A solar-powered pump lifts water from your underground tank to the overhead tank using electricity from panels on the roof. Its benefits in Karachi are water during load-shedding, a lower electricity bill, protection from voltage damage, and no need for batteries, because the full overhead tank is the energy store. It suits houses with a clear, sunny roof and a tank system that is otherwise in good order.
Our work is the tanks at either end of the pump. We see every day how much a household’s water depends on that one motor, and how a dirty tank shortens its life. This guide explains how solar pumping works, what to check before you buy, and how to look after the whole system.
Understanding Solar-Powered Pumps
How it works
- Solar panels turn sunlight into direct current (DC) electricity.
- A controller or inverter conditions that power for the pump. Good controllers track the panels’ best operating point as the sun changes and protect the motor.
- The pump lifts water to the overhead tank.
- Level sensors stop the pump when the overhead tank is full or the underground tank is empty.
- The overhead tank stores the result. Water flows to the taps by gravity whether or not the sun is shining.
The two common arrangements
| Dedicated solar pump | Existing pump on a solar system | |
|---|---|---|
| What it is | A DC pump with its own panels and controller | Your current AC pump run through a solar inverter, alone or as part of a house solar system |
| Batteries | None. Runs when the sun shines. | Optional. Hybrid systems can run it at night. |
| Efficiency | High. No conversion losses. | Lower, but uses equipment you already own |
| Best for | Houses that want an independent water supply | Houses that already have or plan rooftop solar |
Types of pump
- Surface pumps sit beside the underground tank and suit the normal house arrangement.
- Submersible pumps go down a bore or into a deep sump.
The conventional system, and how to maintain it, is described in pump system maintenance.
Water Management in Karachi
Karachi’s water arrives at low pressure and has to be lifted. The city receives about 650 million gallons a day against a need of about 1,200 million (Geo News), so supply comes for a few hours and every house relies on a pump to move it from the underground tank to the roof.
That makes water dependent on electricity. During the June 2015 heatwave, failures of the electrical grid left many areas without fans or working water pumps (Wikipedia). On an ordinary day the problem is smaller but familiar: supply arrives during a power cut, or the power returns after the tank has run dry.
A solar pump breaks that link. It also fits the way Karachi’s system already works, because the storage is built in. See the benefits of overhead water tanks and underground water tanks.
Benefits of Solar-Powered Pumps
Water when the grid is down
As long as there is daylight and water below, the overhead tank fills. A full tank at sunset carries the house through the night.
Lower electricity bills
A pump is one of the regular loads in a house. Running it on sunshine takes that off the bill for the life of the panels.
No batteries needed
Batteries are the most expensive and shortest-lived part of most solar systems. A solar pump stores energy as lifted water instead. The tank does the job a battery would.
Gentler on the motor
Grid voltage in Karachi dips and surges, and motors burn out. A solar pump controller gives a soft start, matches speed to the available power and shuts down safely on faults, including dry running.
Low running costs
There is no fuel and little to wear out. Panels need cleaning and the pump needs the same care as any pump.
Quiet and clean
No generator noise, fumes or diesel to store.
The limits
- It pumps only in daylight unless backed by the grid or batteries. Keep a changeover switch to mains power for cloudy spells and emergencies.
- Output falls in the monsoon and on hazy winter days.
- It needs unshaded roof space. The overhead tank, the stair tower and neighbouring buildings all cast shadows.
- The upfront cost is higher than a conventional pump.
- It does not create water. If the underground tank is empty, no pump helps.
Choosing the Right Size
A supplier should size the system from three numbers.
- How much water per day. Count people and allow about 135 litres each. A family of six needs roughly 800 litres a day. See choosing the right size water tank.
- How high it must be lifted. Measure from the water level in the underground tank to the inlet of the overhead tank, and add an allowance for pipe friction. A two-storey house is typically 10 to 12 metres.
- How many good sun hours you get. Plan on the pump doing its work in the four to five strongest hours of the day.
As a rule of thumb, the panels are rated at about one and a half times the pump motor’s power, so that the pump still runs well when the sun is not directly overhead. A half-horsepower pump is about 370 watts, and one horsepower is about 750 watts. Most houses need less pump than they think. A small pump running for three hours fills a 1,000-litre tank comfortably.
Make sure the overhead tank can hold at least a full day’s use, since it is now your reserve for the night and for cloudy mornings.
Installation and Maintenance
Installation
- Panels face south, tilted at roughly 25 degrees for Karachi’s latitude, clear of shadows from the tank, parapet and neighbours between about 9 am and 4 pm.
