California · modelled at Los Angeles

Solar water pumps in California

California averages 6.02 peak sun hours a day across the year, 4th of 51. The darkest month, Dec, gives 4.21 (5th of 51 for winter sun); the brightest, Aug, gives 7.26. A pump that has to fill a trough in Dec needs 1.7 times the panels of one that only runs in Aug.

By the editors of SolarPoweredWaterPumps.comLast reviewed October 2026

Peak sun hours by month

4.5

Jan

5.2

Feb

6.1

Mar

6.9

Apr

7.0

May

7.1

Jun

7.2

Jul

7.3

Aug

6.4

Sep

5.6

Oct

5.0

Nov

4.2

Dec

kWh per square metre per day on a south-facing panel at 20 degrees in Los Angeles (34.05, -118.24). Source: NREL NSRDB via PVGIS v5.2.

Worked sizing for California

The same two systems are worked for every state so you can compare. Both use 35% or 30% wire-to-water efficiency and a 0.75 array factor; change any input in the calculator.

System	Design sun	Flow	TDH	Pump input	Panels	Tank
20 beef cattle, year-round (80 ft lift, 10 ft rise, 300 ft of 1 in poly)	4.21 h	1.58 gpm	91 ft	77 W	110 W	1,200 gal
Same well, grazing season April to October only	5.58 h	1.19 gpm	91 ft	58 W	80 W	1,200 gal
1,000 sq ft garden in summer, from a pond (8 ft suction, 15 ft rise, 200 ft of 3/4 in poly)	7.16 h	0.21 gpm	23 ft	3 W	10 W	267 gal

Panel figures are the floor from the arithmetic. Real systems usually carry 1.5 to 3 times this so the pump sits in the middle of its curve and the tank refills after cloudy days.

Run your own numbers. The sizing calculator shows every step, for your state, lift and pipe.

Open the calculator

What this means in California

California has strong sun even in Dec, so a direct-drive system sized for winter has a comfortable surplus in summer. Heat is the bigger design issue: hot panels lose voltage, so leave margin above the pump's start voltage.

Related reading: winterizing, livestock watering and USDA cost share.

Sources