Installing PV

Since 2000, the Australian Government has offered incentives for PV installations installed by industry accredited installers. Incentives are being reduced as the prices fall to grid parity. I.e. Equal to the the grid.

PV Systems -

Grid tie - no battery

If you have reliable power, then this is the normal choice. But if the mains goes down, you black out too.

Grid Tie with battery backup

This lets you send daytime power to the battery rather than let the power companies steal it. It gives backup when the grid is down. More expensive and complex an needs maintainance.

Off grid stand-alone

PV and any other generation, with large batteries. If you need to last for a week of rain, then you'll need 7 days of batteries. Hopefully the price and will soon be at a level where the cost matches your hatred of power companies with their inflated grid prices. And the need to feel independent, and green.

PV direct

Sometimes it makes sense to hook a PV directly to a machine that only needs to run when it is sunny. An irrigation pump, pool pump, cooling fan, window blinds, etc.  More

Grid tie

Grid tie with battery backup                   Source


Different types of metering

  • Analogue (spinning wheel),
  • digital (smart meter)

Tariffs to choose from:

Standard tariff

  • All day up to 1700kWh   =24 c/kWh
  • All day above1700kWh   =32 c/kWh

Time of use tariff

  • Peak       2pm-8pm                    =47 c/kWh
  • Shoulder 7am-2pm, 8pm-10pm  =20 c/kWh 
  • Off Peak 10pm-7am                  =12 c/kWh
  • Controlled load                        =10 c/kWh

Fixed charges (No choice)

A power company has say 90% fixed costs and 10% variable. For social equity, the governments of the day charged for usage only, so the poor who used least would pay less. However power companies have been caught out by PV customers who takes their daytime profit, and only buy power when the sun is not shining. They have to have expensive peaking plant on standby. So to redress the problem they are increasing fixed costs. In 2015 I notice they are 30% of our bill. The fight is on, because high fixed charges and low power costs, will make PVs uneconomic.

(Although I understand their problem, and the finacial injustice, I have no simpathy for power companies that put CO2 into the atmosphere. - John Davis)        


If you have batteries, face N for the most power.

If you have PV cells only, face NNW orNW. The most expensive power is in the evening when a home uses most power.

With a stand alone system face N and give the array more tilt to maximise winter production. You'll still get plenty in summer.


Old spinning wheel meter.   With a smart meter you can access your electricity usage details right up to the current day. Source

Smart meters can give a lot of good feedback

Different arrays

  • In Series. Like old Christmas tree lights in series. If one fails all fail. So if one cell is in shadow everything stops.
  • Cells in parallel - not as affected by individual shading.
  • MPPT - Maximum Power Point Tracking - Allows each module to work individually so some can face morning, noon and afternoon sun. Each panel had an optimiser that isolates individual panels in order to improve overall system performance. This can increase power by 5-25%. It can be retrofitted to existing panels. MPPT-Power optimizer-Wikipedia. It is possible to then monitor each panel on your computer or your mobile phone via a website.

The quoted output of a solar module is based on the module being exposed to full sunlight. The effect of shading on a module is greater on crystalline modules, less in amorphous modules. For monocrystalline or polycrystalline modules, if one cell is shaded, power is lost from many cells in the module and possibly from the whole module, not just the one that is shaded. Continued partial shading can damage the module itself. Therefore, solar arrays should not be located near trees that will grow and shade the modules.

Good ref:

Finding an installer

In a very deceptive power supply world, it is hard to know who to trust to install your rooftop PV.

The best guides are:

  • the stability of the installer.
  • Is the installer plugged into the community long term? Local? Does he live nearby?
  • The length of the munufacturers guarantees on the cells and inverter. 23-25 years is good.
  • If the cell manufacturer makes it's own wafer, they keep the best and unload the substandard wafers to cheaper competitors.

A good system will last 25-30 years.

If the deal seems too good to be true....... Cheap ones, only long enough for the installer to do a few more, then get out of the country.

Accredited installers can be found at

Because the field is developing, you'll need to trust the installer on what is available. A competant installer will put in equipment that enhances his reputation, and will give him the least callouts.





Types of PV cells

There is crystalline, and thin film.

The most efficient and expensive are the mono-crystalline silicon cells. They are sliced off a single crystal of silicon. The speckled polycrystalline cells are made from smaller crystals and have a lower output. Crystaline cells are covered with toughened glass, with a waterproof ethylene vinyl acetate resin material on the back.

They need to be mounted for maximum cooling as output reduces by approximately 0.3–0.9% for each Celsius degree. Cells are rated at 25oC.

Thin film modules, are more vulnerable to hail than glass covered cells. They have a thin layer deposited onto low cost substrates, such as glass, walls, roofing materials, etc. The thin film can be cadmium telluride, copper indium gallium arsenide, etc. There is a lot of work being done on both the chemistry, and the application to building materials. PV development page.

Rooftop solar cells are around 20-23% efficient. There are cells that are 44% efficient, but they are expensive, so need to have mirrors or lenses to concentrate the light. And very good cooling.

Thin film PV