Does a Pool Use More Water Than a Lawn? Pool vs Lawn Water Use in 25 US Cities

Does a pool use more water than a lawn, city by city

Per 1,000 sq ft, an uncovered pool and a sprinkler-watered lawn lose water at similar rates, because open water and well-watered grass respond to the same sun, heat and wind. The pool comes out lower than cool-season grass in 22 of 25 cities and close to warm-season grass in most.

The pool figures come from the PC&S evaporation model in our pool evaporation report: NOAA Class A pan evaporation for 1956 to 1970 multiplied by the NOAA TR 33 pan coefficient of 0.7, then reduced by NOAA 1991-2020 normal monthly rainfall. The lawn figures use gridMET grass reference evapotranspiration (ETo) for 1991 to 2020 at the same weather stations, the monthly UC ANR turf crop coefficients (annual averages 0.80 for cool-season and 0.60 for warm-season grass), the same monthly rainfall, and the California MWELO sprinkler efficiency of 0.75.

A result is labelled ‘Pool uses more’ or ‘Lawn uses more’ only when the gap exceeds 10% both with full monthly rain credit and with no rain credit. On that test, the pool exceeds a warm-season lawn’s water use only in Las Vegas (1.17 after rain) and Phoenix (1.23), and the lawn uses more in Fresno (0.89) and Riverside (0.87).

Why rainfall decides the pool vs lawn answer in humid cities

In dry cities the comparison barely moves with rainfall, but in humid cities both the pool and the lawn need little added water and the ratio swings. The rain treatment matters more than any other choice in the model.

Houston gets 51.84 inches of normal rain a year (NOAA 1991-2020), which offsets most of the pool’s 47.4 inches of evaporation and leaves 3.3 inches to top up. A warm-season lawn in Houston needs 3.1 inches of sprinkler water on the same monthly basis, so the two come to 2,057 and 1,932 gallons per 1,000 sq ft per year.

The monthly method treats every inch of rain as useful. A daily soil water balance by UF/IFAS (1980-2009) puts lawn net irrigation needs at 23.6 inches a year in Orlando and 27.6 in Tampa, far above this model’s monthly estimates of 4.8 and 7.2 inches for warm-season grass. Using the IFAS needs instead, the pool uses 0.29 times the lawn’s water in Orlando and 0.31 times in Tampa.

Pool vs lawn water use for the same backyard footprint

A backyard pool comes with a deck or coping, and that paved area needs no irrigation water. With a deck ring 2 ft wide, the pool plus deck uses no more water than a warm-season lawn of the same footprint in 22 of 24 cities modelled.

In Phoenix, a 15 x 30 ft pool loses 18,963 gallons a year after rain, the same as a 555 sq ft warm-season lawn. A deck ring 1.1 ft wide brings the pool and deck footprint to that size. In the 11 arid cities, no city needs a deck ring wider than 1.1 ft, and 22 of 24 cities need 2 ft or less.

How pool covers and grass type change the comparison

A pool cover changes the answer more than anything else a homeowner controls. Grass type matters too: in Phoenix a warm-season lawn needs 34,159 gallons per 1,000 sq ft per year against 43,945 for cool-season grass.

In Las Vegas, a cover that cuts evaporation by 50% brings the pool from 49,493 to 23,437 gallons per 1,000 sq ft per year, and a solid cover cutting 90% (EPA: more than 90%) brings it to 3,225. A warm-season lawn in Las Vegas still needs 42,137.

UC ANR reports that cool-season grass survives with brown patches at about 60% of ETo and warm-season grass gives minimal cover at about 40%. At those levels a Las Vegas lawn needs 36,777 (cool-season) or 23,313 (warm-season) gallons per 1,000 sq ft per year, less than the uncovered pool.

How the pool vs lawn model compares with official water agency figures

Official ETo and turf figures from California, Arizona, Florida and Southern Nevada broadly agree with the model in dry cities, and suggest the model is generous to lawns in Florida. No official figure reverses the main reading.

gridMET reads higher than the official California ETo table in all 5 California cities, from 0.4% in Los Angeles to 13.9% in Fresno. A 2026 EarthArXiv preprint found gridMET overestimates ETo by 10% to 20% at most irrigated cropland stations, with pockets of underestimation in the arid West.

If gridMET ETo is 15% too high everywhere, the pool would exceed a warm-season lawn by more than 10% in 20 cities on the rain-credited basis, mostly humid cities where both figures are a few thousand gallons or less. Against cool-season grass the pool would exceed the lawn in only 3.

Pool and lawn water rules in 2025 and 2026

Most of the rules cited below target nonfunctional grass and lawn watering days. The pool rule is Southern Nevada’s size cap on new residential pools.

