How a solar system actually works, end to end

The four parts

A rooftop solar system has fewer moving parts than most people expect - in fact it has almost no moving parts at all. Panels convert sunlight into DC electricity. An inverter converts that DC into the AC electricity your house and the grid use, and matches it to grid voltage and frequency. A meter measures what flows in from the grid and what flows back out. Optionally, a battery stores what you don't use immediately.

That's the whole system. What separates a system that pays for itself from one that disappoints isn't exotic technology - it's how those four parts are sized and configured against how you actually use power.

Where the electricity goes, moment to moment

Your solar array generates through daylight hours, peaking around the middle of the day. At any given instant, that generation does one of three things, in strict priority order: it powers whatever your house is using right now; any surplus charges your battery if you have one; and whatever's left over is exported to the grid.

This priority order is the single most important thing to understand about solar economics. Power you use directly is worth what you'd otherwise have paid for it - roughly 30 to 40 cents a kilowatt-hour in NSW. Power you export is worth your feed-in tariff, commonly between 4 and 8 cents. The same kilowatt-hour is worth perhaps five times more if you use it yourself.

Everything else in solar design follows from that gap.

Why the inverter is the brains

The inverter does more than convert DC to AC. It tracks the maximum power point of your array as conditions change, monitors grid conditions and shuts down safely if the grid goes down, reports performance data, and - in a hybrid inverter - decides when to charge and discharge your battery.

Inverters are also the component most likely to need replacing before the panels do. Panels typically carry 25-year product warranties and around 30-year performance warranties; inverter product warranties on the ranges we install typically run 10-15 years. Budgeting for one inverter replacement over the system's life is realistic planning, not pessimism.

Oversizing: why the array can exceed the inverter

Australian rules allow a solar array to be oversized up to 133% of the inverter's rated capacity. This looks wasteful and isn't. An array almost never produces its rated output - that figure is measured under standard test conditions that real roofs rarely see. Oversizing means the inverter runs closer to its efficient operating range for more of the day, particularly in morning, afternoon and overcast conditions.

The trade-off is a small amount of 'clipping' at peak production on perfect days. In practice, the extra energy harvested in non-ideal conditions comfortably exceeds the clipped peak. For hybrid inverters paired with batteries, the array can be oversized to the maximum available inverter capacity.

What actually decides your outcome

Three things, in order. First, your load profile - how much you use and when. Second, your tariff structure - what you pay per kilowatt-hour, and whether that varies by time of day. Third, your roof - orientation, pitch, shading, and available area.

Notice what isn't on that list: panel brand. Panel quality matters for longevity and warranty, but between two tier-1 panels the difference in your bill is marginal compared to whether the system was sized to your actual usage.