Solar capacity needed for my Leaf?

Is it a separate meter reading gross production or reading net of usage?

smkettner said:

Is it a separate meter reading gross production or reading net of usage?

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The meter provides two readings. One reading is power drawn from SCE. The other reading is power provided to SCE. I then net the two readings to determine my surplus production.

DarthPuppy said:

Ok, I checked the SCE meter and it appears that over the past year, my 5.8kW (DC) system produced 7400 kWh AC, which exceeded what was used by the house by a little over 1,400 kWh.

smkettner said:

Is it a separate meter reading gross production or reading net of usage?

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The meter provides two readings. One reading is power drawn from SCE. The other reading is power provided to SCE. I then net the two readings to determine my surplus production.

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Wait, doesn't that mean something else?

If you have one meter that is measuring power sent to the grid and power taken from the grid then you don't actually know how much power your system produced or how much power you produced? The only thing you know is how much more/less power you put into the grid than what you took from the grid.

But your 7,400 kwh vs 5.8kw system ratio seems to indicate that would be its total production? So maybe you have a third meter that is showing total production as well?

QueenBee said:

DarthPuppy said:

If you have one meter that is measuring power sent to the grid and power taken from the grid then you don't actually know how much power your system produced or how much power you produced?

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Good point. The missing element would be the power produced and used by the house before feeding excess back to SCE. This would suggest that my production is significantly better than 7,400 kWh over the course of a year. So perhaps a 10 panel system would be overkill.

I now have a little more thinking to do.

DarthPuppy said:

QueenBee said:

DarthPuppy said:

If you have one meter that is measuring power sent to the grid and power taken from the grid then you don't actually know how much power your system produced or how much power you produced?

Click to expand...

Click to expand...

Good point. The missing element would be the power produced and used by the house before feeding excess back to SCE. This would suggest that my production is significantly better than 7,400 kWh over the course of a year. So perhaps a 10 panel system would be overkill.

I now have a little more thinking to do.

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Right. As I mentioned, my 5.16 kW DC system in your same geographic region generates about 8,500 kWh AC per year. If you have south facing siting with little to no shading, you should be generating about 9,500 kWh AC per year.

Last calendar year, I used 3,129 kWh AC to charge my LEAF at home to drive 11,149 miles (184 kWh of public charging also contributed to this mileage.) That translates to about 1.9 kW DC from my solar array, which is the output of about nine of my 215 W panels.

DarthPuppy said:

RegGuheert said:

would equate to about 3000Wp PV panels (grid-tied).

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So 3,000 W is the spec I need to tell the installer that I want to add to my system? Or am I mis-translating? What is a "Wp"?

Thanks!!!

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Maybe it was answered somewhere but I didn't see it: "Wp" is Watts Peak, i.e. under (rated) peak power conditions.

Darthpuppy- We are in the same boat. I'am not far from you and I'am stuck with SCE also. I 'guess-estimated' about 2-3 kW of panels for the Leaf. Since the install is so routine,(DIY) and micro-inverters are plug-in-play, I decided to put in 2 kW of additional panels to start with. I'm using (8) 255 watt Canadian panels on about 28" of railing, with (8) 225 Enphase micro inverters . To check my work and keep the building inspector happy, I paid a good electrician an additional $150. From Craig's List, I got the Solar Panels for $206 plus tax. The Microinverters were on sale for $119 each, also on Craig's List. The railing and hardware (Prosolar) cost about $90 (yep, from Craig's list also). The additional wiring, conduit, & disconnect box came from Home Depot for about $70. Because of Work and other obligations, I took two Saturdays or 10 hours to install. Early mornings are best, to avoid the heat. About April or May next year, I'll reassess and/or add an additional (4) panels w/micro inverters. That will give me a second shot at the Federal 30% rebate. As you see I'am not an engineer either . I also don't do well at heights. Solar equipement is alot cheaper than seven years ago. DIY is a real option.......Good Luck

Thanks Guy for the translation of Wp!

