The honest answer is a range — here it is.

Replacing a 2000-era air conditioner (around 10 SEER) with a new two-stage 16 SEER2 system in an average Tucson home typically saves about 1,700 kWh — roughly $257 a year at TEP's current rates, with an estimated range of about $183 to $367. A system from 2015 or later usually saves too little for efficiency alone to justify replacement.

That range is smaller than what most calculators promise. That's because it's real: metered studies of hundreds of Arizona homes show the industry's standard savings math roughly doubles what homes actually save. The top of our range is the unadjusted nameplate math — an engineering ceiling, not a promise. We'd rather show you a smaller true number than a bigger imaginary one — the same reason we put our workmanship warranty in writing.

Your July bill and your average monthly bill — in plain dollars, right off TEP's site — and two minutes. Results show a typical figure and the estimated range, in both dollars and kilowatt-hours.

Everything in this tool is local. The electric rates are TEP's actual tariff sheets — including the time-of-use plan, where cooling from 3 to 7 p.m. costs half again as much as off-peak, and the solar export credit that changes the math for rooftop-solar homes. The climate inputs are NOAA's 30-year normals for Tucson International Airport. The realism adjustments come from metered studies of Phoenix-area homes in our same hot-dry climate.

One thing this tool deliberately does not do: pile on extra percentages for insulation, duct sealing, or inverter technology. Field data shows those savings don't stack the way sales brochures imply. Duct and envelope work are real opportunities in Tucson attics — which is why we test them with instruments and quote them separately, instead of letting a slider guess.

One scope note: this models central refrigerated-air replacement. Evaporative-cooler conversions and mini-split additions are different projects with different math — talk to us and we'll run those properly.

If your system is from 2015 or later and working properly, replacing it for efficiency alone rarely pays for itself quickly. We'll tell you that at your kitchen table too. The case for replacing a newer unit is comfort, reliability, refrigerant availability, or a failed compressor — not the electric bill.

Annual savings ceiling = your annual cooling kWh × (1 − old SEER2 ÷ new SEER2). We estimate your cooling kWh from two numbers every TEP customer knows — your peak summer bill and your average monthly bill for the year. Because every month's cooling is inside that average (this is Tucson — even April and October run the AC), the non-cooling baseload cancels out algebraically, scaled by Tucson's monthly cooling-degree-day profile from NOAA's 1991–2020 normals (3,424 cooling degree days a year). Then we apply a realization range — model scenarios at 50%, 70%, and 100% of the ceiling — because metered field studies consistently find real homes save less than nameplate math promises. The 100% end is the unadjusted engineering ceiling, not a typical outcome. Dollars = kWh saved × TEP's marginal summer rate for your plan, including the current PPFAC fuel-adjustor credit. That's the whole model. No hidden multipliers, no multi-year totals at assumed rate hikes.

Where every number comes from:

• TEP rates: TEP residential tariff sheet 101, Basic and sheet 102, Time-of-Use, effective September 2023, Arizona Corporation Commission Decision 79065, plus the current PPFAC fuel adjustor from TEP's Statement of Charges (−$0.00715 per kWh, effective April 2026, Decision 81710 — currently a credit) — all verified against the live PDFs August 27, 2026. Smaller riders, surcharges, and taxes are not modeled. TEP has a rate request pending before the Commission; we don't model it, because its headline percentage describes whole-bill effects, not the marginal rate this tool uses. The solar export credit is TEP's Resource Comparison Proxy rate, $0.0513 per kWh (2025–26 Statement of Charges).
• Tucson climate: NOAA NCEI 1991–2020 climate normals, Tucson International Airport station USW00023160.
• Why savings are a range: a Salt River Project / EPRI field study metered 340+ Phoenix-area homes (ACEEE Summer Study 2012) and found high-SEER homes used 14–18% less cooling energy where nameplate math predicts about 30% — and the gap shrinks on 114°F afternoons. A Cadmus review of four metering studies (ACEEE Summer Study 2016) found real cooling run-hours average 60–70% of published values. Individual bill-tracked replacements have matched the full nameplate prediction, but no study shows typical customers generally do — which is why we present that number as the ceiling of the range, never the expectation.
• Natural gas (heating comparison): Southwest Gas Statement of Rates, Schedule G-5 single-family residential — $1.65466 per therm all-in plus $10.70 monthly, effective January 2026, verified against the live tariff August 27, 2026. Southwest Gas has a rate case pending (~10.5%, decision expected 2027) and a separate fuel-component request — both unapproved and not modeled.
• Cooling baseline sanity check: EIA Residential Energy Consumption Survey 2020, Arizona average home air conditioning ≈ 6,013 kWh per year.
• Why we don't add an inverter bonus: the SEER2 test procedure already includes part-load and cycling behavior. Variable-speed systems earn their premium in comfort, sound, humidity control, and fit with time-of-use hours — we won't double-count their efficiency.

Savings vary. These are planning-grade estimates based on the information you enter, current TEP rates, and typical Tucson conditions — not a quote, a promise, or a guarantee of your utility bill. Your actual results depend on your home, your thermostat habits, the weather, install quality, and future TEP rates.

The advisor mode works from your actual home, not guesses. It anchors on your real TEP bills when you have them — field studies show the number-one error in every savings tool is guessing the baseline, and your bills beat every model. Without bills, it models from the nameplate capacity and efficiency, a real duct test, and five-point envelope ratings a trained eye can judge in any home: attic insulation, windows and shading, and building tightness. When both are available, it cross-checks the model against the bills and says so when they disagree — which is usually the most useful conversation of the visit.

It compares your quote options side by side, including downsizing or upsizing capacity, converting from AC-plus-gas-furnace to a heat pump (heating shown as its own line, priced at Southwest Gas's actual rates against TEP's winter rates), and any staging — single-stage, two-stage, or variable-speed, on either system type. And it says the quiet part out loud: when a higher tier's step-up payback runs past ten years, the honest reason to buy it is comfort, sound, and warranty, not the electric bill. Every estimate prints to a one-page summary carrying the inputs, the assumptions, the sources, and the model version.

After an install, we verify the system's actual delivered performance with third-party instrumented testing — refrigerant charge, airflow, static pressure — because commissioning quality is exactly what separates the top of the savings range from the bottom. No guessing. We're testing.