timeout or a cancelled run cannot establish a fresh workbook answer, and the last result stays on the page marked as out of date. Check your unit's label and your own bills before relying on a result for a purchase, and check current prices for the new unit.

Sources and further reading

The calculator reads its model lists, its federal minimum ratings, its climate figures and its default energy prices from reviewed reference tables inside the workbook, with their version shown in the result details. Every table comes from a US federal source. The sources below publish the data and the rules the model applies. They do not endorse this calculator.

• ENERGY STAR Certified Room Air Conditioners (EPA) lists currently certified room air conditioners with their capacity, CEER and yearly energy use, which assumes 750 hours of operation a year (retrieved 2026-10-28).
• ENERGY STAR, Room air conditioners: information for partners (EPA) links the historical lists of room air conditioners certified under earlier specifications, versions 2.1 and 3.1 (retrieved 2026-10-28).
• ENERGY STAR data portal catalog (EPA) lists the EPA's certified-product datasets, among them the room air conditioner list used here (retrieved 2026-10-28).
• DOE energy conservation standards, 10 CFR 430.32 (eCFR) sets the federal minimum CEER for each room air conditioner class; earlier editions give the older EER minimums (retrieved 2026-10-28).
• DOE test procedures, 10 CFR 430 subpart B (eCFR) defines CEER for room air conditioners under appendix F, which rates yearly energy on 750 hours of cooling (retrieved 2026-10-28).
• NOAA NCEI, Climate Divisional Database (nClimDiv) publishes statewide cooling degree-day normals, used here for 1991-2020 (retrieved 2026-10-28).
• NOAA NCEI, U.S. Climate Normals 1991-2020, station files gives the Anchorage and Honolulu airport normals that stand in for Alaska and Hawaii (retrieved 2026-10-28).
• EIA, Detailed state data (Form EIA-861) gives the average residential electricity price by state, used here for 2025 (retrieved 2026-10-28).

This is an educational estimate of running and purchase costs for the equipment and prices you enter, not a product recommendation or a quote. Ratings are measured under federal test procedures, not in your home.