17 August 2008

Solar : Going green good for your green (back)?

( 6 x 175 Watt - 1.05kw Solar Electricity)

We are all encouraged by governments to save the environment in one way or another, and when we do, we will have a warm and fuzzy feeling inside.

But, Just how practical, and cost effective is this kind of exercise? Just what are they NOT telling us?

A 1 kw panel array costs approx. AUD$12,000 installed. This includes the panels, a DC-AC inverter, site survey, plans & permits, etc.

Here is what they are NOT telling you:

The average sunlight for the majority of households in Australia is max 6 hrs per day with 5 being the normal in the southern states.

For Solar cells to be efficient, they should track the sun for a N.E face during the morning, N. face during the afternoon and a N.W. face during the evening. Most solar installations are fixed and face the North, thereby reducing the efficiency even more.

During the transfer from DC to AC there is a loss of energy of approx 10%.

An average household ( family with 2 children), during winter with gas heater and hot water service, can easily consume 1kw/hr during the day, and during the evening during peak - cooking, tv computers etc, can use 1.5kw/hr.

At night during the mandatory sleep period (e.g 8hrs) 0.3kw/h can be consumed, fridge and small electrical appliances.

To have your house totally isolated / independent from the power grid, an OPTIONAL battery backup MUST be present.

Now for the calculations.

Sunshine hrs 5 x 1.05kw x 0.9 (efficiency) = 4.75 kw generated.


Sleep 8hrs x 0.3kw/hr = 2.4 kw

Peak periods breakfast & dinner 3 hrs x 1.5kw/hr = 4.5kw

The remaining 8hrs at 1kw /hr = 8kw.

For ease of calculation, we have used 20kw for the day, and only generated 5. Therefore with 1kw panels we have only met 25% of our power needs.

1kwhr from the electricity grid is worth approx $0.16 to the domestic market. Therefore a day's worth of electricity can be worth $3.20.

During the summer periods it is not uncommon to have an air conditioner (min 3hp /2.2kw) turned on.

A 2kw panel system is worth $22,000 and would supply 50% of the power required.

This is also without the ADDITIONAL battery storage of minimum 4kva for the average household.


If one was to purchase a 2kw system for $22,000 taking a figure of 10% per annum for the capital, $2,200 is more than enough to cover the electricity bill.

Please note:

The above example is only an indication, and other variables can make your application more suitable or less suitable for solar electricity, e.g.
Swan Hill (80% sunshine), the desert,
Tasmania - Wind generators may be more effective, etc.

The government has not really addressed this problem to be beneficial (financially) to the public, but has taken some sort of action, to appear as if it is pro-active.


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