On Sun, 29 Feb 2004 06:51:47 -0500, Gary Coffman
wrote:



Solar hot water is often economical for correctly sited buildings
(many are not) with room for sufficient storage capacity (demand
for hot water peaks in the early morning when the sun hasn't
been heating any water for better than 12 hours).

Our solar-heated water storage tank is about 80 gallons. Wouldn't be a
space issue even if it was twice as big.

But solar electricity is not economical on household and larger
scales, ie where average demand is 15 kW or greater. Solar
electric costs about $5 a peak watt installed, but you can only
get about 4 hours of peak sun, even on a bright sunny day. So
you really need to spend in excess of $30 per average watt to
have sufficient capacity. That's $450,000 for the average
residence.

$450k? That's very misleading. You could build an entire "other than
average" house complete with a hybrid generation system for a lot less
than that. We live off-grid, and our total investment, including
property, home, appliances, and power system is about half that. Not
counting sweat equity of course. :-) Daily consumption varies a lot
depending on shop use etc., but probably averages about 12kWh per day.
System cost, including tracked PV, wind, welder/generator, and
everything else required for a modern off-grid home was about $25K for
Arizona. Decent homes near here complete with a solar system start at
$100k. Five acre parcels IIRC, about 40 minutes from town, but a
bargain for young couples, retirees, weekenders etc.

In addition to that large up front cost, you have periodic battery
replacement costs over the life of the system (the sun isn't shining
during residential peak electricity usage times), and system life
is currently about 20 years (the solar cells degrade).

Grid connected systems don't need batteries at all. Good batteries can
live 20 years when required. PV warranties are 25 years.

No way you can amortize that out to a lower figure than just
buying power from your utility.

Most people can't. In an area with high grid costs and or rebates
tho'.... And don't forget that rates *might* go up. :-) Anyone
interested in the economics of solar would do well to search for posts
by Chris Torek in the energy groups. Regardless, PV payback is a hell
of a lot better than SUV payback, or plasma TV payback. :-)

Even running a diesel genset
works out cheaper (which is why that's the method of choice
at remote sites where grid power isn't available).

I've watched a number of people in our area go the diesel route. It is
cheaper to start with. After a couple of rebuilds and counting the
time for hauling fuel it doesn't come out so well. With rising fuel
costs and declining PV prices, home diesel systems are going to become
a rarity. One guy I know who went on and on about how solar would be
too expensive finally got tired of nursing his generator, sprung for
solar, and has relegated the gennie to backup duty. Running a gennie
overnight rather than using an inverter and batteries is not very
desirable, and neither is living with only part time power.

Solar water heating and solar electric also have to be able to
contend with extended sun outages in most climates. In other
words, clear sunny days are not the norm for weeks at a time
in many areas of the US. This means the systems have to be
even more oversized, and storage has to be huge to see you
through bad weather periods. That costs big $$$.

It's easier and cheaper to size the system for modest periods without
sun/wind, and use a generator as necessary to fill in. Few systems can
dispense with the backup generator altogether, so it's only a matter
of planning its use as a second or third source.

Wayne