Western Power is the state government-owned corporation that owns, operates and plans the majority of the SWIS — the large, interconnected electricity network that covers Perth, the South West and many inland population centres. It’s the single regulated network operator in WA’s SWIS and its decisions shape how big renewable and storage projects connect to the main grid.

Horizon Power is also a state government-owned corporation but with a very different remit: it generates, distributes and retails electricity across wide swathes of regional WA that lie outside the SWIS. That includes the Pilbara’s North West Interconnected System (NWIS), several regional connected networks and dozens of microgrids serving remote communities and stations. Horizon’s work often involves designing hybrid diesel/solar/battery plants and supporting energy access in locations where the economics and logistics of power supply are far more challenging than in the SWIS.

Service areas and network types — why geography shapes everything

The most useful way to think about the difference is interconnected vs islanded:

The SWIS (Western Power) is an interconnected network: transmission and distribution lines link towns and cities, large generators and storage assets, and the system operates with centralised system planning and security considerations. It’s the environment where big utility-scale wind, solar farms and large battery energy storage systems (BESS) connect, and where network access, reliability standards and regulatory processes are well developed.

Horizon Power’s footprint is mostly islanded or multi-islanded systems: small towns, Aboriginal communities and pastoral stations separated by hundreds of kilometres. Many sites run hybrid plants (solar + battery + diesel) or are microgrids tailored to local needs. Reliability and affordability are closely tied to fuel logistics (diesel deliveries), community engagement and local operating practices.

This geographic reality drives almost every technical, commercial and social decision both DNSPs make.

Regulation and customer obligations — one size doesn’t fit all

Western Power’s SWIS operations sit squarely inside WA’s regulated network arrangements and the Economic Regulation Authority’s (ERA) oversight. That means Western Power must justify major investments using regulatory tests, report against service standards, and publish planning documents such as the Whole of System Plan and SWIS transmission and demand assessments. Those frameworks influence tariffs, long-term investment and how new generation and storage can access the grid.

Horizon Power, while also a state government-owned corporation, operates under a different policy mix that reflects its social and regional service obligations. It is responsible for ensuring supply to small and often vulnerable communities, which can mean different commercial models (including subsidy and grant programs), deeper community engagement and bespoke procurement for microgrids and remote projects. In practice that means Horizon’s projects are as much about social outcomes and resilience as they are about pure economics.

Recent developments you should know (and why they matter)

Two trends stand out across WA: big renewable connection activity on the SWIS, and rapid microgrid and hybrid project development outside the SWIS.

Western Power — accelerating large-scale connections.

In recent years Western Power has issued multiple network access offers that together clear the way for several hundred megawatts of new renewable generation and battery storage to connect to the SWIS. In one period alone, Western Power issued access offers totalling about 759 MW for large solar, wind and BESS projects — a tangible sign that the SWIS is preparing for a substantial boost in clean energy and storage capacity. These offers are important because they allow projects to move from planning to construction, signalling that WA’s main grid is transitioning rapidly toward a cleaner mix.

Horizon Power — practical microgrid rollouts in remote communities.

Horizon has been rolling out and tendering hybrid projects across remote communities, many funded under state and federal programs, to replace expensive diesel generation with solar and battery systems that dramatically cut operating costs. A well-known example is the Papulankutja (Blackstone) Hybrid Energy Solution — a community-scale solar array and battery system with backup diesel generation — funded by the WA Government and ARENA. It’s designed to reduce diesel dependence and improve resilience while providing a template for other small communities.

Technical contrasts: grid security, connection processes and control systems

There are some technical contrasts worth calling out for readers who work in energy, live in regional WA, or are considering connecting generation or storage:

System strength and inertia: In interconnected networks like the SWIS, system strength, frequency control and inertia are managed across many generators and network elements. Connecting large amounts of inverter-based generation requires planning for voltage control, dynamic stability and system services — the kinds of things Western Power assesses in network access and the Whole of System Plan. In islanded microgrids, these same services are provided locally and often by a mix of diesel synchronous machines and inverter controls designed specifically for the microgrid.

Connection process: Western Power runs a formal access and connection process for new generators and batteries, including technical studies, offers and commercial agreements. For Horizon Power, many projects are tendered or delivered under government-backed programs with a focus on local outcomes, community benefits and speed of delivery. The different procurement models reflect their distinct goals: securing large capacity for the SWIS versus ensuring reliable power for remote communities.

Control and protection: Microgrids frequently need custom energy management systems and protection schemes that handle anti-islanding, black start and transitions between grid-connected and islanded operation. The SWIS, by contrast, relies on established protections coordinated across a large footprint and centralised control. That difference affects how engineers design inverters, protection relays and battery management systems for each environment.

