Does a solar water pump need a battery?
Almost never. The answer in solar pumping is to store water, not energy. A tank holding a day of water is normally far cheaper than a battery bank holding a day of pumping energy, and it has no replacement date.
There are four cases where a battery genuinely earns its place. They are listed further down, and if you are in one of them you will recognise it immediately.
Store the output
You want water, not electricity. Storing it one step later removes a conversion and its losses.
A tank has no cycle life
A battery bank is a consumable with a replacement date. A tank is not.
Four real exceptions
Fixed delivery times, nowhere for a tank, an existing battery, or pressure with no elevation.
Why the default is a tank
Five reasons, and only the first is about purchase price. The other four are why the answer stays the same even when a battery looks affordable.
| A tank stores the thing you actually want | You are not buying electricity, you are buying water. Storing it one step later removes a whole conversion and its losses. |
| A tank does not age | It has no cycle life and no calendar life worth planning around. A battery bank is a consumable with a replacement date. |
| A tank has no electronics | Nothing to fail in heat, nothing to configure, nothing that needs a technician. On a remote site that matters more than the purchase price. |
| A tank is bought locally | No freight from China, no import duty, no lead time. Often the only item in the whole system that is. |
| A tank gives head for free | Water stored high feeds the field by gravity. A battery gives you nothing at the outlet. |
The comparison in one sentence
A battery has to store enough energy to run the pump for a day; a tank has to hold the water the pump already produced in that day. The second is a plastic or concrete vessel bought locally. The first is an imported consumable that degrades in heat, and pumping sites are hot.
Four cases where a battery does make sense
These are real and we will price them. What we will not do is add a battery to an irrigation system that does not need one.
| Water must arrive at a fixed time, not a fixed volume | Livestock watering on a schedule, or a process that cannot buffer. Rare in irrigation, common in industry. |
| There is nowhere to put a tank | Terrain, land rights or theft risk. Sometimes the tank is the harder problem, not the cheaper one. |
| The same array is already running other loads | If a battery exists for lighting or a cold room, adding the pump to it can be cheaper than a second system. |
| Pressure irrigation with no elevation available | A gravity tank needs height. Flat ground with a drip system sometimes justifies pumping on demand instead. |
Notice that none of them are “so the pump can run at night”. If water is needed at night, the water is in the tank. If the pump has to run at night, which is a different requirement, the usual answer is a grid or generator input on the cabinet rather than a battery.
Sizing the tank
| Start at one day of demand | The daily volume you sized the pump for. This is the usual baseline and it covers a normal cloudy afternoon. |
| Two to three days if the site is remote | Or if the weather is unreliable. Storage is cheap compared with a lost irrigation cycle. |
| Size on daily volume, not on pump flow | A tank sized to hold an hour of pump flow will be far bigger and more expensive than one sized to hold a day of demand. |
| Every metre of tank height is a metre of head | Raising the tank costs pumping energy and buys gravity feed. Worth doing deliberately, and it belongs in the head calculation. |
| Drip and sprinklers usually still need a booster | Drip wants 1 to 1.5 bar at the inlet, which is 10 to 15 m of elevation. Few tank stands reach that. |
Put the tank in the head calculation, not after it
The height of the tank is part of the total dynamic head the pump has to overcome. A 6 m stand is 6 m of head, plus the depth of water inside it. Deciding the tank after the pump is chosen is how a system ends up delivering less than the design figure.
What we supply here
Tanks, tank stands and pipework are not in our scope and we would not ship them from China even if they were: a tank is bulky, cheap and available locally almost everywhere. We supply the pumping and solar side, and we include the tank height in the head calculation so the pump is sized for the system you are actually going to build. If a battery is genuinely the right answer for one of the four reasons above, we can quote that as part of the package.
Tell us the daily volume and where the tank goes
Height of the tank stand and the daily demand are two of the five numbers that make up the head. Send them with the well data and we can size the whole thing properly.
Battery or tank FAQ
Does a solar water pump need a battery?
Almost never. The standard answer in solar pumping is to store water in a tank rather than energy in a battery. A tank holding a day of water is normally far cheaper than a battery bank holding a day of pumping energy, it does not age, it has nothing electronic to fail, and it is bought locally rather than imported.
Why is a water tank cheaper than a battery for solar pumping?
Because you are buying water, not electricity. Storing water removes a conversion step and its losses, and the store itself is a plastic or concrete vessel with no cycle life. A battery bank has a replacement date, needs protection and configuration, and degrades in heat, which is exactly the climate most pumping sites are in.
When does a battery make sense on a solar pump?
When water has to arrive at a fixed time rather than in a fixed daily volume, when there is genuinely nowhere to put a tank, when a battery already exists on site for other loads, or when pressure irrigation is needed on flat ground with no elevation for a gravity tank. Outside those four, a tank is the better answer.
How big should the water tank be for a solar pump?
One day of demand is the usual starting point, and two to three days if the site is remote or the weather is unreliable. Size it against the daily volume you worked out for the pump, not against the pump flow: a tank sized on flow will be far larger and more expensive than it needs to be.
Can a solar pump run at night?
Not on solar alone, and that is by design rather than a limitation. The water pumped during the day sits in the tank and is available all night by gravity. If the pump itself has to run at night, the usual answer is a grid or generator input on the cabinet rather than a battery.
Does the tank need to be elevated?
Only if you want gravity feed or pressure at the outlet. Every metre of tank height is a metre of head the pump has to add, so raising the tank costs a little pumping energy and saves a booster pump. On a drip system needing 1 to 1.5 bar, elevation alone rarely covers it and a small booster is usually still needed.
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