New Cal Fire setback requirement for roof mounted solar?

[russ]

No, that was my quick calculation in my head. I thought that many company's solar panel are rated for around 240 watts and the sunpower x21 which I am geting is 345 watts for the same size. 105/240 is 43.75%. The 43.75% is my calculated number. Is that not correct?

You are talking about physical size - not efficiency - Sun Power does have a bit higher efficiency but not 44%

[J.P.M.]

No, that was my quick calculation in my head. I thought that many company's solar panel are rated for around 240 watts and the sunpower x21 which I am geting is 345 watts for the same size. 105/240 is 43.75%. The 43.75% is my calculated number. Is that not correct?

My salesman told me the 36" rule was going to be enforced in my town on Jan 1, 2014, so get my permits approved before then. I am closer than the 36" to both ridge and edge. He made no reference to the performance advantages of their panels.

The 240's were physically smaller. The Sunpower AREA efficiency advantage tends to run about 25-30% max. comparing other manufacturers' current panels, down to about 15 % advantage or so for some comparisons. Might be ~38-40% if you compare older panels to a Sunpower 345, but I don't know if that's a fair comparison.

I suggested in a previous post that this setback business might be a gifted marketing advantage for Sunpower, making me wonder if they would become cheerleaders for fire safety.

[russ]

The 240's were physically smaller. The Sunpower AREA efficiency advantage tends to run about 25-30% max. comparing other manufacturers' current panels, down to about 15 % advantage or so for some comparisons. Might be ~38-40% if you compare older panels to a Sunpower 345, but I don't know if that's a fair comparison.

I suggested in a previous post that this setback business might be a gifted marketing advantage for Sunpower, making me wonder if they would become cheerleaders for fire safety.

Playing with words again?

SunPower = 21.5% efficient
Canadian Solar = 15.9%
LG = 18.3%

Now where do we come up with 38 to 40%?

[Naptown]

Playing with words again?

SunPower = 21.5% efficient
Canadian Solar = 15.9%
LG = 18.3%

Now where do we come up with 38 to 40%?

21.5 - 15.9 = 5.6
5.6/15.9= 35.2

[J.P.M.]

Playing with words again?

SunPower = 21.5% efficient
Canadian Solar = 15.9%
LG = 18.3%

Now where do we come up with 38 to 40%?

No. Just running some #'s. Read my post. I wrote AREA efficiency advantage. Not conversion efficiency.

Sunpower 345 area ~= 1.63 m^2.

Old LG 250 area ~= 1.61m^2

-->> (345/1.63)_= 212 W/m^2 @S.T.C. as published.

(250/1.61) = 155 W/m^2 @ S.T.C. as published.

LG 300's will yield ~182 W/m^2 -->> ~16% advantage which is the lower end of my estimate.

(212-155)/155 ~= 37% increase in area efficiency.

[eugenep]

No. Just running somw #'s. Read my post. I wrote AREA efficiency advantage. Not conversion efficiency.

Sunpower 345 area ~= 1.63 m^2.

Old LG 250 area ~= 1.61m^2

-->> (345/1.63)_= 212 W/m^2 @S.T.C. as published.

(250/1.61) = 155 W/m^2 @ S.T.C. as published.

LG 300's will yield ~182 W/m^2 -->> ~16% advantage which is the lower end of my estimate.

(212-155)/155 ~= 37% increase in area efficiency.

I think even 16% is pretty substantial especially here in northern california. many houses are two story homes, and the second floor is usually much smaller than the first floor, and the usable roof over the first floor is pretty limited. additionally, the second floor roof is usually pretty cut up. My house is a maximum lot coverage single story house, and it was difficult to use a panel other than sunpower to get the capacity i wanted. my builder had to use 3 or more roof surfaces and therefore less efficient directions. basically, my builder who isn't a sunpower dealer couldn't match my sunpower quote for 21 x-21 345 panels with his panels. My roof is very cut-up except for one roof, and it can hold 21 panels assuming no 36" boundary. So, even without the 36" boundary, my builder couldn't compete. What will happen now with the 36" boundary restriction? Much of my roof isn't 114" of clear space, i.e. 72" + 42", so much of my roof can't even get one panel on it. I really think the area advantage will become bigger and bigger. I guess time will tell.

I see other people quoting 250W, 280W, etc, so at 250W, that is 95/250 == 38%, 65/280 == 23.2%. Those are some big area increases if you don't have the space. Also, it will most likely be even higher, because you will need to put panels on less optimal roofs, therefore requiring even more panels, and the equation becomes even worse.

[russ]

LG 300's will yield ~182 W/m^2 -->> ~16% advantage which is the lower end of my estimate.

(

Right - it is 16% for the LG compared to Sun Power

[J.P.M.]

I think even 16% is pretty substantial especially here in northern california. many houses are two story homes, and the second floor is usually much smaller than the first floor, and the usable roof over the first floor is pretty limited. additionally, the second floor roof is usually pretty cut up. My house is a maximum lot coverage single story house, and it was difficult to use a panel other than sunpower to get the capacity i wanted. my builder had to use 3 or more roof surfaces and therefore less efficient directions. basically, my builder who isn't a sunpower dealer couldn't match my sunpower quote for 21 x-21 345 panels with his panels. My roof is very cut-up except for one roof, and it can hold 21 panels assuming no 36" boundary. So, even without the 36" boundary, my builder couldn't compete. What will happen now with the 36" boundary restriction? Much of my roof isn't 114" of clear space, i.e. 72" + 42", so much of my roof can't even get one panel on it. I really think the area advantage will become bigger and bigger. I guess time will tell.

I see other people quoting 250W, 280W, etc, so at 250W, that is 95/250 == 38%, 65/280 == 23.2%. Those are some big area increases if you don't have the space. Also, it will most likely be even higher, because you will need to put panels on less optimal roofs, therefore requiring even more panels, and the equation becomes even worse.

Sunpower is great stuff and it's a free country. IF you are space limited it may be worth the 20 - 30% price premium for the Sunpower.