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> Will these “guerilla solar” units that plug into a receptacle to back-feed get approved for use? Not practical in the USA with split-phase 120/240 (or 120/20

> Will these “guerilla solar” units that plug into a receptacle to back-feed get approved for use? Not practical in the USA with split-phase 120/240 (or 120/208 open wye) as you need to connect to both hot legs of the system to feed everything. In 230V countries they mostly have 2 wire service with (I hear some have three phase 230/400) so its easier to evenly back-feed a 2 wire system. > I always question why we choose between 0kW solar installs OR multi-kW residential installs ... Agreed. I have a small home server setup that draws 40W idle and I toyed with the idea of replacing the UPS with a small 1-2kW battery inverter plugged into the wall. My concern with rogue solar installs is how does that interact with the utility company? Their smart meters will see reverse flow of current and if I do not have an "official" solar install, will they force me to adopt one or disconnect my system as it is not approved? So I would only build a system which draws from the utility as needed (cloudy days) and dumps excess power - never back feed.

Scoundreller 3y ago
> Agreed. I have a small home server setup that draws 40W idle and I toyed with the idea of replacing the UPS with a small 1-2kW battery inverter plugged into the wall. No idea if this would work in practice, but you might be able to backfeed your battery with a regulated 11.9V onto the 12V lines and backfeed at 4.9V on the 5V lines, so when the power supply shuts off and puts 0V on the 5V and 12V lines, the battery will start back feeding, but when the grids power supply puts out 5V and 12V, no current will move. (Will need blocking diodes to avoid back-feeding the battery that’s kept topped off by its mains charger) Saves you some DC->AC->DC conversions. You might need a 3.3V leg as well. And maybe negative voltages if those are used for anything anymore?
- MisterTea 3y ago
  I have thought of using a DC-DC ATX supply and eliminate the inverter but I want 120V for other things if needed. But the cost and labor of going DC-DC is higher than DC-AC-DC so the goofy inefficient route it is :-/
Scoundreller 3y ago
> Not practical in the USA with split-phase 120/240 (or 120/208 open wye) as you need to connect to both hot legs of the system to feed everything. Just choose which half of your house you want to power :) But presumably these shutoff when grid mains is lost.

Scoundreller 3y ago

> Agreed. I have a small home server setup that draws 40W idle and I toyed with the idea of replacing the UPS with a small 1-2kW battery inverter plugged into the wall. No idea if this would work in practice, but you might be able to backfeed your battery with a regulated 11.9V onto the 12V lines and backfeed at 4.9V on the 5V lines, so when the power supply shuts off and puts 0V on the 5V and 12V lines, the battery will start back feeding, but when the grids power supply puts out 5V and 12V, no current will move. (Will need blocking diodes to avoid back-feeding the battery that’s kept topped off by its mains charger) Saves you some DC->AC->DC conversions. You might need a 3.3V leg as well. And maybe negative voltages if those are used for anything anymore?

MisterTea 3y ago
I have thought of using a DC-DC ATX supply and eliminate the inverter but I want 120V for other things if needed. But the cost and labor of going DC-DC is higher than DC-AC-DC so the goofy inefficient route it is :-/

Scoundreller 3y ago

> Not practical in the USA with split-phase 120/240 (or 120/208 open wye) as you need to connect to both hot legs of the system to feed everything. Just choose which half of your house you want to power :) But presumably these shutoff when grid mains is lost.