What is a stand alone power system (SPS) in WA, and what does one cost?

RENOZ Energy is a Perth battery OEM. We supply LiFePO4 battery platforms that accredited installers design private stand-alone power systems around, so we have a commercial interest in the private path. What we do not do is utility SPS work; Western Power and Horizon Power own and maintain theirs.

Because the utilities' own program is the reference point for the term SPS in WA, this guide reports their published figures alongside the critical reporting. The sceptic material matters as much as the brochure material: farmers in WA's south have documented outages and maintenance problems on utility SPS units, and that record is part of any honest answer.

A stand alone power system is an electricity supply that operates without connection to a main electricity grid. The governing Australian standard, AS/NZS 4509.1, requires the designer to analyse the site's actual energy use, usage habits and peak demand in detail, then size the generation array, the inverter-charger and the battery bank against those figures. It is an installation and safety standard, used alongside AS/NZS 3000 wiring rules, and it is the reason a proper SPS quote starts with a load audit rather than a catalogue.

In practice, a stand alone power system has four parts. Solar panels generate the energy. A battery bank, almost always LiFePO4 chemistry in current Australian designs, stores it for night and cloudy weather. An inverter-charger converts battery DC into 230 V AC household supply and manages charging. A backup generator, usually diesel, covers extended overcast periods and fault recovery. Depth of discharge matters here: LiFePO4 banks are designed for around 80% usable capacity, so a 25 kWh gross bank delivers roughly 20 kWh usable.

The term SPS is not marketing language. It appears in the standard, in Western Power's program documentation and in WA energy policy, which is why suppliers use it and why it is the phrase to search when you want WA providers rather than overseas content.

Western Power's stand-alone power system program(opens in a new tab) replaces selected long, remote overhead network connections in its South West Interconnected System with utility-owned SPS units. Each unit combines solar panels, battery storage and a backup diesel generator with monitoring and control equipment. The utility pays for site investigations, installation, ongoing operation and maintenance, faults and eventual system replacement. As an ABC News investigation reported in July 2026, 498 standalone units had been installed across regional WA by that date, with 100 in the Shire of Cranbrook alone.

The economics only work because of what the program removes. Maintaining kilometres of single-phase overhead line to serve one or two properties is expensive and creates bushfire and reliability risk, so in the right locations a utility-grade SPS is cheaper over its life than the poles and wires it replaces. The Economic Regulation Authority's review material(opens in a new tab) records average capital costs of about $287,000 per SPS in Round 1 and about $229,000 in Round 2, and Western Power has publicly described the cost as roughly $200,000 per system.

That figure is a program cost, not a bill. Properties selected for the program do not pay the $200,000. Customers keep paying their electricity retailer under normal tariff arrangements, and Western Power remains responsible for faults, maintenance and replacement. The trade is that the old grid connection is usually permanently removed, which is exactly where the program has run into trouble.

Horizon Power, which serves regional and remote WA outside the South West Interconnected System, runs an equivalent standalone power systems program(opens in a new tab). The WA Government committed in November 2022(opens in a new tab) to 1,000 SPS units across the state over five years, with a $45.8 million Horizon tranche originally targeting 150 systems. By the 2025-26 budget that Horizon commitment had been adjusted to 94 funded systems, reflecting higher delivery costs and Building and Energy compliance issues, and Horizon's 2024-25 annual report recorded 84 hybrid renewable systems delivered. Concentrations sit around Esperance, Hopetoun, Exmouth and Carnarvon.

Horizon's standard designs supply an equivalent level of service to the removed network connection: around 16-24 kW for properties previously supplied by 10-25 kVA transformers. The state budget papers describe the fleet as ranging from roughly 5-25 kW output with 10-50 kWh of battery storage in older or smaller units, up to about 72 kW output and 86 kWh of battery in the newest systems. Around 80% of the energy those systems delivered came from renewables, and average backup-generator runtime across the fleet in 2024-25 was about 22 hours per month.

Like Western Power, Horizon does not offer SPS installation as a general application program. It identifies candidate properties through asset-management planning and contacts customers directly. You cannot ring Horizon and order an SPS for your block; you can only be selected.

The most specific published figures come from the Economic Regulation Authority's review material: average capital cost of roughly $287,000 per system in Round 1 of the program and $229,389 in Round 2, excluding risk and escalation allowances. Western Power has described the cost as approximately $200,000 per system in public statements, and ABC News questioned value for money on those figures in March 2024(opens in a new tab).

Those figures cover utility-grade scope: engineered design, redundant backup generation, monitoring, remote control, installation at remote sites, and in many cases decommissioning of the overhead line. That is why they dwarf the cost of a private off-grid system with similar headline capacity. The utility unit carries program overheads, network-grade procurement and 20-plus-year maintenance obligations that a private owner never signs up for.

For the landowner the honest summary is: a utility SPS costs you nothing upfront, keeps you on a normal tariff, and hands maintenance to the utility. What it can cost you is control. The ABC's 2026 reporting documented farmers moved onto SPS units without landowner consent being required under WA legislation, and the old grid connection removed in the process. If the system underperforms for a high-load farm, restoring the connection is not a simple ask; one Tenterden farmer's request to go back on the grid was rejected.

