Thread: Ben's Garage
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Old 04-09-17, 11:08 AM   #122
Steve Hull
Join Date: Dec 2012
Location: hilly, tree covered Arcadia, OK USA
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Ben - again very nice videos. I also love the easy set up using the enphase toolbox on my smart phone.

Here are a few suggestions. The debate on enphase M215 vs 250 microinverters will quickly end in 2017 as they are being phased out. The two year old S280 (280 watts) and new IQ 6 series (60 and 72 panel; 290 watts) is being shipped now. Don't date your superb video with quickly out of date issues.

Here is how I work out microinverter choices - calculate the cost per watt. The latest series of the M215 will make 235 watts. On my roof, they will do this for hours and it is not just a "peak" for a couple minutes. Your saw the same 235 W output. But the M250 is 250 watts MAXIMUM, no more. Right now (April 2017), the costs for the two are about $75 for the M215 and about $95 for the M250.

The current cost per watt is $0.32 for the M215 and $0.38 for the M250. You may not think this is big, but on a system, it quickly adds up.

The same calculation metric is appropriate for the 280 and new IQ6 - look at the cost per watt.

The second issue is the real life output of the panels. Sadly, I see people putting up 260 watt panels with M250s. This is a waste. The lab or STC panel output may be 260 watts, but the PTC or real life output is ~ 90% of that. Thus, a 260 watt panel in real life puts out only 234 watts - a perfect match for a M215 and a waste for the more expensive M250.

You alluded to the advantage of the enphase microinverter as if one panel is shaded, then the whole string is not compromised. Me thinks you need to mention more specifically the downside of string inverters. One shaded panel, on a string inverter, means that panel becomes a current sink - a resistor. And the superb enphase software allows you to look at each and every panel and inverter. Then figure in the 25 year NO prorated guarantee (via Siemens) for the inverters.

One of my customers just had me replace bad M190's. That series had problems. We shipped them back and they replaced them with M215's at NO cost (and free return shipping as well for the bad units). Very impressive. I have been told that others installers have not even had to send the bad M190s back as enphase can look and see on their software that they are bad.

Not all utilities will accept the well made and superb Midnight turn off switch. I bought one such Midnight switch for a customer install and had to eat the cost as the utility INSISTED on a manual turn off lock out disconnect switch. Yes, I showed then the lock out portion of the Midnight switch, but some utilities are VERY conservative. You may want to mention in your video of asking the utility if they will accept this Midnight switch (your utility will, Bravo for them!).

In your situation, with a very constrained roof area, you may want to suck it up and go with the more expensive S280 and 320 W panels. This would boost your output by ~ 20%.

Lastly, the new enphase IQ series microinverters will require a new Envoy that are NOT compatible with the older microinverters. The new IQ trunk cable only has two wires and is cheaper. The effective distance for transmission to the new Envoy will also be a lot longer as the signal will not be on the noisy neutral lead, but somehow on the 240 V system. I have been told as far as 1500 feet (500 meters).

I also expect to see an IQ7 (they just released for sale in North America the IQ6 with 290 watts) with 320 watts of power for a price per watt in the low $0.30 range by 2018. That is the stated enphase goal - a "smartphone sized" inverter with 97-98% efficiency in the 300+ watt range, compatible with 60 and 72 panel systems for about $0.30 per watt. Yowza!

That does not help you now. For you right now, I would look at a choice between an M215 based system (260 or so watt panels) or the S280 inverter with 320-340 watt panels with a 20% larger power output. But you are going to pay 20% more for the larger system . . . but for a constrained roof size, you may want to pay the extra 20% for 20% more power.

Budget, budget - I know!! is your friend. The weekly specials are great.

Again, GREAT videos!


ps thanks to pinball a couple years ago that told me about Renvu. Before that I was using another solar warehouse that was (and is) not nearly so good in terms of price, delivery and support If you do call Renvu, feel free to say I recommended them - this has gotten discounts for others! Do not be afraid to dicker as I regularly get discounts for trunk cable. For example, they will give me free "extra" drops to account for the necessary length going from one rack to another. Just gotta ask . . . Make SURE to tell them of your videos and sent them a link.
consulting on geothermal heating/cooling & rational energy use since 1990

Last edited by stevehull; 04-14-17 at 12:33 PM..
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