Plug-In Solar Sizing Calculator: What Size System Does an Australian Home Need?

Sizing a portable or plug-in solar setup for an Australian home comes down to two things most buyers skip over: how much you actually use during daylight hours, and whether you're trying to feed power into your household circuit or just run things directly off a portable power station. Get the sizing wrong and you either waste money on capacity you can't use, or end up frustrated that a cheap kit barely makes a dent. Here's how to work it out properly.

First, understand what you're actually buying

Australia's regulatory position matters here more than in most markets. Under AS/NZS 4777, anything that exports power into household wiring needs a CEC-approved inverter installed by a licensed electrician — there's no equivalent of the UK's "plug it into a wall socket" grid-tied microgenerator category here. That's a big part of why Australia doesn't allow plug-in solar the way the UK now does.

In practice, this means most Australian buyers are sizing one of two genuinely different things:

1. A portable power station with solar input, used off-grid or semi-off-grid (caravan, shed, granny flat, camping)
2. A CEC-approved grid-connected system, sized and installed by a licensed electrician as a proper rooftop or small-scale installation

This guide focuses on sizing the first category, since that's what most people searching for a "plug-in" solution are actually after. If you want a fully grid-interactive system, our off-grid solar guide and a licensed installer conversation are the right next steps instead.

Step 1: Work out your daytime load

Portable solar setups only generate while the sun's up, so the number that matters is what you draw during daylight hours, not your total daily usage. Common daytime loads in Australian households and setups:

• Fridge/freezer running continuously: 0.3-0.6 kWh across a daylight window
• Pool pump: 1.5-3 kWh depending on run time — see solar for pool pumps for a dedicated breakdown
• Fans or evaporative cooling in summer: 0.5-2 kWh, climbing fast in Queensland heat
• Caravan or camping loads (lights, small fridge, device charging): 0.5-1.5 kWh per day — see our caravan and camping guide
• EV trickle charging during the day: 1.5-2 kWh

Most households and setups land between 1 and 5 kWh of genuinely daylight-offsettable usage, before accounting for air conditioning, which can push this much higher in summer.

Step 2: Match that to a system size

Rough daily generation figures for common portable solar system sizes under typical Australian sun (these vary by state — a Perth or Darwin setup will outperform a Hobart one on the same wattage):

Our best portable power stations roundup breaks down specific units against these size bands if you've settled on a rough target and want product options.

Step 3: Factor in your state's tariff structure

Even for off-grid setups, if you're also grid-connected elsewhere in the property, your state's tariff structure affects whether a bigger system is worth the extra cost. States like NSW and South Australia have introduced Solar Sponge tariffs that make midday electricity extremely cheap, which can actually reduce the financial case for a bigger off-grid system if you could just shift that same usage onto the grid at the cheap midday rate instead. Check our NSW Solar Sponge breakdown and the broader feed-in tariff guide before assuming bigger is always better.

Step 4: Consider climate and heat derating

Panel output drops as temperature rises, and Australian summer heat is extreme enough in several states that it meaningfully affects the numbers in Step 2 — particularly through Queensland, the Northern Territory, and inland NSW and WA. Build in a 5-10% derate for peak summer in these regions rather than taking good-sun daily output figures at face value year-round.

Putting it together

For most camping and caravan use, 200-400W is plenty. For a shed, granny flat, or moderate off-grid setup, 600-800W is the sensible default. Only step up to 1,000W+ once you've identified a specific heavier load — a bigger battery bank to charge, air conditioning, or a remote property with no grid connection at all. If what you actually need is a proper grid-connected system, skip the portable category entirely and start with a licensed CEC-accredited installer instead.

Do I need a licensed electrician to size and install a portable solar kit?

No — a standalone, off-grid portable power station with solar panels doesn't require licensed installation, because it isn't exporting into your household wiring. The moment you try to connect it to feed your main circuit, you're in CEC-approved-inverter territory and do need a licensed electrician.

Is a bigger system always better value in Australia?

Not necessarily. With Solar Sponge-style midday tariffs now live in several states, a smaller off-grid system paired with cheap grid electricity during the day can sometimes beat the cost of a much larger standalone setup — it depends on your specific loads and state tariff.

How much does Queensland or NT heat affect sizing?

Enough to matter. Build in a 5-10% output derate for peak summer heat in hot inland and northern regions when sizing, rather than assuming the good-sun figures hold year-round.