Oversized vs Undersized Solar Systems | Right Balance

G’day! So you’re thinking about solar. Smart move. You’ve seen the neighbours get their system up, watched their power bills shrink, and now you’re ready to jump in. But here’s the bit that does everyone’s head in: how big should you actually go?

Do you max out the roof to become a mini power station? Or play it safe with a smaller, cheaper system? Getting this balance wrong is the difference between a ripper investment and a seriously underwhelming one. Let’s break down the overs and unders, Aussie-style.

The All-You-Can-Eat Buffet: The Oversized System

This is the “go big or go home” approach. Slapping on as many panels as your roof (and wallet) can handle.

The Good Oil:

·You’ll make a tonne of power, especially in the middle of the day. You’ll cover all your usage and send heaps back to the grid.

·It “future-proofs” you. Thinking of getting a pool, an air-con for every room, or an EV in a few years? A bigger system means you won’t need to upgrade later.

·Great for day users. If someone’s home all day running appliances, you’ll use more of your own solar as you make it.

The Catch:

·The Sting Upfront. Obviously, it costs more from the get-go.

·Feed-in Tariffs are Rubbish. Let’s be real – what the power company pays you for your extra electrons is peanuts these days. Making a huge surplus you don’t use isn’t the money-spinner it once was. You’re often giving it away cheap.

·You Might Hit a Cap. Most homes have a single-phase connection and a 5kW inverter limit for standard approval. You can put more panels on (say, a 6.6kW system), but they’ll be clipped by the inverter at 5kW of output at any one time. You produce more over the whole day, but you can’t use that extra peak power yourself.

The Snack-Sized Portion: The Undersized System

This is the cautious, budget-friendly start. A smaller system that just covers your basic needs.

The Good Oil:

·Less cash out of pocket. The initial hit to the savings is smaller.

·Quick Return on Investment (ROI). Because it’s cheaper, it can pay for itself faster on paper.

·Fine for low users. If you’re a couple in a small house who are out all day, it might be all you need.

The Catch:

·The “Oops, I Need More” Moment. Your habits change. You get that ducted air-con. Your energy bills creep back up, and you’ve got no more roof space or a system that’s tricky to upgrade.

·You’ll Still Buy a Lot from the Grid. You’ll be at the mercy of those ever-increasing usage rates for your morning and evening power.

·Missing Out on Bigger Savings. The real gold in solar is using your own power, not selling it. A system that’s too small just doesn’t displace enough of your grid purchases.

Finding the Sweet Spot: The “Goldilocks” System

You want the system that’s just right. The goal isn’t to be a power company; it’s to slash your own bill as much as possible.

Here’s how you think about it:

1.Look at Your Bill, Not Just Your Roof. The single most important number is your actual daily consumption (in kWh). A good installer will help you analyse this. The sweet spot is a system that generates close to what you use over a full day, not necessarily what you can fit.

2.Shift Your Load (The “Solar Soak”). This is the game-changer. Run your pool pump, dishwasher, and washing machine during the day when the sun’s blazing. This simple habit means a mid-sized system can cover a huge chunk of your needs.

3.Think About a Battery (But Be Real). Batteries are cool, but they’re still pricey. A better strategy for most right now is to size your solar system with a future battery in mind. Get enough panels to both run your house and charge a battery later. That often means going a bit bigger than you need today.

4.Understand the Inverter Dance. Remember, you can have more panel capacity (e.g., 6.6kW) than your inverter (5kW). This is often smart—it gives you more power in the morning and afternoon, even if you clip the midday peak. Your installer should explain this “oversizing” of panels.

The Bottom Line, Mate

For most Aussie households, the right balance is a system sized to match your daytime usage and future plans, not to maximise exports. It’s often better to go a bit bigger (like a 6.6kW panel system on a 5kW inverter) than a bit smaller, assuming your roof and budget allow.

Don’t let a cheap, tiny system tempt you into false savings. And don’t pay a premium for a massive one just to feed the grid for pennies. Get quotes that clearly explain the estimated self-consumption (the power you’ll use yourself) versus export. The system that gives you the highest self-consumption is usually your winner.

Your Solar Cheat Sheet

·Too Big: High upfront cost, lots of low-value exports, good for future plans.

·Too Small: Cheap start, but you’ll still have big bills and might regret it later.

·Just Right: Covers your daily usage, maximises what you use yourself, and leaves room for a battery or lifestyle changes.

FAQs You're Probably Wondering

Q: Will I get “blacklisted” by the network for sending too much power back?
A: In some areas with really congested grids, there can be limits on how much you can export. A good installer will check this and can even set your inverter to limit exports to a certain level (e.g., 3kW). It’s a thing to ask about.

Q: What if I get an electric car or pool later?
A: This is the strongest argument for going bigger now. Retrofitting more panels later can be messy and expensive. Factor in these plans when you size up.

Q: Are there still government rebates (STCs) for bigger systems?
A: Yep, the STC rebate applies to systems under 100kW. A bigger system gets a bigger dollar rebate, but you pay more overall. It softens the blow, but don’t size up just for the rebate.

Q: How do I know if a quote is for a quality system?
A: Look at the brand of the panels and inverter (not just the wattage). A 6.6kW system with tier-one panels and a reliable inverter is a better buy than a cheap, no-name 8kW system that might underperform or fail.

Q: My installer is pushing me really big. What should I do?
A: Ask them to show you the numbers. “Walk me through why I need this many panels for my usage. What’s my estimated self-consumption versus export?” If they can’t explain it clearly, get another quote. It’s your roof and your money.