How many solar panels do I need to run a well pump?

It depends on well depth and daily water demand. A shallow 80ft residential well pumping 200 gallons/day typically needs 1-2 × 400W solar panels. A deep 300ft well pumping 500 gallons/day may need 3-5 panels. Use a storage tank to avoid battery storage costs.

Can solar power a deep well pump?

Yes. Solar is ideal for deep wells. DC solar submersible pumps can operate at depths over 1,000 feet. Deep wells require more watts, but solar scales easily — just add more panels. Pair with a water storage tank to eliminate battery costs.

Well Pump Solar Calculator

Size solar panels for your off-grid well pump. Enter depth and daily water use — get pump wattage, panel count, and storage recommendations.

Well & water specifications

Well depth?

Daily water demand?

GPD

Pump type?

Peak sun hours?

Storage tank size?

gal

Pump and solar array sizing

250W pump + 1 × 400W panels

Total dynamic head249 ft

Required flow rate0.93 GPM

Solar array size400W

Daily pump energy1.13 kWh

Your 500-gallon storage tank covers at least one day of demand — no battery storage required. Pump during peak sun hours, draw from tank at night.

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How to Use This Calculator

Enter well depth and daily water demand

Input your well depth in feet — this is the distance from the surface to the pump intake (or static water level if you know it). Enter your daily water demand in gallons per day (GPD). Residential household: 50–100 GPD per person. Cattle: 30–50 GPD per head. Horses: 10–15 GPD. Goats and sheep: 2–5 GPD each.

Select pump type

Submersible pumps sit in the water and push it up — the most common choice for wells over 25 feet deep. They're more efficient and can handle much greater depths than surface pumps. Surface centrifugal pumps pull water up from above — limited to about 25 feet of suction lift. Jet pumps are surface-mounted and work for shallow wells only.

Set peak sun hours and storage tank size

Solar well pumps ideally run during peak sun hours and fill a large storage tank. The stored water covers nighttime and cloudy-day demand, eliminating the need for expensive battery storage in most cases. A storage tank of at least 1 day's demand is strongly recommended.

The Formula

Total Dynamic Head (TDH) = well depth + drawdown (15%) + friction (~25ft) + pressure head Example: 150ft well → TDH = 150 + 22.5 + 25 + 46 = 243.5 ft Flow rate (GPM) = Daily GPD ÷ (sun hours × 0.9 × 60 min) Hydraulic power (W) = TDH (ft) × GPM × 0.1885 Pump input power (W) = Hydraulic power ÷ pump efficiency (0.45–0.65) Solar array (W) = Pump input power × 1.30 (surge headroom) Panel count = ceil(Solar W ÷ Panel wattage)

The Total Dynamic Head is the critical design parameter — it's the effective height your pump must overcome, including all friction losses and pressure requirements. A 150ft well doesn't just need to lift water 150ft; it needs to overcome the water level dropping during pumping (drawdown), friction in the pipe, and deliver water at usable pressure.

The 1.30× solar array factor ensures the pump has enough power during the inevitable partial-sun hours at the start and end of each day. Without this headroom, the pump may stall or run inefficiently during morning and late-afternoon hours.

Example

Rural homestead — 280ft deep well, 350 GPD

A rural family needs 350 GPD for household use and a few animals. Well depth is 280ft. Submersible pump (55% efficiency). 5.0 peak sun hours. 1,000-gallon storage tank.

Static water level280 ft

Drawdown (15%)42 ft

Friction + pressure head56 ft

Total Dynamic Head378 ft

Effective pumping time5.0 × 0.9 = 4.5 hrs

Required flow rate350 / (4.5 × 60) = 1.30 GPM

Result

Hydraulic power378 × 1.30 × 0.1885 = 92.7W

Pump input power92.7 / 0.55 = 168.5W

Recommended pump250W submersible

Solar array250 × 1.3 = 325W → 1 × 400W panel

A single 400W panel directly powers this system during daylight hours. The 1,000-gallon storage tank (nearly 3 days' supply) eliminates battery needs. Popular pump choices for this depth and flow: Grundfos SQFlex 2.5-3, Franklin Electric QD Pak, or Lorentz PS2-1800.

FAQ

Do I need a battery for a solar well pump? ▼

Usually not, if you have adequate storage. Solar-direct pumps run only during daylight and fill a storage tank — you draw from the tank at night and on cloudy days. Size your tank for 1.5–2 days of demand without pumping. For 300 GPD, a 500-gallon tank provides about 1.7 days of buffer. If you need 24/7 pumping reliability or can't install a large tank, add a battery bank sized for one night's demand plus a pump inverter. Battery systems cost more but provide complete reliability regardless of weather.

What is Total Dynamic Head and how does it affect pump sizing? ▼

Total Dynamic Head (TDH) is the total equivalent height the pump must overcome: static lift (depth to water) + drawdown (how much the water level drops while pumping, usually 10–20% of depth) + pressure head (height above wellhead you're pumping to, plus pressure for a pressurized system — about 46 ft per 20 PSI) + friction head (resistance in pipes and fittings — 5–20% of total head for properly sized pipe). TDH is the most important specification when selecting a pump — a pump rated for 150 ft TDH will not perform adequately on a 300 ft TDH system. Get your well driller's report if possible; it usually lists the static water level and typical drawdown.

What size storage tank do I need for a solar pump system? ▼

The standard recommendation is 1.5–2 days of total demand in tank storage. For a household using 300 GPD: 300 × 1.5 = 450 gallons minimum, so a 500-gallon tank is the practical choice. For livestock systems: size for the maximum number of consecutive non-sunny days in your climate. Elevated tanks (gravity-fed, at least 10 ft above usage point) eliminate the need for a separate pressure pump and provide ~4.3 PSI per 10 ft of height. Polyethylene tanks (Norwesco, Chem-Tainer) are the most practical choice for most rural installations.

Which solar well pump brands are most reliable? ▼

Grundfos SQFlex is the gold standard for solar-direct well pumps — extremely reliable, AC/DC compatible (runs on solar panels or grid), built-in variable speed drive, and available for depths from 80 to 1,000+ ft. Lorentz PS2 and PS Classic series are another excellent choice with extensive depth and flow range, particularly popular in off-grid agricultural applications worldwide. Franklin Electric QD Pak systems are US-made and use standard 4-inch submersible pumps with a solar controller. Avoid cheap no-brand pumps from online marketplaces for deep well applications — the installation and removal cost far exceeds the pump savings if one fails.