Couple Builds Solar Power Plant — Essential knowledge for Australian off-grid living

Couple Builds 13kW Solar Power Plant: Full Breakdown

The Complete Evolution Of Solar

Most off-grid solar content shows you a finished system or walks through a single weekend install. What Aaron and Josh from Wild Wonderful Off-Grid document is something far more valuable: the complete evolution of a solar system from a basic 12-panel starter setup to a full 13.1kW residential power plant with three MPPT charge controllers, a growing battery bank, and the ability to run a modern household on a cloudy day as if it were sunny. This is not a weekend project. This is what serious energy independence looks like.

Video credit: Wild Wonderful Off-Grid on YouTube.

From Raw Land to Energy Independence

Aaron and Josh started with nothing. Literally raw land with no running water and no electricity. The nearest power pole was half a mile away, making grid connection both expensive and contrary to their goal of complete energy independence. For the first eight months, they ran entirely on a petrol generator while saving for solar.

That initial solar purchase, funded by a Christmas bonus, changed everything. Starting with 12 panels and a basic setup, they proved the concept before scaling up. This phased approach is one of the smartest strategies for off-grid builds: start small, learn your actual consumption patterns, then expand based on real data rather than guesswork.

If you are still in the planning phase, our solar calculator can help you model different system sizes and see what each configuration can realistically power.

The Final System Specs

After the upgrade, the completed system looks like this:

• Solar panels: 32 total (12 x 385W Hanwha + 20 x 425W), delivering 13,100W peak
• Charge controllers: 3 x MPPT 80A controllers, each managing one string
• Inverter: 6,800W inverter/charger
• Battery bank: 6 x 48V Simpliphi batteries (3.8kWh each), totalling 22,800Wh with a goal of 15 batteries (57,000Wh)
• Loads: Two Mr Cool mini-split heat/AC units, dishwasher, washing machine, well pump, microwave, refrigerator, freezer, LED lighting, electronics, air compressor, electric fence charger

The wire sizing from the solar array to the powerhouse was calculated for under 3% voltage drop, which is critical when running cable over longer distances from a ground-mounted array.

Three Strings, Three MPPT Controllers: Why It Matters

One of the most important design decisions in this system is splitting the 32 panels across three separate strings, each feeding its own MPPT charge controller. This is not just about staying within the amp limits of a single controller. There are real performance advantages.

Independent maximum power point tracking

Each MPPT controller independently finds the optimal voltage and current combination for its string. If one string is partially shaded by a cloud while the others are in full sun, only the shaded string's output drops. The other two continue producing at maximum capacity. With a single controller managing all panels, partial shading on any panel can drag down the entire array's output.

Intelligent load management

Aaron demonstrates something fascinating in the video. When the batteries are fully charged and household load is low, the charge controllers automatically ramp down. As loads increase (turning on appliances, running the well pump, firing up the air compressor), the controllers independently ramp up to meet demand. The system intelligently draws power from solar first, only touching the battery when solar cannot keep up.

In their cloudy-day test, with 5,000W of simultaneous load running (two heaters, well pump, air compressor, movie playing, all lights on), the three charge controllers were producing:

• String 1: 980W
• String 2: 1,700 to 1,800W
• String 3: 2,600W

Total solar input: approximately 5,300W on a fully overcast day. Not only was it meeting the 5,000W load, it was still trickling charge into the batteries. That is the power of oversizing your array and distributing it across multiple controllers.

What this means for Australian systems

Multiple MPPT controllers are especially valuable in Australia for several reasons:

• Variable shading: Eucalyptus trees are tall and throw long shadows, especially in winter when the sun is low. Having panels on separate strings means one shaded section does not cripple the whole system.
• Mixed panel orientations: If your roof or ground mount faces multiple directions, each orientation should ideally have its own MPPT controller to track independently.
• Staged expansion: Adding a new string with a new controller is simpler than replacing a single oversized controller every time you add panels.
• Redundancy: If one controller fails, you still have two-thirds of your solar capacity online while you source a replacement.

Running a Fully Modern Home Off-Grid

One of the most compelling aspects of this build is what they are actually running. This is not a spartan, lights-only setup. Aaron and Josh operate a fully functional modern household entirely on solar:

• Two Mr Cool mini-split units for heating and cooling
• Full kitchen with dishwasher, microwave, and refrigerator
• Washing machine
• Well pump for pressurised water
• Multiple TVs and computers
• LED lighting throughout
• Deep freezers
• Workshop power tools
• Air compressor
• Electric fence charger for livestock
• Starlink internet

At the time of recording, they had been running electric heat for multiple consecutive days without using any firewood. On their previous smaller system, they had to be mindful of every load during cloudy periods. Now, they go about their day normally regardless of weather. That is the freedom that comes with proper system sizing.

The Battery Question: Building Over Time

With six 3.8kWh batteries (22,800Wh total), they have a solid base, but Aaron is transparent that their goal is 15 batteries (57,000Wh). This phased battery expansion is common in off-grid builds for one simple reason: batteries are expensive.

At roughly $1,000 to $1,500 per 3.8kWh unit, getting to 15 batteries represents $15,000 to $22,500 in battery investment alone. Building up over time makes this manageable financially.

The critical design decision that enables phased expansion: choosing a battery chemistry and format that supports parallel stacking. The Simpliphi batteries they use are designed for exactly this. You add units, the BMS manages the new capacity, and the inverter adapts automatically.

