Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Project Sunroof

google.com

Post reply on HN
Print view View original

141–150 of 233 posts

Re: Project Sunroof

#141

Post by JshWright »

mikeash wrote: post #111
dreamcompiler wrote: post #96

Earlier quoted context omitted.

Everything above is correct. (I'm a volunteer firefighter.) Firefighters nowadays are trained to deal with the high-voltage DC that's present in hybrid and electric cars. It may take a little longer to extricate a victim, but it won't stop us. As for houses, we won't bother entering a burning residence at all unless we're likely to find a person still alive, or the nature of the fire is such that the danger to us --…

I assume part of the training is how to locate the right stuff to cut to shut off the high-voltage connection? Have you ever had to do that in practice, and if so how hard is it on a car that's been mangled?

Tesla actually does a really nice job of providing training materials to first responders:

http://www.teslamotors.com/firstresponders

You can watch a Tesla get cut up in this video:

https://www.youtube.com/watch?v=ntK3rvVl2Qw

Re: Project Sunroof

#142

Post by freehunter »

dafrankenstein2 wrote: post #140
mbostleman wrote: post #139

Earlier quoted context omitted.

That may or may not be the case, but the claims that these systems are "cheaper" prey on economic ignorance.

Mind your comment and wait and see what will happen after 20 years

20 years doesn't change their price today.

Re: Project Sunroof

#143

Post by dhess »

birken wrote: post #60

I live in San Francisco and just had a solar system installed last week, so I have a few comments about this. 1) It vastly overestimated how big a solar system that could fit on my roof (by about 5x). It didn't care about chimneys or skylights (which are easily visible through Google maps), nor SF fire code which states that you need a 3-foot empty pathway on both sides of the crest of your roof [1]. So for almost ev…

Which installer did you choose, and would you recommend them?

Re: Project Sunroof

#144

Post by URSpider94 »

mbostleman wrote: post #126
birken wrote: post #60

I live in San Francisco and just had a solar system installed last week, so I have a few comments about this. 1) It vastly overestimated how big a solar system that could fit on my roof (by about 5x). It didn't care about chimneys or skylights (which are easily visible through Google maps), nor SF fire code which states that you need a 3-foot empty pathway on both sides of the crest of your roof [1]. So for almost ev…

I always find it a bit dishonest sounding when these things are referred to as producing a "savings". Solar on a residential rooftop is not financially sustainable when you consider the cost of capital and require a market ROI. So I assume that lessors in this case are receiving a non-trivial government subsidy. Which means, in the end, that whatever the lessee is "saving" and then some is being paid in additional ta…

The common definition of "savings" is a reduction of cash outlay for the purchaser. The fact that there are government subsidies (or surcharges) involved is not relevant for that calculation.

The Google site is extremely thorough -- for the case where the consumer is buying the panels, they calculate the time to break even, but also a net present value given a 4% cost of capital. Same thing for the lease cases -- for an example I ran, the lease would cost $96 per month (fixed for the 20-year life of the lease), and offset $115 of a monthly $120 electrical bill at today's rates. So, it would generate cash savings for me from day one. Most solar leases in fact GUARANTEE that you will pay less for electricity after the install. So, "savings" should not be in quotes, it's a real savings for the lessee.

As for your argument that we might all be better off if we didn't have to pay higher taxes for the subsidy -- maybe, but my decision to install solar or not is going to have a negligible impact on my personal tax rate, so I should value any savings against a fixed tax rate that doesn't change as a function of my decision.

Re: Project Sunroof

#145

Post by mbostleman »

URSpider94 wrote: post #144
mbostleman wrote: post #126

Earlier quoted context omitted.

I always find it a bit dishonest sounding when these things are referred to as producing a "savings". Solar on a residential rooftop is not financially sustainable when you consider the cost of capital and require a market ROI. So I assume that lessors in this case are receiving a non-trivial government subsidy. Which means, in the end, that whatever the lessee is "saving" and then some is being paid in additional ta…

The common definition of "savings" is a reduction of cash outlay for the purchaser. The fact that there are government subsidies (or surcharges) involved is not relevant for that calculation. The Google site is extremely thorough -- for the case where the consumer is buying the panels, they calculate the time to break even, but also a net present value given a 4% cost of capital. Same thing for the lease cases -- for…

You are correct - the impact on your personal tax is negligible. Solar accounts for something well under 2% of total energy generation and residential rooftop far less. So almost all of your subsidy is paid by others. That doesn't make the over all analysis any more sound. What if we all had solar on our rooftop? Energy would cost more. The savings would be negative.

