How much water does solar save vs coal power?

Solar PV saves approximately 0.49 gallons of water per kWh produced compared to coal power plants. A typical 8 kW home solar system producing 10,500 kWh/year saves about 5,145 gallons per year vs coal, or over 128,000 gallons over 25 years.

Why do coal plants use so much water?

Coal plants use the Rankine steam cycle — coal heats water into steam to spin turbines, then the steam must be cooled and condensed using cooling towers or river water. This cooling process evaporates enormous quantities of water. Solar PV generates electricity directly from sunlight with no moving parts and no cooling water needed.

Water Savings Calculator

Solar panels save thousands of gallons of water per year by displacing fossil fuel power plants that need cooling water.

Your solar production

Annual solar production?

kWh/yr

Replace which source??

System lifetime?

years

Water saved vs US average grid mix

4,095 gallons saved per year

Lifetime savings102,375 gal

In liters387,489 L

Equivalent showers6,022

Swimming pools5.1

Link copied to clipboard

How to Use This Calculator

Enter your annual solar production

Input your system's annual energy production in kWh/year. This is the energy your solar panels produce that would otherwise come from the grid. Use your installer's production estimate, PVWatts output, or results from our Solar Panel Output Calculator. Click a scenario button to pre-fill a typical home system size.

Choose the comparison source

Select which fossil fuel source your solar is replacing. Coal power plants use the most water — approximately 0.49 gallons per kWh — because steam-cycle coal plants need large quantities of cooling water. Natural gas combined-cycle (CCGT) plants use about 0.25 gal/kWh. The US average grid mix at 0.39 gal/kWh accounts for the blend of coal, gas, nuclear, and hydro on the typical US grid.

Set system lifetime

Enter the number of years for your lifetime calculation. Most solar panels are warranted for 25 years and regularly operate for 30+ years. The lifetime figure compounds your annual water savings into a total that's often surprisingly large.

The Formula

Annual water saved (gal) = Annual solar production (kWh) × Water factor (gal/kWh) Lifetime water saved (gal) = Annual savings × System lifetime (years) Equivalent showers = Lifetime gallons ÷ 17 gal/shower Equivalent pools = Lifetime gallons ÷ 20,000 gal/pool Water factors: Coal: 0.49 gal/kWh (USGS operational water consumption data) Natural gas: 0.25 gal/kWh (CCGT with once-through cooling average) US grid mix: 0.39 gal/kWh (EIA-weighted average 2024)

These figures represent water consumption (water that is evaporated or not returned to the source), not water withdrawal (all water taken in, most of which is returned). Solar PV consumes essentially zero water during operation — only a small amount for occasional panel cleaning.

Nuclear power also has significant water consumption (~0.67 gal/kWh) due to steam cooling. The US grid's nuclear component raises the average above pure gas-cycle figures.

Example

Average home — 8 kW solar replacing US grid mix

An American family installs an 8 kW solar system that produces 10,500 kWh per year, replacing electricity that would otherwise come from the US average grid mix (0.39 gal/kWh water consumption).

Annual solar production10,500 kWh

Grid mix water factor0.39 gal/kWh

System lifetime25 years

Result

Annual water savings4,095 gallons

Lifetime water savings102,375 gallons

Equivalent showers~6,022 showers

Swimming pools~5.1 pools

This single home solar system saves over 100,000 gallons of water over 25 years — water that would have evaporated from cooling towers at power plants. In water-stressed regions like the American Southwest, where both solar resources and water scarcity are high, this benefit is particularly significant.

FAQ

Why do power plants use so much water? ▼

Thermoelectric power plants (coal, gas, nuclear) generate electricity by heating water to create steam, which spins a turbine. The steam must then be cooled and condensed back to water for reuse. This cooling process uses enormous quantities of water. In once-through cooling systems, cool water is drawn in, heated, and discharged. In recirculating systems (cooling towers), water evaporates to carry away heat. The US thermoelectric sector withdraws about 100-200 billion gallons per day — more than any other water use category.

Does solar use any water at all? ▼

Rooftop solar PV uses essentially no operational water — the sun shines on solid-state cells, generating electricity directly without any cooling water. The only water use is occasional cleaning: a typical 8 kW residential system might need 20-40 gallons of water per year for panel washing, which is negligible compared to thermoelectric alternatives. Large utility-scale solar farms may use some water for robotic panel cleaning systems, but far less than any fossil fuel alternative.

How does concentrated solar power (CSP) compare to PV for water? ▼

Concentrated solar power (CSP) with wet cooling uses significant water — about 0.9-1.1 gallons per kWh, more than natural gas and approaching coal. CSP uses mirrors to focus sunlight, create steam, and drive a turbine — it needs cooling water just like fossil plants. CSP with dry cooling uses much less water but has lower efficiency. Rooftop PV (what this calculator covers) has no such water requirement, making it the most water-efficient electricity generation technology available.

Is water savings a significant environmental benefit of solar? ▼

Yes, particularly in water-stressed regions. A study by the Union of Concerned Scientists found that a large-scale shift to solar and wind power in the western US could reduce power sector water consumption by 97%. In California, Texas, and the Southwest, where both solar resources and water stress are highest, the water savings benefit of solar may be as economically significant as the carbon reduction benefit as water becomes scarcer.