Quote for SunPower system - Good Price

[gbp1s]

Hi everyone,

Newbie here from Los Angeles, CA and am looking for some help on a system purchase. I have a quote for 18 x E20s with 1 x SPR650-1F-240, producing 5.89kW (DC), 5.10kw (AC). Estimated 1st year production is 8586kwh for a cost of $27K (after $3K SunPower family/friend discount but before state/fed rebates). My monthly usage averages about 900kwh and I am being told that this system will just about cover 98% of electrical bill. I have no shade issues since I live in a newer track housing community. My house faces south and the panels will point towards the direction of the west.


My questions

- Is the quote competitive?
- Will the system generate enough to cover me 100% in real world settings or too optimistic?

Thanks,
Kevin

[gbp1s]

My apologies

Meant to add a "?" at the end of the topic

[silversaver]

I'm assuming you are using SP 327W panels. The price is about right. Do you have limited roof space for more panels? If your roof is not space limited, try something else. SunPower is good, but higher price isn't good for ROI. Base on my search, the SunPower isn't that much better than other makes unless you have limited roof space.

I know there are better website but I like to use CSI calculator because it is really easy to use:

http://www.csi-epbb.com/default.aspx

BTW, average usage per month is 900kWh X 12 months = 10,800kWh I don't think you need any additional input from others. Log on to your utilities and check for your past 12 months usage for corrct sizing of your solar system.

[Volusiano]

Hi everyone,...Estimated 1st year production is 8586kwh ... My monthly usage averages about 900kwh and I am being told that this system will just about cover 98% of electrical bill. My house faces south and the panels will point towards the direction of the west.

My questions

- Will the system generate enough to cover me 100% in real world settings or too optimistic?

If you do the math, estimated production 8586 kwh/12 months = 715.5 kwh/month, which is only 79.5% of your 900 kwh/month usage. So why is the installer telling you that it will cover 98% of your electrical bill? Can't they even do the math right?

[gbp1s]

I'm assuming you are using SP 327W panels. The price is about right. Do you have limited roof space for more panels? If your roof is not space limited, try something else. SunPower is good, but higher price isn't good for ROI. Base on my search, the SunPower isn't that much better than other makes unless you have limited roof space.

I know there are better website but I like to use CSI calculator becasue it is really easy to use:

http://www.csi-epbb.com/default.aspx

Yes quoted for SP327W panels. I do have more available real estate space on the roof. ROI is important but I am also looking for reliability. I have a second quote for

30 x Premium 7.500 KW (DC) Canadian Solar system with Fronius USA Inverters with Estimated first year electrity production: 10433 kWh. Price is $28,125.

My understanding is that the SunPowerP panels are more efficient so there is a inclination to go with SunPower but I have yet to make up my mind.

[gbp1s]

If you do the math, estimated production 8586 kwh/12 months = 715.5 kwh/month, which is only 79.5% of your 900 kwh/month usage. So why is the installer telling you that it will cover 98% of your electrical bill? Can't they even do the math right?

I think there estimates for generation is not real world. My friend who lives in the area has a 5.2KWH SunPower system installed several months ago. At the current rate of production, he expects to get closer to 8.2kwh in one year. So my guess is that my 8.586 system can cover 100% of usage in real world generation?

[gbp1s]

If you do the math, estimated production 8586 kwh/12 months = 715.5 kwh/month, which is only 79.5% of your 900 kwh/month usage. So why is the installer telling you that it will cover 98% of your electrical bill? Can't they even do the math right?

Also, please note that 8586kwh is the guaranteed electricity generation for the system.

[silversaver]

If ROI is important to you, I'll avoid using SunPower since you do have more roof space.

Higher efficient SP only give you more Watts per panel, doesn't mean you get more energy. For example, you get 327W per panel vs. 250W per panel. If you do have the space for solar panels, why spend more money on SP?

[inetdog]

Also, please note that 8586kwh is the guaranteed electricity generation for the system.

If you have time of day (TOD) pricing you can net zero your bill while not zeroing your consumption as long as you use a good fraction of your consumption during off-peak hours. The solar contribution will be mostly during the higher priced on-peak times.
A west of south orientation can increase this effect, by moving your production more into the afternoon and early evening times instead of before noon when the rates are lower.