Fill and refill restrictions on pools in drought stages are tracked city by city in our cost to fill a pool report. Swim-season length by city, which affects how long a cover can stay on, is in our pool season length report.

Scenarios we modeled

Download the calculation sheet (CSV)

What the comparison shows

• In a PC&S model of 25 US cities (1991 to 2020 climate), an uncovered pool used less water per square foot than a sprinkler-watered cool-season lawn in 22 cities and about the same in Las Vegas and Phoenix, using NOAA pan data and UC ANR turf coefficients.
• Against warm-season grass such as bermudagrass, the pool used more in 2 cities (Las Vegas and Phoenix), less in 2 (Fresno and Riverside), about the same in 7, and the answer depended on how rain is counted in 13.
• In Las Vegas, an uncovered pool loses 49,493 gallons per 1,000 sq ft per year after rain, against 53,170 for a cool-season lawn and 42,137 for a warm-season lawn (1991 to 2020 climate).
• The Southern Nevada Water Authority puts average pool evaporation at 48.6 gallons per square foot per year, while its Water Smart Landscapes program projects 55.0 gallons saved per square foot of grass replaced (2026 pages).
• A cover that cuts evaporation by 50%, the top of the DOE 30% to 50% range, puts the pool at least 10% below a warm-season lawn in 24 of 24 cities with any modelled water need.
• Per footprint, a 15 x 30 ft pool plus a deck ring at least 1.1 ft wide uses no more water than a warm-season lawn of the same footprint in all 11 arid cities in the model.
• Low-water plants on drip irrigation need far less than either: a pool uses 2.5 to 12.1 times as much water as a planting at the top of the California MWELO low-water range in the 11 arid cities.

Results

1. Las Vegas: an uncovered pool loses 49,493 gallons per 1,000 sq ft per year after normal rain, vs 53,170 for a sprinkler-watered cool-season lawn (PC&S model; NOAA 1956-1970 pan data, gridMET 1991-2020 ETo).
2. Phoenix: pool 42,137 gallons per 1,000 sq ft per year vs 43,945 for a cool-season lawn and 34,159 for a warm-season lawn (1991-2020 climate, PC&S model).
3. Phoenix: University of Arizona AZMET data put acceptable-quality lawn water use at 49.9 inches a year (1987-2000), while modelled pool evaporation is 74.8 inches, a ratio of 1.5 before sprinkler losses.
4. Fresno: pool 27,177 gallons per 1,000 sq ft per year vs 30,481 for a warm-season lawn, one of 2 cities where the pool uses at least 10% less than warm-season grass on both rain bases (1991-2020, PC&S model).
5. Los Angeles: pool 21,256 vs warm-season lawn 21,006 gallons per 1,000 sq ft per year, a ratio of 1.01 (1991-2020, PC&S model).
6. Dallas: pool 11,781 vs cool-season lawn 18,451 gallons per 1,000 sq ft per year after rain (1991-2020 NOAA normals, PC&S model).
7. Atlanta: normal rainfall of 50.43 inches a year (NOAA 1991-2020) leaves an uncovered pool needing 1,621 gallons per 1,000 sq ft per year, against 6,794 for a cool-season lawn (PC&S model).
8. Across the 11 arid cities (under 20 inches of rain, NOAA 1991-2020), the median pool loses 24,746 gallons per 1,000 sq ft per year, vs medians of 36,403 for cool-season and 28,424 for warm-season lawns (PC&S model).
9. Across the 9 humid cities (40 inches of rain or more), the medians are 2,057 gallons per 1,000 sq ft per year for a pool, 6,794 for a cool-season lawn and 1,932 for a warm-season lawn (PC&S model, 1991-2020).
10. Southern Nevada: average pool evaporation is 48.6 gallons per square foot per year (SNWA), and SNWA projects 825,000 gallons a year saved for an average 15,000 sq ft grass conversion (SNWA), or 55.0 gallons per square foot.
11. United States: a pool cover can prevent up to 95% of evaporation (EPA WaterSense), but only 15% of pool owners have and regularly use one (EPA, citing the 2016 Residential End Uses of Water study).
12. California: swapping gridMET ETo for the official MWELO Appendix C values (Spatial CIMIS 2004-2021) gives pool to lawn ratios of 0.91 to 1.04 for warm-season grass and 0.72 to 0.8 for cool-season grass in the 5 California cities.
13. Florida: UF/IFAS daily soil water balances (1980-2009) put lawn net irrigation needs at 23.6 inches a year in Orlando, 27.6 in Tampa and 37.6 in Miami, several times the monthly-normal estimates in this model.
14. United States: residential outdoor water use is nearly 8 billion gallons a day, mainly for landscape irrigation (EPA WaterSense).

