How much does it cost to run a 500-gallon hot tub per month?

Data checked October 2026

Short answer

A 500-gallon hot tub that meets California's standby limit costs about $45.67 a month to keep at 102°F — $548 a year (3,013 kWh) at the U.S. average 18.19¢/kWh.

California Title 20 caps a hard-shell spa's standby power at 3.75 × V^(2/3) + 40 watts: 276 W for 500 gallons, measured covered with water at 102°F and normalized to a 37°F water–air gap.
Outdoors it peaks in January at $66.98 and falls to $27.21 in the warmest month (U.S. population-weighted normals).
Turning the water down 2°F to 100°F saves about $23.79 a year.
The inflatable limit for the same volume is 441 W — inflatable spas are allowed to lose more heat.
Soaks with the cover off add more. Industry estimates for a full year of use run 1,500–3,500 kWh; many tubs also test well under the legal cap, so enter your tub's listed standby watts for a closer figure.

Adjust it to your exact job

Your hot tub

Type

Fill volume

gal

On the spec sheet or the tub's California Energy Commission listing (filled to mid-skimmer).

Standby power

Title 20 caps how much a covered spa may draw just to stay hot. Many tubs test well under the cap.

Settings

Water temperature

°F

Location

Electricity rate

Where the tub is

Price per kWh

EIA's state average: total residential revenue ÷ kWh sold, so delivery and fixed monthly charges are spread over every kWh.

500-gallon hot tub costs

$45.67a month on average

3,013 kWh a year · January up to $66.98 · $1.50 a day

At 18.19¢/kWh — U.S. average, Jan–Aug 2026 (EIA).

Per year: $5483,013 kWh
Coldest month (Jan): $66.98air 36°F
Standby rating: 276Wat a 37°F water–air gap
Average draw: 344Win an average U.S. climate

Monthly cost outdoors in an average U.S. climate

Turn it down a notch

Yearly cost by water temperature
Water	Per year	vs 102°F
98°F	$500	−$47.59
100°F	$524	−$23.79
102°F	$548	—
104°F	$572	+$23.79

What this includes

Keeping the covered tub at temperature, with its default filtration cycles — the condition California tests. Soaks with the cover off and jets running add more on top; industry estimates for a full year of use run 1,500–3,500 kWh.

Using the legal maximum

276 W is the most a 500-gallon hard-shell spa sold in California may draw in standby. Enter your tub's listed rating for a closer figure.

How to cut it

Keep the cover on and replace it once it's waterlogged or sagging — the cover is part of the tested rating.
Heat loss grows with the gap between water and air: each degree lower saves roughly the share shown in the table.
Most of the year's cost lands in the coldest months — an enclosed or indoor tub sees a smaller gap; switch Location to compare.

Energy budget

3,013 kWh 500-gallon hot tub — keeping it hot for a yearcovered standby at 102°F, 18.19¢/kWh$548

Estimated total$548

Did this answer your question?

Compare

The same tub in colder and warmer states, at each state's Jan–Aug 2026 rate

State	¢/kWh	kWh a year	Per year	Coldest month
Minnesota	16.44	3,902	$642	$84.45
Colorado	16.8	3,698	$621	$71.82
New York	29.26	3,404	$996	$122.42
Ohio	18.81	3,358	$632	$79.07
Washington	14.42	3,372	$486	$52.30
Texas	16.03	2,303	$369	$47.85
California	32.58	2,730	$889	$95.10
Arizona	15.36	2,294	$352	$45.03
Florida	15.32	1,931	$296	$34.67

How this was worked out

500^(2/3) = 63; × 3.75 + 40 = 276 W at a 37°F gap. Heat loss through the cover and shell scales with the gap, so each month we multiply by (102°F − average outdoor temperature) ÷ 37 and by the hours in the month.

Prices: EIA average residential rates for Jan–Aug 2026. Outdoor temperatures: NOAA Climate Prediction Center population-weighted normals.

The full method, material data and tips are on the main hot tub cost calculator page.

