My Solar Quote and Hoymiles Microinverter Question

[SamNewMelle]

I just got a quote for 21 Jinko 405 Watt Panels (JKM405M-72HL-V) and 21 Hoymiles MI-350 inverters. I would love any feedback you all have about this system. It is 8.505 KW DC and 10,150 kWh estimated production in the first year.

A few questions:
1. The installer also quoted 22 Vsun panels (VSUN370-120BMH) and 22 Hoymiles MI-300 inverters. This has less KWs on both the DC and AC side and is quoted as more expensive (only about $500 more). However, the installer says that they will have more estimated output (about 200 more KWs per year). I'm having trouble seeing the advantage here. Am I missing something?
2. I saw that Hoymiles also has an inverter that is the HM 350 NT. This seems to have an external antenna and "reactive power control."

Any opinions on one inverter (MI 350 vs. HM 350 NT)? What are your experiences with Hoymiles Inverters? Any questions I am not asking that I should be??

The quote is for around $25000 (before any incentives, rebates, etc.). I am located in St. Louis, MO.

 

[peakbagger]

Hoymiles is a new name in inverters. Looks like they have been around for 10 years and based out of China without a lot of presence in the US. I havent seen a lot of reference to them on the forums. They have a slick website but wondering how long they are going to stay around in this market? For such a key component that has proven problematical durability, I would like to see a third party backed warranty. Assuming this array is going on a residential roof, it most likely has to be rapid shutdown compliant. Therefore, it they offer a string inverter they are going have to install optimizers to meet the RSD requirements.

Panel efficiency can vary even by model. Manufacturers build them and then sort them by efficiency plus different designs and materials can also have higher efficiency. Higher efficiency usually translate to higher cost. In both cases the panels will "clip" as the inverters have a lower capacity than the nameplate of the panels. This is typical but the first quote has better ratio (86%) than the second one (81%). I personally so not like to undersize inverters especially on a roof under a panel as it means the inverters are running at high capacity more often but that is typical of the current industry.

Inverters sold in most states need to meet UL 1471 SA requirements which include the capability to be remotely dispatched for power factor correction (reactive power is used to correct power factor). Its a capability that few utilities attempt to use on residential systems. The utilities typically pay incentives to generators for that capability. I am not aware of any universally adopted standards on how the inverters would be sent a signal to go into this mode. Given its got an antenna it could be wireless standard?. Unless your utility has a program in place to dispatch this capability, there is no use for the capability but many utilities just require it anyhow in case they do put in program. Its far more important for large solar farms.

Some other questions.

Does your electrical panel have enough capacity to support the array? or are they doing a line sized tap. If you have a 200 AMP panel you should be good.

Is the install going on a new roof?. If you have standard shingles and they are 10 years old its going to be expensive to replace the roof with array on it in 10 years.

What sort of mounting system are the using between the racking and the roof? It should be a commericial flashed in system that is not dependent on "goop" for sealing. No matter how good the "goop" it just will not last.

Can the system run without communication with the manufacturer?. This is turning into a big issue, in many cases , new inverters have minimal local diagnostics, they communicate to the mothership and any diagnostics have to come back from the mothership on the web. Probably the biggest issue I hear with PV systems is communication issues between the array and the mothership and frequently the mothership will only talk to the installer. The installers may do diagnostics for free early on but manufacturers are always doing updates and many are buggy and on occasion lock up the array into not running. The installer has to come and straighten it out. If they go out of the business it can be a real problem.

Your price per installed watt is right in the normal range.. Its market dependent in some areas with reasonable labor costs, the price per watt could be lower while in other markets with higher labor costs it could be higher. I assume you have gotten a few competitive quotes from other installers.

 

[SamNewMelle]

Thanks so much for your reply! After lots of research and many more quotes, I am about to pull the trigger on a system with Qcells 400 panels and enphase IQ8 microinverters ($2.75 per watt installed). MY QUESTION: Does using the IQ8+ inverters (vs IQ8M) make sense to you guys? Based on the specs I see for these, it doesn't sound like I would have trouble with clipping. Thanks!

 

[peakbagger]

IMHO I would go with the IQ8 plus, looking at the spec sheet https://enphase.com/sites/default/files/2021-10/IQ8SP-DS-0002-01-EN-US-2021-10-19.pdf The typical wattage input range for the IQ8 is 235 to 350 watts . The input range for the plus is 235 to 440 watts. The STC watts for the Q cell panel is 400 watts (the PTC) is 373 watts. So the regular IQ8s are undersized, they are not going to burst into flames, but will clip your output for more than the IQ8. Looking at peak output the IQ8 output is 245 and 300 for the IQ8. Inverters put out peak output in the colder temps of winter so at peak sun with snow on the ground, the same array of panels, assuming 21 panels, the peak output 5145 for the IQ 8 versus 6300. Obviously, you do not get peak sun all day, so payback for any cost increase between the inverters would have to be modeled for your site to see if the extra clipping with the IQ8s is worth the cost savings. Installers and Enphase usually use the cheapest as most buyer want the initial cost to be cheap and the Fed rebate is for installed wattage not actual power production.

