Solar Water Pump Calculator

How to use this calculator

Enter six values and the calculator returns the hydraulic energy your application needs each day, the electrical energy the pump will draw, the PV array size in watts-peak, how many panels you need at the wattage you choose, the pump’s operating power during sunlight hours, and the average flow rate it will deliver.

1. Daily water demand (litres/day) — total volume you need each day. Common Canadian targets: 55–80 L/day per beef cow, 70–110 L/day per dairy cow, 6–10 L/day per sheep, 4–6 L/m²/week for irrigated horticulture in summer, 100–200 L/day per off-grid resident.
2. Total dynamic head (m) — pumping water level in your well in metres, plus any rise to a tank stand.
3. Peak sun hours/day — annual-average daily irradiance from NRCan’s PV-monitor and CanmetENERGY data. Typical figures: Calgary 4.5, Edmonton 4.2, Regina 4.5, Saskatoon 4.4, Winnipeg 4.3, Toronto 3.9, Ottawa 4.0, Montreal 3.8, Halifax 3.7, Vancouver 3.4, Whitehorse 3.0.
4. Pump wire-to-water efficiency (%) — overall pump efficiency. 45% is a sound default for a submersible if you don’t have manufacturer pump curves.
5. System derate (%) — losses from controller (3–5%), wiring (2–4%), and panel soiling/temperature (5–10%). 85% is the standard default; drop to 80% if your panels see heavy snow accumulation in winter and aren’t cleared.
6. Panel wattage (W) — your chosen panel. The 2026 standard CSA-listed module is 400–435 W; 540 W bifacial modules are common in ground-mount installs.

How solar water pumping works

A solar water pumping system has three components: the photovoltaic array, the pump controller, and the pump. Unlike a grid-connected solar electric system, there is usually no battery and no inverter — the controller takes raw DC from the panels and feeds the pump directly.

The controller does two important jobs. First, MPPT keeps the panels at their peak even as irradiance changes. Second, it varies the pump speed throughout the day — faster at noon, slower at low irradiance, clean shutdown when output falls below the pump’s minimum start power. This is why solar pumps keep running through overcast weather while a fixed-speed mains pump would short-cycle.

The pump itself is typically a brushless DC submersible (for wells) or a surface-mounted DC pump (for streams, ponds, and shallow installations). Grundfos SQFlex, Lorentz PS2, and Sunpumps dominate the Canadian rural water market. Helical-rotor pumps from Lorentz and Sunpumps are the right choice for high-head, low-flow applications — moving 500–3,000 L/day from 60–150 m wells.

The physics, derived from first principles

The hydraulic energy needed to lift volume V of water through vertical height H is determined by physics:

E_hydraulic_Wh = ρ × g × V_m3 × H_m / 3600
              = 1000 × 9.81 × V_m3 × H_m / 3600
              ≈ V_m3 × H_m × 2.725

Electrical input energy is hydraulic energy divided by efficiencies:

E_electrical_Wh = E_hydraulic_Wh / (η_pump × η_system)

PV array in watts-peak is electrical energy divided by PSH:

PV_Wp = E_electrical_Wh / PSH

Worked example

A 4,000 L/day Prairie stock-water installation at 35 m of head in southern Saskatchewan (PSH 4.4), with a Grundfos SQFlex pump (45% wire-to-water), 85% system efficiency, 400 W panels:

• V_m3 = 4 m³
• H_m = 35 m
• E_hyd = 4 × 35 × 2.725 = 382 Wh
• E_elec = 382 / (0.45 × 0.85) = 998 Wh
• PV needed = 998 / 4.4 = 227 Wp
• Panels = ceil(227 / 400) = 1 panel for annual mean

December PSH in southern Saskatchewan is closer to 1.5, so the worst-month-sized array would be 998 / 1.5 = 666 Wp — two 400 W panels minimum. Most Prairie ranchers run 3 panels (1,200 Wp) so the pump still produces meaningfully even in late-December cloudy conditions, and use a 5,000 L insulated tank to ride through outright zero-sun days.

Canadian sizing rules of thumb

For solar-direct pumping with tank storage in Canadian conditions:

• Design the tank to hold 5–10 days of demand. Prairie December and January are routinely snowed-in and cloudy.
• Size the array for the worst sun month (December across most of Canada).
• Add 30–50% PV oversizing to the worst-month calculation.
• For Prairie cattle pumping at 30–40 m wells, expect 0.4–0.7 Wp per litre-per-day at annual mean PSH, or 1.2–2.0 Wp per litre-per-day if you size to December.
• Plan for snow clearing: tilt the array steeply (60° or more in southern Canada) so snow slides off, or schedule regular clearing during the worst months.

Pump types compared

For most Prairie cattle applications under 10,000 L/day from a well under 60 m, a Grundfos SQFlex or Sunpumps SDS-D submersible is the standard choice. For deeper wells (100 m+), Lorentz PS2 with the helical-rotor cartridge maintains flow at low input power.

Canadian incentives and cost-share

• NRCan Greener Homes Loan — interest-free up to C$40,000 for residential energy improvements including off-grid solar; applies to remote homes that use solar pumping for domestic supply.
• Agricultural Clean Technology Program (AAFC) — federal cost-share for adoption of clean technology on farms; solar pumping has been a funded category.
• Alberta CASA Farm Stewardship and Drought Response programs — historical cost-share for off-grid stock watering systems.
• Saskatchewan Farm Stewardship Program (SFSP) — has funded solar stock-watering systems as part of riparian and dugout management.
• British Columbia Environmental Farm Plan — Beneficial Management Practices grants cover livestock watering systems, including solar.
• Provincial sales tax exemptions — most provinces exempt agricultural solar equipment from PST.

Common mistakes that hurt Canadian solar pumping performance

• Sizing to annual mean PSH instead of December. A system sized to the 4.4 annual mean will deliver only 35% in late December across the Prairies.
• Above-ground pipe runs that freeze. All surface piping must be heat-traced or buried below the frost line — 1.8 m in southern Manitoba, 2.4 m in northern Saskatchewan.
• Uninsulated tanks that freeze solid. A 5,000 L poly tank in southern Alberta will form 5–10 cm of surface ice in mid-winter without thermal management. Insulated Bohlmann, Miraco, or Ritchie waterers are the Prairie standard.
• Submersible installed above frost. The pump itself must sit well below the well’s frost-safe level — typically 6–8 m down minimum.
• Flat-mount panels in snow country. A panel mounted flat or near-flat won’t shed snow. Tilt steeply for the latitude — 50–60° in southern Canada, near-vertical in Yukon and NWT.

Sources

• NRCan — Solar PV Atlas of Canada — peak sun hour data by region
• CanmetENERGY — research on cold-climate renewable energy
• Agricultural Clean Technology Program (AAFC) — federal farm clean-tech cost-share
• Alberta CASA Farm Stewardship — provincial cost-share programs
• Solar Industry Canada — Solar pump case studies — performance data from cold-climate installations
• Grundfos SQFlex sizing guide — pump curves and selection charts referenced for efficiency defaults