Questions owners ask

Prices and rules used

• 2026-04City of Tampa: once-per-week lawn watering, now limited to before 4 a.m. or after 8 p.m., effective April 3, 2026.
• 2026-03Denver Water declared a Stage 1 drought on March 25, 2026, limiting single-family lawns to 2 watering days a week, with drought pricing through April 30, 2027.
• 2026-01Colorado SB24-005: on and after January 1, 2026, local governments may not allow new nonfunctional turf on commercial, institutional, industrial or common-interest property.
• 2025-09Austin Water moved to Conservation Stage restrictions on September 2, 2025, keeping once-per-week automatic irrigation.
• 2025-01California’s MWELO Appendix C ETo table was replaced, operative January 2, 2025, with Spatial CIMIS averages for 2004 to 2021.
• 2027-01Coming: Nevada’s ban on Colorado River water for nonfunctional grass (SNWA) and the first phase of California’s AB 1572 potable-water turf ban both start January 1, 2027; neither covers single-family yards.

More questions

Evidence tiers

Tier 1: primary and government sources (32)

• NOAA National Weather Service: NOAA Technical Report NWS 33
• NOAA National Weather Service: NOAA Technical Report NWS 34, monthly Class A pan tables
• NOAA National Centers for Environmental Information: U.S. Climate Normals product page
• Climatology Lab (Abatzoglou), University of California Merced: gridMET dataset description
• UC ANR Center for Landscape & Urban Horticulture: Turfgrass Crop Coefficients (Kc), Table 1
• University of Arizona Cooperative Extension: AZ1195 Converting Reference Evapotranspiration into Turf Water Use
• University of Arizona Cooperative Extension (AZMET): AZ1314 Turfgrass Consumptive Use Values for the Phoenix Area
• University of Arizona Cooperative Extension (AZMET): AZ1313 Turfgrass Consumptive Use Values for the Tucson Area
• California Department of Water Resources (via Cornell LII): Cal. Code Regs. tit. 23, sec. 490.2 (MWELO definitions)
• California Department of Water Resources (via Cornell LII): Cal. Code Regs. tit. 23, ch. 2.7, Appendix A (MWELO worksheet)
• California Department of Water Resources (via Cornell LII): Cal. Code Regs. tit. 23, ch. 2.7, Appendix C (Reference Evapotranspiration Table)
• University of Florida IFAS Extension: AE481 Net Irrigation Requirements for Florida Turfgrass Lawns: Part 2, Table 3
• University of Florida IFAS Extension: AE482 Net Irrigation Requirements for Florida Turfgrass Lawns: Part 3, Table 3
• Southern Nevada Water Authority: Pools and spas
• Southern Nevada Water Authority: Understand laws and ordinances
• Southern Nevada Water Authority: Water Smart Landscapes Rebate
• U.S. Environmental Protection Agency: WaterSense: Pool Water Efficiency
• U.S. Environmental Protection Agency: WaterSense: Making a Splash, Pool Water Efficiency guide
• U.S. Environmental Protection Agency: WaterSense: Outdoors
• U.S. Department of Energy: Energy Saver: Swimming Pool Covers (archived 2025-01-10; live page now 404)
• Town of Flower Mound, Texas: Pool Evaporation
• Denver Water: Stage 1 drought declaration
• Austin Water (City of Austin): Austin Water drought response
• City of Tampa Water Department: My Allowed Watering Days and Hours
• San Antonio Water System: SAWS customers return to Stage 3 watering rules
• Dallas Water Utilities (City of Dallas): Frequently asked questions
• Fort Worth Water (City of Fort Worth): Twice-a-Week SmartWatering
• Los Angeles Department of Water and Power: Water Conservation Ordinance
• California Legislature: AB-1572 Potable water: nonfunctional turf (Chapter 849, Statutes of 2023)
• Colorado General Assembly: SB24-005 Prohibit Landscaping Practices for Water Conservation
• University of Idaho Northwest Knowledge Network / Climatology Lab: gridMET daily reference ET (grass), THREDDS data catalog
• NOAA National Centers for Environmental Information: U.S. Climate Normals 1991-2020, monthly station files (example: Las Vegas)

Tier 2: trade bodies, public companies, market research (2)

• EarthArXiv preprint (OpenET team): Assessing and Correcting Bias in Gridded Reference Evapotranspiration over Agricultural Lands Across the Contiguous United States (preprint)
• Arizona Municipal Water Users Association: How Does Your Water Use Stack Up?