What this means for different audiences in WA

For homeowners in Perth or regional towns on the SWIS:
More large-scale renewables and battery systems mean the network is preparing for higher proportions of clean energy, which can translate to lower wholesale prices and more options for zero-emission power. It also means Western Power will continue managing network reinforcements and operational changes. If you’re installing rooftop solar or a home battery, expect structured connection processes and technical requirements to maintain grid stability.

For businesses and developers:
The SWIS presents significant market opportunities. Access offers and transmission planning documents signal where grid hosting capacity is being enabled. Developers should engage early with Western Power’s connection process to align project design with available capacity and reduce approval time.

For remote communities and local councils:
Horizon Power’s microgrid programs are reshaping energy supply for regional WA. By combining solar, batteries and smart controls, these systems reduce diesel reliance, improve reliability and lower long-term costs. For communities, that often means cleaner and more affordable local power. Consultation and training are key — Horizon Power typically works closely with community leaders to ensure projects suit local needs.

Case study: the Papulankutja (Blackstone) hybrid project — a model for remote WA

Papulankutja (also known as Blackstone) in far-east WA is a small Aboriginal community that historically relied on diesel generation for electricity. The new hybrid system delivers a community solar array, multi-megawatt-hour battery storage, and backup diesel generators for reliability.

The project’s goals are straightforward but powerful: drastically reduce diesel use, improve supply reliability, and create a model that can be replicated for similar remote communities across WA. It demonstrates Horizon Power’s community-centred approach — technically tailored systems designed for local conditions, supported by government funding to ensure financial viability.

It’s also an important testbed for integrating smart control systems that balance solar generation and storage in real-time, providing consistent power without the need for continuous diesel operation.

Case study: Western Power’s access offers — enabling utility-scale clean capacity on the SWIS

In the SWIS, Western Power’s network access offers for multiple renewable and battery projects — totalling around 759 MW — are a concrete milestone. These offers effectively greenlight a new wave of utility-scale solar, wind and battery plants across WA’s southwest.

This surge in clean energy projects has several benefits. It strengthens WA’s renewable credentials, helps decarbonise electricity supply, and supports emerging industries like green hydrogen and electric vehicle manufacturing. It also lays the groundwork for future demand growth in the mining and industrial sectors, where reliable access to clean power is becoming a key factor in investment decisions.

However, integrating these projects isn’t simple. Western Power must carefully manage system stability, transmission upgrades, and network costs while maintaining reliability for existing customers. Balancing these competing priorities is one of the DNSP’s biggest ongoing challenges.

Challenges both DNSPs face (but in different flavours)

Western Power:

• – Integrating large volumes of inverter-based generation while maintaining system stability.
• – Upgrading and expanding transmission lines to carry renewable power from remote generation zones to cities and industrial centres.
• – Balancing the cost of network upgrades with fair and affordable tariffs for customers.

Western Power’s Whole of System Plan outlines these challenges and the need for smarter grid management, flexible demand, and investment in system services like frequency control.

Horizon Power:

• – Replacing high-cost diesel generation across dozens of isolated sites.
• – Managing logistical hurdles such as fuel transport, maintenance access, and remote communications.
• – Ensuring local participation and training to sustain new technology deployments.

Many Horizon Power projects rely on public funding and partnerships to balance the economic realities of serving small populations across vast distances. The social impact — cleaner, more reliable energy for regional communities — is often just as important as the technical achievement.

Both providers also face broader pressures: limited skilled labour in regional areas, supply chain constraints, and the growing need for cybersecurity in modern grid systems.

What to watch next

Transmission build-out in the SWIS:
The pace of new transmission development will determine how quickly renewable energy can reach demand centres. Western Power’s planning and delivery of new lines will directly influence project viability and regional investment.

Microgrid replication across regional WA:
Successful hybrid projects like Papulankutja could become templates for dozens of similar communities. Expect Horizon Power to continue rolling out solar-battery systems, supported by state and federal funding.

Regulatory evolution:
As renewable penetration increases, regulators and policymakers will adjust frameworks for energy storage, distributed energy resources (DER), and cost-sharing for network upgrades. Expect continued discussions about how both DNSPs can use non-network solutions — such as community batteries or demand management — to defer expensive infrastructure.

Practical advice for readers

If you live or do business on the SWIS, stay informed about Western Power’s upcoming projects and connection requirements. Early engagement will save time and reduce costs if you’re planning new solar, storage or load expansions.

If you live in a remote community served by Horizon Power, keep an eye on local energy programs. Many projects involve community consultations, job opportunities and training, so there’s value in getting involved early.

For engineers and technical professionals, understand the unique design differences between interconnected and islanded systems. Issues like inverter control, fault protection and black-start capability are crucial in both contexts, but the technical requirements differ significantly.