7kW Solar System: Power Output, Cost, Savings, ROI, and More

Feature image for 7kW solar system. Image shows a solar installer in blue overalls installing a 7kW solar array on a rooftop.

A 7 kW solar system is one of Australia’s most popular system sizes. It can potentially generate 10,663.83 kWh/year of solar power. This saves you about ~$3,400 per year on power bills. Installing solar panels of this size will cost you roughly ~$8,000 and take about 2.5 years to completely pay off.

Plus, modern 7kW solar systems are built so well that they’re warranted for 25 years. That means you have about 22.5 years of free electricity. It’s sounding more and more like a no-brainer, isn’t it? Well, let’s dive into more detail about what you need to know.

How much does a 7kW solar system cost in Australia?

Typically, solar systems in Australia cost about $1,146 per kW. However, it’s different for every state because different places produce varying amounts. See quotes from CEC-certified installers if you want the most accurate data. But here’s a list for you that’ll hopefully help:

CityCost per kW ($)Total Cost for 7 kW System ($)

The data above isn’t unchangeable, as the final cost of everything will heavily depend on many factors. I suggest you have a good conversation with either the installation team lead or the provider themselves.

How much power does a 7kW solar system produce?

There’re a couple of answers to this question just because of the many variables that go into the equation. We have dedicated articles for this topic if you want a deep dive, but just to summarize, the things that affect actual electricity production from your solar system are:

  • angle and tilt of solar panels
  • solar power ratings
  • system location
  • the weather

Okay, so, just to answer the question, I listed the estimated daily, monthly, and yearly outputs for each Australian capital city below using the PV Watts calculator under these settings:

  • Roof pitch: 22.5%
  • Inverter efficiency: 96%
  • Quality and type of solar panels: Standard
  • Installation type: fixed, roof-mounted
CityDaily Output (kWh)Monthly Output (kWh)Annual Output (kWh)

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How many panels are in a 7kW solar system?

This is pretty straight-forward. To get the answer, we have to know the panel array’s power rating, Then, we divide the system size (7 kW or 7,000 watts) by that rating. Voila, you have the answer. Let’s show that with an example.

Say you choose to install LONGi’s Hi-MO 6 Explorer (LR5-54HTH-440M), which has a rated capacity of 440 watts (W).

  • number of solar panels = system size ÷ solar panel rated capacity
    • 7,000 W ÷ 440 W/panel =15.91 (we then round up since we can’t have 0.91 of a panel)
    • 16 solar panels mounted flush on your roof area

Let’s illustrate a cheaper option. Say you’re installing panels with rated capacities of 300 watts only.

  • number of solar panels = 7,000 W ÷ 300 W/panel = 23.3
  • 24 solar panels mounted flush on your roof area

For further reading:

How much roof space would you need for a 7kW solar system?

So first, we need to account for the dimensions of each panel. Since every brand has different dimensions, let’s take the average/most typical size, which is 1.7m tall by 1m wide.

Then we add into the equation how many panels you’ll actually install. And as we’ve tackled before, the higher the panel wattage rating, the fewer panels we need to put up. Therefore, the less roof space we need. It makes sense, right?

For today, let’s assume you’re installing 440W panels at the aforementioned average dimensions. You’ll need 16 panels to complete a 7kW solar system. The panels will need to occupy a total surface area of 27.2 square meters. Here’s the calculation:

  • Step 1: Calculate the area of one solar panel.
    • Area = height x width
      • 1.7m×1m
      • 1.7 m2
  • Step 2: Multiply the area of the solar panels by how many solar panels you need.
    • Required roof space = solar panel area x number of panels
      • 1.7 m2 x 16
      • 27.2 m2

The financial implications of a 7kW solar system

Let’s see your monthly savings, ROI, and payback period. Again, we have other articles tackling those, but let’s talk a bit about them here.

How much money can you save with a 7kW solar power system?

How much money you save depends on:

  • exact geographical location
  • initial cash-out
  • energy consumption
  • electricity cost

You can find below wide estimates of the monthly and yearly savings you may get with each capital city.

CityMonthly Savings ($)Annual Savings ($)

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What about ROI and payback periods?

It’s easy to think that your payback period will, of course, take a long time, right? Well, you’d be surprised! Let’s take a look at your payback period calculations and your ROI, because these should wow you!

To calculate this, we need numbers on installation costs and savings.

Here’s an easy equation you can use:

  • ROI = (total savings ÷ total cost) x 100
  • Payback period = total cost ÷ annual savings

Feel free to use the numbers listed above if you want an estimate, or check the table below.

CitySystem Cost ($)Annual Savings ($)Net Savings (25 years) ($)ROI (%)Payback Period (years)

The math says it all: ROI is over 1000%. The savings are astounding! Now you see why people go solar.

That said, though, these calculations are near-accurate estimations with a bit of oversimplification. It’s impossible to account for every single thing, after all. Your solar energy output (and power usage) won’t always be at maximum, even in ideal conditions.

Thus, realistically, payback is expected to be around six to ten years. But even then, that leaves you with around twenty years of free energy.

It really is a no-brainer!

Conclusion: Would your household benefit from a 7kW solar system?

As I said, no-brainer! Every household would benefit from a 7kW solar panel array. This is especially true if your home’s entire energy consumption can be satisfied by a typical residential solar system.

Still need help? You can always ask a professional. We have a network of pre-vetted solar installation professionals. These guys can give you 3 FREE quotes right away.