Boomer, your numbers are spot on versus the analysis from last year's install of the 5.8 kWh system = 9,500 kWh over the year.

I now have a proposal for 10 SolarWorld (US made) 250 panels with Enphase M215 inverters. That study is estimating a little over 3700 kWh over a year.

From what I've gleaned from these posts, that should cover at least 13,500 miles in my Leaf. Since this past month's driving suggests I'll do 14,000 miles over the year, that size should work well for me. 2 fewer panels and I likely won't have full coverage. 2 more panels and I'll likely be supplying more excess to SCE than I'm interested in.

You folks are awesome in providing insight! Thanks!!!!

Perhaps in 3 years when the MB B-Electric isn't 1st year production run, I'll add a second EV and add more solar then. I love the combination of solar power and BEV.

DarthPuppy said:

I now have a proposal for 10 SolarWorld (US made) 250 panels with Enphase M215 inverters. That study is estimating a little over 3700 kWh over a year.

From what I've gleaned from these posts, that should cover at least 13,500 miles in my Leaf. Since this past month's driving suggests I'll do 14,000 miles over the year, that size should work well for me. 2 fewer panels and I likely won't have full coverage. 2 more panels and I'll likely be supplying more excess to SCE than I'm interested in.

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That sounds like a nice addition to your system, assuming your roof and your wallet can handle it.

The MTBF study I did indicates that the reliability of the M215s is extremely high to date (MTBF > 1200 years) and the price on those should be very good now that the M250s are out. Since the M250s are brand new, nobody knows whether they will be able to achieve the same high level of reliability so I think the M215 is the right choice. With a 250W panel, you do not need anything bigger than the M215s (which can actually put out 225W).

Good luck with your new addition! Please give us the link to the public website for it once you get it up and running (assuming you are also installing a Envoy).

I was told by the Enphase people that they intentionally have more panels with smaller inverters because the generation on a daily basis is a bell curve with a flat top. The total power generated is the area under the curve. The claim is that the total area is greater with more panels with a "flat top" than if you purchased fewer panels with inverters that could handle the maximum output of the panels. Just looking at rated capacity of the panels assumes that you are comparing the maximum power output of the panels without regard as to how the power ramps up and down over the course of a day. With a few more panels the power generated at ramp up comes on more quickly than fewer panels and the same with ramp down. Thus, the area on the sides of the bell curve before "flat top" is reached is greater than the amount lost at the peak.

We have Enphase inverters rather than a central inverter and they have been trouble free for over three years now. However, our array is not subjected to the extreme heat of the desert. We are at 6,700 ft. so they are relatively cool by comparison and we have less atmospheric shading. Having said that, there are a couple of good reasons to consider a centralized inverter. First is that the centralized inverter does not need to be mounted on the roof and can be cooler. This of course just depends on your climate. Second, if you ever plan on having a battery back up and going off grid, then a central inverter may be better. The reason is that when you use a battery back up, the power needs to be reverse inverted from DC back to AC. With many micro inverters this would require and additional inverter to get the power back to AC.

To further make the decision difficult, there are many reasons to go with micro-inverters and you are probably already aware of them. They do lend themselves to additional panels down the road. They function independently so if one fails the entire system doesn't fail as opposed to the central inverter. However, one caveat is that, at least in our local, the utility will not allow any more than 20% of your main electrical panel capacity to be solar. Thus, if you have 200A service to your house, then the maximum solar would 40A, thus depending on your initial installation, adding more panels later may be a moot point.

Finally, welcome to the club. We have been totally pleased with our decision.

ERG4ALL said:

I was told by the Enphase people that they intentionally have more panels with smaller inverters because the generation on a daily basis is a bell curve with a flat top.

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That is only true if you use a tracker OR the inverter limits the output. Otherwise, the curve looks almost exactly like a bell (no flat top).

Fortunately, the OP will almost never see a flat top with his new array. For that to happen, it has to be quite cold and clear and the sun needs to very close to the boresight of the array. That will likely occur only a handful of times each year. If the roof is very flat, then it likely will never happen.

