Estimate your evaporative cooler running cost from watts, use time, electricity price, and optional water or upkeep costs.
Advanced options
Table of contents
How to use our Evaporative Cooler Running Cost Calculator
- Enter Cooler power draw from the cooler label or manual. Use running watts, not starting watts.
- Enter Hours used per day and Days used in estimate for the period you want, such as 30 days for a rough month.
- Enter Electricity price from your bill in $ per kWh. Use your best flat average if your bill has several rates.
- Open Advanced options only if you want to include Water use, Water price, or Pad or upkeep cost for this estimate.
- Check Total electricity used and Total water used. If either looks far too high or low, recheck watts, hours, days, and gallons per hour before using the cost.
Definitions
Cooler power draw: The electric power the cooler uses while running, entered in watts.
Watt: A unit of electric power. A higher watt number means the cooler uses electricity faster while it runs [1].
Kilowatt-hour (kWh): A unit of electric energy used for electric bills. A 1,000 watt load running for 1 hour uses 1 kWh [1].
Electricity price: The cost of one kWh of electricity, entered as dollars per kWh.
Water use: The gallons of water the evaporative cooler uses per running hour.
Water price: The water cost entered as dollars per 1,000 gallons.
Pad or upkeep cost for this estimate: An optional extra cost, such as pads or cooler-only maintenance, added to the same time period as the estimate.
Common mistakes and quick fixes
Mistake: Entering amps in Cooler power draw instead of watts.
Fix: Use watts from the label, or multiply volts by amps before entering Cooler power draw .
Mistake: Using a full 24 hours in Hours used per day when the cooler only runs part of the day.
Fix: Enter the average running time for days you use it, not the whole day unless it truly runs all day.
Mistake: Mixing up Days used in estimate with a whole cooling season when you wanted a monthly estimate.
Fix: Use 30 for a rough month, or enter the actual number of days in the period you want.
Mistake: Typing a total monthly bill into Electricity price instead of the price per kWh.
Fix: Enter the energy price in $ per kWh, such as 0.15, not the total bill amount.
Mistake: Entering the water bill total in Water price when the input asks for $ per 1,000 gallons.
Fix: Use the billed rate per 1,000 gallons, and leave Water price at 0 if you do not want water cost counted.
Mistake: Adding a yearly pad cost to Pad or upkeep cost for this estimate while Days used in estimate covers only one month.
Fix: Enter only the upkeep amount you want included for the same period as Days used in estimate .
Limitations & Key Assumptions / Boundary Conditions
- The calculator uses one flat Electricity price. It does not model time-of-use rates, tiered rates, taxes, demand charges, or fixed utility fees.
- Cooler power draw is treated as constant for all running hours. Real coolers can use different power when fan speed, pump cycling, or controls change.
- Water use is treated as a steady gallons-per-hour amount. Actual water use can change with weather, bleed-off settings, pad condition, and cooler size.
- Pad or upkeep cost for this estimate is not estimated automatically. The calculator only adds the amount you enter.
- The estimate covers operating cost only. It does not include purchase price, installation, duct work, repairs not entered as upkeep, or any change in home comfort.
- Negative values are blocked because costs, days, hours, watts, and water use cannot be negative in this running-cost model.
Methodology
Calculation steps
The calculator first finds total running hours from the daily use time and the number of days.
running_hours = hours_per_day * days_used
It converts watts to kilowatts by dividing by 1,000, then multiplies by running hours to get electricity use. The kilo prefix means 1,000 [2].
kwh_used = (cooler_power_w / 1000) * running_hours
Electricity cost is the energy used times the entered electricity price.
electricity_cost = kwh_used * electricity_rate_per_kwh
Water use is calculated only from the entered gallons per hour and running hours.
water_gallons = water_use_gph * running_hours
Water cost uses the entered price per 1,000 gallons.
water_cost = (water_gallons / 1000) * water_price_per_1000_gal
The total adds electricity cost, water cost, and the optional pad or upkeep amount.
total_cost = electricity_cost + water_cost + upkeep_cost_for_estimate
The average daily and hourly costs divide that total by the entered time.
average_cost_per_day = total_cost / days_used
cost_per_running_hour = total_cost / running_hours
Mini-example
For a 500 W cooler used 8 hours per day for 30 days at $0.15 per kWh, running hours are 240. Electricity use is (500 / 1000) * 240 = 120 kWh, and electricity cost is 120 * 0.15 = $18.00. If water use is 4 gallons per hour, water price is $6 per 1,000 gallons, and upkeep is $25, water use is 960 gallons and water cost is (960 / 1000) * 6 = $5.76. Total running cost is $18.00 + $5.76 + $25.00 = $48.76.