Considering AMERICAN HOMETEC tankless/coilless... Pros-Cons?

Hi all... I'm new to the forum and to this whole tankless hot water system thing. Over the last couple of days I've gotten a pretty good crash course and have a basic working knowledge and have a couple different tankless models in mind. Sorry this is likely to be long.

I've read a lot of the threads in this section and several things scare and confuse me about tankless systems seeing as how I would need to install an electric model, live in a big house, and in a cold region. I'm at that point where I'm so conflicted between all the stories on both pros and cons I'm just ready to have hubby put in a 50-80 gallon standard hot water tank.

Things that worry me about tankless:
1. this "cold sandwich" thing I keep reading about... what exactly IS that?
2. Temperature fluctuation. how consistant is the hot water supply? Our water demands aren't high, is this a worry?
3. wanting to add a dishwasher in the near future. I heard this could be a problem... why?
4. Living in North Western Pa on lake Erie we see cold long winters. How will this affect tankless performance?

Our house:
we live in a house in suburb type community. House was built in 1850 with last plumbing update likely in the late 70's. House is plumbed for 2 hot water tanks (use to be a two unit dwelling), one gas, one electric. The mainly used tank is the electric, the upstairs is gas (but we'd like to go all electric as we're planning a change to solar power in the next 5 years). The house is 3000 sq feet has 2 bathrooms (upper and lower). Upper is just a bath (going to be remodled to accomodate a nice tub tho, something jetted and deep). Also upstairs is a second kitchen that is going to be changed over to accomodate a laundry room. Downstairs is currently a bath and a seperate shower (going to be remodeled next year to just a walk in shower with 3 heads). No dishwasher as of yet but also a plan in the next year, and simple plumbing to the kitchen (no garbage disposal. That's what dogs are for ).

I asked hubby what amp for service and he says 100 in the box, also with half inch pipe. There are 4 inthe house, 2 adults, 1 teen 1 under 10. We tend to use more water for laundry than anything else. We have city water, no well.

So this is the tankless I was considering:

http://www.americanhometec.com/homeowners/index.php The AHQ-T16
and AHQ-TB32


I liked that it was no coil, and no maintenance as we do have hard water here, plus the warranty was impressive.

ON the other hand I'm so conflicted over it all I'm just ready to have hubby install the 60-80 gallon standard hw tank for the downstairs and then something like a 30 gal for the upstairs after the laundry room and bathroom are finished.

Sooo that's where I'm at... Thoughts? Advice? Please ...

The 16kw unit would be ridiculously under-powered for serving more than a kichen sink or a single shower with the flow throttled way back. It's just not enough juice to boost the temp enough at even modest flows at YOUR wintertime in coming water temperatures.

For serving a 2 bathroom house in a 4-person household on lake Erie, fuggedaboudit- not enough flow for more than 1 scaled down shower load at a time in January.

For serving a 3- head shower ANYWHERE fuggedaboudit- not enough flow to run all 3 heads at once.

Hard water can also lime up any tankless pretty quick too- call that strike-3.

Or maybe strike- 9, new inning, since you'd also be spending money upgrading the panel, and maybe even the service drop or transformer to provide the peak power all to run even that inadequate tankless.

As finish-heat to a solar thermal nstallation it can make sense, provided also have backup elements keeping the solar tank up to at least room temp.

Running even a 40 gallon a gas fired tank would provide more hot water gallons than a big electric tank, but since you're bound for all-electric, not that bigger electric tanks don't have dramatically higher standby losses than smaller tanks. For a 4 person family, go with an 80 gallon unit.

How are you heating the place? There are various options for heating hot water (or pre-heating) with the heating system that might be more satisfactory or effient than another electric tank.

If your's is mostly a showering type family rather than tub-bathers, a drainwater heat recovery heat exhanger can more than double the apparent capacity (and efficiency) of any water heater, with much shorter payback than any solar-electric. To compare efficiencies between models, see: http://oee.nrcan.gc.ca/residential/personal/retrofit-homes/drain.cfm?attr=4 These are standardized numbers at 2.5gpm (single shower) flows. Efficiency goes up a bit with lower flow, down a bit at higher flow, but a 50% unit would still be delivering better than 40% energy return with 3 showerheads running. Without drainwater heat recovery you can run into capacity issues with 3-head shower, even with an 80 gallon tank, and the recovery time on a depelete 80 gallon electric can be fairly long. The walk-in shower is likely to account for well over half your hot water use, and an electric tank + drainwater heat recovery would give you both the peak flow you need, and run BETTER efficiency than a tankless.