G's guide to solar panels

G Magazine

It’s the renewable option that’s going gangbusters as thousands of Aussies opt for solar panels on their homes. But with so many options and an abundance of info out there, it can be mighty confusing. Here’s everything you need to know.

solar guide

Credit: iStockphoto

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Living in the sunburnt country has its perks. Australia soaks up more golden rays per square metre than any other continent, and we’re finally starting to tap into this incredible resource. More solar power was added to the grid between January and October in 2010 than the total amount over the previous decade! Across the nation, 105,520 solar panel systems were fitted to homes in nine months.

And why not? While energy prices are soaring, the cost of solar panels is plummeting. Aside from saving you money on electricity bills, harvesting sunlight can also prevent greenhouse gas emissions. A 1.5 kilowatt (kW) system, for example, prevents the generation of about three tonnes of carbon dioxide per year.

“Environmentally and financially, it’s a no-brainer,” says Alan Ropers, director of renewable energy at Todae Solar. However, figuring out what size system you’ll need, deciding which type of panels are best suited to your situation and how rebates and tariffs work in your area could prove taxing on the grey matter. To make life easier, we’ve broken this information into cell-sized chunks.

What are solar panels?

Solar panels convert sunlight into electricity. They do this through photovoltaic cells (‘photo’ means light and ‘voltaic’ means energy), usually arranged in rows and columns within a frame. The cells produce direct current (DC). Another device, called an inverter, converts the DC electricity into alternating current (AC), which can be used to power appliances.

Can I get them on my house?

Solar panels work best when they’re pointed directly at the sun, so you’ll need an area of unshaded roof, preferably facing north. In Australia, the right tilt is usually equivalent to the latitude of your location, plus or minus five degrees, says Ropers. “Most of the houses in Sydney have a pitched roof of around 23 degrees, so that’s ideal.”

The amount of solar energy reaching the ground varies from place to place. Alice Springs and Darwin have greater exposure to the sun than Melbourne and Hobart, for example. The number of sunlight hours fluctuates with the seasons. Generally, though, conditions for installing home solar panels in most Australian towns and cities are excellent.

What are the different types?

Photovoltaic cells come in two main categories: crystalline and thin film.

Crystalline cells are so-called because they’re made from silicon crystals. Those cut from a single crystal are called ‘monocrystalline cells’. These panels are usually black and have a real-world efficiency of 12 to 15 per cent. Cells made from many crystals crushed together are called ‘polycrystalline’. They have a speckled blue appearance and a real-world efficiency of about 11 to 13 per cent. However, the technology is improving rapidly, and efficiency rates are increasing all the time.

Thin film cells can be applied as a layer to glass or plastic. You’ve probably seen them on pocket calculators, though they can also coat windows, roof tiles and even curved surfaces. At the moment, most thin film cells have an efficiency of about six per cent.

There are several key differences between these technologies. Crystalline cells are more efficient but require more energy and materials to manufacture. Thin film cells are less efficient but cope better at higher temperatures.

It sounds counterintuitive but, as a general rule, the performance of solar cells decreases as the temperature increases. If you live in a hot climate, ask your installer or manufacturer how the panels will perform at the peak of summer.

How many panels will I need on my roof?

The answer depends on three factors: household electricity consumption, the available roof space, and budget.

You can start by looking at previous power bills to work out how many kilowatt hours (kWh) of electricity your household consumes each day. Then decide what percentage of that you would like your panels to generate.

According to the Clean Energy Council (CEC), the average Australian household consumes about 18 kWh per day, so a 1 to 2 kW system would cover about 25 to 40 per cent of your average electricity bill.

Of course, it pays to make your home more energy-efficient before doing these calculations and installing solar panels, so all that clean, green energy doesn’t go to waste.

Next, consider roof space. A 1.5 kW system will take up around 12 square metres. Ropers advises customers to focus on the area required rather than the number of panels. Different models have different dimensions and this is a common cause of miscalculations.

In Australia, most people opt for smaller systems because the federal government rebate applies to only the first 1.5 kW (for grid-connected systems). However, Ropers says more consumers in Queensland, the ACT and New South Wales are choosing 3 kW systems, “which starts to make a difference to their electricity bill
and carbon emissions as well.”

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