For a full comparison framework and method-selection guide, see the Budget Methods hub.
For challenge frameworks, implementation plans, and realistic savings systems, see the Saving Challenges hub.
For a full comparison framework and method-selection guide, see the Budget Methods hub.
For challenge frameworks, implementation plans, and realistic savings systems, see the Saving Challenges hub.
Air conditioning is typically the single largest electricity cost in a home. Here’s exactly what it costs per hour and per month—and how to keep the bill down.
Quick Reference: AC Cost Per Hour
| AC Type | Wattage | Cost Per Hour* | Cost Per Day (8 hrs) |
|---|---|---|---|
| Central AC (2-ton) | 2,400W | $0.29 | $2.30 |
| Central AC (3-ton) | 3,000W | $0.36 | $2.88 |
| Central AC (4-ton) | 4,000W | $0.48 | $3.84 |
| Central AC (5-ton) | 5,000W | $0.60 | $4.80 |
| Window unit (5,000 BTU) | 500W | $0.06 | $0.48 |
| Window unit (10,000 BTU) | 1,200W | $0.14 | $1.15 |
| Window unit (15,000 BTU) | 1,500W | $0.18 | $1.44 |
| Mini-split (12,000 BTU) | 1,000W | $0.12 | $0.96 |
| Mini-split (18,000 BTU) | 1,500W | $0.18 | $1.44 |
| Portable AC | 1,400W | $0.17 | $1.34 |
*Assumes $0.12 per kWh (US average). Adjust for your local rate.
How to Calculate Your Exact Cost
The Formula
Cost per hour = (Watts ÷ 1,000) × electricity rate
Example: 3,000-watt central AC, $0.12/kWh electricity:
(3,000 ÷ 1,000) × $0.12 = $0.36 per hour
Adjust for Your Electricity Rate
| Electricity Rate | 3-ton Central AC (per hour) | Window Unit 10K BTU (per hour) |
|---|---|---|
| $0.08/kWh | $0.24 | $0.10 |
| $0.10/kWh | $0.30 | $0.12 |
| $0.12/kWh (avg) | $0.36 | $0.14 |
| $0.15/kWh | $0.45 | $0.18 |
| $0.20/kWh | $0.60 | $0.24 |
| $0.25/kWh (CA, NY) | $0.75 | $0.30 |
Check your electricity rate: Look at your electric bill—it shows cents per kWh. Divide your total bill by total kWh used.
Monthly AC Costs
Central AC Monthly Cost
| Usage Per Day | Monthly Cost* | Summer Season (3 months) |
|---|---|---|
| 4 hours | $43 | $130 |
| 6 hours | $65 | $194 |
| 8 hours | $86 | $259 |
| 10 hours | $108 | $324 |
| 12 hours | $130 | $389 |
| All day (24 hrs) | $259 | $778 |
*3-ton central AC at $0.12/kWh
Window Unit Monthly Cost (10,000 BTU)
| Usage Per Day | Monthly Cost* | Summer Season (3 months) |
|---|---|---|
| 4 hours | $17 | $51 |
| 6 hours | $25 | $76 |
| 8 hours | $34 | $101 |
| 10 hours | $43 | $130 |
| 12 hours | $51 | $152 |
*At $0.12/kWh
What Affects Your AC Cost
1. Unit Size and BTU Rating
Bigger homes need bigger AC units. Bigger units use more electricity.
| Home Size | Recommended Central AC | Monthly Cost (8 hrs/day)* |
|---|---|---|
| 700-1,000 sq ft | 1.5-2 ton | $58-$72 |
| 1,000-1,500 sq ft | 2-2.5 ton | $72-$86 |
| 1,500-2,000 sq ft | 2.5-3 ton | $86-$108 |
| 2,000-2,500 sq ft | 3.5-4 ton | $108-$144 |
| 2,500-3,500 sq ft | 4-5 ton | $144-$180 |
*At $0.12/kWh
2. SEER Rating (Efficiency)
SEER = Seasonal Energy Efficiency Ratio. Higher SEER = cheaper to run.
| SEER Rating | Description | Relative Cost |
|---|---|---|
| 13-15 | Minimum legal (new units) | Baseline |
| 16-18 | Above average | ~15% less than 14 SEER |
| 19-21 | High efficiency | ~25% less |
| 22-26 | Ultra-high efficiency | ~35% less |
Example: Upgrading from SEER 14 to SEER 18 saves ~$130/year on a typical central AC system.