Tier 3: journalism and expert commentary (1)

• Stanford Magazine: Watering a Lawn vs. Putting in a Pool: Essential Answer

References

1. NOAA National Weather Service. NOAA Technical Report NWS 33. Accessed 2026-10-07.
2. NOAA National Weather Service. NOAA Technical Report NWS 34, monthly Class A pan tables. Accessed 2026-10-07.
3. NOAA National Centers for Environmental Information. U.S. Climate Normals product page. Accessed 2026-10-07.
4. Climatology Lab (Abatzoglou), University of California Merced. gridMET dataset description. Accessed 2026-10-07.
5. EarthArXiv preprint (OpenET team). Assessing and Correcting Bias in Gridded Reference Evapotranspiration over Agricultural Lands Across the Contiguous United States (preprint). Accessed 2026-10-07.
6. UC ANR Center for Landscape & Urban Horticulture. Turfgrass Crop Coefficients (Kc), Table 1. Accessed 2026-10-07.
7. University of Arizona Cooperative Extension. AZ1195 Converting Reference Evapotranspiration into Turf Water Use. Accessed 2026-10-07.
8. University of Arizona Cooperative Extension (AZMET). AZ1314 Turfgrass Consumptive Use Values for the Phoenix Area. Accessed 2026-10-07.
9. University of Arizona Cooperative Extension (AZMET). AZ1313 Turfgrass Consumptive Use Values for the Tucson Area. Accessed 2026-10-07.
10. California Department of Water Resources (via Cornell LII). Cal. Code Regs. tit. 23, sec. 490.2 (MWELO definitions). Accessed 2026-10-07.
11. California Department of Water Resources (via Cornell LII). Cal. Code Regs. tit. 23, ch. 2.7, Appendix A (MWELO worksheet). Accessed 2026-10-07.
12. California Department of Water Resources (via Cornell LII). Cal. Code Regs. tit. 23, ch. 2.7, Appendix C (Reference Evapotranspiration Table). Accessed 2026-10-07.
13. University of Florida IFAS Extension. AE481 Net Irrigation Requirements for Florida Turfgrass Lawns: Part 2, Table 3. Accessed 2026-10-07.
14. University of Florida IFAS Extension. AE482 Net Irrigation Requirements for Florida Turfgrass Lawns: Part 3, Table 3. Accessed 2026-10-07.
15. Southern Nevada Water Authority. Pools and spas. Accessed 2026-10-07.
16. Southern Nevada Water Authority. Understand laws and ordinances. Accessed 2026-10-07.
17. Southern Nevada Water Authority. Water Smart Landscapes Rebate. Accessed 2026-10-07.
18. U.S. Environmental Protection Agency. WaterSense: Pool Water Efficiency. Accessed 2026-10-07.
19. U.S. Environmental Protection Agency. WaterSense: Making a Splash, Pool Water Efficiency guide. Accessed 2026-10-07.
20. U.S. Environmental Protection Agency. WaterSense: Outdoors. Accessed 2026-10-07.
21. U.S. Department of Energy. Energy Saver: Swimming Pool Covers (archived 2025-01-10; live page now 404). Accessed 2026-10-07.
22. Arizona Municipal Water Users Association. How Does Your Water Use Stack Up?. Accessed 2026-10-07.
23. Town of Flower Mound, Texas. Pool Evaporation. Accessed 2026-10-07.
24. Denver Water. Stage 1 drought declaration. Accessed 2026-10-07.
25. Austin Water (City of Austin). Austin Water drought response. Accessed 2026-10-07.
26. City of Tampa Water Department. My Allowed Watering Days and Hours. Accessed 2026-10-07.
27. San Antonio Water System. SAWS customers return to Stage 3 watering rules. Accessed 2026-10-07.
28. Dallas Water Utilities (City of Dallas). Frequently asked questions. Accessed 2026-10-07.
29. Fort Worth Water (City of Fort Worth). Twice-a-Week SmartWatering. Accessed 2026-10-07.
30. Los Angeles Department of Water and Power. Water Conservation Ordinance. Accessed 2026-10-07.
31. California Legislature. AB-1572 Potable water: nonfunctional turf (Chapter 849, Statutes of 2023). Accessed 2026-10-07.
32. Colorado General Assembly. SB24-005 Prohibit Landscaping Practices for Water Conservation. Accessed 2026-10-07.
33. Stanford Magazine. Watering a Lawn vs. Putting in a Pool: Essential Answer. Accessed 2026-10-07.
34. University of Idaho Northwest Knowledge Network / Climatology Lab. gridMET daily reference ET (grass), THREDDS data catalog. Accessed 2026-10-07.
35. NOAA National Centers for Environmental Information. U.S. Climate Normals 1991-2020, monthly station files (example: Las Vegas). Accessed 2026-10-07.