Enphase microinverter vs. SMA inverter- cost delta for a ~28 panel system - justifiable?

vsheetz

I am seeing approx $2000.00+ more for a system with Enphase vs. SMA, for a system with about 28 panels.

Sound about right?

• Warranty
• Performance (site is nearly due south facing, little or no shading, 3/12 roof, located in SoCal)

What other benefits? How to cost justify?

thx!

jaggedben

Re: Emphase microinverter vs. SMA inverter- cost delta for a ~28 panel system - justifia

The cost difference seems 'about right'. Maybe a little low, but I'm not sure if you are including everything. Be sure to include the Enphase cabling and the Envoy in your Enphase cost.

Enphase main advantage is dealing with shading, so if that's not a concern for you then that argues for the SMA. (I would advise you to take shading readings and not just say 'it looks okay'. I've been fooled many times in both directions, and I've done hundreds of sites professionally.)

Other advantages to Enphase:
- includes online monitoring at no extra cost (with the Envoy)
- if one inverter fails, the rest of your system keeps working
- slightly safer without 600V DC on your roof.
- Safer and simpler for you to install yourself, if that's what you're doing.

Advantages to SMA (besides cost):
- Doesn't require going on the roof to replace inverters every now and then.

rollandelliott

Re: Emphase microinverter vs. SMA inverter- cost delta for a ~28 panel system - justifia

well just really depends on the warranty. if enphase is around in 25 years and honors their warraty it favors enphase.
if enphase goes belly up (there are 4 other competitors entering into its monopoly right now) then you should get sma.

i would agree if you are DIY, enphase or enecysys micro inverters are the way to go.

DanS26

Re: Emphase microinverter vs. SMA inverter- cost delta for a ~28 panel system - justifia

If your array is located a long distance (say > than 150 ft) from your point of common connection, then you might want to check voltage drop calculations for the Enphase microinverters.

This is an important calculation in the planning stages. If you have to size up your cables to mitigate the AC voltage drop, it could be costly.

In my case, I paid for my string inverter in wire savings alone.

Just something to plan for if your array is not close to the point of common connection.

BB.

Re: Emphase microinverter vs. SMA inverter- cost delta for a ~28 panel system - justifia

DanS is talking about the fact that Enphase output 240 VAC -- And you have specific limits you have to meet (around 212 volts minimum and 264 VAC maximum) for the GT inverters to "qualify" the AC voltage as being good...

If your power to the property is already a bit "dodgey" (high or low at the properly line, variable because of summer A/C and pumping loads, etc.)--Sometimes the added voltage drop (really voltage rise) from the meter to an outbuilding/barn can take a 254 volt summer morning nominal + 8 volts "rise" due to wire length/resistance, and cause the inverters to shutdown for 5 minutes until the power is stable again.

When you use a central inverter--You can run upwards of Vmp~400 volts DC from the array to the GT Inverter/Meter location--Have lower current (higher DC voltage) and not worry about "drop/rise" because of the extra run length to the array (voltage drop is not an issue on the DC side--other than the few extra percent of power loss to to resistance heating).

And--That does get back to accurately measuring the utility voltage at your home/meter/shop and make sure that there is nothing "strange" going on with it... Even with properly installed systems, there have been installations where the power company just does not regulate the line voltage that well (old equipment, variable industrial loads, too far back to the substation/regulating equipment, etc.).

Probably more of a rural problem than a city problem. Small utilities (such as in Puerto Rico) have been having real problems with large solar arrays on old/small utility systems.

ggunn wrote: »

It's not without its problems. I don't know the grid structure out there - does each island have its own autonomous grid or are they connected by undersea cables? Even assuming they are interconnected, though, it's still a very small grid compared to anything on the mainland, and the more solar is on the grid, relatively speaking, the more problematic grid stabilization becomes, since grid tied solar inverters are current sources and produce what they produce irrespective of demand. To keep the line voltage stabilized, grid administrators must allocate generation resources much more dynamically than they would if solar were a smaller component of the overall picture.

When I was out at SPI, I talked for a bit with a grid administrator from Puerto Rico. This has become a big problem for them since (I believe) the Air Force installed a very large grid tied PV system on base. Their out of date control structure is having major problems with grid stabilization; voltage fluctuations plague them.

-Bill

Inverter_Herder

Re: Enphase microinverter vs. SMA inverter- cost delta for a ~28 panel system - justifia

JaggedBen brings up some good points, however SMA also has free monitoring so no advantage there, although Enphase does have the module level monitoring. Enphase's community site shows that these failures are not uncommon but are quickly taken care of by their service people. http://community.enphaseenergy.com/enphase_energy_community/topics/multiple_microinverter_failures

JB and Enphase make good points concerning system failure when just one micro goes down vice one SMA, but as we see, how many times do you feel comfortable with climbing up on the roof to replace them? SMA makes solid inverters and even if it does fail, they are quick to get a replacement up, 24 hours sometimes. Plus, they have been around forever and make their inverters in Denver vice China, if that means anything anymore.

