Purchased a 20kw Kohler package with an ATS that has a built in load control system for a little over $4000. Did the install myself, mine is on LP as natural gas isn't available in my area. Haven't installed the relays for the load management system yet which I may not need as long as I monitor what is used when/if we are on emergency power. 
One word of caution if you buy a standby is to check everything over very well right away when you get it home. I was laid up from a surgery when I bought mine and didn't get it installed the first year. The factory told me that would not be a problem for the warranty as long as I had a factory authorized agent do the initial startup. When I went to install it the following spring I found the synthetic base and generator support were broken from being dropped evidently. It was a very big hassle to get them to cover it under warranty but they finally did. Had a factory authorized servicer do the initial startup so the warranty would start at that point. 
Working good now, it is one of those items you purchase that you hope you never have to use.