4kW Solar System Costs, Output, Returns

4kW Solar System Overview

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A 4kW solar system is a slightly smaller system compared to the typical residential solar install in Australia. We commonly install 4kW solar systems for clients with limited roof space or lower than average energy bills and electricity consumption habits.

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Despite being smaller than average, a 4kW solar system can still produce more than enough power to drastically reduce your energy bills.

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If you’re concerned about future-proofing your system, you’ll be pleased to know that yes, you can usually connect a battery to your 4kW solar system. As with any size solar system, connecting a battery that will properly charge and discharge depends on how much energy you are exporting to the grid in winter months when the days are shorter.

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How Much Will a 4kW Solar System Generate?

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A 4kW solar system will generate different amounts of energy depending on where you’re located in Australia, if you have shading present, the pitch of your roof, and the orientation of the panels.

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As a guide, a 4kW solar system installed on an entirely north facing, unshaded, 21 degree pitched roof in Northern NSW or South-East QLD would generate approximately 5,500kWh a year on average.

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How Much Will a 4kW Solar System Save Me Off My Energy Bill?

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If we take the above production example, we can do a simple solar savings calculation. In reality, what you’ll actually save is dependent on how much solar energy you’re able to self-consume (the more, the better!) and your actual electricity consumption and feed-in tariffs.

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Assuming that you’re paying an electricity tariff (or consumption tariff) of $0.35 and self-consuming all of your solar energy instead of exporting it to the grid, savings for 5,500kWh a year could be up to $1,925 or nearly $500 a quarter.

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What Actually Is a 4kW Solar System?

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It’s not altogether straightforward, but it’s common to quote the actual amount of PV power (solar panels) connected to the inverter when referring to solar system size. So for a 4kW solar system, it’d actually be 4kW of solar panels paired with a 3kW (or potentially larger) inverter.

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Calculating system size is straightforward - just multiply the number of panels by rated panel power. For example, if you were using…

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…410W panels - 9x panels would equate to a 3.69kW system size

…420W panels - 9x panels would equate to a 3.86W system size

…475W panels - 8x panels would equate to a 3.8kW system size

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The formula is simple: [Panel power (kW) each] x [Number of panels].

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So My Solar System Is Close to but Not Exactly 4kW Total?

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You’d actually technically be correct if you called it a 3.8kW or 3.86kW solar system, but for simplicity’s sake the industry tends to round off to the nearest whole number.

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We prefer to fit a 3kW inverter for most of our 4kW solar systems. If, however, you opt for a 4kW inverter (e.g. Fronius), you could technically add a few panels later on - but the cost of doing this isn’t usually worth it.

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The reason this is possible is most solar inverters are specified to have up to 1.33 times the inverter output connected. So for a 3kW inverter, you could have up to 3.99kW of PV (solar panels) connected. For a 4kW inverter, you could have up to 5.33kW of PV (solar panels) connected. Importantly, you’d also still be able to claim the STC government incentives up to this amount.

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Is a 4kW Solar System Right for Me?

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We’re going to sound like a broken record here, but it’s difficult for us to say without fully assessing your property, energy bills, and consumption habits.

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In general terms, a 4kW solar system is better suited for homes with smaller roof space available or lower than average energy bills.