Google DIY Solar Australia: April 2012

Thursday, April 19, 2012

Power Usage vs. Power Generation

You may have taken the time to look at your energy bill, do some calculations of your usage, but how does all that relate a kW rating given for a system?  We have all seen the ads on TV "buy a 1.5kW a 3kW system..." etc. etc.

So now for some information on how much electricity you can generate for a 1.5kW and 3 kW system, and then from these examples examine the reduction in grid energy usage these will achieve.

This will vary upon how close you live to the equator and the (average or mean) number of sunny days per year your region receives.  So this depends upon weather conditions and is therefore dependent on an average prediction.  There is a very good website to help with solar power prediction and in fact will give you comprehensive information.

Experiment with this website if you feel ambitious.

I will use Melbourne as the example location.  Melbourne probably has some of the lousiest weather in Australia, so therefore less sunny days for generation.  Almost anywhere else in this country, the result will be higher.  I live there so I know the syndrome of "four seasons in one day".
Here is the results for a 3kW system:
And the results for a 1.5kW system:
The results give total predicted kWh generated per month. 
If we go back and examine the chart of average daily usage, our consumption for Dec, Jan, Feb was approximately 13kWh per day (peak reading only). Multiplied by 30 days is 390kWh per month, so a 3kW system would provide about the same or more energy than we consume over the Summer months.  Winter is a little more challenging at about 11 kWh per day, 330kWh per month where solar generation would drop to 140kWh for the month of June.  Having said that, average usage in Spring per month is 300kWh so a 3kW solar power system would generate more than we would consume, hence no power bill for that quarter and a return on grid feed in.

So check you bill.  What is your average usage and how much can you cut your bill by installing a solar system? Compare your usage to the 1.5kW and 3kW calculations above.  I would love to hear some feedback, leave a comment below and please share this if you think its worthy.