Interested in installing solar cells on your roof?

May 2014: Australian Solar Council launches "trust mark" seal of approval

Aug 2014: Australian PV Institute tools

Some points to consider...

Technological progress

There are many competing technologies, with research groups around the world competing to raise efficiency, cut costs, and improve reliability.  At the low end, there are dirt cheap systems only a few percent efficient; at the high end, stacked concentrated PV is approaching 50% efficiency.

The commercially available systems today (May 2014) are around 15-20% efficient at harnessing the sun's power and cost about $2.30/W fully installed (before REC discount).  So a 2kW system should cost around $4500.  See the Solar PV Price Check entry for the current month under NSW on our News page.

Renewable Energy Certificates (RECs)

To promote solar power, the Federal Government grants RECs based on the electricity your system is likely to generate.  This takes into account the orientation of the panels and the geographical location.

Electricity companies have to buy RECs to meet minimum percentages of renewable energy mandated by the government.  So you can sell your RECs (the price varies with supply and demand) to offset the cost of your system.  But please bear in mind that by doing so you are allowing an electricity company to emit more greenhouse gases.

Typically, the RECs might amount to 20% of your system cost. 

Suppliers and installers promoting their services assume you will sign the RECs over to them, so the price they quote will normally be already discounted.

For more information see http://www.energymatters.com.au/carbon-trading/recs/index.php

Feed-in tariff

Feed-in tariffs allow you to sell the electricity your system makes into the grid.  There are two types, gross and nett.  A gross tariff pays you the feed-in rate for all the electricity your system makes, and charges you at the standard rate for all that you use.  So if the feed-in rate is higher than the standard rate you still make money even if you use all that you make.  With a nett tariff, what you make you use free of charge, but you will only be paid for the excess you feed into the grid.

The NSW Government had a too-generous 60c/kWh gross feed-in tariff, but it proved so popular that the funding ran out early and it was cut to 20c/kWh.  Now there is no mandated tariff, but some utilities will pay you 6c-8c/kWh.  You may need to negotiate.

For further information see http://www.energymatters.com.au/government-rebates/feedintariff.php

Suppliers and Installers

A list of accredited designers and installers can be found here.

How big a system?

Larger systems will generally be more cost-effective.  You'll never be self-sufficient since it won't generate electricity at night.  Sufficient batteries are still a bit too expensive.

For each kW of installed system, a Sydneysider can expect 4kWh per day averaged over a year.   Average Sydney household consumption is 14kWh/day, but most days do not follow a nice smooth average profile. 

Your meter measures net consumption from the grid in half hour intervals.  If there are some half hour periods where you generate more than you use then the excess will feed into the grid and you will receive little or nothing for it.  This works well for refrigerators and air-conditioning since they tend to use electricity for at least part of each half hour, particularly on a sunny day.  Other high-demand devices, such as tumble dryers, ovens, and dishwashers, may not be spread as well.

It is especially difficult to make good use of what you generate if the house is empty for most of the day.  Here are a few tips:

  • Immersion hot water

Problem: Between 6am and 8am, everyone in the house takes a shower.  The immersion heater switches on and brings the tank back to full heat by 9am, say.  Then the sun hits your PV panels, and the immersion heater doesn't want any.

Solution: Put a timer switch on your immersion heater circuit to prevent its coming on between 6am and 10am.  The full tank it starts with will generally be enough to get the family off to a clean start, and it can recharge from your PV power from 10am on.

  •  Aircon

Problem: You get home at 6pm on a hot summer's day and turn on the aircon.  That's too late to make much use of your PV.

Solution: Set your aircon to come on from 3pm to 4pm, say.  If the house is adequately insulated, it will stay cool enough for hours.  If your demand profile is generally higher in the late afternoon, you should also consider orienting your panels a bit to the West.  Your installer may be able to advise you on this.  Note that this may affect your RECs, though.

Planning permission

Your council will have requirements for the installation of a solar photovoltaic system on your rooftop.

In the Leichhardt municipality Solar PV panels are covered under the Development Control Plan 35 - Exempt and Complying Development. If all the requirements are met you do not need to put in a Development Application. If, however, the house is within a heritage conservation area, as is much of the Balmain peninsula, then you may need to put in a DA. The heritage areas can be seen among the maps here.

Call Inner West Council for more information

See also http://www.energymatters.com.au/index.php?main_page=news_article&article_id=849

 

Suitable sites

Obviously the roof needs to be more-or-less north-facing.  The ideal orientation depends on daily weather patterns. 

In Sydney, the ideal tilt angle is 24 degrees.  Most roofs are close enough to this not to need any additional framework.

With the usual 'string' inverters, shading must be avoided.  Uneven shading loses a disproportionate amount of power and can damage the system.  Microinverters can solve this.

For more information see http://www.yourhome.gov.au 

The Economics

A key question is whether the capital outlay is money that would otherwise have earnt modest interest at the bank (amounting to very little after tax and inflation), or money you have to borrow (perhaps in the sense of not paying a mortgage off as fast as you would have done).

Some illustrative graphics: