How Much Is a Solar System in 2025? A Scenario-by-Scenario Guide (With Real Numbers)

When someone calls me about solar, it's rarely a casual "I'm just thinking about it" conversation. In my role coordinating solar installations, it's usually one of three things:

"My bill is out of hand and I need something before summer."

"My inverter died on Tuesday and I need power back before the weekend."

"The feed-in tariff is changing next month. Can you get it installed in time?"

I've spent eight years doing this work—mostly in Adelaide, some regional. Some jobs are planned six months out. Others are emergency swaps where an inverter failed and the customer is bleeding money at retail rates while they wait. So when someone asks me how much is a solar system, my honest answer is: it depends on which situation you're in.

That's not helpful on its own. So here's a scenario-by-scenario breakdown using numbers I'm actually seeing in the Adelaide market right now.

Why There's No Single Price for a Solar System

When I first started in this industry, I assumed there was a going rate. You ask for a 6.6kW system, you get a quote, that's the price. Took me about three months in the field to realize how wrong that was.

The cost swings on a bunch of variables:

• System size (obviously)
• Single-phase vs three-phase supply
• Battery now vs battery later vs never
• Roof complexity—tile, tin, pitch, orientation
• Inverter brand and quality (this is where Growatt enters the conversation)
• Metro vs regional installer travel

That's why a system that costs one person $5,000 can cost their neighbor $8,500. Both quotes can be legitimate. Neither person is being ripped off.

Scenario A: Modest Home, Just Want Lower Bills

Who this is for: You're using maybe 10–15kWh a day. Your quarterly bill is $300–$500. No EV, no pool, no ducted air running all day. You just want to stop paying retail rates for every single kilowatt.

What works: A 6.6kW PV system with a 5kW Growatt inverter. Single-phase is fine for most Aussie homes, and Growatt's single-phase range is solid—reliable, well-supported, and priced sensibly.

The numbers: Based on quotes I've seen over the past twelve months in Adelaide:

• Installed cost: $4,500–$7,500 AUD
• Annual bill savings: $500–$1,200 depending on your tariff and usage timing
• Payback: typically 4–7 years

Not amazing. Not terrible. Serviceable. That's the reality of a small system on a modest home. But it's real money, every quarter, for decades.

Scenario B: Big Home with Real Loads

Who this is for: You're running ducted reverse-cycle air conditioning, a pool pump, maybe an EV in the garage. Your quarterly bill regularly blows past $800. A 5kW inverter won't cut it—you need a 12kW Growatt inverter or equivalent.

This is where the bigger Growatt models earn their keep. A 12kW inverter is three-phase, which means it can feed generation across all three phases of your switchboard. What I mean is: a 5kW single-phase inverter can only offset consumption on the one phase it's connected to. A 12kW three-phase inverter spreads that solar across the whole home—which matters when your ducted air con is pulling on one phase while the EV charger pulls on another and the pool pump runs on the third.

Typical setup: 10–13.2kW of panels (you'll need roof space—roughly 30–40 panels with modern efficient modules) paired with the 12kW inverter.

The only time I'd tell you to size down from a 12kW inverter is if you're truly single-phase. Not every home can support three-phase, and if yours can't, the 12kW unit isn't the right fit. Check your switchboard before you fall in love with the spec sheet.

The numbers: For a 13.2kW system with a 12kW Growatt three-phase inverter:

• Installed cost: $9,000–$14,000 AUD
• Annual savings: $1,500–$3,000+ depending on usage
• Payback: 4–6 years in most cases

If your usage justifies it, the bigger system is actually better value per watt. The jump from 6.6kW to 13.2kW costs less than double, but the output doubles. And you're not paying much more per panel—mostly just the inverter upgrade and extra panels.

Scenario C: Storage, Backup, and Adelaide-Specific Math

Who this is for: You've had four outages this year (hello, metro Adelaide). You're on a time-of-use tariff that penalizes evening usage. Or you're regional SA, where outages aren't a nuisance—they're a fact of life.

Growatt solar storage in Adelaide has quietly become a much better deal over the past two years. Battery prices fell through 2024, and South Australia's electricity prices—among the highest in the developed world, ironically for a state that runs on wind and solar—make the storage payback faster here than almost anywhere else in Australia.

But here's something vendors won't tell you: a battery isn't about saving money. Not in the short term. Adding a 10kWh Growatt battery to a solar system adds roughly $8,000–$15,000 to the install price. That pushes your payback period past the simple PV-only numbers. The financial case is real, but it's not the headline.

A battery IS about:

• Having power when the grid drops out
• Shifting your daytime surplus to the evening peak (where SA rates are brutal)
• Genuine energy independence, not just bill arbitrage

What most people don't realize is that a battery only makes financial sense if your PV array is sized to generate a surplus in the first place. If your 6.6kW system barely covers daytime usage, the battery has nothing to store. You need the bigger array plus storage as a combined package. That's why Growatt storage systems pair naturally with the 12kW inverter—you get the generation headroom and the battery in one ecosystem.

The numbers: For a 13.2kW array + 10.4kWh Growatt battery in Adelaide:

• Installed cost: $17,000–$24,000 AUD
• Payback: 6–10 years depending on usage patterns
• Peace of mind: priceless (cliché, but true when it's 39°C and the grid just went down)

SA Power Networks' evening tariff rates are punishing. A battery that shifts 10kWh of daytime solar to the evening peak can save you $3–$5 a day. That's $1,000–$1,500 a year, which changes the storage math significantly versus most other states.

Scenario D: Commercial and Small Business

Who this is for: You're running a workshop, office, or retail space with serious daytime loads. Solar is actually more valuable to you than to a typical homeowner because you're offsetting consumption during business hours—when rates are highest.

Commercial systems start around 20kW and scale up. Growatt's commercial three-phase range goes well past 100kW, but for small business, the 20–50kW range is the sweet spot.

Commercial installs run roughly $1.00–$1.40 per watt fully installed—so $20,000–$28,000 for a 20kW system. More complex roofs, three-phase switchboard upgrades, or shade structures push that higher.

Don't use a residential installer for this. Find someone accredited for CEC commercial installations. Compliance paperwork, electrical design standards, and insurance requirements are different, and getting it wrong is a headache you don't want.

What a 48-Hour Emergency Taught Me About Buying Solar

In December 2024, a client in Adelaide's eastern suburbs called me on a Thursday afternoon. A storm had rolled through the night before, and their inverter was fried. They had a 12kW system and a pool pump running daily. Their parents were arriving on Saturday for a week-long stay.

The quote to fix it: $2,900 for a replacement inverter. But installation slot? Eleven days out.

The alternative: wait, let the family sit in 36-degree heat, and pay retail electricity rates for the entire Christmas week. Or pay $400 extra in rush freight and overtime and have power restored by Saturday morning.

We paid the rush fees. The client's alternative—a week of no air conditioning during an Adelaide heatwave plus $600 in retail electricity—was significantly worse than the $400 premium.

That's the thing I think people miss when comparing solar quotes. The value of guaranteed turnaround isn't just speed—it's certainty. A cheaper inverter that arrives in twelve days is worthless if your current one died in a storm and the next one might too. Sometimes, the certain option is the only rational option.

That experience is exactly why I now refuse to quote a system without surge protection. More on that below, because it ties directly to what happened.

Two Components You Shouldn't Skip (In Every Scenario)

I could end the article here, but there are two things that separate a system lasting 15 years from one that dies in 3. Neither gets top billing in sales brochures. And both are cheap compared to the cost of replacing things.

MPPT Solar Charge Controller with Bluetooth

If your system includes batteries—especially hybrid or off-grid setups—the MPPT solar charge controller is arguably more important than the inverter. It's the component that extracts power from the panels and feeds the battery at the correct voltage. A good MPPT controller can harvest 10–15% more energy from the same array than a cheap one.

Getting a controller with Bluetooth connectivity isn't a luxury. It means you can check system performance from your phone without walking out to the shed or digging out the laptop. Growatt's inverters and battery systems integrate with their app, and I genuinely wish more customers cared about this before they bought—not after. When you can see your system's output daily, you notice problems early, when they're cheap to fix.

Diversitech Surge Protector

In the December incident above, the cause wasn't a manufacturing fault. It was a lightning strike three streets away that sent a surge through the mains. The inverter took the hit. A $200 Diversitech surge protector installed between the array and the switchboard would have taken that surge instead of the $2,900 inverter.

A Diversitech surge protector costs about $150–$250 installed. A replacement 12kW Growatt inverter costs $2,500–$3,000 plus install. The math isn't complicated—but here's the twist that most people don't know: it's not just about lightning. In Adelaide, voltage spikes also come from grid switching, pool pumps starting, and even your own appliances cycling. These micro-surges degrade electronics over time, not just in a dramatic storm event.

(Not that I'm keeping a tally, but I've replaced four inverters that were killed by surges. Three of them had no protection. The one that had protection? It survived. The outage knocked out the neighbor's system, but not the one with the surge protector installed.)

A lesson learned the hard way. Now every quote I write includes surge protection as standard. I'm not trying to upsell—I'm trying to stop getting middle-of-summer emergency calls from customers whose expensive equipment just got fried.

How to Tell Which Scenario You're In

Still not sure which category fits? Here's my quick litmus test:

• Bill under $500 per quarter and no major appliance additions planned: go with Scenario A. Save your money. Skip the battery. A modest system will serve you fine.
• Bill over $800 per quarter, three-phase supply, maybe an EV or plans for one: Scenario B. Size up to the 12kW Growatt inverter and make the most of your roof.
• Outages more than twice a year, or you're on a punishing evening time-of-use tariff: Scenario C. Budget for storage, or at minimum make sure your inverter supports battery retrofitting later.
• Running a business with daytime consumption: Scenario D. Stop reading consumer guides—even this one—and get tailored commercial advice from a CEC-accredited commercial installer.

Whichever scenario fits, don't skip the surge protector. And make sure your gear is CEC-approved. The Clean Energy Council publishes a list of approved inverters, and Growatt's residential models are all on it—which also means you're eligible for STC rebates and, in SA, any applicable state incentives.

That gives you a baseline. The next question is choosing an installer, and that's a topic I have strong feelings about. But it'll have to wait for another article.