7kW solar systems, once relatively uncommon, have grown in popularity in Australia as the average solar system size has increased. A 7kW solar system could be the perfect match for an ordinary household with higher-than-average electricity consumption, or for a small business with accordingly small electricity needs.

Back when Australia’s solar industry began booming around 2008, the most popular (and affordable) solar system size was 1.5 kilowatts (kW), due mainly to the high price of solar photovoltaic (PV) technology. Solar system prices have since come down considerably, however, leading to growth in average system sizes across the nation. 1.5kW systems are now a relatively unpopular choice given the proportionally greater financial benefits possible by investing in larger systems.

These days, depending on your state, the size range for a residential solar system is ordinarily between 3kW and 5kW. With 5kW being one of the most popular system sizes in the country – 7kW is only a bit above average, and not much of a stretch economically for households with a flexible budget for a solar system.

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How many panels in a 7kW solar system? How much area required?

A modern-day 7kW solar system using 250 watt (W) to 320W modules will consist of about 23-28 panels.

Each panel generally measures out to about 1.7m2, so the roof area required for a 7kW system will be about 40-48m2 – or possibly more depending on how your roof is laid out and whether you require tilt frames (which need to be spaced out more than panels mounted flush on the roof).

Pricing for 7kW solar systems

Solar Choice publishes a monthly Solar PV Price Index that tracks pricing trends in every capital city in Australia. Although we’ve been publishing the Index since 2012, we only added data for 7kW systems in November of 2017 – when we completely revamped our format and began including microinverter and ‘premium’ offer data as well.

Historic pricing for 7kW solar systems through to early 2018.

As of early 2018, a 7kW solar system costs between about $6,000 and $13,000 – or just under $10,000 on average. You can get a comparison of up-to-date quotes by filling out the form on this page – our service is free for anyone to use.

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5kW rooftop Solar PV array, near Tamworth NSWTypical power output 7kW solar system

Depending a number of factors, the actual power output of a 7kW solar power system will vary. These factors include:

-Geographic location and associated climate

Orientation and tilt angle of the solar panel array

The degree to which the panels are shaded by nearby objects

-Operating temperature of the panels (generally a function of climate)

-The performance of the individual components (mainly panels and inverter)

As mentioned in the first point above, different areas receive different amounts of sunlight. The amount of sunshine falling on a solar panel array has a direct impact on the system’s power output. If your system is in Darwin, for example, you can expect to receive more sunlight on the average day than you would if you live in Hobart.

The table below provides some rough guidelines as to how much energy you can reasonably expect a north-facing 7kW solar system (operating at a 75% efficiency ratio) to produce in Australia’s capital cities. Please note that the figures in the table are daily averages; in reality, a system will produce more energy in the longer days of summer and less in the shorter days of winter.

7kW solar system
Capital City Approx daily solar energy production
(annual average)*
Adelaide 25-29kWh
Brisbane 27-29kWh
Canberra 25-29kWh
Darwin 31kWh
Hobart 20-23kWh
Melbourne 22-25kWh
Perth 28-31kWh
Sydney 24-26kWh
*Via PVWatts & Bureau of Meteorology

 

Payback period & ROI for a 7kW solar system

Payback periods for any size solar system are contingent on a number of factors, but one of the most important ones for homes and businesses going solar these days is ‘self-consumption’. These days, with only low solar feed-in tariffs on offer in pretty much every state, the business case for going solar is based mainly on how much of  the solar power the home or business in question can consume themselves.

Here’s why: If you own a solar system, the electricity it produces is worth much more to you if you consume itself yourself than if you allow it to be ‘exported’ to the electricity grid. If you self-consume 1kWh of power, you avoid purchasing 1kWh of electricity from the grid, thereby saving anywhere from 18¢-¢40 on your power bill, depending on your location and what your electricity retailer/utility charges you for electricity. By contrast, if you allow the power to be exported to the grid, you will generally earn between 7-13c/kWh in solar feed-in credits.

So how can you make sure you use as much of your solar power yourself? Step 1 would be ensuring that you get a solar system that is appropriately-sized for your needs. Step 2 would be understanding your electricity usage profile and working to optimise your power usage. (Note that power from a system’s solar panels will automatically go straight into any appliances that are running, and the excess will automatically flow into the grid.)

That being said, the table below provides some indicative payback period figures for 7kW solar systems in a handful of capital cities in Australia. You can experiment with the numbers yourself using Solar Choice’s Solar PV System Payback Calculator.

Indicative returns for 7kW solar systems at average prices in select capital cities

(Assuming 30kWh electricity consumption/day)

 Sydney

(assumes 11c/kWh feed-in tariff, 25c/kWh retail rate)

 Brisbane

(assumes 11c/kWh feed-in rate, 21c/kWh retail rate)

 $7,500  $8,800
 @ 20% self-consumption  @ 40% self-consumption @ 20% self-consumption @ 40% self-consumption
 ~6 year payback  ~4.8 year payback  ~6.6 year payback  ~5.5 year payback
 ~16% IRR ~21% IRR  ~15% IRR  ~18% IRR
 ~$1,200 annual savings  ~$1,500 annual savings  ~$1,300 annual savings  ~$1,500 annual savings
Melbourne

(assumes 11.3c/kWh feed-in tariff, 21c/kWh retail rate)

Perth

(assumes 7c/kWh feed-in rate, 27c/kWh retail rate)

$10,000 $7,500
@ 20% self-consumption @ 40% self-consumption @ 20% self-consumption @ 40% self-consumption
~9.1 year payback ~7.6 year payback ~5.8 year payback ~4.3 year payback
~9% IRR ~12% IRR ~17% IRR ~23% IRR
~$1,050 annual savings ~$1,300 annual savings ~$1,250 annual savings ~$1,700 annual savings

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{ 3 comments }

Dr. Ranjith Obeyesekera 9 December, 2015 at 5:16 pm

Very useful information.thank you.

Paul J Camire 21 September, 2014 at 1:57 am

I have a company here in NH who just quoted a 7KW ground mounted system for Just over 30K, with the 30% government tax credit and $3500 of state cash back it came out to a little over 17K our cost. Our electricity bill is on average $150 a month for 12 months. I am 55 yrs old and don’t see the payback of 12yrs as being worth it. I would do all the site work – level area where pads are to be laid, cut trees, and dig trench for electrical from panels to house, and poke a hole thru my foundation for the conduit. Price seems more than excessive don’t you think?

Solar Choice Staff 23 September, 2014 at 3:09 am

Hi Paul. I can’t really comment on the situation in New Hampshire as we service the Australian market. The 7kW system at $30k works out to around $4.30 per watt–that’s definitely on the expensive end for a system of that size installed in most places in Australia. Payback periods here are more in the range of 4-7 years.

Is that the best price you’ve been able to find for your area? And I assume you’re not entertaining the idea of going with a leasing deal?

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