Payback Time
Letter from Reader
Good day, Nick.
I am a South African electronics engineer who has retired. Having done a bit of research I established that a typical 4 person household (with a standard geyser) uses 18KW/Hr, daily. In this country that translates into R1,000-00 per month or roughly $100-00, US.
If recent trends are followed then in ten years this will be $351, very approximately. Using solar power and batteries known for long life (note, a duty cycle of 25%) the payback point will be achieved after eight years.
In that household the regular consumption is 2KW (all figures are in KW/hour) with short term peaks going up to 12KW. Thus the inverter must cope with surges up to 15 KW. As mentioned (and this is well researched) a typical 4 person household uses 18KW. This is the house. If one is on a farm or not, the household will use the same amount.…