Found this kit at
Hurd Solar | Dump Controllers
un-assembled Controller Kits - $14.50 each (plus S&H of $3)
Instead of using a power FET (IRFZ44N), It looks like you could skip using
LED2 and take those LED wires right to the control inputs of a Solid State Relay (SSR).
The SSR could be used to connect a load to an inverter, or provide AC power
to any device you choose.
Looks like a neat little package.. The website explains how to tweak the hysteresis a bit.