Short answerFor most stock and irrigation systems, direct drive into a storage tank is cheaper and longer-lived than a battery. Add a battery when you need water at pressure on demand, at night, or for a pond aerator.
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Key takeaways
- In a direct-drive system the tank is the battery, and it lasts decades.
- Batteries earn their place for pressure on demand, night use or pond aeration.
- LiFePO4 must be kept above freezing to charge.
The two designs
| Direct drive | Battery | |
|---|---|---|
| How it works | Panels feed the pump (often through a pump controller); water fills a tank | Panels charge a battery through a charge controller; the battery runs the pump |
| Storage | Water: tank sized for 3 or more days | Electricity: battery sized for 1 to 3 days |
| Pump rate | Varies with sunlight, zero at night | Steady, any time |
| Parts that wear out | Pump, controller | Pump, controller, charge controller, battery |
| Energy losses | Lowest | About 10% more lost through the battery |
| Winter | Short days mean less water; a bigger tank helps | Battery must be kept above freezing to charge (LiFePO4) |
| Best for | Stock tanks, gravity tanks, irrigation by day | Pressure systems, night use, pond aeration, house supply |
Why water storage usually wins
A 1,500 gallon poly tank stores the output of several sunny days, has no charge controller, does not mind cold as long as it does not freeze solid, and lasts for decades. Storing the same energy in a battery means buying, protecting and eventually replacing it. For livestock and irrigation, put the money into tank capacity first.
A raised tank gives you pressure for free: every 2.31 ft of height is 1 psi. A tank 20 ft up a hill supplies about 8.7 psi, enough for low-pressure drip and stock troughs with float valves.
When a battery is worth it
Size the battery from the pump's daily energy, the days you want to cover, and 80% usable depth for LiFePO4. Our calculator does it in battery mode. Then size the array to refill it in the design month, allowing for the round-trip loss.
- You want pressurised water at the tap without a raised tank.
- The use is at night: aeration for a pond, where dissolved oxygen is lowest around dawn.
- The source yields too little to pump at the daytime rate a direct-drive pump would need.
- You already have a battery bank for a cabin and the pump is a small load on it.
Eco-Worthy 12V 100Ah LiFePO4 battery
1.28 kWh of storage for night or cloudy-day pumping. Low-temperature charge protection.
- Chemistry
- LiFePO4
- Capacity
- 12.8V 100Ah (about 1.28 kWh)
- Extras
- Bluetooth, low-temperature protection
on eco-worthy.com, 18 October 2026
Eco-Worthy Cubix100 48V 100Ah LiFePO4 rack battery
About 5.1 kWh at 48V: the battery side of an inverter-driven AC well pump.
- Chemistry
- LiFePO4
- Capacity
- 51.2V 100Ah (about 5.12 kWh)
- BMS
- 100 A
- Expands
- Up to 32 units in parallel (merchant figure)
on eco-worthy.com, 18 October 2026
LiTime 12V 100Ah self-heating LiFePO4 (Canadian store)
For a battery that has to charge in a cold pump house. Sold from LiTime's Canadian store, priced in CAD.
- Chemistry
- LiFePO4, Group 24
- Capacity
- 12.8V 100Ah
- Extras
- Self-heating, Bluetooth
on ca.litime.com, 18 October 2026
We have not tested these products; specifications are the merchant's own. Affiliate disclosure.
The hybrid
A common middle path: direct drive to a tank, plus a small battery-powered booster pump for the house. The well pump never needs a battery and the booster's load is small.
Put your own gallons, lift and pipe in and see every step of the working.