Solar basics

family.jpgConfused about solar? Start here...

There are now more than 33,000 solar panel installations in Tasmania. Is your home next? For the vast majority of Tasmanian households, rooftop solar panels are a financially positive investment, with environmental benefits to boot. Here we cover the basics...

Solar panels

Panels go on your roof. They convert energy from the sun into electricity. They are typically about 100cm by 160cm in size. Panels are rated according to the power they can nominally produce, which typically ranges from 250W up to 360W. We recommend selecting panels that give you the most power per dollar of upfront cost, provided they are from a reputable manufacturer and have decent warranties.

Common brands include LG, SunPower, Flex, Jinko, JA Solar, Canadian Solar, and SunTech. Panels comes with two different warranties. The first is a 'product warranty' that covers manufacturing defects and is typically 10 years or 12 years (some even longer). The second is a performance warranty, which guarantees the panels' performance won't degrade too much over time. Typically they specify power output will be at least 90% of their rating after 12 years, and >80% after 25 years.

Currently, 305W panels are generally the most cost effective. But if you have limited suitable roof area you might opt to go for more efficient panels, which produce more power from the same size panel. These come at a cost premium, so we only recommend these if you have limited suitable roof area.

Inverters

The inverter is installed on a wall. It converts electricity from the panels into a form ready for use. Physical sizes vary. As an example, a Solis 5kW inverter is about 35cm x 40cm. Inverters are rated according to their power output. Again, we recommend selecting based on cost effectiveness, provided the inverter is of a reputable brand and has a decent warranty.

Top-end inverter manufacturers include Fronius, SMA, Solar Edge, and Enphase. They generally come with a 10 year warranty. Mid-range inverter manufacturers include Solis, Zever, SunGrow, Goodwe, and SolaX. Their efficiencies are generally just as good as top-end inverters, however their standard warranty is shorter at 5 years. There is the option of extending the warranty on mid-range inverters to 10 years for a small cost, and this is generally what we recommend.

Financial aspects

How much energy your solar panels generate depends on the size of the system, along with variables like which way they face, if they experience shading throughout the day, and so on. The most common (and currently best value for money) system size is 5kW, which will typically produce about 6,400kWh of electricity per year in Tasmania. 

How much money that saves you depends on how much of the solar energy you use onsite vs selling back to the grid...

  • When you're using electricity in your home while the solar panels are generating (the orange shaded area in the diagram below) that energy is effectively free.
  • When you're using more electricity than you're generating (blue shaded areas) it costs you the same as it does for electricity now (26.431c/kWh if you're on Tariff 31).
  • When you're generating more electricity than you're using, the excess (yellow shaded area) is sold back to the grid at the feed-in tariff, which is currently 8.541c/kWh.

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So, the more of your solar energy you use onsite, the more money it will save you. The proportion of your solar energy that you use onsite is referred to as your "solar self-consumption". In Tasmania, this varies widely, from 15% up to 80%, with 40% being about average for a 5kW system. The biggest factor affecting this is how much energy you use; households with low energy use tend to have low solar self-consumption and export more to the grid. Of course, when you use energy also matters... If you're often home during the day you can expect to have higher solar self-consumption than if you're hardly ever home during the day.

A north-facing 5kW system can save a Tasmanian household between $540 and $1,700 per year, with $1,000 being typical. The upfront cost is usually $5,500 - 8,500. At these prices, a system will pay for itself in between 3 and 15 years, with 5-8 years being typical. Given the panels last 25+ years, most Tasmanian households will save significant sums of money by investing in solar.

Factors that can drive up costs

There are a number of factors that can drive up the upfront cost of installing solar panels. These include:

  • Shading - If your roof experiences significant shading from nearby buildings, trees, hills, etc, then you may need to install power optimisers or microinverters to ensure good performance - otherwise these technologies aren't necessary.
  • Limited usable roof area - If you don't have much suitable roof space available, you may need to opt for higher efficiency panels, which cost more.
  • Tile roof - This increases installation costs.
  • Multi-storey building - This may require scaffolding at an additional cost.
  • Remote location - This may incur a travel fee from installers.

The most detailed techno-economic modelling for Tasmania ever!

We hope you've found this post useful and informative. See this blog post for more results and recommendations from our modelling, as well as to learn how we did it.

Note that some details may have changed since this article was first published on 10 Dec 2018.

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