Arizona Pre-Cooling Savings Calculator (2026)

Why Pre-Cooling Works So Well in Arizona

Three things make pre-cooling the single highest-leverage summer move for Arizona homeowners on time-of-use rates:

1. The peak-to-off-peak spread is enormous. APS peak electricity costs $0.3439/kWh — 3.7x more than super off-peak ($0.0935/kWh). SRP peak costs $0.11/kWh vs $0.07/kWh off-peak, plus a $14.50/kW demand charge that scales with whatever your AC does during the peak window.
2. Arizona homes have usable thermal mass. Most Phoenix-metro construction — stucco-over-frame, masonry block, tile floors — holds coolness for 4-6 hours once you've driven the temperature down. You can realistically ride the entire 3-hour APS peak or a substantial chunk of the 6-hour SRP peak with AC nearly off.
3. The compressor is the entire load. For most Arizona summer bills, the AC compressor accounts for 60-75% of total kWh. Shift that one piece of equipment out of peak and you've moved the needle on everything.

How Pre-Cooling Actually Works

Pre-cooling doesn't lower your thermostat setpoint during peak — it raises it. The work is done earlier, when electricity is cheap.

The simple version: an hour or two before peak starts, drop your thermostat to somewhere between 70-73°F. The AC runs aggressively during the cheap window. When peak hits (4pm APS, 2pm SRP), raise the setpoint to 78-82°F. The house is already deep-cooled, so the AC barely runs. By the time peak ends (7pm APS, 8pm SRP), the house has drifted up to your peak setpoint and the AC resumes normal cycling in the off-peak window.

On APS, the cheap pre-cool window is 10am-3pm super off-peak at $0.0935/kWh. On SRP, the cheap window is overnight off-peak (8pm-2pm next day). APS customers get a better deal because super off-peak overlaps with peak solar production hours — if you have rooftop solar, you're pre-cooling with your own free electricity.

Choosing Your Pre-Cool Strategy

The calculator presets cover three aggressiveness levels:

• No pre-cooling (78°F all day): Baseline. AC runs hardest during the most expensive hours. Most expensive strategy on TOU rates.
• Moderate (73°F → 79°F): Pre-cool to 73°F by the start of peak, allow drift to 79°F. Works well for average Phoenix-metro homes with decent insulation. 4-6°F of thermal coast.
• Aggressive (70°F → 82°F): Deep pre-cool to 70°F, allow drift to 82°F. Works for well-insulated masonry homes or anyone comfortable with a wider temperature swing. Can ride the entire peak window with the compressor nearly off.

If you're not sure which fits your home, start with moderate. Watch how fast the indoor temperature rises after pre-cool ends — if you're still under 78°F at the end of peak, you can go more aggressive next time.

Pre-Cooling on APS vs SRP

Both utilities reward pre-cooling, but the mechanics differ:

APS (Saver Choice Plus): The 4-7pm weekday peak is only 3 hours long, which makes pre-cooling easier — most homes can coast through. The 10am-3pm super off-peak window is also the cheapest electricity APS sells, so aggressive daytime pre-cooling is essentially free compared to peak. If you're reading this in April, the APS summer rate switch on May 1 makes pre-cooling even more important — peak energy jumps 60% vs winter.

SRP (E-27): The 2-8pm peak window is 6 hours, which is much harder to coast through. Most SRP homes pre-cool overnight (8pm-2pm next day) and accept some AC runtime during peak. The other SRP trick is demand charge management: SRP bills the highest 30-minute kW reading during peak at $14.50/kW in summer. Pre-cooling flattens that peak demand, often saving $30-60/month on the demand charge alone — on top of energy savings. See the SRP demand charge guide for the full math.

The Smart Thermostat Payback Case

Any programmable thermostat can execute a basic pre-cool schedule. But smart thermostats — ecobee Premium, Nest Learning Thermostat, Honeywell T10 — do three things that matter in Arizona:

1. Automatic TOU detection. The ecobee Premium recognizes APS and SRP rate schedules and suggests pre-cool times automatically. No manual scheduling.
2. Learn your home's thermal response. After a week or two, the thermostat knows how fast your house loses coolness and starts pre-cooling just deep enough to coast through peak — not more, not less.
3. Remote overrides. Coming home early? Having guests? Adjust from your phone without cancelling the whole schedule.

A $220 ecobee Premium typically pays for itself in under 6 months of summer pre-cooling savings in Arizona. APS also offers a Cool Rewards bill credit ($25-40/year) for enrolling a smart thermostat in their demand-response program, which further shortens payback.

How This Calculator Works

The calculator models your AC as a simple kW × duty-cycle × hours equation in each rate window:

1. AC running kW: Based on tonnage — 2-ton = 2.5 kW, 3-ton = 3.5 kW, 4-ton = 4.5 kW, 5-ton = 5.5 kW (SEER 14-16 single-stage central AC running in 110°F Phoenix-metro afternoon heat).
2. Peak-window duty cycle: The fraction of the peak window the compressor is actually running. Without pre-cooling, a 3-ton AC in 110°F heat runs about 75% of the time during peak. Moderate pre-cool drops that to ~25%. Aggressive pre-cool drops it to ~5%.
3. Pre-cool window duty cycle: Aggressive pre-cooling drives the compressor to 80-95% duty during the pre-cool window to bank the coolness.
4. Cost: (kW × duty × hours) × applicable rate. APS uses super off-peak ($0.0935/kWh) for the pre-cool window; SRP uses plain off-peak.
5. Savings: Your strategy's daily cost subtracted from the no-pre-cool baseline. Scaled to 22 weekdays × 6 summer months (pre-cooling matters less on weekends when no peak window applies on either utility).

Your actual savings will vary ±25% based on insulation, shade, window orientation, and how hot your specific summer runs. The calculator uses typical Phoenix-metro values.

Related Reading

Frequently Asked Questions

What is pre-cooling and does it really save money in Arizona?

Pre-cooling is running your AC harder during cheap off-peak hours to drive indoor temperature a few degrees below your comfort setpoint, then letting the home drift during expensive on-peak hours. Because APS peak energy costs 3.7x more than super off-peak, a typical Phoenix home saves about $31/month in summer — enough to pay off a $220 smart thermostat in 8 months.

What temperature should I pre-cool my house to?

Moderate strategy: 73°F during pre-cool, drift to 79°F during peak. Aggressive: 70°F → 82°F. Start moderate and watch how quickly the indoor temperature rises after pre-cool ends — that tells you how much thermal mass your home has and whether you can go deeper.

Does pre-cooling use more total energy?

Slightly — maybe 3-8% more kWh. But those extra kWh are at super off-peak rates ($0.0935 on APS) instead of peak ($0.3439). You're trading expensive kWh for cheap ones. The math wins by a wide margin in Arizona.

Do I need a smart thermostat to pre-cool?

No — any programmable thermostat can pre-cool. But a smart thermostat like the ecobee Premium auto-detects APS/SRP TOU windows and learns how fast your house coasts, so it pre-cools exactly the right amount. Typical Arizona payback is under 6 months from pre-cooling savings alone.