7kW solar systems: Prices, output & return on investment
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.
How many solar panels in a 7kW solar system? How much area required?
A 7kW solar system using 275 watt (W) to 320W modules will consist of about 25-28 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 average pricing trends in every capital city in Australia.According to Solar Choice’s own data, the average 7kW solar system price in Australia as of November 2021 is about $0.95 per watt – or about $6,670.
The table below, from October 2019, provides a snapshot of price trends for 7kW solar systems in capital cities around the country.
Historic pricing for 7kW solar systems through to May 2021.
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Typical 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 (e.g. Darwin generates much more energy than Hobart)
–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
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 systemCapital CityApprox daily solar energy production
(annual average)*Adelaide25-29kWhBrisbane27-29kWhCanberra25-29kWhDarwin31kWhHobart20-23kWhMelbourne22-25kWhPerth28-31kWhSydney24-26kWh*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 will directly used by the home or business.
Here’s why: If you own a solar system, the electricity it produces is worth much more to you if you consume it 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.
Indicative returns for 7kW solar systems at average prices in select capital cities
(Assuming 30kWh electricity consumption/day)
(assumes 11c/kWh feed-in tariff, 25c/kWh retail rate)Brisbane
(assumes 11c/kWh feed-in rate, 21c/kWh retail rate) $6,760 $7,190 @ 20% self-consumption @ 40% self-consumption@ 20% self-consumption@ 40% self-consumption ~5 year payback ~3.9 year payback ~5.3 year payback ~4.4 year payback ~19% IRR~26% IRR ~19% IRR ~23% IRR ~$1,302 annual savings ~$1,664 annual savings ~$1,334 annual savings ~$1,601 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)$8,010$5,660@ 20% self-consumption@ 40% self-consumption@ 20% self-consumption@ 40% self-consumption~6.7 year payback~5.5 year payback~4.6 year payback~3.3 year payback~14% IRR~18% IRR~22% IRR~31% IRR~$1,131 annual savings~$1,398 annual savings~$1,199 annual savings~$1,696 annual savings
You can experiment with the numbers yourself using Solar Choice’s Solar PV System Payback Calculator.
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