Estimates the installed cost of a central air conditioning or heat pump replacement, the annual cooling energy saving, and how long the saving takes to cover the cost.
Which cell does what, and which worksheets the model reads. These are the assignments you recreate when you import the file.
| Cell | Role | Note |
|---|---|---|
| B1 | Input | Conditioned floor area in square feet. Drives equipment sizing in B6. |
| B2 | Input | Age band of the existing system, stored as its effective SEER (8, 10, 12 or 14) rather than a year count, so B9 can divide by it directly. |
| B3 | Input | SEER2 rating of the proposed system. Used twice: as the VLOOKUP key for cost per ton in B7, and as the divisor for new energy use in B10. |
| B4 | Input | Retail electricity rate in cents per kWh. Divided by 100 in B11 to get dollars. |
| B5 | Input | Left blank. Marks the end of the input block. |
| B6 | Result | Tons of cooling. B1/600 gives raw tons, CEILING to the next half ton, then clamped between 1.5 and 5. |
| B7 | Lookup | Installed cost per ton, read from the Equipment rates sheet by SEER2 tier. |
| B8 | Result | Installed cost: tons times cost per ton, plus a flat $1,800 for labor, line set, permit, disposal and thermostat. |
| B9 | Result | Current annual cooling kWh. Tons x 12,000 BTU/h x 1,200 equivalent full-load hours / 1,000, which collapses to tons x 14,400 / SEER. |
| B10 | Result | Same formula as B9 with the new system's SEER2 rating. |
| B11 | Result | Annual dollar saving. kWh difference floored at zero so a downgrade never shows a negative saving, times the rate in cents, divided by 100. |
| B12 | Result | Simple payback: installed cost divided by annual saving, to one decimal. Returns 0 when there is no saving to divide by. |
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The payback shown divides the entire installed cost by the cooling energy saving. Most of that cost buys a working system, not efficiency. If you are replacing a failed unit anyway, the more useful comparison is the extra cost of stepping up from a 14.3 SEER2 system to a higher tier, which on a 3-ton job is roughly $1,000 to $3,150 and pays back far faster.
No. The saving is cooling-season only. If the new system is a heat pump replacing electric resistance heat or an old furnace, real annual savings will be higher than the figure shown, sometimes substantially so.
Sizing here uses a 600 sq ft per ton rule of thumb. A contractor performs a Manual J load calculation that accounts for insulation, window area, orientation, ceiling height and air leakage, and may size the system differently. Ductwork replacement, electrical upgrades, refrigerant line changes, roof or attic access and zoning are also outside this estimate.
SEER2 is the test standard that replaced SEER in 2023, measured at a higher external static pressure that better reflects real duct systems. A SEER2 number is roughly 4.5 to 5 percent lower than the old SEER number for the same equipment, so 14.3 SEER2 is about the same machine as a 15 SEER unit.
No. Utility rebates, state programs and federal efficiency tax credits are excluded, and they can reduce the installed cost by several hundred to several thousand dollars on higher-efficiency equipment. Ask the contractor which ones apply in your area.
A lot. The calculation assumes 1,200 equivalent full-load cooling hours a year. A home in Phoenix or Houston may run closer to 2,000 hours, which raises the saving and shortens the payback by roughly 40 percent. A home in Minneapolis may run 600 hours, which roughly doubles the payback.