Re: Project Sunroof

#146

Post by URSpider94 »

MRSallee wrote: post #112

Can anyone with more knowledge of solar technology speak to this? I know nothing about solar technology developments. I am interested in adding solar to my house some day, but concerned about spending a lot of money today for solar panels that will either (a) be much cheaper in 5-10 years, or (b) be replaced by much more effective panels in 5-10 years. Assuming that the economics of it are the only motivation for goi…

My take: Further increases in efficiency could mean that you could install more capacity on your roof, or the same capacity in fewer panels. Assuming that you can fit enough panels to cover 95% of your demand on your roof, installing more panels doesn't make sense (over-generation is not really profitable today). At the same time, a lot of the installation costs are independent of number of panels (permitting, estimates, wiring to the junction box), so installing fewer panels won't bring the cost down tremendously.

At the same time, tax subsidies are scheduled to start phasing out, and utilities are making noises about discontinuing some of the more favorable rate plans that allow 100% net metering (generated power is credited at the full retail rate, not at the wholesale rate). Either of those changes would negatively impact ROI.

It's hard to know what will happen in the future, but with the current environment, many people can lock in a favorable 20-year ROI for a system today.

Re: Project Sunroof

#147

Post by bmelton »

birken wrote: post #76
jvm wrote: post #63

Forgive my ignorance, what does one do during non-insolated hours? Do solar cells typically come with battery packs or does one just pull from the grid? If the latter then the cost savings are a bit less impressive than stated. Also can you put power back into the grid in San Francisco? Is that benefit included in the cost savings estimate?

If you are already connected to the grid, then you can simply just feed the electricity back into the grid when over-producing (which is tracked by your meter), and then use electricity from the grid at night. This actually works in your benefit if you have solar panels, because electricity prices are higher during the middle of the day (more demand). So you can "sell" daytime electricity (at high prices) [1], and th…

Except that, as pointed out above, the utilities only pay the wholesale rate for the electricity they buy back from you, and sell the overage to your neighbors for full price. Meanwhile, you're likely losing money selling your peak day electricity for 5 cents and buying it back for 15.

Re: Project Sunroof

#149

Post by pdx6 »

birken wrote: post #60

I live in San Francisco and just had a solar system installed last week, so I have a few comments about this. 1) It vastly overestimated how big a solar system that could fit on my roof (by about 5x). It didn't care about chimneys or skylights (which are easily visible through Google maps), nor SF fire code which states that you need a 3-foot empty pathway on both sides of the crest of your roof [1]. So for almost ev…

Their vendors also don't include the roofing type. For example, I have a flat tar roof and many vendors, such as Sungevity, won't install on it. Local vendors will, but are not on the list, and require I install a new roof first. There goes the $24k in savings for buying outright!

Re: Project Sunroof

#150

Post by mikeash »

dreamcompiler wrote: post #120
mikeash wrote: post #111

Earlier quoted context omitted.

I assume part of the training is how to locate the right stuff to cut to shut off the high-voltage connection? Have you ever had to do that in practice, and if so how hard is it on a car that's been mangled?

The car manufacturers use bright colors (typically fluorescent orange) on cables that carry high voltage. We don't cut them! Too dangerous. Instead we avoid them, and assume that the car is energized. http://www.nfpa.org/~/media/files/research/research%20founda...

I know you wouldn't cut high-voltage wiring, but I know at least on a Tesla there's a low-voltage loop exposed for firefighters to cut, which then isolates the high-voltage system as well as disabling the air bags and such. That's shown on page 10-13 here:

http://www.teslamotors.com/sites/default/files/downloads/en_...

I have no idea if this is a common thing or not. Anyway, thanks for the PDF, very interesting stuff. Assuming the car is energized seems sensible. Even with a loop like Tesla has, I imagine you can't count on that having the intended effect after the car has crashed.

Post reply on HN