A privately commissioned SPS is priced from your load audit, but WA market pricing gives stable bands. A small weekender or bush-block system runs $15,000-$30,000 installed including solar, inverter and battery. A standard three-bedroom rural home with refrigeration, pumping and normal household loads typically lands at $40,000-$65,000. Farm and high-load sites with bore pumps, cold rooms or workshops run $70,000-$120,000 and beyond, with batteries typically 40-50% of system cost.

The federal Cheaper Home Batteries Program(opens in a new tab) applies to these private off-grid systems: roughly 30% off the battery cost at point of sale via STCs, with no grid connection required, as confirmed by DCCEEW. The WA Residential Battery Scheme does not apply, because it requires VPP enrolment on the Synergy or Horizon grid. Requirements for the federal rebate are a CEC-approved battery and an SAA-accredited installer; our WA rebate and CEC approval guide explains how to check both.

For context on scale, the Harvey farm case study in WA is a private system: 35.8 kWh of gross battery, 21 kWp of solar, a Selectronic SPMC482 with Fronius Primo AC coupling, installed after the owner received a $200,000 grid connection quote. That single quote is the hinge point most private SPS decisions swing on. For the full cost breakdown by system class, see what an off-grid system costs in WA.

A utility SPS suits a property the network itself no longer wants to serve: an existing grid customer at the end of a long, fault-prone single-phase spur, with household-scale loads and no plans to expand them. If Western Power or Horizon Power selects your property, you get utility-grade equipment, someone else's maintenance problem, and your existing tariff. You give up the grid connection and, with it, headroom for a workshop, big pumps or future sheds.

A private SPS suits the property the network never reached, or reaches only at a price that makes no sense. If you are facing a connection quote in the tens of thousands of dollars, or your block sits more than 1 km from the grid, the federal battery rebate and the economics of private off-grid are in your favour. The CER's off-grid rebate eligibility rule hinges on being more than 1 km from the grid or facing a connection cost above $30,000, so verify your distance and your quote before you decide anything.

The farmers the ABC interviewed who struggled with utility SPS units had one thing in common: loads and expectations bigger than the system was sized for. Capacity limits, automatic shutdowns on high draw, and generator noise near living areas were the recurring complaints. A private system sized to your actual load audit avoids exactly that failure mode, at the price of owning the maintenance yourself.

The strongest sceptical reporting on WA's SPS program is the ABC's July 2026 investigation. Farmers described roughly 70 power outages(opens in a new tab) on one system since its 2022 installation against three or four a year on the old grid, generator noise audibly close to bedrooms, and years-long waits for remediation on early units. A Cranbrook shire chief executive described an 85-year-old resident told her power was being cut off only when crews arrived on her property, because WA legislation does not require landowner consent.

Western Power's response to that reporting was that the program is delivering strong outcomes, with 96% of users experiencing better reliability since installation, and that some initial units required remediation and upgrades as the utility learned more about individual customer needs. Both things can be true: most customers get better reliability than a failing overhead line, and the customers at the margin, particularly high-load farms, have worn real disruption.

The transferable lesson for private buyers is about design authority and local support, not about whether SPS works. Systems fail when loads are not audited honestly, when the generator is undersized or badly located, and when the service response is measured in days of travel time. Those are procurement decisions you control on a private build.

If your property is already grid-connected and Western Power or Horizon Power approaches you about an SPS, the utility drives the process: energy audit, site inspection, agreement, design, installation, cutover, and removal of the redundant line. Ask specifically about sized headroom for future loads, generator location relative to bedrooms, automatic reset capability, and what happens to your tariff and consumer protections. Horizon commits to the same tariff and protections as network customers; get any promise in writing.

If you are not yet connected, or you are holding a connection quote you cannot justify, the private path starts with a load audit and ends with quotes from SAA-accredited off-grid installers. There is no application to the utility and no waiting for asset planning to select you. The design obligations under AS/NZS 4509.1 sit with your installer, and the battery must be CEC-approved to qualify for the federal rebate.

The middle case matters too: a grid connection that exists but fails regularly. Before accepting a utility SPS replacement or paying for private off-grid, price three things: the utility's own repair record on your line, what a private system sized to your loads would cost, and what a generator-only interim would cost you. Our fringe-of-the-grid guide for WA walks through that decision.

Every credible SPS design starts from daily kilowatt-hours, not from panel or battery branding. Walk through every appliance, note its wattage and hours of use, total the daily kWh, then multiply by your target days of autonomy and divide by 0.8 for LiFePO4 depth of discharge. A 3-bed rural WA home at 18 kWh per day with 2.5 days of autonomy needs about 56 kWh gross, which is 11 RENOZ 5.12 kWh modules. Our WA battery sizing guide runs the full method with worked examples.

Two loads break casual sizing assumptions. Motor loads such as bore pumps draw 4-8 times their running current at startup, which sizes the inverter in kVA rather than the battery in kWh. And generator runtime is the hidden operating cost: a private SPS that leans on its genset every overcast day carries fuel, servicing and noise that a bigger solar array would have avoided. Horizon's own fleet averaged about 22 generator hours per month in 2024-25, which is a useful public benchmark for a well-run system.

Design the generator as an emergency backstop, not a daily participant. Oversize the solar array before the battery in WA's climate, keep high-draw jobs like pumping and welding in daylight hours, and the generator becomes the 2-hours-every-few-days machine it should be. Our guide on moving a WA farm from diesel to battery covers that transition in detail.