Yes, but they can also be nicely tied into a hybrid that can handle AC coupling (something like a SA or Deye).
Are micro invertors the future of residential installations?
- Thread starter Noho
- Start date
ncsolarelectric
Engineering Support CEO
The temperature spec for Enphase is -40C to 60C.
The temperature spec for Hoymiles is -40C to 65C, but they are tested at 85C immersed in hot water for 1000 hours.
I consider that to be amazing, having done environmental testing on inverters and other components many times in the past. Never did we consider testing them at such extremes. In the 1990's I was responsible for testing replacement parts for the inverters used in nuclear power plants, and we didn't test them to those extremes. I for one am impressed by these tests and specs, but you are correct. We shall see how they hold up over 25 years.
However, given the low cost of Hoymiles HM-1500NT at $299 for a 1.44kW output Quad microinverter, the payback is short enough that it won't matter to me. I can afford to replace these after 25 years more easily than I could a string inverter that may fail after the 10-year warranty is up, or the possibility that Enphase denies my claim for whatever reason.
FYI: The O&M crews I've worked with replace a helluva lot more string inverters than they do microinverters, again and again. These are 3-phase commercial string inverters in the 14kw to 30kW range. The old ABB units are a nightmare of return and repair. We send them out for refurbishment, re-install them and they break again within months. The old RefuSol inverters are constantly shutting off because they get false ground faults on their unusual bipolar arrays when the arrays are unbalanced and won't restart. We end up installing isolation transformers to establish a clean N-G bond out in the solar field to get them to behave. The large 500kW Advanced Energy inverters with the bipolar array do it too, same fix. The SMA string inverters aren't much better with their ground fault and arc fault issues preventing startup (mostly resolved). It's an ongoing issue all over California commercial PV sites. I've replaced 3 SolarEdge since moving to NC in the past 2 years. The string inverters I've had the best luck with are Chint Power Systems (CPS). If one of those fails, THEIR techs are on-site promptly to repair them without our having to do a truck roll to remove the inverter, crate it up and ship it back. Great service! Thankfully these do not fail very often.
Microinverters on the other hand, we can stock them in the back of the truck and they are easy to replace all in one trip. No return trips or crating necessary. So on that front, they're just better for business. Optimizers double the labor because after you install them, the inverter still needs to be installed, and string inverters now require RSD devices on the panels so again for an installer and an O&M crew, string inverters require a lot more labor and it is ongoing over the years. I feel sorry for a bunch of utility-scale sites that probably lost millions of $ because they used the wrong string inverters.
“However, given the low cost of Hoymiles HM-1500NT at $299 for a 1.44kW output Quad microinverter”
I looked into inverters. Just never seemed to have the power I was looking for. Since my panels can go up to 575W (I know, will never see it), the most I could hook up to the HM-1500NT would be three panels. The Optimizer/RSD units I’m buying can handle 900W (-40 C to +85 C) and I’m at about $150 for three panels. So that is half the cost there and no power limitation. I was getting the hybrid inverters regardless, so micros wouldn’t save me that cost.
I looked into inverters. Just never seemed to have the power I was looking for. Since my panels can go up to 575W (I know, will never see it), the most I could hook up to the HM-1500NT would be three panels. The Optimizer/RSD units I’m buying can handle 900W (-40 C to +85 C) and I’m at about $150 for three panels. So that is half the cost there and no power limitation. I was getting the hybrid inverters regardless, so micros wouldn’t save me that cost.
fromport
Solar Addict
I recently had my annual true-up:
-7911kWh
Retail value: -$1000
Check I got: $341
So I got paid $0.043 /kWh for my excessive electricity
And that is because I got 10% more from my Community Choice Aggregation then from my utility.
Ampster
Renewable Energy Hobbyist
Under what theory? Do they issue 1099s?
Almost the same exact deal where I live on rate and capacity, except it's a variable rate, roughly $0.02-$0.05. Oh, we now also have the opportunity to sign an agreement that says you agree to sell ALL your solar output to them for a little higher locked in rate for 20 years, but you also must agree to buy all your electricity from them at whatever rate they see fit (since you can't use your own solar production). No thanks!
I'm still looking at different ways to build my system (DC and AC coupling, panel locations, system size, etc), but one thing is for certain, I will not be signing on to their NM program!
I would think a big corporation like a power company would. But your tax rate may be zero if you don’t have much or any other “income.”
ncsolarelectric
Engineering Support CEO
Same here but all the time, not just true-up. EnergyUnited Coop only pays wholesale $0.043 for any energy I send back to the grid and limits the system to 10kW AC. I can connect a system larger than 10kW, no problem, but then they pay $0 for the energy sent back to the grid. They also have a program that pays 1 to 1 at $0.0767, but they add a $/kW fee/tax, which amounts to about 40% of the revenue generated by the system.