[Volusiano]

Yes quoted for SP327W panels. I do have more available real estate space on the roof. ROI is important but I am also looking for reliability. I have a second quote for

30 x Premium 7.500 KW (DC) Canadian Solar system with Fronius USA Inverters with Estimated first year electrity production: 10433 kWh. Price is $28,125.

My understanding is that the SunPowerP panels are more efficient so there is a inclination to go with SunPower but I have yet to make up my mind.

So it looks like the Canadian Solar quote is 27% bigger in size with 4% higher cost.

There are 2 kinds of efficiency for solar panels. One is the space efficiency -> capacity/panel area. The other is name plate to actual efficiency under real world test condition (STC for name plate and PTC for real world).

SunPower for sure has better space efficiency, but this only matters if you don't have enough roof space.

Canadian Solar PTC/STC rating is 91% PTC/STC. I don't know what the SunPower PTC/STC ratio is, but I would guess it's in the same vincinity.

SunPower has 25 years product and production warranty (with 87% output at end of 25 years). Canadian Solar has 10 year product/25 year production warranty (with 80% output at end of 25 years).

[Volusiano]

I think there estimates for generation is not real world. My friend who lives in the area has a 5.2KWH SunPower system installed several months ago. At the current rate of production, he expects to get closer to 8.2kwh in one year. So my guess is that my 8.586 system can cover 100% of usage in real world generation?

Regardless of real world or not, your installer can't give you an estimate and say that this estimate will cover 98% of your demand when the math says it only covers 80%. It just means your installer can't even do the math right.

Instead of relying on the installer's conservative estimate, why don't you go on PVWatts (maybe the beta version) and do your own estimate? Just put in the pertinent info, and instead of using the default and most often time pessimistic DC to AC derate factor of 0.77, use something less pessimistic based on the actual derate factor your system has. I use 0.874 for my Canadian Solar/SMA system.

[gbp1s]

So it looks like the Canadian Solar quote is 27% bigger in size with 4% higher cost.

There are 2 kinds of efficiency for solar panels. One is the space efficiency -> capacity/panel area. The other is name plate to actual efficiency under real world test condition (STC for name plate and PTC for real world).

SunPower for sure has better space efficiency, but this only matters if you don't have enough roof space.

Canadian Solar PTC/STC rating is 91% PTC/STC. I don't know what the SunPower PTC/STC ratio is, but I would guess it's in the same vincinity.

SunPower has 25 years product and production warranty (with 87% output at end of 25 years). Canadian Solar has 10 year product/25 year production warranty (with 87% output at end of 25 years).

Thank you. This helps shed more light on the purchase. Looks like I need to verify how many hours of generation per by is applied for the annual production figure from both SunPower and Canadian Solar bid.

[gbp1s]

Regardless of real world or not, your installer can't give you an estimate and say that this estimate will cover 98% of your demand when the math says it only covers 80%. It just means your installer can't even do the math right.

Instead of relying on the installer's conservative estimate, why don't you go on PVWatts (maybe the beta version) and do your own estimate? Just put in the pertinent info, and instead of using the default and most often time pessimistic DC to AC derate factor of 0.77, use something less pessimistic based on the actual derate factor your system has. I use 0.874 for my Canadian Solar/SMA system.

Will do. Thanks.

[silversaver]

PVWatt:

http://pvwatts.nrel.gov/

[Volusiano]

Thank you. This helps shed more light on the purchase. Looks like I need to verify how many hours of generation per by is applied for the annual production figure from both SunPower and Canadian Solar bid.

Sorry, I had a typo (I've fixed in my original post) -> Canadian Solar 25 year production warranty has 80% (NOT 87%) output at the end of 25 years. Also, the Canadian Solar warranty has third party bankruptcy insurance.

All in all, SunPower does have a little bit better warranty. However, since panels from reputable companies are generally reliable already, and there's no moving part to worry about, the better warranty from SunPower may not have as much weight to some people. For example, my installer gave me 20 year part and labor warranty for the entire system, even though the Canadian Solar panels only has 10 year product warranty. That goes to show that they're pretty confident about the reliability of the solar panels enough to extend it out from 10 to 20 years.