Hot Tub Electricity Cost Calculator

Related Calculators

Table of contents

• How to use
• Common mistakes
• Definitions
• Methodology
• Limitations & assumptions
• Sources

kW (kilowatt): A measure of electrical power, or how fast equipment uses electricity.

kWh (kilowatt-hour): A measure of energy. Using 1 kW for 1 hour uses 1 kWh.

Electricity rate: The price charged for each kWh of electricity, shown here as $ per kWh.

Heater running time: The percent of a 24-hour day when the heater is actually on. This is also called a duty cycle.

Average monthly cost: A planning estimate based on 365 days divided by 12, so it is not the cost for a specific calendar month.

Mistake: Entering the total utility bill as the Electricity rate.
Fix: Enter only the energy price in $ per kWh from the bill.

Mistake: Treating Heater running time as hours instead of percent of each day.
Fix: Enter 25 for a heater that runs about one-quarter of a day, or about 6 hours total.

Mistake: Using watts in Hot tub power or Heater power when the label asks for kW.
Fix: Divide watts by 1,000 first; 4,000 watts is 4 kW.

Mistake: Entering more than 24 for Power-on time each day or Pump run time each day.
Fix: Use an average from 0 through 24 hours per day.

Mistake: Filling only Lower heater running time or only Higher heater running time.
Fix: Fill in both fields to calculate a range, or clear both and use the main estimate.

Mistake: Making Lower heater running time greater than Higher heater running time.
Fix: Make the lower percent no greater than the higher percent.

• The estimate uses the power, daily runtime, and electricity rate you enter. It does not measure your hot tub directly.
• The realistic style treats heater cycling and pump runtime as separate inputs, but it does not calculate heat loss from outdoor temperature, water temperature, insulation, cover condition, wind, or how often the cover is opened.
• Actual heater runtime can change by season and use, so a single Heater running time may not match every month.
• The cost estimate uses one Electricity rate. It does not include time-of-use pricing, tiered rates, fixed utility charges, taxes, or credits unless they are already included in the rate you enter.
• Yearly cost uses 365 days. Monthly cost uses an average month of 365 divided by 12 days; real months have different numbers of days.
• Pump power should describe the pump covered by the Pump run time each day entry. Other loads, such as lights or a separate circulation pump, are not included unless you include them in your entered power.

Calculation method

The quick style multiplies one entered power draw by its daily power-on time. The realistic style estimates heater energy from its power and running-time percent, then adds scheduled pump energy.

Quick daily energy (kWh per day) = Hot tub power (kW) x Power-on time each day (hours)

Heater electricity used each day = Heater power (kW) x (Heater running time / 100) x 24

Pump electricity used each day = Pump power (kW) x Pump run time each day (hours)

Estimated electricity used each day = Heater electricity used each day + Pump electricity used each day

Estimated average monthly electricity cost = Estimated electricity used each day x (365 / 12) x Electricity rate

Estimated yearly electricity cost = Estimated electricity used each day x 365 x Electricity rate

Worked example

With 4 kW of heater power, a 25 percent Heater running time, a 1.5 kW pump running 2 hours each day, and an Electricity rate of $0.15 per kWh, heater use is 4 x 0.25 x 24 = 24 kWh per day. Pump use is 1.5 x 2 = 3 kWh per day. The combined daily estimate is 27 kWh, and the average monthly cost is 27 x (365 / 12) x $0.15 = $123.19.

Optional cost range

When both optional heater-time fields are filled in, the calculator repeats the realistic calculation using each entered percent. The pump energy stays the same, so the range changes only the heater portion.

Range monthly cost = [Heater power x (entered range heater time / 100) x 24 + Pump electricity used each day] x (365 / 12) x Electricity rate