Here is where my opinion comes in, electronics generally operate at peak efficiency at less than 100% input, microinverters are located under the panels in a very hot location which is tough on electronics. When an inverter is clipping, its at 100%. Every brand of microinverters has had struggles with longevity including Enphase. Enphase has had recalls and higher than normal failure rates for at least two of their past models and most installers plan on some call backs to replace defective inverters if the homeowner even notices that some inverters are dead, Enphase pays $125 to the installer for labor to swap a panel but depending on the install that may not be enough to cover the total cost for a swap out. The installer may eat the difference early on but over the long run they may not. Odds are if they get out of the business, the firm you hire will not. My opinion is to underload inverters to keep them out of the peak input range as long as possible to extend their life. Knock on wood I have had extended life on my string inverters and I attribute it to them being slightly oversized and located in far cooler environment than on the back of panel on roof.

I also have an ulterior motive as my utility approves systems based on nameplate inverter capacity not panels installed. I have about 4.6 KW of panels for my three arrays, while I have 6 KW of approved inverters. My rate plan is true net metering and is now closed to new customers, the replacement rate tariff for new systems is far less attractive. Therefor if I need more capacity, I could add panels to fill out the inverters and still be under the attractive old tariff. Actually, what I would do is probably put in a new 6 KW inverter with multiple MPPT inputs.

 

[Solarguy3500]

Thanks so much for your reply! After lots of research and many more quotes, I am about to pull the trigger on a system with Qcells 400 panels and enphase IQ8 microinverters ($2.75 per watt installed). MY QUESTION: Does using the IQ8+ inverters (vs IQ8M) make sense to you guys? Based on the specs I see for these, it doesn't sound like I would have trouble with clipping. Thanks!

I haven't been on here in a while and I'm just seeing this now. Not sure if you already signed up for the system or not, but here's my two cents.

The IQ8+ is rated for ~290W continuous AC output while the IQ8M is rated for 325W output, so with a 400W panel, the system will experience less clipping (power limiting) with the IQ8M than with the 8+. Enphase also makes an IQ8A which is rated for 349W continuous output and an IQ8H which is 380W continuous output. When I design systems with higher wattage panels like 400W or higher, I usually spec out the 8A or the 8H to reduce the incidence of clipping.

Can you ask the installer for a cost difference to switch to the 8A or 8H?

 

[stoveliker]

The utility of those higher capacity inverters depends a lot on the orientation of the panel array. If not facing directly south, you'll have a decent decrease in power exposure because of the angle of incidence onto the panels. That means the power rating of the inverters can be lower.

If you have a decent installer he should be able to tell you what inverter you need to not waste the max power exposure you will have based on the orientation of the panels.

 

[Solarguy3500]

The utility of those higher capacity inverters depends a lot on the orientation of the panel array. If not facing directly south, you'll have a decent decrease in power exposure because of the angle of incidence onto the panels. That means the power rating of the inverters can be lower.

If you have a decent installer he should be able to tell you what inverter you need to not waste the max power exposure you will have based on the orientation of the panels.

Good point.

Without more info about the site characteristics, it's hard to know if a higher wattage inverter would provide much benefit. Heavy shading for most of the day could also negate the benefit of the higher wattage inverters as the panels would seldom run at their nameplate rating under shady conditions.

 

[SamNewMelle]

Thanks so much for each of your thoughts! I am located near St. Louis, MO and my panels will mainly face East and Southeast. So, I am wondering if the installer suggested the 8+ for this reason. I contacted them and they said that they would go up to the 8M "if they can get them" (they are having some supply issues apparently). I'm hoping they can get them, but am not going to worry to much.

P.S. I found this reference very helpful in thinking about clipping. My latitude and days of sun is most similar to either Newark or perhaps Dallas. Each of these seems to have negligible effect of clipping with 8+ (especially over 25 years and especially considering my orientation). https://enphase.com/download/iq8-pv-module-rating-larger-inverter-rating

 

[SamNewMelle]

Helpful resource website on IQ 8 series and clipping: https://enphase.com/download/iq8-pv-module-rating-larger-inverter-rating Posting here to make it more visible for others who search in the future.