ASFA Pump & Power Check

01 / How the tool works

Water power

The power that the flow and the head themselves take: water (1,000 kg a cubic metre) times gravity (9.81 m/s²) times the flow in cubic metres a second times the head in metres. 3.6 m³/h lifted 10 m takes 0.098 kW. No pump does it without losses, so the pump and motor need more.The same sum the ASFA design apps use.

Total head

Everything the pump pushes against, in metres of water: the height from the water level to the highest outlet, the pressure the outlets need (1 bar is about 10.2 m), and the losses in the pipes, fittings and valves. The Pipe & Fittings Sizer works it out for a drip zone.

Pump and motor efficiency

The pump turns 68% of the power at its shaft into water power, and the motor turns 88% of the electricity it draws into shaft power: together about 60% from the wire to the water. 88% for the motor is the published figure of the Nebraska Pumping Plant Performance Criteria, which take 75% for a well-run pump; fully loaded motors of 5 to 250 hp (about 4 to 190 kW) run at 83–94%, and pumps peak at about 55–82%. 68% for the pump is our planning figure: it keeps the two together at the 60% our design apps use before a pump is chosen, since small pumps rarely reach their peak. Change either to your pump maker's figures, from 30 to 85% for the pump and 60 to 97% for the motor.Irrigation Systems Management, 8.7 Energy Consumption (Nebraska criteria) ↗

The motor to ask for

A motor's rating is the power it gives at its shaft, so it must give at least the pump's shaft power. The check takes the first rated output at or above it from the list of rated outputs in the EU motor efficiency rules, 0.12 to 160 kW (0.37, 0.4, 0.55, 0.75, 1.1, 1.5, 2.2, 3, 4, 5.5 kW and so on). Motors are made in other sizes too; ask the pump maker for the one they fit. This is the smallest motor that covers the pump at your duty point; it adds no margin. The pump maker may fit a larger motor so it is never overloaded anywhere on the pump's curve.Ratings: the rated outputs at which Commission Regulation (EU) 2019/1781, Annex I, Table 1 ↗ sets minimum motor efficiencies.

Energy and grid cost

The motor's draw times your pumping hours gives the kilowatt-hours (kWh) for a pumping day; your days a week and the months you pump give the year. Hours brought from the Drip Planner are its peak month's, so a year worked from them is an upper figure. The cost is that energy times the tariff. The default is AEDC Band A, 209.50 ₦/kWh (Non-MD, MD1 and MD2), as listed in NERC's order; VAT is charged on top. The list also holds AEDC's Bands B to E for Non-MD meters; if you are on an MD1 or MD2 meter in those bands, type your tariff from your bill. Other distribution companies have their own tariffs, and they change: type yours from your bill. This is your own running cost; we show no prices of ours.AEDC (Abuja Electricity Distribution Company), NERC MYTO 2026 Final Order (May 2026), as published by AEDC: the spreadsheet's sheet 'Abuja (2)', 2026 column, Band A for Non-MD, MD1 and MD2, Bands B to E for Non-MD. NERC MYTO 2026 tariff file (AEDC, spreadsheet) ↗; AEDC tariff downloads page ↗

Generator

The check gives the power the generator must supply while the pump runs (the motor's draw) and its energy each pumping day. We do not hold a published fuel-use figure we can stand behind for small generators, and a motor draws much more for a moment as it starts, so we size the generator and work out its fuel with your quote.

Solar array

The panels (in kWp, their power in full sun) must give the energy of the pumping hours the sun can run, at most 8 a day, in the month you pump with the least sun: that energy divided by the month's sun, in kWh on a square metre a day, and by 0.75, the share left after heat, dust, wiring and the controller. The energy counted is the pumping hours inside the solar day, capped at 8 hours, which is how our design apps do it; hours past that need a tank, batteries or a second source, and the check says how much energy they take. The panels must also give the motor its full power in full sun, the draw divided by 0.75; the check takes the larger. The sun is a modelled figure for flat ground. Panels tilted to face south collect more in the dry season but a little less from about May to August, when the midday sun is to the north, and those can be the months that set the size; we check the tilt with your quote. 0.75, the 8 hours and the larger-of-the-two rule are our planning figures, the ones our design apps use.Sun: NASA POWER climatology, AG community, January 2001 to December 2025, all-sky radiation on a flat surface (ALLSKY_SFC_SW_DWN), MJ/m² a day divided by 3.6. NASA POWER ↗

02 / What the check leaves out

• The suction sideA surface pump can only lift water a few metres up its suction pipe. Lift it higher and the pressure at the pump's inlet falls so low that the water turns to bubbles of vapour (cavitation), which wear the pump and cut its flow. The pump's chart gives the inlet pressure it needs, its NPSH required; your site must give more than that. We check the suction lift, or set a submersible in the borehole, with your quote.
• Pump curvesA real pump gives more flow at a lower head and less at a higher one, and its efficiency changes along the curve. We match a maker's curve to your duty with your quote.
• Starting current and cablesA motor draws several times its running current as it starts, which sets the supply, the starter and the generator. The cable size depends on the motor's current and the cable's length; we size both with your quote.
• Borehole drawdownThe water level in a borehole falls while it is pumped, and falls further in the dry season, so the lift grows. Your borehole's test pumping record tells us how far; the check takes the head you give.
• Tariff changesNERC reviews tariffs, and your band depends on the hours of supply your feeder gets. The cost shown is at the tariff on the page today, as listed in NERC's order; VAT is charged on top.
• One pumping day for every monthThe energy and cost a year use the hours you give for every month you tick. Hours from the Drip Planner are the peak month's, so the year is an upper figure; untick the months of the rains you do not pump.
• Batteries and storageThe solar size is for pumping in daylight with no batteries. Pumping at night, or more hours than the sun gives, needs a tank, batteries or a second source, worked out with your quote.
• Panel tilt and shadeThe sun is for flat ground, on an average day of the month, in a modelled grid cell, not your site. A south-facing tilt gives a little less than flat ground in the rainy-season months. Shade from trees or buildings cuts what the panels give. The 0.75 allows for some dust, but panels that are not cleaned lose more.

Need the flow and head first? Try the Pipe & Fittings Sizer, or start with the ASFA Drip Planner. Ready to go further? Request a quote.