The Argument for Enphase Micro Converters

jcgee88 · May 2011

Re: The Argument for Enphase Micro Converters

Solar Guppy wrote: »

The OP has 6200 watts of PV, the enphase limit to 199 AC watts or 5400 AC watts maximum. The installer claims of 10-20% more with Enphase is strictly based on comparing a 5000 watt sting inverter to the 5400 watts of Enphase units, not the the Enphase is more efficient

Since the site has no shading, I recommended the SPR-7000m, which is the 7kw Sunnboy, the very highest performance inverter on the market, also backed by the largest and oldest inverter manufacture of GT equipment

Yes you could use a 6kw and in cool weather or partly could conditions clip the output to that, in partly cloud conditions, you lose allot of generation, as with the edge of cloud effect going to +20% , it really hurts production on those day

Also, inverter efficiency goes down as you approach maximum rated output, a 7kw inverter at 6kw output will out perform a 6kw unit by 2-4%, depending on the manufacture of the inverter

If I was to buy this system, the 7kw Sunnyboy is the best choice, enphase has NO advantages in this proposed system

No offense, but some of your facts for this situation are a little off.

First, the Enphase model in question is the M210, not the M190.
As a previous poster explained, the M210 is the only Enphase
product that can be used with the prospective SunPower modules.
Thus, the inverter limit is not 199w, but should be 221 watts
(210 watts plus 5%). At the clipping limit, this would yield 5967
watts from 27 panels.

Second, the OP said that "someone" told him this:

"the SPR7000m Inverter will outperform Enphase by 10-20% in DC Watts".

You have that reversed in your reply.

Lastly, even if the Sunnyboy inverter and the Enphase inverters
performed exactly identically from a power production point of
view, Enphase does have advantages over Sunnyboy (and vice
versa). For example, when an Enphase micro-inverter goes down,
only the panel it is associated with goes down, not the entire
array. Enphase comes with 15 year warranty and Sunnyboy 10
years. Thus, to say that Enphase has NO advantages is stretching
it.

If production were equal, then Sunnyboy's advantage is initial cost.
The SPR-7000m is about $4K at the NAWS store, and 27 M210s
would cost about $6K. Thus, the SPR-7000m will come in about
$2000 cheaper in this case. That works out to be $1000 cheaper in
real money after typical 50% rebates and incentives.

It's hard to say if this is truly cheaper in the long run, because if
you make a worse case assumption that the inverter will die just after
it comes off warranty, then you'd need 2.5 SPR-7000m's over the 25-
year life of an array. That would be $4K * 2.5 = $10K at today's
prices. Including the first year 50% inventives/rebate would lower
that by $2K, to $8K. With 15-year warranted micro-inverters,
you'd nominally need 1.6 sets of micro-inverters, and that would be
$6K * 1.6 = $9.6K. Again subtracting the first year incentives/
rebate of $3K, that leaves you at $6.6K. Of course, you can't buy
one half of a Sunnyboy inverter, so the absolute worse case is that
you would end up buying three inverters over the 25-year life of the
array. That would be $4K *50% + $4K + $4K = $10K. Thus, the
Enphases would be 34% cheaper on a total life cycle basis at
today's prices for the worse case. The worse case doesn't always
happen...but Murphy's Law isn't ubquitous for no reason.

John

mike95490 · May 2011

Re: The Argument for Enphase Micro Converters

jcgee88 wrote: »

....Enphase does have advantages over Sunnyboy (and vice versa). For example, when an Enphase micro-inverter goes down, only the panel it is associated with goes down, not the entire array. ...

Ever been on a roof after 3 years, and try to unbolt panels, and get to the middle of an array to change out hardware? Did the installer use all SS hardware ? Not something I would look forward to.

Cariboocoot · May 2011

Re: The Argument for Enphase Micro Converters

Can someone tell me how high the percentage rate of failure is for 'central' grid tie inverters that it makes the Enphase 'only one panel is lost' claim worth considering?

In the off grid world, failure is not an option.

tonystewart · May 2011

Re: The Argument for Enphase Micro Converters

Thanks jcgee88 for the thorough explanation

stephendv · May 2011

Re: The Argument for Enphase Micro Converters

In Europe you can buy a 25 year warranty for a sunny boy, the cost of the extension is the same as the unit itself. So we could deduce that SMA believes the average life expectancy is about 12.5 years for the SB.

