Is this an automatic transfer switch or a manual one? You can run pretty much anything you want with that generator, but only one at a time, sort of. Resistance heating of air or water takes a lot of power. Big motors take a lot of power to start up. Motors will easily take up twice the running current in starting. Look at your meters when your pump triggers and see what happens! As an illustration, you can sometimes start up a big load and then when it settles down, add smaller loads that would be too much while staring a pump. This really does not apply to your case, however, since the water pump will be on and off a lot. Ronnatalie is right, if you want to run all of that suff seamlessly, you need a bigger generator, much bigger. If you want to be selective and run large loads, like the water heater and pump, one at a time, install a manual transfer switch and use the circuit breakers to turn everything else off.

I hope your dryer is gas. Standing outside in a storm switching over power is not my idea of fun. My friend who has a set up like this has the generator outside connected to an outlet box. This runs to the inside panel. He basically checks the transfer switch on the way out the door, goes out and starts the genny, connects it, comes back inside and hits the switch. He then turns on whatever he needs. He doesn't have to go outside to switch loads when necessary.

Most likely not. The usual reason that two panels are put in side by side is not a shortage of current capacity but that they ran out of breaker positions. With only 30A going to the generator, it seems unlikely that only moving a few circuits over is going to make any real overload issues.

Wayne, Thanks for replying. 1) I was adding another circuit to the main panel later in the day of my original posting, so I checked the heater circuit. It was 5kW, not the 3kW I originally posted, but it's in addition to the heating element installed as part of the HVAC (probably wasn't clear in my original post)... the cost was $100 if I had the extra circuit installed by the time they put in the main HVAC unit, so I said "why not". This is the circuit I think I can now do away with as it's not needed with the new pellet stove keeping us warm. The "standard" heating element in the HVAC is now the "emergency" element, if you will. 2) So you're suggesting bringing a short main panel circuit outside to the transfer switch, thereby allowing for a single long run from the switch to the subpanel. Hmmm, that idea has a lot of merit. I would definitely want to go with an ATS, then, so I don't have to walk outside to swap things out (and shoveling snow to get to that side of the house... like the 4' we had in 3 days last year :( ). 3) I'll read it after posting this... 4) I was thinking of a Kohler or a Cummins-Onan, though I hear Kohler is often more expensive in the long run because they do their best to force you into using their own guys for general service. In that case, Cummins-Onan has a serious edge.