3. Thermostat Setting
| Setting | Effect on Cost |
|---|---|
| Every 1°F lower | +3% on cooling bill |
| 78°F vs 72°F | Save ~18% |
| 80°F vs 72°F | Save ~24% |
| Thermostat Setting | Monthly Cost* | Savings vs 72°F |
|---|---|---|
| 72°F | $107 | — |
| 74°F | $101 | $6 |
| 76°F | $95 | $12 |
| 78°F | $88 | $19 |
| 80°F | $81 | $26 |
*3-ton central AC, 8 hours/day
4. Home Insulation Quality
| Insulation | Effect |
|---|---|
| Poor insulation | AC runs 30-50% more |
| Air leaks | Can add 15-25% to costs |
| Single-pane windows | ~30% more heat gain |
| Double-pane windows | Significantly lower cooling load |
Central AC vs. Window Unit: Which Is Cheaper?
Upfront Cost
| Type | Purchase Price | Installation |
|---|---|---|
| Central AC | $3,000-$7,000 | $2,000-$5,000 (included) |
| Window unit | $150-$600 | DIY ($0) |
| Mini-split | $700-$2,000 | $500-$2,000 |
| Portable AC | $300-$700 | None needed |
Operating Cost Comparison
| Type | Monthly Cost (cooling 1 room)* |
|---|---|
| Central AC | $86 (whole house) |
| Window unit | $34 (1 room) |
| Mini-split | $26 (1 room) |
| Portable AC | $51 (1 room) |
*If you only need to cool one room, a window unit costs far less than central AC.
Efficiency vs. Access
| Situation | Best Choice |
|---|---|
| Cool whole house daily | Central AC |
| Cool 1-2 rooms only | Window unit or mini-split |
| Renters who can’t install | Portable AC |
| Supplement central AC | Window unit in bedroom |
How to Lower Your AC Bill
Immediate Changes (Free)
| Action | Estimated Savings |
|---|---|
| Raise thermostat 2°F | ~6% |
| Use ceiling fans (feel 4°F cooler) | Up to 15% |
| Close blinds/curtains during day | 5-10% |
| Turn AC to 85°F when away | 10-15% |
| Clean AC filter | 5-15% |
Low-Cost Changes ($20-$200)
| Action | Cost | Savings | Payback |
|---|---|---|---|
| Programmable thermostat | $25-$100 | ~$100/year | 3-12 months |
| Weatherstrip doors | $20-$50 | $50-$150/year | 4-12 months |
| Caulk window gaps | $10-$30 | $50-$100/year | A few months |
| Window film (south windows) | $30-$80 | $50-$150/year | 6-18 months |
| Attic insulation | $300-$1,000 | $150-$400/year | 2-4 years |
Larger Investments
| Action | Cost | Savings | Payback |
|---|---|---|---|
| Smart thermostat | $100-$250 | $75-$150/year | 1-3 years |
| Upgrade to high-SEER unit | $3,000-$7,000 | $150-$400/year | 10-20 years |
| Add attic insulation | $1,000-$3,000 | $200-$500/year | 4-8 years |
AC Cost by State
Electricity rates and climate vary dramatically.
| State | Avg Rate (¢/kWh) | Cooling Days/Year | Typical Summer AC Bill |
|---|---|---|---|
| California | 25¢ | 80 days | $400-$600 |
| New York | 23¢ | 50 days | $300-$450 |
| Texas | 12¢ | 130 days | $300-$500 |
| Florida | 12¢ | 150 days | $350-$550 |
| Arizona | 13¢ | 160 days | $400-$600 |
| Illinois | 13¢ | 60 days | $150-$250 |
| Washington | 10¢ | 20 days | $50-$100 |
Frequently Asked Questions
How much does it cost to run AC all night?
8 hours overnight: Central AC (3-ton) ≈ $2.88, window unit (10K BTU) ≈ $1.15. Monthly for all night every night: central AC ≈ $86, window unit ≈ $34.
Is it cheaper to run AC all day or turn it off?
If away 8+ hours, the DOE says raising the temperature 7-10°F while away (vs. turning off completely) saves ~10%. Turning off completely and restarting takes about the same energy as maintaining a higher temperature. A programmable thermostat handles this automatically.
Does AC use more electricity going up vs. maintaining temperature?
Maintaining a cool temperature uses less total energy than letting the house heat up and cooling it back down. But maintaining a comfortable temperature all day costs more than raising it while you’re away.
How do I find my central AC wattage?
Check the yellow EnergyGuide label on your unit. The SEER rating and BTU capacity let you estimate wattage: Watts = BTU ÷ SEER. A 36,000 BTU (3-ton) unit at 16 SEER = 2,250 watts.
Related Guides
Central AC costs about $0.36 per hour for a typical home—roughly $86/month if you run it 8 hours a day. Window units cost far less per room but only cool one area. The single biggest lever: raise the thermostat 2-3°F and use ceiling fans. These two changes alone can cut your AC bill by 10-15% with zero sacrifice in comfort.
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