Where should I mount the microinverter on a plug-in solar kit?

Mount it outside, in the shade, close to the panel, and within reach of your outlet. Plug-in solar is one or two panels and a small microinverter that plug into an ordinary household outlet, with no roof work and no electrician. The microinverter is the flat box that turns the panel's DC output into the AC your home runs on, and it is built to live outdoors. The Hoymiles HiFlow Pro LV unit in our kits carries a NEMA 6 / IP67 enclosure rating and an operating range of minus 40°F to 149°F. It has no fan. It sheds heat by natural convection, so it needs open air around it and a spot out of direct sun. Fix it to something solid near the solar panel, and do not leave it hanging on its cables. The supplied AC cable is 15 feet long, and that is what sets how far the inverter can sit from your outlet.

Can the microinverter get rained on?

Yes. The enclosure is rated NEMA 6 / IP67, which means it is sealed against dust and against temporary immersion in water. Rain, snow and spray are within what it is designed for. Mount it so water drains away and does not pool against the case, and keep the plug and the connections up off the ground.

Should I mount it on the back of the panel?

Not flat against it. The unit has no fan. It is cooled by natural convection, which means it relies on air moving freely around its case, so give it clearance on all sides and do not shut it inside a sealed box. A wall, a post, a railing upright or a bracket that holds it clear of the panel all work. It weighs 4 pounds and measures about 7 by 6.5 by 1.2 inches, so almost any solid fixing will hold it.

How far can the microinverter be from the outlet?

Fifteen feet, on the cable that comes with the kit. The plug-and-play AC cable is 15 feet of 14 AWG with a standard Type B plug. Decide where your outlet is first, then place the panel and the inverter inside that radius. Measure it before you drill anything.

Can I put the microinverter indoors instead?

You can, but there is no weather reason to. The case is rated for outdoor use at temperatures from minus 40°F to 149°F. Moving the inverter indoors means extending the DC cables between the panel and the inverter, and the kit does not include extra solar cable. Keeping it beside the panel keeps that run short and uses the kit as it ships.