Calculating Load

Appliances, lights, plug points and other utilities in a house hold are referred to as load. Every utility that uses electricity has a watt (W) rating. This is the amount of power it uses to work. A fridge has for instance 130W input rating and uses 130Wh energy an hour. Because a fridge is insulated it will keep its temperature and switch on occasionally to regulate its temperature. It will thus not run for 24 hours at a time. It will run for maybe 30% of the time in a day. This is called a duty cycle. The usage per day would be 130Wh x 24h x 30% which gives you 936Wh.

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Now for instance a 60W florescent light in the hallway uses 60Wh x 24 = 1440Wh a day if it is on the whole day.

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It is important to determine what utilities you want to run on solar power by day (when the sun shines) and what do you want to keep on when it is load shedding.

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Its is best to replace light bulbs with energy efficient bulbs and don't expect your battery to run a 2400W bar heater.