Keeping Pumps, Sheds, and Homesteads Running on Off Grid Power Systems

A rural property is rarely one load in one place. There is a homestead, a machinery shed a hundred metres away, a workshop with a welder in it, a bore somewhere out the back, and troughs further out again. An off grid system has to serve all of it, and the usual failure is not that the system is too small overall. It is that one load starves another.

CW Rural Power & Electrical designs off grid power systems for whole properties across New South Wales and Queensland. This is how the spread gets handled.

Map the Load Before Choosing Equipment

The first job is a list: every building and remote load, with three things recorded against each one.

• How much it draws when running
• How often and when it runs
• How far it is from where the plant will sit

That third column is the one people skip, and it is frequently the one that changes the design most.

Find the Motors First

Motors set the inverter requirement, not the lights and the fridge. Bore pumps, irrigation pumps, compressors and welders draw several times their running current at startup.

The worst case is not the sum of everything on the property. It is the biggest motor starting while whatever else normally runs is already running. That combined peak is the number worth designing against, which is why the irrigation pump coming on and the homestead dimming is such a common complaint.

Apply Diversity Honestly

If you size a system to the sum of every nameplate rating on a working property you get a quote nobody will accept and a system nobody needs. Not everything runs at once.

The skill is being honest about what genuinely coincides. Morning milking and the bore pump probably do. The welder and the irrigation almost certainly do not. Getting diversity right is the difference between a system that is adequate and one that is extravagant in the wrong places and short in the right ones.

Decide What Gets Cabled

Cable is charged by the metre, and voltage drop forces a larger conductor the further you go. That cost curve is steep.

Past a certain distance it becomes cheaper to put generation at the load than to run supply to it. A bore several hundred metres out is often better served by a standalone solar pump than by a trench, which is why so much of our solar pumps work exists. Our guide to solar water pumps covers that sizing.

Working out the crossover point for your actual runs is a calculation, not a rule of thumb.

Subboards Where the Load Is

Anything beyond a light and a power point deserves its own subboard. Local isolation and local protection mean a fault in the workshop gets dealt with at the workshop, rather than someone walking back to the house to work out which breaker it was.

It also keeps a fault in one building from taking out circuits in another, which on a working property is worth a great deal at the wrong time of year.

Stage the Big Starts

Where several large motors exist, the answer is often sequencing rather than a bigger inverter:

• Soft starters to reduce inrush on the largest motors
• Staged starting so two big loads cannot kick in together
• Time of day scheduling, running heavy pumping while the array is producing rather than off the bank at night

That approach uses the system better and costs considerably less than oversizing everything. Our agricultural and rural electrical page covers the distribution side.

Leave Room to Grow

The next shed is always coming. Spare ways in the board, capacity in the supply cable and headroom in the inverter cost very little at installation and a great deal to retrofit.

Why People Choose Us

• Licensed in both states - NSW 163931C and QLD 1512016.
• CEC Solar Accredited - Accreditation S2931181.
• High Voltage Cable Jointer qualified - For larger rural infrastructure.
• Whole property approach - Homestead, sheds and remote loads designed together.
• Allianz public liability insurance - Fully insured for work on working properties.

Get in Touch

Call 0483 347 898 with a rough picture of your buildings, your pumps and the distances between them, and we will tell you how it would sensibly be put together.

Frequently Asked Questions

Can one off grid system run the house, the shed and the pumps?

Usually yes, provided it was designed for the combined peak rather than the sum of everything. The question is not whether the loads total more than the system, it is whether the ones that genuinely coincide do. That is why load mapping comes before equipment selection.

Why does the house dim when the irrigation pump starts?

Because the motor inrush is pulling more than the inverter can deliver cleanly, or the cable to the pump is undersized so the voltage sags under starting current. Both are fixable, usually with a soft starter, correct cable, or staging so the big starts do not coincide.

Is it better to run cable to a distant pump or give it its own system?

It depends entirely on distance. Cable is charged by the metre and voltage drop forces larger conductors the further you go, so past a certain point a standalone solar pump at the bore costs less than connecting it. We work out the crossover point for your actual runs.

Do sheds need their own switchboards?

On anything beyond a light and a power point, yes. A subboard gives local isolation and protection, which means a fault in the workshop is dealt with at the workshop rather than requiring someone to walk back to the house to find the right breaker.

What happens when we add another building later?

If headroom was designed in, it is a straightforward addition. If the system was sized exactly to the day it was commissioned, it can mean a new board, a bigger inverter or a larger supply cable. Leaving margin at installation costs very little compared with retrofitting it.