ERG4ALL- Thanks for the info. I never really understood the the " flat part of the curve before". I wounder how that would apply to the newer microinverters that are made for larger solar panels. SMA, Energy One, and Enphase are the only companies I know of that address the need for those solar panels above 255 watts.
One last note SMA has anew line of central inverters that will shift from "grid" to non-grid DC production during a power outage. My older central inverter systems may need replacement some day. These new SMA would be a nice adaptation. Right now, expanding the older array with microinverters for my Leaf is working out fine.........Thanks again.

Burr said:

ERG4ALL- Thanks for the info. I never really understood the the " flat part of the curve before". I wounder how that would apply to the newer microinverters that are made for larger solar panels. SMA, Energy One, and Enphase are the only companies I know of that address the need for those solar panels above 255 watts.

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All PV inverters will clip if you send too much DC power to them. Higher rated inverters simply start clipping at higher power levels.

Burr said:

One last note SMA has anew line of central inverters that will shift from "grid" to non-grid DC production during a power outage. My older central inverter systems may need replacement some day. These new SMA would be a nice adaptation. Right now, expanding the older array with microinverters for my Leaf is working out fine.........Thanks again.

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SMA has had this for a while using their Sunny Island product - the Sunny Island integrates with existing SMA inverters.

Oooohhhh! I didn't think one existed like this. I'm intrigued.

Is there any barrier to installing one of these SMA with the SPS functionality in California or with SCE?

Looking at online vendors, it looks like one SMA 3000 with the SPS feature would cost about $100 more than the 10 Enphase M215s for my solar expansion. I'm thinking that would handle the 10 250 W panels and have room to add 2 more down the road. (Am I interpreting this stuff correctly?)

While I like the flexibility of the micro-inverters and the fact that I don't take such a production hit if I get a damaged panel, the SPS feature is very tempting. Being completely without power when the grid is down is really annoying. I'm thinking that 1500 W through the SPS would be enough to operate the trickle charger that came with the Leaf. (Please confirm if I'm correct on that???) So an extended power outage wouldn't force me to switch to an ICE. :idea:

And I see that the SMA inverter is US made. Anyone have these installed and can speak to their quality? So far, I've heard lots of good stuff about the M215s.

Thanks!

DarthPuppy said:

Anyone have these installed and can speak to their quality?

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The Sunny Boys are well designed and manufactured. The difference is that you only get a 10-year warranty with them instead of the 25-year warranty with the M215s. That is mainly due to the electrolytic capacitors that the Sunny Boy uses. The good news is that you can pay extra to get a 25-year warranty on the Sunny Boy if you like. By way of anecdotal information, DesertDenizen has stated in my thread on MTBF, failure modes, etc. that his lower-power Sunny Boys have served him without any problems for over 10 years in Arizona. Of course no one has that much history with any Enphase inverters.

I have two old SMA's that have been working for about seven years. One installer referred to them as being " bullet proof". At that time they were also called "Sunny Boys", and were made in Germany. As far as adding solar panels' little by little' and DIY, the microinverters will work best for me. The Enphases are 'plug & play'. If you make a few calls, you'll find the warranty process is much more user friendly at Enphase than Power One or SMA.. Two installers said that Enphase was their first choice based on the warranty processes. That SMA back-up feature is really tempting........Good Luck

I have two old SMA's that have been working for about seven years. One installer referred to them as being " bullet proof". At that time they were also called "Sunny Boys", and were made in Germany. As far as adding solar panels' little by little' and DIY, the microinverters will work best for me. The Enphases are 'plug & play'. If you make a few calls, you'll find the warranty process is much more user friendly at Enphase than Power One or SMA.. Two installers said that Enphase was their first choice based on the warranty processes. That SMA back-up feature is really tempting........Good Luck

Thanks for the info. I've revised the bid request to the sma with the sps outlet. I wish I had known about this option a year ago when we did our first solar install if it was available then. But fortunately we can get it this time around.