The often quoted "your whole array doesn't go down when an enphase fails" seems like something not really worth considering. We're talking a once in 25 years event, say it takes 3 days to replace a string inverter that's 0.03% of total production. Also, replacing a string inverter will cost less in labour since it's a one time fix. Getting up onto the roof to replace every enphase after they fail at different times is going to take longer.

jcgee88 · May 2011

Re: The Argument for Enphase Micro Converters

stephendv wrote: »

In Europe you can buy a 25 year warranty for a sunny boy, the cost of the extension is the same as the unit itself. So we could deduce that SMA believes the average life expectancy is about 12.5 years for the SB.

Stephen, thank you for the information about the amount charged
for the extended warranty. I was wondering about that, but could
not find any source which listed the extended warranty prices.

I also agree with your assessment of the probable life expectancy.
I worked for a major computer manufacturer, where in my role, I
was educated on how companies do their strategy for warranties.
There is a lot of work and thought that goes into setting the
duration of a warranty. For example, you wouldn't want to do a
five year warranty on a product that fails on average after three
years, you'd lose your shirt on that product. Conversely, you
wouldn't want to do a one year warranty for a product that
typically last five years, since you would be giving up a marketing
advantage to your competitors. The duration of a warranty would
therefore be set principally to minimize cost for warranty repairs and
secondarily to maximize marketing advantage. Thus, people's
sense that what they buy often fails "just after the warranty
expires" has its basis in fact.

stephendv wrote: »

We're talking a once in 25 years event.

Using your own figure of 12.5 years, you would have two events in 25 years.

stephendv wrote: »

...say it takes 3 days to replace a string inverter that's 0.03% of total production. Also, replacing a string inverter will cost less in labour since it's a one time fix. Getting up onto the roof to replace every enphase after they fail at different times is going to take longer.

It would be interesting if anyone who has incurred a string
inverter failure would chime in. How long did it take to figure
out the inverter failed? How long did it take to get it replaced?
[Bill, didn't you go through this?]

I sense that your "3 days" would be tight. Takes a day or two
for you to figure out something is wrong. Takes a day or two
for the contractor to come out to verify. Takes three days to ship
in a new unit to the contractor. Takes a day or two to get the
unit and the contractor back out to your house and get the unit
installed. No work or delivery on the weekend. My GUESS
would be that you are looking at a week best case and
probably closer to two weeks. Also remember that these boys
weigh a LOT. The traditional kind (with transformers) weighs
140 lbs, so it takes two people to lift and install one. I suspect
it takes the better part of a day for these two people to
de-install/re-install/test a complete unit. By the way, you are
paying for this labor, since the warranty explicitly states that
labor is not covered:

"This warranty does not cover costs related to the removal,
installation, or troubleshooting of your electrical systems."

Source: SunPower warranty for SPR-7000m

It takes 5 minutes to install a micro-inverter (two screws and
plug in two cables), so let's say it takes one person 20 minutes
to de-install/re-install. If we assume replacing a string inverter
would take two people times four hours = 8 manhours, then
you would need to have incurred 24 micro-inverter failures to
be equivalent.

John

BB. · May 2011

Re: The Argument for Enphase Micro Converters

My system--Took about 7 hours of two people to R&R and test each panel for my central inverter system. (around 3 hours to remove, and ~3-4 hours to install 20 new 175 watt panels). The system was a little over 5 years old at failure.

To change out the inverter took about 1 hour (not really that bad, includes unboxing/boxing and a bit of modification because the new inverter has a much larger disconnect box vs the original). The inverter was working fine and already out of warranty--but Xantrex/Schneider had some earlier life failures and this was a customer satisfaction replacement (my guess).

BP paid somewhere around 1/2 of the R&R bill for the panels and I paid $500.

Xantrex/Schneider paid for the R&R of the inverter.

It took about 3.5 months to get the new panels from BP (I didn't raise a ruckus with BP--but it was getting close. My installer said BP was running about 1-3 months for warranty panels).

At this point--getting most of my equipment solar equipment replaced after a 5+ year failure of panels--I am not going to believe that any of this stuff will last forever--and would make post warranty service a definite part of my planning.

Towards that end, the great unknown is the true lifetime of the Enphase inverters. My believe is that it may make sense to replace one or two failed inverters (out of ~20). But for the 3rd +, you probably should plan on replacing all of them as the R&R of the panels to get to a failed inverter (if you have a large array mounted flat to roof) is going to eat you alive (given that Enphase is not paying for R&R).

So--what is Enphase's warranty detail if you have multiple failures over time?

BP's, as I understand, was panel for panel replacement for first 2 service calls, 100% replacement for 3rd call. Unless >=20% failure--then all panels replaced at once.

