Power One v. Enphase Microinverters

[Darmok]

With 255-260W panels, it seems power production would be better with Power One Aurora microinverters, which have maximum output power of 250W, instead of Enphase microinverters, which have maximum output power of 215W (this according to the data sheets on both). Does that make sense, or is it more complex than that? Would I be leaving power on the roof at peak production with Enphase?

Also, am I better off with the film capacitors in the Power One over the electrolytic capacitors in Enphase?

Thanks.

[megalo]

I believe the Enphase M215s do not use electrolytic capacitors.

[MidOhioValleySolar]

Maximum output of Solar PV is typically 80% of nameplate

I think i can help with this question. The one issue that everyone realizes once panels are purchased and placed on the roof is that the performance is typically 80% (rarely 90%) of the nameplate. So a 255W panel, on average produces 205 to 230W max. The enphase M215 microinverter can handle some oversaturation. A larger microinverter (along with other electrical costs) are now seen as a larger percentage of the costs of the overall system, so it makes sense to size (an not oversize) correctly.

I hope this helps and makes sense. One of the technical experts (i am in sales) may be better able to describe this microinverter - panel size relationship.

Regards,

Lance

[Darmok]

Thanks Lance. In my case, the bid with the power one inverters is cheaper, so no cost for the added capacity, if it actually is extra capacity.

[jim@xmxpower.com]

Enphase M215 match with module

For instance, using a Canadian Solar CS6P245MX module has a PTC rating (real life test performance) of 222 DC watts.

Enphase units are 96% efficient at the inverter conversion of DC to AC meaning 222 DC watts translates into 213 AC watts which is below the microinverter output specs. That being said we regularly get slightly higher output readings during peak periods. I suspect this is because the solar modules and the microinverters are performing better than specs. This is a pleasant surprise.

See below for an example of power output greater than specs:

Screen Shot 1675.jpg

[bonaire]

Enphase will allow 225W max. Many people are getting larger modules these days, such as 260w. Why not get 250w microinverters if you need higher peak output and have good sun. However, not everyone needs micro inverters. Power one string inverters have dual Mppt controllers and if you don't have shading issues, the aurora string inverters are cheaper than micros. The whole point is building a system for as low a cost per watt as possible with similar production.

[jim@xmxpower.com]

Enphase Advantage

Enphase will allow 225W max. Many people are getting larger modules these days, such as 260w. Why not get 250w microinverters if you need higher peak output and have good sun. However, not everyone needs micro inverters. Power one string inverters have dual Mppt controllers and if you don't have shading issues, the aurora string inverters are cheaper than micros. The whole point is building a system for as low a cost per watt as possible with similar production.

Enphase recommends maximum DC input of 260W.
Enphase puts out a very good whitepaper on the subject at http://enphase.com/wp-uploads/enphas...ightsizing.pdf
However, as my previous comment explained I believe that modules with a 222 watt PTC rating are ideal. If you have less than ideal pitch and azimuth you could go larger with no danger of power clipping.

Enphase has advantage over string inverters on multiple levels. For instance, Enphase units carry a 25 year warranty whereas string inverters typically carry only 10 - 15 year warranty. String inverters require DC wiring from module to inverter. As a practical matter this is often a complication for a residencce. DC wiring requires either metalic conduit through house or exposed conduit which is potentially unsightly. Enphase installs require AC wiring from modules to load center and therefore only require Romex through the house which can easily be run through attics and fished through walls. There is also no need for wall space for equipment meaning Enphase circuits can be connected to interior load centers rather than at the meter section. The system monitoring is fantastic due to ability to see module level performance which is a necessity if you are to ever know for sure if all your modules are performing properly.

Up-front low cost is nice but not at the expense of necessary quality and customer satisfaction. By the way, once you become familiar with installing an Enphase system we feel as if the typical labor savings offsets much of the extra cost.

[Darmok]

Thanks Jim. The white paper is interesting reading. With the proposed 260 W panels and the fact that we won't have optimal azimuths on our panels, the loss to inverter saturation appears to be minimal to nonexistent.

[bonaire]

I don't know if enphase will be around in 25 years to support the warranty. They have never turned a profit as a company. Can't do that for 25 years. Now, they have two competitors with micro inverters to compete against. SMA and power one, the top two inverter companies in the world.

