samhill wrote:when the grid goes down can you still basically shut off the feed to the grid & run your own house if the sun is out?
With my system, from a scientific, technical standpoint, yes, but in reality, no. You see, the inverters that change the DC into 240 volts AC and connect to the grid are constantly "sniffing the grid". When they sense the grid is down in a couple of milliseconds they shut the inverters off. When the grid comes back up, they sniff the grid for five full minutes. Once they determine the grid is up and stable they allow the inverters to go back to work. So, in order for me to disconnect from the grid and have my panels power my house, I'd have to have some way of tricking the inverters into thinking they were connected to the grid and also it would require a bank of batteries. You can NOT simply run AC things direct from solar panels and an inverter. Think about it....if you have no batteries, & you have somehow tricked the system into making power and you are running the fridge and watching TV. Then a cloud covers the panels for 10 seconds. What happens? You see it can not work without batteries. Much, much simpler and cheaper to have a generator.
That being said.... there is a company that does make a combo unit. It will allow you to have batteries and connect to the grid. It charges the batteries first, then the remaining goes to the grid for credit. I did not go that direction for several reasons. One, it's old technology and not all that dependable. Also I did not want the added expense and maintenance of batteries, and the inverters I have are approximately 11% more efficient than the combo type systems. I have "Micro inverters". I have 30 panels and 30 inverters. Each panel is it's own separate system. Other systems have "central inverters". All the panels are connected to make one one system. If a shadow covers one panel, ALL panels drop their output to that of the lowest panel. If I have a shadow cover one panel, the other 29 still put out full power. That's most of the 11% difference.
Electricity rates keep going up, but sunshine doesn't!
PS: Today was a bitter cold but very sunny day. It proved to be the record day for 2012, and only 7 KWHs away from the all time record. We use 20-25 KWHs a day. Today we made 40.4. I expect before this August we will break the all time record.