What do you need to know before you install solar panels?

Solar panels buying guide
What do you need to know before you install solar panels?

Installing solar panels

By Lily Gomez

As energy prices around the country soar and concern about electricity bills mounts, solar panels are increasingly being installed by homeowners wishing to take advantage of a system that produces greener energy and insulates them from rising energy prices. But what do you need to know before installing a solar panels  system on your roof?

This article explains how solar panels work and the many things to consider about rebates, feed-in tariffs and more.

For information about specific brands and models, see our solar panel review for details of our current test, and our member survey for the best brands for solar panels and inverters as rated by our members.

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About solar panels

How does a solar system work?

Certain materials can be made to produce electricity when light falls on them; this is called the photovoltaic effect. Solar panels use this effect to convert energy from sunlight into direct current (DC) electrical energy. An inverter unit then changes this into alternating current (AC) for your home's electrical circuits. Any excess energy can be fed back to the electricity grid, for which you may be paid an agreed feed-in tariff, or it could be fed into a battery storage system so you can use the stored power later (at night, for instance).

Solar panels work best when they're north facing, pointed directly at the sun, at an optimal angle and not blocked by trees or shading. The effectiveness of solar panels also depends on where you live and the weather.

Cells, modules, panels and arrays

Most solar cells are made of silicon. Solar panels, also called modules, are each made of several solar cells, connected together and sandwiched between protective glass and a backing plate, the whole panel usually surrounded with an aluminium frame. All the tested panels have 60 cells except the Sunpower which has 96. The solar panels we're testing weigh around 18 to 19kg each. A typical installation includes several panels connected together in an array.

Types of solar panel

Monocrystalline panels are typically black in colour and have a reputation for higher efficiency than multi-crystalline (or polycrystalline) models, which are typically dark blue and are sometimes said to have better temperature tolerance (see efficiency below). The differences come from the manufacturing processes of the silicon cells in each case. In practice there's not necessarily a clear advantage either way; as with most high-tech products, solar panels are a complex assembly of many components and the overall performance depends on more than simply the type of cell.

Interdigitated back contact solar cells (IBC), or rear contact solar cells, are a variant of standard solar cells. They can achieve higher efficiency by having all the electrical contacts on the rear of the cell (rather than at the front), so there are no metal contact strips preventing light getting to the cell surface. The Sunpower panel in this test uses IBC cells.

Thin film solar cells are made from a thin layer of photovoltaic material (such as amorphous silicon, cadmium telluride or copper-indium-gallium-selenide) on a base plate of glass, metal or other substance. This technology is evolving and while it promises more flexible applications than standard solar panels, it's so far generally less efficient and is rare in rooftop arrays. It’s used in various large and small applications, from building-integrated PV systems to solar-powered calculators and garden lamps.

Efficiency

This is simply a measure of the panel's electricity output (in watts) compared to its surface area. Generally, the higher the efficiency, the more power you can get from a given roof area, and you might have lower installation costs too. However, if you have plenty of roof space, you might find it more economical to buy cheaper panels with lower efficiency and just use more of them.

This may come as a surprise, but although solar panels are meant to sit on roofs in direct sunlight, they actually become less efficient as they get warmer, due to the physics of the photovoltaic effect. So you will sometimes get less power from the panels on a very hot day than on a mild day (and remember, even on a 25°C day, your rooftop panels could be operating at well above 40°C). Solar panel power ratings are based on standard conditions (25°C panel temperature). Some panels have better temperature tolerance than others (look for a lower 'temperature coefficient') and are therefore a better choice in hot climates. Correct installation is also important; that's why panels should be installed in a way that allows air to circulate underneath the panels to help keep them cooler.

Choosing an installer

The Clean Energy Council (CEC), Australia's peak body representing the clean energy sector, accredits both installers and systems that meet certain standards. To be eligible for any small-scale technology certificates, systems must be installed by a CEC-accredited installer.

Retailers can also sign up to the CEC's voluntary code of conduct, which demonstrates a commitment to best-practice installation.

So your best bet is to look for an accredited company that is a signatory to the code of conduct, has been in business for a while and has an established track record, relevant experience, specialist expertise, and a good reputation.

Does the solar PV system meet standards?

You should ensure that any solar PV system you consider has met Australian and international standards. To be eligible for small-scale technology certificates, your solar panels must be certified – ask your installer to supply proof. You can check the CEC's list of currently approved inverters and modules to confirm.

How much panel capacity do you need?

Nowadays you don't make much money from feeding electricity back into the grid. So you want to maximise your own use of your solar PV and minimise your export into the grid.

Unless you're able to get (increasingly rare) high feed-in tariffs or store your surplus energy using (still expensive) batteries, to get a system that is going to pay for itself quickly, you need to calculate how much electricity you use in your home during daylight hours when your panels are generating at their peak and match the size of your system to that consumption pattern. You can find useful information about your energy use by looking at the previous year's energy bills.

If you don't consume much energy during the day then you'll want a smaller system. If you do, you'll want a bigger one.

Warranty period

Manufacturer warranties range up to 25 years. Solar systems should last at least that long, so you look for an installer who's offering a warranty or guarantee for that length of time.

The solar panels we've chosen for our test have 25-year performance warranties (typically warranting that the panel will still produce at least 80% of its claimed power rating after 25 years) plus a 10 to 12 year warranty for the product itself. An installer may also give warranties for the mounting frame, workmanship and so on. Sunpower is an exception, with a 25-year warranty for both performance and product, and higher performance criteria in the warranty.

Considering installing solar panels in Melbourne or elsewhere in Victoria? Land a great deal on fully installed solar power system through One Solar Australia..