Bollocks. I've been making grid connected hardware for decades, there is nothing magical about any of that. You just need to be careful, use proper fusing and you need to know how to read the electrical code.
Competent electricians are licensed professionals who (1) stand to make money on selling gear and (2) have customers that hire them simply because they don't want the hassle or the liability. Obviously a licensed professional is not going to install your home brew inverter, but at the same time if you can design a homebrew inverter you probably don't need a licensed professional anyway.
I've rewired lots of homes and have never had an issue with any of this and designed my first inverter when I was 17 to power my room when my betters decided I should go to sleep and cut the power.
This stuff is not magic. If someone designs a modern open source inverter I'm definitely going to build and install it. Fortunately insurance companies here are reasonable: if your homebrew device wasn't the cause of the mishap then you are still insured.
The one thing they are very strict about is gas, because there is no such thing as a 'fuse for gas'. But if you've properly designed and fused your gear then it should be no less safe than any other grid connected device, even if the magic UL or TUV mark isn't there.
The big one is EMI, that can be hard to get right and you need some gear for this, which is why it pays off to pool the money for an open source design to be certified. And once certified of course the design is 'type approved' and frozen, so you can't change any of the hardware without going through recertification. This is expensive, but if you don't do it every other week should still be well within the means of a properly set up open source project.
Why the fearmongering? It's not as if we're 12 here.
>Bollocks. I've been making grid connected hardware for decades, there is nothing magical about any of that. You just need to be careful, use proper fusing and you need to know how to read the electrical code.
I would say that rules out about 80-95% of DYI users.
This is 'hackernews', not 'consumersRus'. Though on odd days you might think differently.
And even days. And twice on Sundays.
> Why the fearmongering?
The main concern is exporting to a downed grid that line-workers are trying to restore.
If you can design and build your own inverter I would take it as read that you know how to read code and know how an actual inverter should function:
If you're grid connected and see valid phase on the input for a certain amount of time of matching phase and measuring voltage you can provisionally connect at exactly that phase and voltage but without injecting power. After that you are allowed to slowly ramp up your output by leading the phase (while raising the voltage within certain limits) as long as you observe the effect that you have on the grid. If the grid phase drops away or there is any other anomaly (such as a voltage drop or rise of more than x V/s you are required to immediately disconnect, there are many other disconnect requirements but that's the main one with respect to line worker safety.
Three disconnects within a short period of time = no reconnect attempts for a much longer time. If the situation persists that's a failure and you are no longer allowed to connect to the grid until there has been an intervention and an inverter reset.
If your inverter is of the islanding variety then the rules are slightly different, then the transfer switch only gets energized when you match voltage and frequency but in the meantime the (usually battery backed up) inverter can supply local consumers.
By the time you come up with the idea of rolling your own inverter you have either become familiar with the requirements (which differ from region to region, and which in a properly designed inverter are mostly a matter of tweaking firmware parameters) or you will have to do so because you realize your responsibilities.
Anybody up for this kind of project will with a high degree of likelihood have the required knowledge because that knowledge is a lot simpler to acquire than the knowledge to build an inverter that isn't going to result in you being laughed out of the room when your EE buddies come look at your creation.
I would expect you to do a better job than 95% of the imported ones that I've taken apart and which all had massive shortcuts taken, good enough to pass first inspection and a year into warranty, not good enough for long term safe deployment. This ranges from unsuitable connectors, low quality inductors, even lower quality relays, undersized FET boards, insufficient cooling, bad cast aluminum housings, in general bad housings (not rodent and/or insect proof) and so on.