Compare evaporative cooler and AC season costs using your power, runtime, electric price, water use, and upkeep numbers.
Advanced options
Table of contents
How to use our Evaporative Cooler vs AC Cost Calculator
- Enter Evaporative cooler power and AC power in kW, using running power from the appliance label when possible.
- Enter Cooling time, Electricity price, and Cooling season length for the season you want to compare.
- Open Advanced options if you want to include Evaporative cooler water use, Water price, Evaporative cooler upkeep, or AC upkeep.
- Choose the Number display style you prefer, then select Calculate.
- Sanity-check the result: if Cooling time is over your real daily use, or if either power value is peak startup power instead of running power, the season costs can be too high.
Definitions
kW: Kilowatt, a measure of power. One kW equals 1,000 watts.
kWh: Kilowatt-hour, the energy used by running 1 kW for 1 hour. Electric bills commonly charge by kWh [1].
Electricity price: The cost for each kWh of electricity, written as $ per kWh.
Cooling season length: The number of days in the season when you expect to use cooling.
Evaporative cooler water use: The gallons of water the evaporative cooler uses each hour while running.
Upkeep: Seasonal costs you choose to include, such as pads, filters, cleaning parts, or service.
Evaporative cooler savings this season: AC season cost minus evaporative cooler season cost. Positive means the evaporative cooler costs less.
Common mistakes and quick fixes
Mistake: Entering watts in Evaporative cooler power or AC power even though the input needs kW.
Fix: Divide running watts by 1,000 first, so 600 watts becomes 0.6 kW.
Mistake: Using startup watts for AC power .
Fix: Use running power from the label or meter because startup power lasts only a short time.
Mistake: Putting a monthly bill total into Electricity price .
Fix: Enter the price per kWh from your bill, such as 0.18, not the full bill amount.
Mistake: Entering more than 24 in Cooling time .
Fix: Enter the average hours per day the cooling system actually runs, with 24 as the maximum.
Mistake: Leaving Evaporative cooler water use or Water price at a value you do not want counted.
Fix: Enter 0 for either water input if you want an electricity-only comparison.
Mistake: Treating Evaporative cooler savings this season as installation payback.
Fix: Use it as an operating-cost comparison only; installation, replacement, and unentered repairs are not included.
Limitations & Key Assumptions / Boundary Conditions
- The calculator compares operating costs for the same Cooling time and Cooling season length. It does not decide whether both systems cool the home equally well.
- Evaporative coolers work differently from regular AC and are most affected by outdoor conditions and ventilation needs [2]. Comfort can differ even when the cost looks lower.
- Power values are treated as steady running power. Variable-speed equipment, cycling, thermostat settings, and duct losses can make real use higher or lower.
- Water cost uses only Evaporative cooler water use and Water price. Sewer charges, tiered water rates, and local drought fees are not added unless you include them in the water price.
- Upkeep costs are user-entered. The calculator does not estimate installation, replacement, rebates, repair risk, home size, or equipment life.
- A negative Evaporative cooler savings this season is allowed. It means the AC is cheaper for the values you entered.
Methodology
Cost math
The calculator first finds electricity use from power and runtime. Power in kW times hours gives kWh, and kWh times the electricity price gives cost [1].
evap_electric_cost = evap_power_kw * cooling_hours_per_day * cooling_days * electricity_rate
ac_electric_cost = ac_power_kw * cooling_hours_per_day * cooling_days * electricity_rate
Water cost is added only to the evaporative cooler side.
evap_water_cost = evap_water_gal_per_hour * cooling_hours_per_day * cooling_days * water_rate_per_1000_gal / 1000
Season costs add the electricity cost, water cost where used, and the upkeep amounts you entered.
evaporative_season_cost = evap_electric_cost + evap_water_cost + evap_maintenance_per_season
ac_season_cost = ac_electric_cost + ac_maintenance_per_season
The main savings result keeps its sign instead of forcing negative values to zero.
seasonal_evap_savings = ac_season_cost - evaporative_season_cost
daily_electric_savings = (ac_power_kw - evap_power_kw) * cooling_hours_per_day * electricity_rate
upkeep_cost_gap = ac_maintenance_per_season - evap_maintenance_per_season
Mini example
With an evaporative cooler at 0.6 kW, an AC at 3.5 kW, 8 cooling hours per day, 120 cooling days, and electricity at $0.18 per kWh, the evaporative cooler electricity cost is 0.6 * 8 * 120 * 0.18 = $103.68. The AC electricity cost is 3.5 * 8 * 120 * 0.18 = $604.80. If water use is 4 gallons per hour at $6 per 1,000 gallons, water cost is $23.04. Adding $80 evaporative cooler upkeep and $100 AC upkeep gives an evaporative cooler season cost of $206.72 and an AC season cost of $704.80, so savings are $498.08 for the season.
Rounding and choices
Money outputs are rounded for display, but the comparison is calculated from the unrounded values. If the two displayed season costs are equal, the cheaper option is shown as a tie.