You said,
"our dishwasher and washer heat their own water. Do these actually work, and would it make just as much sense to eventually get three individual units sized to the applications vs. a whole house heater? "
So we need to clear up these statments before it's possible to make good dicissions. If the laundry washer actualy heats water or if all laundry use is cold,pou heaters at kitchen and bath might be viable if you don't consider extra expense of all electric as apposed to gas. A single 30 gallon electric could serve bathtub and basin. I don't reccomend that aragment due to operating expense.
A small pou at kitchen sink and bath basin makes a lot of sense. They work very well for the problem you have with waiting for hot water. Maybe a case could be made that time wasted waiting for elevators,traffic lights,toast to pop up and water to get hot would be better spent fishing or earning some extra cash.

There is another option available besides another water heater. There are circulating pumps available which turn on when the water cools and pump it back to the water heater, replacing it with hot water in the pipes. See the link below for one example, which is a retrofit unit. A separate hot water loop is also possible so the cold water isn't warmed.

I do not have any experience with these pumps nor with tankless water heaters, but it is something you may want to consider.

Here is a link that might be useful: Instant hot water pump

This post was edited by DreamingoftheUP on Mon, Feb 10, 14 at 15:04

Thanks--yes, our dishwasher and washer are both newer European models that can be plumbed only to cold.

I hadn't heard of the hot water recirculating systems, so will explore those. It looks like the price point of the versions the big box stores sell is about the same as the point of use water heaters (except that with the heater I think we'd want to add a dedicated electrical outlet for it, too). So if it gets to the same end, that might be a good solution too. We're actually less concerned about the waiting time than we are about the water down the drain. Our natural gas costs are also proposed to go up substantially in the near future so I'm not sure we actually save a whole lot using a gas heater vs. an electric heater--will have to see if I can get some numbers on that. (Our current heater is 50 gallons, too, so I suspect we're paying to heat a lot of water we don't use as it is, too.)

Any other feedback on either of these solutions? Thank you!

Does it actually take 3-4 minutes to get hot water at the tap? That's a really long time and you probably wouldn't be waiting around for that. It probably just seems like 3-4 minutes. Probably more like 30 seconds.

Regardless, to see how much water you're wasting, put a bucket under the tap and run the water until it's hot. Then estimate how many times you do that in a day, look at your bill to calculate out how much money you're paying for that wasted water.

Then you can figure out if it makes financial sense to install something more local.

If you just want it for practical reasons (ie. sick of standing around waiting for hot water) instead of financial ones, that's a different story.

Using electrical resistance to heat water is THE most expensive way to do it. You could afford to waste a lot of water waiting for it to come from a gas heater before coming anywhere near the cost of using alternative electric heaters. That goes for your dishwasher and clothes washer too. I also have units with internal heaters but we always run the hot water in the nearby sink to be sure that they're not heating stone cold water to run their cycles.

"Our natural gas costs are also proposed to go up substantially in the near future so I'm not sure we actually save a whole lot using a gas heater vs. an electric heater"

You don't say where you live, but where I am in Northern California, most of our electricity IS produced from natural gas. That will increasingly be the case nationally as coal is phased out so electricity prices will also increase as gas does too. No matter what happens to the price of natural gas, it'll always be cheaper to burn your own in a water heater than to use electricity.

If you decide a recirculating system can work for you (are your hot water pipes accessible?), have it done so that the hot water runs in a circle to/from the water heater, not the kind that dumps "cold" hot water into a cold water pipe.