Shading is where these micros really show their stuff and will smoke a string inverter in production. The DIYers will also love how easy those micros go in and how little effort it takes to lift one compared to an SMA beast.

ggunn

Re: Enphase microinverter vs. SMA inverter- cost delta for a ~28 panel system - justifia

Inverter_Herder wrote: »

JaggedBen brings up some good points, however SMA also has free monitoring so no advantage there, although Enphase does have the module level monitoring. Enphase's community site shows that these failures are not uncommon but are quickly taken care of by their service people. http://community.enphaseenergy.com/enphase_energy_community/topics/multiple_microinverter_failures

JB and Enphase make good points concerning system failure when just one micro goes down vice one SMA, but as we see, how many times do you feel comfortable with climbing up on the roof to replace them? SMA makes solid inverters and even if it does fail, they are quick to get a replacement up, 24 hours sometimes. Plus, they have been around forever and make their inverters in Denver vice China, if that means anything anymore.

Shading is where these micros really show their stuff and will smoke a string inverter in production. The DIYers will also love how easy those micros go in and how little effort it takes to lift one compared to an SMA beast.

FWIW, SMA makes a microinverter now. I'm not sure if they are available yet in the US.

jaggedben

Re: Enphase microinverter vs. SMA inverter- cost delta for a ~28 panel system - justifia

Inverter_Herder wrote: »

JaggedBen brings up some good points, however SMA also has free monitoring so no advantage there, ...

Not really true. Utilizing SMA's monitoring requires an additional hardware purchase such as a Sunny Web Box.

It's like this:
SMA inverter alone: LCD display
Enphase system with Envoy: LCD Display and internet connectivity
SMA inverter plus Web Box: LCD Display and internet connectivity

I suppose one could argue that the Envoy is an additional purchase on the Enphase system, but it really is an integral part of the system that one wouldn't do without. Put it this way, I've installed hundreds of Enphase systems, and the Envoy is always included. The only monitoring for SMA systems I've installed is for third-party lease partners. So in reality the Enphase monitoring is 'included in the prince' whereas the SMA is not.

While we're on the subject, SMA's micro-inverter system (which I don't think has 'hit the streets' yet) will include the ethernet connection but not the LCD display.

Dashadeaux

Re: Enphase microinverter vs. SMA inverter- cost delta for a ~28 panel system - justifia

I live near Phoenix AZ where the summer day air temp can exceed the derating point of an SMA Inverter. Does anyone have an opinion regarding whether or not 113+ degree air temp will have a noticeable affect on an SMA output?

jaggedben

Re: Enphase microinverter vs. SMA inverter- cost delta for a ~28 panel system - justifia

A couple points...

-High temperatures are going to decrease the output of your panels so even if the SMA begins to derate you probably aren't losing much production.
-The Enphase operating temperature goes higher but the temperature on the roof is also likely to be higher, so it comes out about the same.
-High heat is going to reduce the life of your inverters no matter which type you choose. However with a string inverter you can consider putting it in a garage or someplace that may be a bit cooler or a lot cooler. (Also, relative to other geographic regions, your replacement costs on inverters may be offset by higher production from more sun).

BB.

Re: Enphase microinverter vs. SMA inverter- cost delta for a ~28 panel system - justifia

For central inverters, I always recommend to keep them out of full sun and in a well ventilated area.

Mine is in a cool garage. A few folks have put a lamp timer and small fan pointing at their inverters for hot summer afternoons.

-Bill

drees

Re: Enphase microinverter vs. SMA inverter- cost delta for a ~28 panel system - justifia

BB. wrote: »

Mine is in a cool garage. A few folks have put a lamp timer and small fan pointing at their inverters for hot summer afternoons.

In Phoenix, unless you air condition your garage it's going to be far from cool - more like 95-115F during the summer months - day and night!

solar_dave

Re: Enphase microinverter vs. SMA inverter- cost delta for a ~28 panel system - justifia

drees wrote: »

In Phoenix, unless you air condition your garage it's going to be far from cool - more like 95-115F during the summer months - day and night!

I have mine mounted outside on the east side of the house, they are shaded during the peak heating times but get a chance to start the day pretty cool. If they are In a closed garage here they would be quite warm always. I have considered placing a small awning to protect them from the morning sun.

Dashadeaux

Re: Emphase microinverter vs. SMA inverter- cost delta for a ~28 panel system - justifia

My interest in the SMA inverter is purely academic. I have a Fronious located inside the garage and it will operate a full output up to 122 degrees. As stated earlier by another poster the panels will be supplying less than STC potential long before it gets to 122 degrees. In July last year my 11.4 kW panels peaked at 11.6... I'm not sure how this happened or how often it happened.

In the heat (115+) last summer I visited a few homes that have an SMA, some in direct afternoon sun, in an attempt to ascertain if they were indeed derating. I found no evidence of them derating, and wondered if anyone else has done any investigation.

If I install another solar system, I hope to use AC panels.

solar_dave

Re: Emphase microinverter vs. SMA inverter- cost delta for a ~28 panel system - justifia

I have a pair of PVPowered 5200 inverters mounted facing east outside. While it is a rare event, on a cool day when the sun is 90 degrees to the panels, they will clip at the max value for a while around noon on a clear day. Pretty much a good design where the panels match the inverter capacity. Now cloud edge effects are a different story, I saw a 10 to 15 minute stretch under less than ideal conditions where the inverters "topped out" from a long chunk of cloud edge effect. Again it is a rare event.

Generally my panel output is below the inverter capacity.