If you have one inverter fail at year 10, 2 fail at year 11, another fail at year 12, etc... What would Enphase's policy be?

If your array is tilted and you can get to the back without R&R'ing some panels to get a a failed unit--then Enpase does not worry me as much.

In my case, R&R'ing panels was certainly more costly (~2 people 7 hours for 20 panels) vs less than 1 hour for one person with a central inverter change out...

Note that my array did not have zero output when it failed. It was probably at 50% output... Taking 3+ months for warranty replacement during winter for a grid connected home is just irritating. 3+ months during summer would have been expensive because of loss of power (and high summer power rates for TOU/Seasonal power billing). 3+ months waiting for on off-grid home--large generator runtime costs.

-Bill

RacerChris · May 2011

Re: The Argument for Enphase Micro Converters

jcgee88 wrote: »

Second, the OP said that "someone" told him this:

"the SPR7000m Inverter will outperform Enphase by 10-20% in DC Watts".

OP here. The "someone" I was referring to was Solar Guppy. I did not want to post his name at the time because he said it in a PM. But now that he has chimed in, perhaps he can clarify this statement?

Chris (OP)

jcgee88 · May 2011

Re: The Argument for Enphase Micro Converters

BB. wrote: »

...what is Enphase's warranty detail if you have multiple failures over time?

If you have one inverter fail at year 10, 2 fail at year 11, another fail at year 12, etc... What would Enphase's policy be?

If your array is tilted and you can get to the back without R&R'ing some panels to get a a failed unit--then Enpase does not worry me as much.

I have read the warranties for both Enphase and SPR-7000m.

They are similar, other than Enphase being 15 years vs 10 years.

Neither warranty covers labor to de-install and re-install.

For both manufacturers, a unit that has been repaired/replaced
will have a warranty that is valid for the remaining balance of the
original warranty, or 90 days, whichever is longer.

As to your question about serial/multiple failures, Enphase's warranty
does not specifically address that issue. I would think that any failure,
whether one by one, several over time, or multiple all at once are
nevertheless covered as if each were a single instantiation of the
warranty. That is, they are required to repair or replace any
defective unit that is still under warranty. In the case of a
systemic failure that might affect the entire lot, as in your case
with your BP panels, I suspect that the contractor and Enphase
would handle such situations on a case by case basis, as was
was done for you.

I do have eight panels that are uptilted. While their inverters
are easy to access and visually inspect, they aren't easier to
replace than inverters on a flush mount. That's because they are
mounted on the rails, not on the panels; as the panels sit on the
rails, you still have to remove the panels (four bolts) to expose
the part of the rail where the inverter is mounted.

John

Solar Guppy · May 2011

Re: The Argument for Enphase Micro Converters

The sunnyboy will never limit the arrays output, the post/pm was using the 199 limit or 5400 watts on a 6200 watt array, similar to the installers comment on comparing the Enphases to a output limited 5kw inverter

Since it seems your using a unit that has a combined limit of 5967, then it would be less of a difference. In cooler weather the Sunnyboy will have a distinct advantage

At this point, I'm bowing out of the conversation as there is nothing factual to add

halfcrazy · May 2011

Re: The Argument for Enphase Micro Converters

Assuming a system that is mounted on standoffs on the roof where one would have to remove a panel at least to get to the Enphase I guarantee I could change out the string inverter in minutes compared to the Enphase. Trust me I have experience changing out Xantrex GT inverters. Think about the time required to harness up and follow all the OSHA regs that are required on the roof.

While I think the Enphase is a novel Idea I worry about the longevity of electronics baking and freezing all the time under the panels and will Enphase be there in 15 years?

If shading is not an issue I would agree with Solar Guppy on this one.

RacerChris · May 2011

Re: The Argument for Enphase Micro Converters

Hi all, original poster here,

I have made my decision - No on micro-inverters at my site, but i am upgrading the String Inverter from 5kw to 6kw for my 6.21kw PV Solar GT. I think is the right decision for me at this particular house while saving me two grand. If I were in a place where I would, in the future, want to add to the system, then I would have gone with the Micro-inverters. Although I really like the monitoring associated with micro-inverters, the one that comes with the Sunpower system includse the added ability to see your Use along with production.

Thanks everyone for all your input. The opinions I heard here, lead me to the research that ultimately allowed me to make an informed decison on what is best for us. THANKS!

Chris

Cariboocoot · May 2011

Re: The Argument for Enphase Micro Converters

That's what we're here for.
That and the free donuts.

The Argument for Enphase Micro Converters

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