TryBuildCalcAir Conditioner Running Cost Calculator (Central & Window A/C Cost Estimate)
Calculate your A/C running cost.
🕒 Last updated: August 28, 2026
Inputs
Equipment
Pick a preset for a typical starting point, or choose Custom and enter your equipment's actual nameplate watts and usage pattern.
Equipment 1
ℹ️For equipment that draws a small amount of power even when off but still plugged in.
Electricity Rate
ℹ️Found on your utility bill — sometimes called the energy charge or price per unit (1 unit = 1 kWh).
ℹ️A fixed monthly fee your utility charges regardless of usage — include it for a full bill estimate, leave blank to see energy cost only.
Estimated Monthly Cost: $109.58
From 730.50 kWh/month at $0.1500/kWh
Cost by Period (Energy Only)
| Period | kWh | Cost |
|---|---|---|
| Day | 24.00 | $3.60 |
| Week | 168.00 | $25.20 |
| Month | 730.50 | $109.58 |
| Year | 8,766.00 | $1,314.90 |
Equipment Breakdown (Monthly)
| Equipment | kWh | Cost | Share |
|---|---|---|---|
| Central A/C (3-ton) | 730.50 | $109.58 | 100.0% |
Assumptions Used
Month = 30.4375 days (365.25 ÷ 12) average, year = 365.25 days — avoids a lumpy figure tied to any one calendar month. Uses a flat electricity rate, not tiered or time-of-use pricing. This is a reference estimate — confirm against your actual utility bill and rate structure.
Planning backup power instead of running cost? UPS Battery Capacity Calculator →
Sizing a generator for this same equipment list instead? Generator Size Calculator →
Looking for the verification checklist, reference tables, tips, or common mistakes?See the complete Electricity Running Cost Calculator.
Air conditioner running cost
Air conditioning is one of the largest single contributors to a summer electricity bill in most homes — this page is pre-set to a common central A/C unit running 8 hours a day.
Edit the wattage and hours to match your specific unit and climate; window/portable A/C units use significantly less than central systems.
- Central A/C units commonly draw 2,500-4,000W; window units commonly draw 900-1,500W.
- Running hours vary hugely by climate and season — adjust hours/day and days/week to your actual usage pattern.
- Compare a higher-efficiency unit's lower wattage against this same usage pattern to estimate potential savings.
Running Cost Formula: How Is It Calculated?
The core formula converts power (watts) and time (hours) into energy (kilowatt-hours), then applies your electricity rate.
Step 1 — Weekly Active Energy
Active kWh/week = (Watts × Quantity × Hours/Day × Days/Week) ÷ 1,000
This is the energy consumed while the equipment is actively running.
Step 2 — Weekly Standby Energy (Optional)
Standby Hours/Week = (24 × 7) − (Hours/Day × Days/Week)
Standby kWh/week = (Standby Watts × Quantity × Standby Hours/Week) ÷ 1,000
For equipment left plugged in, this adds the phantom-load energy consumed during all the hours it's not actively running.
Step 3 — Cost by Period
Weekly Cost = (Active kWh + Standby kWh) × Rate per kWh
Daily = Weekly ÷ 7, Monthly = Daily × 30.4375, Yearly = Daily × 365.25
Every equipment row's cost is summed together, and an optional monthly service charge is added on top to estimate a full bill.
Worked Example
This example walks through your current inputs above, using the same steps as the Formula section.
Input Values Used
| Input | Value | Why it is used |
|---|---|---|
| Equipment | 1 items | Sets total energy consumption |
| Rate | $0.1500/kWh | Converts kWh to cost |
| Service Charge | None | Adds a fixed fee to the total bill estimate |
Step 1 — Weekly Energy per Equipment
Each row's active-hours energy is (Watts × Quantity × Hours/Day × Days/Week) ÷ 1,000. Any standby watts add energy for the remaining hours in the week (168 total).
| Equipment | Active Calculation | Standby Calculation | Weekly kWh |
|---|---|---|---|
| Central A/C (3-ton) | 3000W × 1 × 8h × 7d ÷ 1000 = 168.00 kWh | — | 168.00 |
Step 2 — Total Energy by Period
Every row's weekly kWh is summed, then converted: Daily = Weekly ÷ 7, Monthly = Daily × 30.4375, Yearly = Daily × 365.25.
| Period | Calculation | Total kWh |
|---|---|---|
| Week | 168.00 | 168.00 |
| Day | 168.00 ÷ 7 | 24.00 |
| Month | 24.00 × 30.4375 | 730.50 |
| Year | 24.00 × 365.25 | 8,766.00 |
Step 3 — Cost by Period
Each period's total kWh is multiplied by your electricity rate ($0.1500/kWh).
| Period | Calculation | Energy Cost |
|---|---|---|
| Day | 24.00 × $0.1500 | $3.60 |
| Month | 730.50 × $0.1500 | $109.58 |
| Year | 8,766.00 × $0.1500 | $1,314.90 |
Therefore, at $0.1500/kWh, your equipment costs approximately $109.58 per month ($1,314.90 per year) to run.
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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.