Solar PanelsContinued …

George Skarbek 9th July 2014

Why purchase Solar Panels?

There are a number of reasons• Help the environment• Cut the power bill• Eventually reach a payback period• Receive a better return on your investment than you can get

elsewhere• Or probably several of the above reasons

Reducing the power bill

• Reducing the power bill is probably one of the main reasons to install solar panels• However, you can reduce your power bill just by making

some alterations to your house and life style without adding any solar panels• Some ways are:• Replace incandescent globes with energy efficient globes such LEDs• Prevent draughts• Turn down the thermostat a bit in winter (put on a jumper) or turn it up in

summer when cooling

What PV size should you install?• This is probably the hardest question to answer• You can ask for advice or obtain from your electricity provider 12

months of half hourly generation data and spend days trying to work it out based on the average solar generation in Melbourne by months. However, even then you may not get it quite correct but you will be close.• Optimum orientation is facing North. Facing due East or due West you

will lose about 14% of energy. East is slightly preferable.• Avoid shade as this has a HUGE effect unless you have micro inverters

on the panels. See: http://www.aussiemadesolar.com/micro-inverters-explained/ for Tinda panels.

Payback period

• This is asked very often but the installers tend to give quite optimistic estimates as they want your business• The Feed In Tariff (FIT) is 8 cents/kWh• Percentage of energy exported is the single most important factor in

determining the payback period• In Melbourne, if exporting 10% of your generation the payback period

is 6 years, exporting 50% it is 9 years and exporting 90% it is 24 years (Business spectator) This assumes that the price of electricity will not change over this period.

• A high regular load, such as a pool pump, will reduce the payback period

Vested interests in payback calculations?

Return On Investment (ROI)

• A better way of looking at the economics is to use ROI first and then the payback period. I will illustrate with our example. Our solar 2 kW installation cost $2,800 and was installed in July 2013. The eight panels had to face due West.• The money in Macquarie bank was earning 2.5% therefore interest lost

was $72 pa.• In the last 12 months solar energy generated = 1,825 kWh• Solar energy Exported was 850 kWh @ 8 c/kWh or $68 rebate • Solar energy provided 975 kWh saving in energy @ 25c / kWh = $244• Therefore the nett saving is $312 giving a ROI of 7.7%

Oversizing the PV array

• The inverter is the single most expensive component.• However, as PV panels have come down in price, by adding more

panels than the inverter’s capacity it is possible to gain additional energy for a small additional cost. Say, install 2.5 kW of panels and a 2 kW inverter.• When the solar generation exceeds the capacity of the inverter, it will

just go into a less efficient mode, without any damage, in most cases.• Check with your installer and with their recommended inverter before

oversizing. Do not oversize above 50%.

Oversizing the PV array

Who to get for your installation

• Start by obtaining at least three quotes.• If you have a very old switchboard in your house (over 40+ years old)

then you may need a switchboard upgrade. This will cost $600+ on top of the installation cost, if required. Send in photos if nobody inspects your house.• A good starting point is this site: http

://www.solarquotes.com.au/installers/ • There you can obtain three quotes and then look at the reviews of the

installers.

Generation profile on a sunny March dayThis is for a 5 kW system

March usage for our 2 kW system

Any Questions?