- Mount them on a frame fixed to the structure, strong enough for monsoon winds. Use galvanised or aluminium frames and stainless fasteners, because sea air rusts ordinary steel quickly.
- Do not shade or crowd the tank. Leave room to open its lid and for a cleaning crew to work. See choosing the right location for your tank.
- Use proper DC cable, connectors, breakers and earthing, with the controller under cover and ventilated.
- Fit level sensors in both tanks so the pump stops when the top is full and when the bottom is empty.
- Keep a mains changeover.
- Use a qualified installer and get the wiring diagram and warranty in writing.
Maintenance
| How often | Task |
|---|---|
| Every two to four weeks | Wash dust and bird droppings off the panels with plain water and a soft cloth, early in the morning. Karachi’s dust cuts output noticeably. |
| Monthly | Check for new shadows, loose cables and corrosion. Listen to the pump. Note how long it takes to fill the tank. |
| Every 6 months | Clean both tanks, the foot valve, the strainer and the level sensors. |
| Yearly | Have the installer check connections, earthing, the controller and the pump seal and bearings. |
Why the tanks matter to a solar pump
A solar pump runs on limited power, so anything that makes it work harder costs you water.
- Sludge in the underground tank jams the foot valve and wears the impeller and seal.
- Scale from hard water narrows the pump passages and pipes. See Karachi’s hard water problem.
- Scale and slime on level sensors give false readings, so the pump runs dry or does not start.
- Leaks and overflowing float valves waste water the panels worked to lift. See detecting and preventing leaks.
Cleaning both tanks every 6 months keeps all of these in check. See how often to clean your water tank.
Solar-Powered Pumps in Karachi
Why the city suits them
- Strong sunshine for most of the year.
- Flat concrete roofs that can carry panels.
- Every house already has an overhead tank to store the output.
- Electricity is expensive and interruptions are common.
What to watch for locally
- Dust and droppings. Panels near busy roads and under bird perches need washing more often. Birds that soil panels also soil tank lids. See bird contamination in rooftop tanks.
- Salt air. Near the coast, check frames, fasteners and terminals for corrosion.
- Monsoon. Secure panels before storm warnings and expect lower output for those weeks.
- Roof crowding. Panels, tanks, dish antennas and outdoor AC units compete for space. Plan the layout so the tank stays reachable.
- Quality. Buy panels, controllers and pumps from established brands through a supplier who will be there in five years.
Is it worth it?
It makes most sense if you have frequent outages, high bills, a sunny roof, or a bore pump that runs for hours. If you are already installing solar for the house, add the pump to that system. If your pump is small and your power is reliable, the saving is modest and the main gain is security of supply.
Prices for panels and pumps change too fast for a figure here to stay accurate. Get two or three itemised quotations and compare the panel wattage, pump model, controller features and warranty, not just the total.
The wider picture
Solar pumping is one of several ways a household can depend less on strained public systems. Others are collecting rain and wasting less. See the benefits of rainwater harvesting, rainwater harvesting and tank cleaning for sustainable living and climate change and water tanks in Karachi.
Frequently Asked Questions
Can I run my existing water pump on solar?
Yes. An AC pump can run through a solar inverter sized for its starting current. A dedicated DC solar pump is more efficient but means buying a new pump.
Does a solar pump work without batteries?
Yes. It pumps while the sun shines and the overhead tank stores the water for later.
How many panels does a home water pump need?
Roughly one and a half times the pump’s wattage. A half-horsepower pump needs about 550 to 600 watts of panels, and a one-horsepower pump about 1,100 to 1,200 watts. Your installer should confirm this for your lift and pump.
Will it work in the monsoon?
At reduced output. Keep a mains changeover for long cloudy spells.
Does a solar pump need a clean tank?
More than a mains pump does. It has less power to spare, so grit, scale and a jammed foot valve cut its output quickly.
Keep Both Tanks Clean for Your Pump
Call or WhatsApp 0313-2796778 to have your underground and overhead tanks cleaned. We work across Karachi, including Bahria Town, Gulshan-e-Maymar and Orangi Town. The method is on our service procedure page and the rates on the charges page. All the areas we cover are listed under service areas.
About the author: Ahmar Shoaib is the founder of Karachi Tank Cleaning. He holds a BS in Chemical Engineering from Karachi University and has run the company’s cleaning and disinfection work since 2007. This article follows our editorial policy.
Sources: PCRWR figures on Karachi’s water demand and supply, reported by Geo News (May 2025); Wikipedia, 2015 Pakistan heat wave.
