Changeover Switches

What kind of switches are you guys using to change a circuit from grid power to inverter power? I'm tired of plugging/unplugging extension cords around the house and want to wire them properly.

I was looking at something like this, but it's $300!
http://www.ebay.com/itm/311820513322

For manual i use normal 1-0-2 switches.

Ebay links below:
Example: https://goo.gl/6aUGOX

And for din rail mount: https://goo.gl/i2oJum

Im looking into automatic stuff now though and my electrician will come and visit in 2 days to decide how to do next phase of my project.

So basically some sort of contactor like shown here: http://new.abb.com/low-voltage/products/motor-protection/4-pole-contactors-for-power-switching
But approvred for switching loads. Same as is in many UPS systems.

Those are nice din rail switches, and nicely priced, too. I might need to keep these on the to-buy list