TryBuildCalcSEER to SEER2 Savings Calculator (Fair Normalized Comparison)
Get a fair SEER-to-SEER2 comparison instantly.
🕒 Last updated: September 18, 2026
Inputs
ℹ️Same capacity assumed for both the old and new unit — this isolates the efficiency difference as the only variable.
ℹ️Prefills a typical annual cooling hours estimate below — edit that field directly if you know your actual usage.
ℹ️A smart thermostat's own runtime log (if available) is more accurate than this climate-zone default.
ℹ️Use your summer/peak-season rate if your utility has time-of-use pricing, for the most realistic cooling-season estimate.
Current (Old) System
ℹ️Most units installed before 2023 carry a SEER rating, not SEER2.
ℹ️From the nameplate or an AHRI Directory lookup by model number, not guessed from the unit's age.
New / Replacement System
ℹ️Virtually every unit sold since 2023 carries a SEER2 rating.
ℹ️From the specific quoted model's spec sheet, for the exact indoor/outdoor combination being installed.
ℹ️Enter your NET cost after any rebates/tax credits to unlock a simple payback period below.
Estimated Annual Savings
$140
17.2% less cooling energy use per year
Current (Old) System
Entered rating: 13 SEER
SEER2-equivalent: 12.4
Annual energy use: 5,799 kWh
Annual cost: $812
New / Replacement System
Entered rating: 15 SEER2
SEER2-equivalent: 15
Annual energy use: 4,800 kWh
Annual cost: $672
Cumulative Savings Over Time
Year 1
$140
Year 5
$700
Year 10
$1,400
Year 15
$2,100
Year 20
$2,800
Assumptions Used
Annual kWh = (Tonnage × 12,000 BTU/ton ÷ SEER2-equivalent rating) × Annual Cooling Hours ÷ 1000, computed once for each unit and multiplied by your electricity rate. A rating entered as SEER (pre-2023) is normalized to an approximate SEER2-equivalent by dividing by 1.047 before this formula runs — DOE's 2023 M1 test procedure reads roughly 4.5-5% lower than the old SEER test for identical equipment, though the real difference varies by equipment type (variable-speed ~3-4%, single-speed ~5-6%), so this is a published approximation, not an exact per-unit conversion. Annual cooling hours default from your selected climate zone as a broad planning estimate — no single authoritative national table exists, so your own smart-thermostat runtime log (if available) is more accurate than this default. The payback period (when shown) is simply net installed cost ÷ annual savings, and the cumulative savings table assumes a flat electricity rate with no future inflation, financing costs, or maintenance-cost differences between the two units — this is a planning estimate, not a full financial analysis.
Looking for the verification checklist, reference tables, tips, or common mistakes?See the complete SEER Savings Calculator.
SEER-to-SEER2 normalized comparison
Comparing a 13 SEER old unit directly against a 15 SEER2 new unit without normalization makes the efficiency gap look smaller than it really is — the 13 SEER figure translates to roughly 12.4 SEER2-equivalent once normalized to the same 2023+ testing basis, since SEER2's tougher M1 test procedure reads lower for identical equipment, meaning the old unit is actually less efficient than its raw 13 SEER number suggests.
This page defaults to a 2.5-ton system in a warm climate — edit the inputs above and watch both the raw and normalized SEER2-equivalent figures in the result.
SEER Savings Formula: How Is It Determined?
The same formula runs once for each unit, using each unit's normalized SEER2-equivalent rating, then the two results are compared.
SEER-to-SEER2 Normalization
If rating type is SEER2: SEER2-equivalent = entered value (no change)
If rating type is SEER: SEER2-equivalent = entered value ÷ 1.047
DOE's 2023 M1 test procedure for SEER2 uses much higher external static pressure than the old SEER test, so identical equipment reads a lower SEER2 number. 1.047is a commonly-cited approximate conversion factor — the real difference varies by equipment type (variable-speed/ECM systems see a smaller ~3-4% drop, single-speed/PSC systems a larger ~5-6% drop), so treat this as a planning approximation, not an exact per-unit figure. If you have a unit's actual AHRI-certified SEER2 rating, use that directly instead.
Annual Energy Use and Cost
Annual kWh = (Tonnage × 12,000 BTU/ton ÷ SEER2-equivalent) × Annual Cooling Hours ÷ 1000
Annual Cost = Annual kWh × Electricity Rate
This runs once using the old unit's normalized SEER2-equivalent and once using the new unit's — both assuming the SAME tonnage and cooling hours, so the only variable being measured is the efficiency-rating difference.
Annual Savings and Percent Reduction
Annual Savings = Old Unit Annual Cost − New Unit Annual Cost
Percent Energy Reduction = (Old Annual kWh − New Annual kWh) ÷ Old Annual kWh × 100
A negative annual savings figure means the "new" unit is actually less efficient than the "old" one once both are normalized — this calculator reports that honestly rather than hiding it.
Payback Period (Optional) and Cumulative Savings
Simple Payback Period = New System Installed Cost ÷ Annual Savings
Cumulative Savings (Year N) = Annual Savings × N
Payback period only appears when an installed cost is entered and savings are positive (and the payback period is under 100 years). The cumulative savings table assumes a flat electricity rate over time, with no adjustment for future rate inflation, financing costs, or maintenance-cost differences between the two units.
Worked Example
This example walks through your current inputs above, using the same steps as the Formula section.
Input Values Used
| Input | Value |
|---|---|
| Cooling capacity / climate zone | 2.5 tons / Zone 3 — Warm (Deep South, Coastal CA) |
| Annual cooling hours / rate | 2400 hrs / $0.14/kWh |
| Old unit rating | 13 SEER (pre-2023 rating) |
| New unit rating | 15 SEER2 (2023+ DOE rating) |
Step-by-Step Calculation
| Step | Calculation | Result |
|---|---|---|
| Old unit SEER2-equivalent | 13 ÷ 1.047 | 12.4 |
| New unit SEER2-equivalent | 15 (already SEER2) | 15 |
| Old unit annual kWh | (2.5 × 12,000 ÷ 12.4) × 2400 ÷ 1000 | 5,799 kWh |
| New unit annual kWh | (2.5 × 12,000 ÷ 15) × 2400 ÷ 1000 | 4,800 kWh |
| Old / New annual cost | kWh × $0.14 | $812 / $672 |
| Annual savings | $812 − $672 | $140 |
Therefore, replacing this 2.5-ton system rated 13 SEER (pre-2023 rating) with a new one rated 15 SEER2 (2023+ DOE rating) saves an estimated $140 per year (17.2% less cooling energy).
Disclaimer: This calculator provides approximate results for planning and estimation purposes only. Actual requirements may vary based on site conditions, materials, workmanship, and local building regulations. Always consult a qualified engineer, architect, or construction professional before making final decisions.