inverter on every panel or not ?

[bdunham7]

Sounds great! I didn't know Enphase has wireless power modules these days...

All things considered I'm not sure what qualifies as safer. Either way you need cabling on the roof. The mains grid has an awfull lot of power behind it. Sure current can be limited by fuses but still it can push 3kW+ into something to cause a fire. Not to mention a large current surge ability. A string of solar panels can push a lot less power.

You may not be familiar with the system, but what he is getting at is that there are no splices, combiner boxes or any other wiring assembly done on the roof.  The cabling comes preassembled, you plug in the modules and the other end goes back through a feed-through so that all of the splicing and connection is done inside.

As for 'what qualifies as safer', instead of speculating whether a 240VAC (think about the AC part) limited by a 20A breaker is less of a fire hazard than 800VDC limited to ~8-10A typical with no off switch, we can just look at the incident rate for installed systems over the past decade or so.  I think there are three reasonable conclusions:

1) Most if not all of the fires have been in HVDC systems.  That includes all the burnt Wal-Marts as well as small burnt-up things like Dave Jones' isolator box.

2) The overall reliability rate of each type is not readily ascertainable, at least not to me.  Neither is perfect.  Enphase had a whole batch of unreliable inverters early on and apparently you've seen some issues with the contactor-thingies.  OTOH, when I installed my system installers were routinely replacing the HVDC inverters which failed fairly often.  Most systems that I see or hear of nowadays that aren't working are plain string systems, but that's a small, localized sample.

3) Either type of system works pretty well if you manage to avoid the defective components and the installer does a good job.

[nctnico]

I agree. Without proper statistics you can't tell what is safer or not. It is very likely that there are more DC systems out there versus micro-inverter so in absolute numbers you'll likely see more failure from DC systems. But that doesn't mean they are relatively more toublesome. Also add to the equation that a lot of (older) solar systems have been installed by non-certified engineers and there is a lack of regulations / certifications where it comes to installing solar systems.

A plug & play system like the micro-inverters offer does take away some of the complexity of installing a solar system properly but OTOH you can do the same using pre-made wires for DC systems.

[kaz911]

My setup is now Enphase as well.

I would say - IF you have a "complex" setup - I prefer Micro Inverter. So if you have panels scattered around for both SE/SW or S/W etc. it is by far the best solution. But if you have an easy to access ground based installation and you don't plan on changing it a lot - then DC Inverter is probably the "best". But I would still go MicroInverter.

DC Inverters are most efficient at close to their rated input range. So if you have "split" systems you are rarely running fully optimised unless you run multiple inverters. But with Micro Inverters you are. Then each inverter outputs to the best of its abilities and the panels abilities.

Right now I'm testing different panel setups for our "re-design" of our house. So I'm "pitching" a few panels against each other before I make the decision. Right now I have a Q-CELL up against a Panasonic HIT and plan to add 2-3 more to get some good data. The Q-CELL is about 1/2 the price of the Panasonic HIT - and the price difference more than pays for the micro inverter. I wanted to test the Panasonic as it is said to be "much better" in low light. It is better - but enough to warrant the price difference (so far - lets see what winter brings)

Our plan is to "over dimension" the setup enough to have surplus to charge the car and house battery.

My plan is for energy independence - not necessarily "<10y capital return" - we are building the house to be cheap to live in "post pension age" so we can afford to stay and operate the house 30 years from now.

And Enphase can run off-grid with the correct setup both in US and UK. Don't know the regulation elsewhere.