Well, I'd like to thank both John and Robin for shining a light on a part of the topic that has interested me from way back; I make no claims about relative geriatry.

On the New England (the colloquial expression for my locality) we're in a transitional climate zone between temperate and subtropical, which means we get clear days (and night) during winter and a (more or less) summer maximum rainfall, where most of it falls in the afternoons. This means we have high insolation and it doesn't take much roof area to collect a fair swag of what's on offer.

Being relatively new the house has been designed and built to take advantage of this, as well as cope with the low (by Oz, rather than US standards) temperatures on winter mornings. Passive solar houses here have to cope with about two months where there is just not enough grunt in the sun to bring even the best house to what architects call the comfort zone but, even so, I get by with minimal heating and the summer's heat is (to me) not so great as to make me bother about air conditioning. The hot water is all solar.

During the design phase we considered photovoltaics (and even designed a location for the special batteries) but, even with a rebate, the cost was about 40% more than the cost of connection to the grid; I've never been happy about the use of such batteries in a domestic situation and my partner was a city gel who hadn't really come to terms with the sorts of changes to one's behaviour patterns that are required when you live away from automated supplies of everything.

So I let the idea lapse until the govt started getting people interested in encouraging domestic customers to put excess photovoltaic power from their own installations back into the grid. My current understanding is that batteries are not involved, although an inverter is, and the reverse flow through the meter only diminishes one's bill until and unless one generates more than one uses. I have both the roof area and the minimal consumption (my annual carbon load, according to the electricity distributor, is 1.4 tonnes) to be able to do this so your information is quite interesting.

And, being out in the bush, the stars are spectacular. Lunar eclipses are observed from the patio, while horizontal in (or on, depending on season) the swag and the kangaroos are very friendly.

Cheers, Rowan