Regardless, however, my energy bill was approaching $400/mo, so I'm happy to save what I can and I have a battery to save what I can't use right now, but if any energy does go back to the grid, I think $0.043 is still better than $0.
ncsolarelectric
Engineering Support CEO
IF there were a lawyer in the room, the conversation would've been settled much faster.
ncsolarelectric
Engineering Support CEO
With smaller systems, what they pay you for the energy doesn't matter, they won't get much of it. It just offsets what you are paying to them.
Hedges
I See Electromagnetic Fields!
- Joined
- Mar 28, 2020
- Messages
- 21,204
Anybody know what inverters are best for peak shaving (of export as well as consumption) that support DIY or server-rack batteries?
Something like Sunny Boy Storage, but with an open battery interface (or available BMS; I don't know if REC with high voltage battery talks the right protocol.)
Sunny Boy Storage 3.8-US / 5.0-US / 6.0-US | SMA America
Discover the flexible Home Energy Solution: The SMA Sunny Boy Storage 3.8-US / 5.0-US / 6.0-US battery inverter! ► Find out more about its benefits!
IF there were a lawyer in the room, the conversation would've been settled much faster.
Not if they could drag it out
And and once settled you would have been billed already ???
Ampster
Renewable Energy Hobbyist
I get distracted when someone posts information that does not appear correct. In California, rebates are not treated as compensation. .I believe Net Metering Compensation should be treated the same as rebates, as a savings and not compensation. I have not seen an IRS ruling and @Danke did not offer proof of his theory.
Last edited:
ncsolarelectric
Engineering Support CEO
If you want peak shaving, you need a grid-tied AC coupled battery, like a Powerwall, Enphase, or maybe Generac. Something that can be programmed with limits in both directions. I haven't seen an interface like that yet, but that doesn't mean there isn't one. There are companies that make peak shaving inverter/battery systems, mostly 3 phase, 50kW and up are what I've seen in use.Anybody know what inverters are best for peak shaving (of export as well as consumption) that support DIY or server-rack batteries?
Something like Sunny Boy Storage, but with an open battery interface (or available BMS; I don't know if REC with high voltage battery talks the right protocol.)
Sunny Boy Storage 3.8-US / 5.0-US / 6.0-US | SMA America
Discover the flexible Home Energy Solution: The SMA Sunny Boy Storage 3.8-US / 5.0-US / 6.0-US battery inverter! ► Find out more about its benefits!www.sma-america.com
Not if they could drag it out
And and once settled you would have been billed already ???
These are my Enphase options.
Last edited:
Ampster
Renewable Energy Hobbyist
My Outback Skybox has TOU settings that let me support loads during peak rate periods. I do not know how you define shaving consumption? That would typically be done by something like a Span breaker panel.
Same with any size, no? You are not using grid, offsetting what I would have used.
Hedges
I See Electromagnetic Fields!
- Joined
- Mar 28, 2020
- Messages
- 21,204
I mean charge batteries to limit or eliminate export to grid from PV, also invert from batteries to AC to limit or eliminate import from grid.
If we have an export agreement for say 5kW, we may want to install 10kW of PV, curtail production if CT shows export reaches 5kW. With battery inverter, can suck power into battery until full before curtailing.
Then for consumption, use battery to provide loads during peak time of use rates. Or reduce peak instantaneous draw from grid if rate plan includes a "demand charge".
I know Sunny Boy Storage does UL-1741-SA and works on-grid. Also responds to commands from a network.
What I don't know is whether it would work with Sunny Island, not only curtailing AC output as frequency increases, but turning around to ramp up battery charging as frequency increases further (all before GT PV Sunny Boys curtail production.)
It is intended to help with zero or limited export, and provide battery backup. But it uses a 400V proprietary battery (too expensive, need $0.05/kWh server rack batteries to make financial sense.)
ncsolarelectric
Engineering Support CEO
Correct, for an off-grid system. What you generate and use, you didn't buy from the grid. But when you have a grid-tied system, even a small one, there are times of day when the battery is charged and the house isn't using much energy. My home gets down to 250W at times and my system can generate 2.9kW. So most of it would be exported at that time. On an off-grid system, during that time the inverter simply doesn't use the excess solar energy available. Grid-tied I'll get "something" for that excess energy, off-grid, I get nothing for it. Batteries are expensive, so this is a cheaper option.
Sol-ark??
I have TOU rates and a 15kwh battery which charges off solar and from grid at-off peak rates. Battery ? covers my electricity use during peak rates. Saves us a lot of money and once programmed works seamlessly.
Electric car charges at off peak rates from the grid. Monthly electricity bill is $70 per month including car charging saving us over $300 per month on gas
️ and electricity.