Hi everyone...

I'm having a PV system installed on my house soon, consisting of 30 Sunpower SPR-225-blk panels and a Sunpower SPR-6000m inverter. I have a few questions about the inverter.

1) is the 6000m inverter big enough for my setup? I'm thinking it's not, but the installer says otherwise. Comments?

2) Sunpower is beta-testing a monitoring system with an in-home monitor and an on-line monitor with real-time data. I think Sunpower inverters are basically rebranded Xantrex inverters....do I have any good monitoring options from the start, or do I have to wait for Sunpower to come out with their own setup?

I'm a total noob at all this, so use small words when you reply!!

Thanks in advance!

JimmyD

JD,

To size your system, you need to know your loads... Since this is an existing home(?) you can start with your last year or two's utility bills. And, you need to know how your local utility will be billing you with Grid Tied Solar (flat rate, TOU, 1 year net metering, 1 month net metering, differential rates between the power you buy and what you sell back, etc.).

A 6kW grid tie system is not small--but if you use a lot of power for A/C, it is certainly within the realm of a reasonable system.

Basic questions:

1. How much power do you use, per month, per year in kWhrs.
2. Where do yo live (nearest large city with similar weather as yours).
3. Are the panels facing south, and tilted to your lattitude?
4. Any shading (shading--should be none between 9am-3pm at least, winter/summer)
5. Utility company/rate plan/rates
6. Any other issues (not south facing, split East/West, etc.).
7. Anything else? (battery backup/off-grid).
8. Trying for rebates?

In the end, it is almost always better for you to spend your first money on conservation rather than generation. Depending on where you live, rebates, and your particular system costs & issues, your "solar power" system probably cost you around $0.20 to $0.35 per kWhr

For most people in the US, these kWHour costs--excluding interest, taxes and rebates--is still more expensive than their current electric power bill. So it is doubly more important to reduce you energy usage before/as you install solar grid tie.

If your heating costs are high (oil, electric heat, etc.) solar thermal heating (typically domestic hot water and radiant heating) is also something else to look at... The solar thermal systems are typically much less costly per watt of heat supplied vs solar electric--but it is also more of a pain (plumbing, tanks, leaks, freezing, antifreeze, maintenance, etc.).

-Bill

Average is about 960kWh/month. I went back 2 years for the average.
Oceanside, Ca. Basically, coastal San Diego
Facing south-southeast. Roof mounted, on whatever tilt my roof is pitched.
Virtually none. I'm removing a couple palm trees that would be in the way in the winter months.
SDG&E uses a tiered system. Don't know the rates offhand.
Nope.
Nope.
I'm doing the Performance Based metering plan for California. It's $.34 per kWh that my system produces.

Between myself and my installer, we've covered all the bases and the system we've come up with will be exactly what I want (and maybe a little over). I'm ok with a little over production, because we get our fair share of cloudy days (marine layer effect), so we factored that in, too.

My biggest question is is the inverter big enough for the 30 panels? I know the panels won't put out a full 225 watts each, but still....the 6000 inverter seems a tad small to me.

JimmyD

I think your right on questioning the installer, the inverter being under sized, 6750 watts of Sun Power panels will put the Sunnyboy 6kW into power limit everyday for sure. SPR-6000m

Someone has been down this path before you, check out this thread Another CA installed system with an undersized inverter with Sun Power Panels

If you change, I would recommend a pair of Xantrex GT4.0's ( whatever the Sun Power part number is as they are just re-labeled ) . This would also allow you to use SG-View for free and monitor , log and have web available data for free ... something you can't do with a Sunnyboy with out extra costs. A pair of GT 4.0's from here are $4348 or a SB7000 for $3755 would be another option, I don't know if the SB7000 is resold by Sunpower, the GT4.0's are for sure.

A Pair for GT4.0's will never power limit, will be near there peak efficiency and run cooler which should allow a long life for the inverters

Regards, do NOT let the installer put a SPR-6000m in a system with 6750 watts of panels. Sun power panels have proven they meet name plate power and in your location ( cool weather ) you will probably be push closer to 7kw more times than not

That's what I was getting at. I'll check with the installer (we haven't ordered anything yet) and see about upgrading to a Sunpower SPR-7000m. I'd like to stick with Sunpower equipment for the efficiency and piece of mind. I hope I'm not a victim of advertising!!

The system designer is coming out Wednesday to survey my house, figure panel placement, etc. I'll talk with him then about the inverter.

Thanks! (I can't wait for the system to actually start going in!!)

JimmyD

The Sun Power versions of the GT4.0's are SPR-4000x

http://www.gosolarcalifornia.org/equipment/inverter.php

And as far as efficiency, they are similar, you would have to find out the array operating voltage and typical power level to see if there is any real difference

SPR-7000m ~96+ peak depends on the array voltage

SPR-4000x ~95+ peak depends on the array voltage

Thanks for the info, SG.

I'll discuss my options with the designer go from there.

JimmyD

In terms of how much solar panels... 6,750 watts, San Diego, SSE (assume 150 degrees), assume latitude roof tilt, and Grid Tied power. From this solar calculator,

9,751 kWhrs per year or ~812 kWhrs per month.

-Bill

That's about what my installer estimated. The system has a CEC rating of 5.93 KW (AC), with estimated monthly production of 837 kWh (10,049 kWh/yr)

JimmyD

Great choice going with a Sunpower system!

The Sunpower 6000m or 7000m is a SMA/Sunnyboy inverter, so to go online you need to purchase the add-in networking card which was about $500 last time I looked.

I have a 5.5kw Sunpower system (27 205BLK's) at my home, running a Xantrax/Sunpower 5000x inverter. I considered the 5000m for my install and the -m series inverters are all very nice units. The pros are the clean design and good efficiency, better than the Xantrex I think by a hair. But the cons are the added cost to go online, and it is also a fan cooled design wheras the -x series is convection-cooled which seemed like a more robust design overall.

For sure you will need to upsize the inverter to either the 7000 or 2 4000x units, my setup has pegged my 5000x on numerous occasions and your install will be more so based on your design specs.

One other pro for the 4000x is you can get a hardwired monitor panel included (check the SPRx monitor link in the Sunpower website), your installer can probably throw this in the deal, again SMA makes one but it is rather costly and relies on WiFi.