Yes, yet another "hot water takes too long" question... We used to live in a small split-level house with the hot water heater directly under the kitchen, and half a floor away from both bathrooms. Hot water was took a couple seconds in the kitchen, and a couple seconds longer in the bathrooms.
A couple years ago, we built a 2-story house. I wanted to minimize the hot water delay to each fixture, so I went with a PEX manifold setup with dedicated 1/2" runs to each fixture. I hoped the smaller inner diameter would mean shorter wait times. Unfortunately, it still takes an irritatingly long time everywhere. The kitchen is the biggest PITA (and the most noticed by my wife), so that's what I'd like to fix.
There's about 35' of 1/2" PEX between the hot water heater and the sink, all of it accessible along the unfinished basement ceiling. There is a power outlet in the base cabinet under the sink. The options I'm considering are:
1. Insinkerator (or other) instant hot-water dispenser in the base cabinet under the sink
My wife wants me to install an Insinkerator (or other) instant hot-water dispenser. I'm not a fan of that. Sure, near-boiling hot water is nice if you want a quick cup of tea, but it's too hot for washing hands or dishes. In my mind, this doesn't really solve the delay for the common uses. Plus, I read about these units leaking, and I'm not really looking to deal with leaks ruining the base cabinet. Oh yeah, we have a 2-year-old too, who will be able to reach the sink some day.
2. Small point-of-use hot water heater mounted just under the kitchen floor
Another option I'd considered is a small point-of-use water heater installed in the basement, mounted right underneath the kitchen floor. I could use Unistrut to make a nice sturdy ceiling mount for it. It would only have to supply enough water to keep the water hot until the water from the main heater mixed into the small tank sufficiently.
3. Recirculation pump
An option I've only recently thought of is installing a recirculation pump under the sink. I have an outlet down there, so it might be pretty straightforward. Perhaps if I do a good job insulating the kitchen supply pipe in the basement, the loss would be minimized.
What are the relative efficiencies of #2 and #3? I'm leaning towards #3, with attention paid to the insulation on that home run. The water heater is an 80gal Whirlpool energy-smart water heater (3" insulation), although for a recirc pump, I think all that matters is the energy loss in the recirc loop and the resistance heat energy required to replace it.
In retrospect, I really wish I'd installed a traditional supply trunk, designed from the beginning to have a single recirculation pump in the furthest fixture. Well, it's too late now - I have home runs in the walls and that's not getting changed.