"What is the most cost effective way reduce power consumption and going off the grid using solar."
The first step in reducing your power consumption is to eliminate the high power usage devices and appliances.
Replace standard electric geysers with solar water heated geysers.(you can save up to 80% of your consumption on your standard geyser)
Replace electric stove and oven with gas, or induction stove.
Replace all standard lights with LED lights
Remove or limit usage of tumble dryer (tumble dryers use between 1.8KW – 5KW).
After implementing the above power saving measures, calculate your average and peak power consumption to see what your requirements will be either to reduce your power consumption further or totally eliminate grid power consumption. (see going off the grid)