If you go with any sort of solar system, make sure it has a gas backup and not electric. My energy costs went up $100/month when I added our solar system down here in San Diego. I am now getting it corrected with the installation of a small gas tankless unit, using the solar storage system as a pre-heater. If you're building the home then many of the traditional drawbacks of tankless don't apply to you. You can build in the correct gas line and venting from the start. If I were in your shoes I'd probably go tankless (30 percent tax credit this year -- see the stimulus law or visit www.energystar.gov). If a single unit won't handle your demand then get two. And plumb it with the small tank system (10 gallon) for recirculation and to overcome any sandwich problems. This approach has been detailed in this forum somewhere.

We have a Noritz feeding 2 bathrooms only. Kept the tank heater for the kitchen and laundry, but it was too far away for regular bathroom use. We've been using it for a little over a year now without problems. It's mounted outside, which eliminated some of the cost associated with vent piping. But not the cost of increasing the gas line. I looked at Noritz and Takagi mainly. Think I chose Noritz due to slightly bigger burner or flowrate- it's been a while so the memory is a touch fuzzy. I've debated w/ one of the pro plumbers here about this. I can't run everything that's hooked up to the tankles w/o noticing reduced flow at the outlets (that's 3 lavs, two tub fillers, and 2 showerheads). The pro thought the heater was actually limiting water flow to try to meet its setpoint. I thought maybe my incoming cold water line is too small or that their isn't a direct enough path in terms of pressure drop to the heater inlet to get the flow at the fixtures with everything turned on. And there's a valve in the crawlspace that I can open and run hot water from the non-electrified tank heater during a power outage. Rinnais appear to only be available via certified dealers. In our case that would've meant paying someone separate from the plumbing sub who was working on the project anyway. I could buy the Noritz and get it installed by our plumber, which I think saved money over the Rinnai route (even with the $500 incentives the gas co was offering on Rinnai only at the time).

Thanks everyone for your comments. (And thanks Greg for confirming I’m not crazy since I didn’t see a wire and....it just seems odd on the back of a door). Yes, I want to save water. I live in CA and in past years we’ve had water restrictions. I‘ll be waiting for hot water to arrive, whether the tap is running or not. Also, someone I know says she can hear hers when it’s running on schedule. Why listen to it heating water that I don’t need? Plus, as Lawrence pointed out, I‘d save energy vs. the scheduled recirc. FWIW, I had assumed that I could schedule and have these buttons supplement it but when I was researching yesterday, some website said it was an either/or thing. Seems like very poor design. Maybe they fixed that. I guess if I hate the buttons I could always use the schedule feature like normal people. ;) Jake, were you joking about motion detector? I.e. every time I walk into one of those rooms it would kick on, even if I don’t need it? Lawrence, funny you should say “Can you imagine having to find your phone...?” Yes, I did try to imagine it LOL and thought low-tech was the way to go (as long as I could hide these buttons). Another aside: my plumber offered the option of installing a water softener. I don’t like soft water. So I’ve been researching other options to avoid the mineral build up. My thoughts: flush regularly (maybe more often than recommended). Also, use this hot button so I’m only heating the water I actually need to be hot. So I guess I’d be using this as a whole house water-on-demand system. Maybe I’m weird (?)

riellebee So I'm going to rough-in some numbers: Range: 15k btu/h Fireplace: 80k btu/h Furnace: 75k btu/h (x2) = 150kbtu/h water heater 200k btu/h (x2) = 400k btu/h Total potential load: 645k btu/h - again, an estimate. You can check your furnaces if you want to be be sure. is it likely that you would have enough things on at the same time to exceed your 425k btu/h service? - Yes, it's quite likely. What happens when you exceed the capacity of the service? The gas pressure drops and the range and the gas logs will just not run at full capacity - no big deal. But the things like the furnace and water heaters will throw error codes showing low gas pressure. The water heaters are likely to have that problem anyway, because at 30' of 3/4" pipe they are only getting about enough gas to run one of those heaters full tilt (the water heaters are variable input). The meter may be 20' away, but in actual length of pipe it's probably close to 30' including elbows. I can see close to 10' of pipe in the photo. The fact that the return line for the circulation isn't warm suggests it's not working. Fix that and insulate your pipes and your immediate problem will probably go away. BTW: Insulating the pipes is not expensive or difficult. Foam pipe insulation comes in 4' sections that just snaps around the pipes and uses self adhesive strips to hold it closed. It cuts with scissors. Even if you just did the exposed pipes in the basement you would reduce a lot of heat loss. My guess is that the builder can't really fix the "over-subscribed" gas service at a reasonable cost. One solution is to use a different water heater. A hybrid tank/tankless would solve the problem. The link goes to an AO Smith Vertex 75 gal water heater 100k btu/h and is 92% efficient and vents with the PVC vent pipe you have. I'm not particularly endorsing that brand - just using it as an example. It would provide you with plenty of hot water (you could run 1 shower continuously) and would reduce your BTU load by 300k BTU/h (gas service problem AND undersized gas pipe to water heater solved). In addition, because it's a tank of hot water - along with about 6' of hot water in the pipe - your wait would be significantly reduced even without a circulation pump. It sucks for your builder because it would cost them about $3500-4000 to fix it. They could probably realize some salvage value from the tankless heaters - say $1000-1500. But If they are only out $2-3k total I'd say they should consider themselves lucky.