Some people store the excess electricity in batteries for use at night or when the sun isn't shining, and can go "off the grid" entirely.
There are even some dinky little hybrid systems which heat water and generate electricity. They can do this because the water is used to cool the PV cells - the heated water is used for your domestic shower etc, and the electricity runs your lights, freezer or whatever. You could probably be better off by more than $1200 a year in power that you don't have to buy from the power company, or money they will pay you for power that you sell them.
One company will pay you 17 cents per unit, and another will pay about 27 cents, but only for the first five units each day, and thereafter the price more than halves. You need to calculate carefully which company you would go with.
If you wanted to sell your house, one New Zealand study indicates that it could be worth an extra 15 times the annual saving in power costs - say, $15,000 to $18,000 extra. Most PV panels will last a good 25 years.
The only problem with this exciting technology is how to store your energy for when the sun isn't shining. Batteries are expensive and just a tad cumbersome; "grid-tied" systems are good because they are based on an easy-to-understand financial formula - the householder is paid for their excess power by the power company per unit, and buys power back at night from the same company. The rates vary, but one company charges about 50 per cent more for the power it supplies back to you than it pays you for the power you supply it.
This form of "storage" is cheaper and easier than batteries.
It makes sense for the country because if enough people convert to solar generation, we may not have to build another hydro station and kiss goodbye to another river so that we can run our computers, freezers and spa pools all day. They aren't making any more rivers.
As you will have noticed, the main problem with generating electricity from the sun is that you have to be able to store some for use at night.
Good news - there is an Israeli invention that will produce hydrogen from water when sunlight hits a cell containing a thin film of rust (ferrous oxide). It will be possible to store the hydrogen for later use and the system promises to be inexpensive.
It is not known how long it will be before this rust-powered energy factory will be available for you and me, but my bet is that we shouldn't wait for it as it could take many years to develop.
If it were me, I would seriously consider installing photo-voltaic panels. Today.
