A farm battery pays its way when two things are true at once: the array regularly produces more than the farm uses around midday, and there are evening or early-morning loads that cannot simply be moved into daylight. If only one of those is true, a timer, a tank or a larger array is often the cheaper fix. When both are true, sizing comes down to three numbers: how much surplus you reliably have, how many kilowatt-hours the evening loads need, and how much power they draw at once.

Map when each load runs

Batteries are sized on timing, not on the farm's daily total. Before looking at any product, build a simple load timing map:

1. Pull twelve months of interval data for the farm connection. It shows the half-hours when you import and when you export.
2. List every motor over about 1 kW with its nameplate rating and typical run hours: bore and transfer pumps, irrigation pumps, milking plant, refrigeration and workshop compressors.
3. Mark each load as fixed (it must run at a set time) or flexible (it could run any time within the day).
4. Note which loads are critical during an outage.

Many farms find that their fixed evening demand is smaller, and their flexible load larger, than they expected.

Move the load before you store the energy

Every kilowatt-hour that goes into a battery loses a little on the way in and out (LFP batteries typically return around 90% or slightly more), and battery capacity costs far more than a contactor or a timer. So the first job is to shift anything that can be shifted.

A smart load controller that switches pumps or heaters on when solar is available can do much of this automatically. Whatever stays fixed in the evening is what the battery has to cover.

Sizing the battery: energy and power

A battery has two ratings that matter on a farm. Energy, in kilowatt-hours, is how long it can run the loads. Power, in kilowatts, is how much it can supply at once, and with motors involved that is often the limiting factor.

Here is an illustrative example. An evening irrigation pump drawing 4 kW for two hours needs 8 kWh, and the afternoon milking tail plus vat cooling after sunset adds 6 kWh. That is 14 kWh delivered. Allowing for conversion losses and a reserve left in the battery, usable capacity would need to be somewhere around 16-18 kWh. Then check the power side: the inverter must supply the pump, the milking loads running at the same time, and the starting surge of the largest motor.

Finally, check winter. A battery the array cannot refill on a short June day will only be fully used for part of the year. Sizing to the surplus you reliably have in the cooler months usually gives the best return, with the grid or a generator covering the rest.

Three-phase farm loads

Many pumps, milking plants and workshop machines are three-phase, which shapes the design:

• A single-phase battery inverter cannot run a three-phase motor. To supply those loads from storage, you need a three-phase hybrid inverter and a battery matched to it.
• Start-up current matters. Soft starters or variable speed drives on large pumps reduce the surge the inverter must deliver.
• Rural networks may apply export limits, which makes storing midday surplus more attractive than exporting it.
• Spreading single-phase loads evenly across the phases makes better use of the inverter's rating.

Some farms run a three-phase hybrid system for the sheds and pumps and a separate single-phase system for the homestead. Which layout suits depends on distances, switchboards and where the loads sit, so have a licensed electrician and an accredited designer assess it on site.

Set a backup priority before the storm

If the battery is backup-capable, decide in advance what it should keep running. A common order of priority is:

1. Stock water and anything that keeps animals safe.
2. Refrigeration: milk vats, cool rooms and freezers holding produce.
3. Communications, gates and security.
4. Homestead essentials such as lights and the kitchen fridge.
5. Workshop and non-urgent loads, which usually wait for the grid or a generator.

Only the top tiers normally go on the backup circuit. Through storm and fire season, raise the minimum reserve the battery holds back, so an outage does not arrive after a night of load shifting has left it nearly empty. Most modern systems let you change that setting from the monitoring app.

When a battery is not the answer

Skip or delay the battery if the farm exports little at midday, if most large loads already run in daylight, or if the evening load is a single pump that a tank could move. Very large, infrequent loads, such as a few weeks of seasonal irrigation, are often better handled by the grid or a generator than by storage that sits underused for the rest of the year.

If you are unsure, install solar first with a battery-ready hybrid inverter, and review a full year of monitoring data before choosing a battery size. Real import and export figures from your own farm are a far better guide than any estimate made in advance.

Next steps

For the load side, the guide to livestock and irrigation loads is a useful companion, and battery backup for rural properties explains outage-focused designs. To have your load timing, switchboard and phases checked on site, request a free assessment from Blue Energy Solar. Farm Battery Storage is listed in the energy market from $14,900 per farm system, installed; the price is indicative and confirmed after a site assessment.

Frequently asked questions

How long does a farm battery last?

LFP batteries are commonly warranted for 10 years, usually with conditions such as a limit on total energy throughput or a minimum retained capacity. Actual life depends on how deeply and how often the battery cycles, and on its operating temperature. A battery kept in a shaded, ventilated location and not routinely run flat will generally age more slowly than one in a hot, closed shed.

Can we add more battery capacity later?

Often, if the original system uses a modular battery and the inverter has spare capacity. Added modules generally need to be the same model with compatible firmware, and some manufacturers restrict adding new modules to a battery that has already aged for several years. Planning for expansion at the start, including wall or floor space and inverter size, keeps that option open.

Do battery incentives apply to farm batteries?

They can. The federal Cheaper Home Batteries Program provides roughly 30% off the installed cost of an eligible battery installed with solar, and NSW business battery incentives began on 1 September 2026 for eligible business batteries from 20 kWh. Eligibility depends on the battery, the property and the installer, and values step down over time, so confirm current details on the official government pages before signing.