I don't know how long this can continue: http://finance.yahoo.com/q/is?s=ENPH

[Darmok]

I don't know if enphase will be around in 25 years to support the warranty. They have never turned a profit as a company. Can't do that for 25 years. Now, they have two competitors with micro inverters to compete against. SMA and power one, the top two inverter companies in the world.

I don't know how long this can continue: http://finance.yahoo.com/q/is?s=ENPH

Right. So which is better. A ten year warranty from a solid company (no chance of warranty coverage after year 10) or a twenty five year warranty from a startup (some chance of warranty coverage after year 10, but a greater chance of no coverage sooner if the company folds)?

[bonaire]

If anyone is interested, you can buy extended warranties from PowerOne. Or most any of the inverter companies. I honestly think that Enphase established the 25 year warranty as a "sales tool" with full expectation that they probably won't be able to cover it in the out-years. My own solar installer said that the 190 micro inverters had a "good number of" field failures.

The way I look at it: How many warranties have you ever had to use over your lifetime? I have never used either a regular warranty or extended one. Inverters are something that many of us actually have to expect to replace before 20 years. I plan on buying a 15 year warranty on my PowerOne Auroras.

[Naptown]

If anyone is interested, you can buy extended warranties from PowerOne. Or most any of the inverter companies. I honestly think that Enphase established the 25 year warranty as a "sales tool" with full expectation that they probably won't be able to cover it in the out-years. My own solar installer said that the 190 micro inverters had a "good number of" field failures.

The way I look at it: How many warranties have you ever had to use over your lifetime? I have never used either a regular warranty or extended one. Inverters are something that many of us actually have to expect to replace before 20 years. I plan on buying a 15 year warranty on my PowerOne Auroras.

Ah but there is a flaw in that logic. Enphase is a publicly traded company. Under SEC rules they are required to escrow money for warranty claims in the event they go out of business.

[bonaire]

Ah but there is a flaw in that logic. Enphase is a publicly traded company. Under SEC rules they are required to escrow money for warranty claims in the event they go out of business.

But probably only at the rate of failure that they can document. So, perhaps 2-3% of the unit sales? I wonder if they need to also pay the T&M of the installer going out to service the warranty replacement - you may know if that's the case. if I had an Enphase system put up, I would surely buy one or two spare microinverters and put them in storage just in case.

I'm waiting and watching to see how Enphase does in the next couple years. I've even bought some stock in their company within the dip a few days ago. I also own Power One stock and am looking to find a buying time for SunPower. There is a future for these companies - but it's hard to know what it is. But their stocks sure are tradeable. As I watch Enphase's stock lately - I see market makers messing around with 100 share blocks. Not a lot of real trades either. I wonder if there really isn't something more going on to keep their stock value up. They need to break through this quarter with a profit or risk dropping below $4 late in May. And what are they designing with 8-10 million in R&D per quarter over the last year? That's a lot of spend. 300W 96-cell micro-inverter? Something else that can supply power even with the grid down? Waiting to see.

[Naptown]

But probably only at the rate of failure that they can document. So, perhaps 2-3% of the unit sales? I wonder if they need to also pay the T&M of the installer going out to service the warranty replacement - you may know if that's the case. if I had an Enphase system put up, I would surely buy one or two spare microinverters and put them in storage just in case.

I'm waiting and watching to see how Enphase does in the next couple years. I've even bought some stock in their company within the dip a few days ago. I also own Power One stock and am looking to find a buying time for SunPower. There is a future for these companies - but it's hard to know what it is. But their stocks sure are tradeable. As I watch Enphase's stock lately - I see market makers messing around with 100 share blocks. Not a lot of real trades either. I wonder if there really isn't something more going on to keep their stock value up. They need to break through this quarter with a profit or risk dropping below $4 late in May. And what are they designing with 8-10 million in R&D per quarter over the last year? That's a lot of spend. 300W 96-cell micro-inverter? Something else that can supply power even with the grid down? Waiting to see.

Our failure rate has been less than 1% and most of that was right out of the box or lightning.
They have paid us for the failures so far and handsomely I might add. But the failures so far have been easy to get to and did not require a lot of disassembly to get to them.

[silversaver]

Naptown,

Enphase has recently up the spec to support 270W Panels. I'm thinking to combo up with LG260 or Solarworld SW270. Which one will be a better match with M215? Forget about warranty..etc, just the panel.

Thanks