For Australian builders, plan your battery expansion from day one. This means:

• Choosing an inverter that supports a battery capacity range beyond your initial install
• Installing cable runs and bus bars sized for the final battery count, not just the initial one
• Leaving physical space in your battery enclosure for additional units
• Ensuring your charge controllers can deliver enough current to charge the larger bank efficiently

Our master off-grid calculator can help you model staged expansion scenarios so you know your end-state system size from the beginning.

The Install Process: Practical Lessons

The timelapse and commentary reveal several practical lessons that are easy to miss in planning but important during execution.

Removing and reinstalling panels

The upgrade required removing all 12 original panels, replacing the entire rail system, then reinstalling the originals alongside 20 new panels. This is a full day of physical labour involving working at height with heavy, fragile glass panels. If you are planning a staged build, consider whether your initial racking system can accommodate additional panels or whether you will need to replace it entirely (as they did).

Wire sizing for voltage drop

They specifically call out sizing the wire from the solar array to the powerhouse for under 3% voltage drop. This is critical for ground-mounted arrays where cable runs can be 20 to 50 metres. In Australia, AS/NZS 5033 specifies maximum voltage drop requirements. As a rule of thumb, use 6mm² cable for runs up to 15m at 48V, 10mm² for 15 to 25m, and 16mm² or larger for runs beyond 25m. Always calculate based on your actual current and distance.

Weather does not wait

The video captures them installing panels with snow on the ground. They also had newborn lambs arriving mid-project, requiring them to stop and attend to their livestock. Off-grid life does not pause for your solar install. Plan for interruptions and do not schedule your install during a period when you cannot afford delays.

Cloudy Day Performance: The Real Test

The most impressive segment is the cloudy-day stress test. With fully overcast skies, they intentionally loaded up the system to over 5,000W: every light in the house, both heaters, well pump, air compressor, and entertainment systems running simultaneously. The result? The system handled it without touching the batteries.

This is the benchmark for a properly sized off-grid system. Not "it works on a sunny day" (any system can do that) but "it works on a cloudy day without compromise." If your system cannot maintain your normal daily routine through a cloudy day, you are either undersized on panels, undersized on battery, or both.

In Australia, cloudy-day performance is particularly important in:

• Coastal Queensland and NSW: Summer wet season brings extended cloud cover
• Victoria and Tasmania: Winter months (June to August) can see a week or more of heavy overcast
• Anywhere during La Niña years: Extended wet and cloudy periods across eastern Australia

A 13kW array is admittedly large for a residential off-grid system, but even at reduced output (say 30% on a heavily overcast day), that is still nearly 4kW of available power. Scale this to your needs: if you require 3kW on a cloudy day, you need roughly 10kW of panel capacity to achieve it.

Cost Considerations for Australian Builders

While the video does not provide a detailed cost breakdown of the upgrade, we can estimate based on current Australian pricing:

• 32 panels (mixed 385W and 425W): $6,000 to $10,000 depending on brand and supplier
• 3 x MPPT 80A charge controllers: $1,500 to $4,500 (depending on brand: Victron, EPEver, or similar)
• 6,800W inverter/charger: $3,000 to $6,000
• 6 x 48V 3.8kWh batteries: $9,000 to $15,000
• Racking, cable, breakers, and misc: $3,000 to $5,000
• Estimated total: $22,500 to $40,500 AUD

That is a significant investment, but compare it to the cost of grid connection in a remote area ($20,000 to $80,000 for poles and wires) plus decades of electricity bills. Over 20 years, the off-grid system is almost always cheaper, and you own your energy supply outright.

Scaling This Approach

Not everyone needs 13kW of solar. But the principles demonstrated here scale beautifully:

1. Start with a functional minimum. Their original 12 panels ran the household with mindful usage. You do not need the final system on day one.
2. Choose expandable components. Inverters, charge controllers, and batteries that support parallel expansion mean you never waste your initial investment.
3. Add solar first, batteries second. Panels are cheap and immediately reduce generator reliance. Battery expansion can follow as budget allows.
4. Use multiple charge controllers. Even if you start with one, design your wiring so adding a second or third controller is straightforward.
5. Test under adverse conditions. Do not assume your system works. Deliberately stress-test it on your worst weather days.

Recommended Products

Building a large off-grid solar system requires quality components. Here are the key categories to research:

• 400W Solar Panels (Monocrystalline): High-efficiency mono PERC panels are the standard for modern off-grid builds. Buy in bulk for significant per-panel savings.
• Dual/Multiple MPPT Charge Controllers 80A: Running multiple controllers gives you independent string tracking, redundancy, and easier expansion. Look for 80A or 100A units rated for 48V systems.
• Large Battery Bank (48V LiFePO4): Stackable rack batteries with CAN bus communication allow you to build capacity over time. Prioritise brands with Australian warranty support.
• Solar Panel Ground Mount Frames: Adjustable aluminium frames designed for Australian wind zones. Essential if roof mounting is not an option.
• Cable Management Supplies (UV-Rated): UV-stable conduit, cable clips, and junction boxes. Australian sun destroys standard PVC in 2 to 3 years. Always use UV-rated components for outdoor cable runs.

Prices and availability vary. For large system components, consider contacting specialist off-grid suppliers for bulk pricing.