[mythtv-users] [Slightly OT] solar power for all our gadgets

[Marc MERLIN]

On Mon, Mar 09, 2009 at 06:06:04PM +1300, Nick Rout wrote:
> > In other words, you don't pay for the install and you pay them a flat
> > 15cent/Kwh or whatever the rate is, which is cheaper than tiers 3-5 from
> > PG&E.
> > The other good news is that the said rate will not go up, it'll remain
> > whatever it is forever, whereas PG&E is raising rates every year.
> 
> Until the vendor goes broke from such a "forever the same price" policy

Assuming that happens, since you didn't spend any of your own money, why do
you care?
Worst case, if no one buys them, you end up with free panels on your roof :)

On Mon, Mar 09, 2009 at 07:32:35PM +1300, Steve Hodge wrote:
> Since the cost to the vendor is established at the same time as the rate
> that the customer pays I don't see this as a problem.

That's what I've seen with the ones I worked with. Some are pretty big
companies, not fly by night.
 
> I'd be interested to see how it works in terms of ownership of the panels
> though.

If you lease, they aren't yours. You just pay them for electricity less than
you'd pay PG&E for the higher tiers.

On Mon, Mar 09, 2009 at 10:37:11AM -0400, John Drescher wrote:
> I think the only problem with this is if they did not first install
> enough panels to supply your home so that even with the panels you are
> still drawing power from the grid. However by that time if they plan
> correctly (size the inverter ... for expansion ) they should be able
> to expand with cheaper panels that are more energy efficient than what
> we have today.

Actually most people do not want to offset their entire bill. That's because
the lower 2 PG&E tiers, at least in CA, are still cheaper than solar, or
almost the same price.
The higher tiers jump from 20c to 43c per Kwh, at which point, solar is a
done deal.

On Mon, Mar 09, 2009 at 09:39:18AM -0500, Jeff Walther wrote:
> The idea that solar panels pay for themselves is such a myth (not the
> *good* kind of Myth) in most locales.  But it does depend on what you pay
> for electricity.
 
Right. I was talking about CA. We may likely be the state with the biggest
Sun received x electricity price combination. 
Since our electricity is quite expensive, and we get a lot of sun, if you
add a 50% CA + fed subsidy, Solar has become a no brainer here.

If you live in Washington State, or other places with cheap hydro and little
sun, the equation changes a lot.
 
> An installation with a nominal generating capacity of 3000 watts will cost
> about $27,000, installed.   The city will reimburse for half of that so

I got about the same: 6000W DC or 8100KwH/Y for $44K pre-subsidies ($26K my cost).

> that my cost is $13,500--but the poor tax payer footed the bill for the
> other $13,500.

True, same here, but understand that similar subsidies are going into Solar
or Wind plants. One of them might as well be on your roof :)

> While you might expect that 3000 watts of capacity would yield
> approximately 3KW X 12 hours/day X 30 days/month = 1080 KWH/month, the
> reality is that you'll get about 400 KWH/month if you're lucky.  Further
> north, e.g. in Ohio, you could expect 300 KWH/month.

The math isn't quite right, but the general idea is. All the quotes I got 
have estimated production per year, which is what you should care about
(they include your location and design factor).
I got 8100Kwh/Y for 6000W DC (talking per month is worthless since all
months aren't alike).

> Our marginal rate for electricity (the higher rate we pay after some base
> usage) is $.12/KWH (Including fuel charge).   So that 400 KW/month will
> yield about $50/month if I'm lucky.

Doesn't work that way either. Just about everywhere, electricity costs more
to make during the summer in the 12:00 -> 18:00 hours (high demand with AC).
This is also when your system makes the most electricity (peak sun) and
therefore you get more credit for it.
One KhW in that peak time may be worth 3KhW of night electricity.

My 8000KwH system is going to offset about 12000KwH of electricity I use.

> Have you ever tried to pay off $13,500 at a rate of $50 per month?   At 5%
> interest, the interest would cost more than the rate of return.  And
> that's ignoring what you just cost the taxpayer.
 
Whoever you talked to didn't do their job right. Math is more complex than
that and with the correct numbers and assumptions applied, my system breaks
even in 5 years-ish and pays for itself within 8-9Y out of a 30Y life.
 
> Furthermore, the idea that all of that $50/month is available for paying
> down the cost assumes no maintenance cost.   Anyone who has been a
> homeowner for more than a few years knows that no matter what they tell
> you, everything has a maintenance cost.   If nothing else, one must wash
> the pollen off panels when things are blooming (yellow oak pollen here)
> and dirt after dust storms.

Sure. I can go on my roof and hose them off a few times a year. Your grass
has a maintenance cost too: it must be cut sometimes.
The only real maintenance cost is replacing the inverter after 10-15Y. This
is factored in the return spreadsheet. Everything else is warrantied and
covered, so not for me to pay if anything ahpppens.

> Anyway, this topic kind of chaps me because I frequently hear the media
> non-critically hyping how wonderful it is to have solar panels, and the
> fact is that anyone who can do simple math (and doesn't live somewhere
> with really expensive electricity) can see that they make no economic
> sense whatsoever.

No offense, but 1) the math is not that simple 2) you don't seem to have be
told about the entire equation.
That said, your electricity might be much cheaper than mine. If you don't
have tiers over 15c/KhW, then solar is not likely to help you as much as
it helps me.

On Mon, Mar 09, 2009 at 08:01:40AM -0700, Brian Wood wrote:
> All true, but you have left out the energy cost to manufacture the panels, the 
> inverter and everything else involved in the installation.
 
That's true. Now, if the system pays for itself in a 3rd of its life, the
question is what you describe is worth 2/3rd of the energy it produces, or
not. 
I'm hoping it's less but I don't have math/research to back that up.
 
> It's like the compact florescent lamps, once you factor in the energy 
> rerquired to make them, and transport them here from China, it's a net loss 
> for the planet, even if we ignore the mercury disposal problem, both at the 
> manufacturing plant and the ultimate home setting.

That's most likely true, indeed :(

> We're not there yet, but if nobody steps out on the dance floor first, nothing 
> will ever happen

True too.

On Mon, Mar 09, 2009 at 03:14:02PM +0000, Simon Hobson wrote:
> Jeff Walther wrote:
> >>Anyway, this topic kind of chaps me because I frequently hear the media
> >>non-critically hyping how wonderful it is to have solar panels, and the
> >>fact is that anyone who can do simple math (and doesn't live somewhere
> >>with really expensive electricity) can see that they make no economic
> >>sense whatsoever.
> 
> Ahh, so not just me then !
 
Sorry, but things have changed. Prices are definitely going down right now,
and the equation has changed, at least in states with lots of sun and
expensive electricity.
 
> Same with this "cheap, clean, zero-emissions" hydrogen fuel stuff as well.

Yeah, that one I'm not quite sold on yet. 
 
> >Alas, the ability to do simple math and a PV analysis is sorely 
> >lacking in the US... Witness the current housing meltdown.
> 
> Not just the US, seems normal over here in teh UK as well.
 
The equations are a bit different there. No offense, but the UK gets a lot
less sun :)
 
> It's not just that it's a specialty, it's that these things really 
> are non-trivial to make. Effectively, each panel is a silicon chip 
> the size of ... well a large panel. New designs come along from time 
> to time, but at the moment, the bulk of panels are big silicon chips.
 
Not really. One of my panels is made out of 55 chips.
Also, with thin film, it's made out of cheaper materials and process
than silicon.

Marc
-- 
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems & security ....
                                      .... what McDonalds is to gourmet cooking
Home page: http://marc.merlins.org/