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Sources

Data behind this answer

California Energy Commission — Title 20 portable electric spa standard (Docket 18-AAER-02) — max standby 3.75·V^(2/3)+40 W (standard spas), 7·V^(2/3) (inflatable), normalized to a 37°F water–air difference · checked October 2026
EIA Electric Power Monthly, Tables 5.6.A & 5.6.B — residential price by state (August 2026) — latest month and Jan–Aug 2026 year-to-date average for every state; preliminary, refreshed monthly · checked October 2026
NOAA Climate Prediction Center — population-weighted state degree days — monthly normal heating and cooling degree days by state (base 65°F) · checked October 2026
EIA Electric Power Monthly technical notes — average price = revenue ÷ sales, including fixed customer charges, fuel adjustments and surcharges · checked October 2026

Short answer

A 500-gallon hot tub that meets California's standby limit costs about $45.67 a month to keep at 102°F — $548 a year (3,013 kWh) at the U.S. average 18.19¢/kWh.

California Title 20 caps a hard-shell spa's standby power at 3.75 × V^(2/3) + 40 watts: 276 W for 500 gallons, measured covered with water at 102°F and normalized to a 37°F water–air gap.

Outdoors it peaks in January at $66.98 and falls to $27.21 in the warmest month (U.S. population-weighted normals).

Turning the water down 2°F to 100°F saves about $23.79 a year.

The inflatable limit for the same volume is 441 W — inflatable spas are allowed to lose more heat.

Soaks with the cover off add more. Industry estimates for a full year of use run 1,500–3,500 kWh; many tubs also test well under the legal cap, so enter your tub's listed standby watts for a closer figure.

Adjust it to your exact job

Your hot tub

Type

Fill volume

gal

On the spec sheet or the tub's California Energy Commission listing (filled to mid-skimmer).

Standby power

Title 20 caps how much a covered spa may draw just to stay hot. Many tubs test well under the cap.

Settings

Water temperature

°F

Location

Electricity rate

Where the tub is

Price per kWh

EIA's state average: total residential revenue ÷ kWh sold, so delivery and fixed monthly charges are spread over every kWh.

500-gallon hot tub costs

$45.67a month on average

3,013 kWh a year · January up to $66.98 · $1.50 a day

At 18.19¢/kWh — U.S. average, Jan–Aug 2026 (EIA).

Per year: $5483,013 kWh
Coldest month (Jan): $66.98air 36°F
Standby rating: 276Wat a 37°F water–air gap
Average draw: 344Win an average U.S. climate

Monthly cost outdoors in an average U.S. climate

Turn it down a notch

Yearly cost by water temperature
Water	Per year	vs 102°F
98°F	$500	−$47.59
100°F	$524	−$23.79
102°F	$548	—
104°F	$572	+$23.79

What this includes

Using the legal maximum

276 W is the most a 500-gallon hard-shell spa sold in California may draw in standby. Enter your tub's listed rating for a closer figure.

How to cut it

Keep the cover on and replace it once it's waterlogged or sagging — the cover is part of the tested rating.
Heat loss grows with the gap between water and air: each degree lower saves roughly the share shown in the table.
Most of the year's cost lands in the coldest months — an enclosed or indoor tub sees a smaller gap; switch Location to compare.

Energy budget

3,013 kWh 500-gallon hot tub — keeping it hot for a yearcovered standby at 102°F, 18.19¢/kWh$548

Estimated total$548

State

¢/kWh

kWh a year

Per year

Coldest month

Minnesota

16.44

3,902

$642

$84.45

Colorado

16.8

3,698

$621

$71.82

New York

29.26

3,404

$996

$122.42

Ohio

18.81

3,358

$632

$79.07

Washington

14.42

3,372

$486

$52.30

Texas

16.03

2,303

$369

$47.85

California

32.58

2,730

$889

$95.10

Arizona

15.36

2,294

$352

$45.03

Florida

15.32

1,931

$296

$34.67

How this was worked out

Prices: EIA average residential rates for Jan–Aug 2026. Outdoor temperatures: NOAA Climate Prediction Center population-weighted normals.

The full method, material data and tips are on the main hot tub cost calculator page.