First replacing a big tank water heater if you already have a gas one you will have plenty of gas volume and pressure there. I had a 80 gallon and at least 25 foot of vent altogether to vent that pig. You don't need to run a condensate line unless so many feet of vent is use and I was well below that mark so no expense there.
Both of these points are misleading or wrong. I'm not trying to say tankless water heaters are bad, but homeowners must go into it knowing what the real costs are.
You cannot simply hook up a gas line designed for 40KBTU to a 200KBTU heater. If you don't understand that, you should not be making an argument to do so. Look up "gas pipe sizing chart" for further information. This common mistake has caused a lot of trouble and has made municipalities now require gas pipe calculations be included with the permit applications for water heaters in many areas.
The OP specifically stated the tankless would be "condensing". Older tankless heaters and conventional water heaters are not condensing and require no condensate line. Newer, condensing ones do. Simple as that. They drip constantly while running.
Tankless heaters don't always save gas, but they do always cost much more to install. Especially in retrofit applications. I have to laugh when I hear people talk about "never running out of hot water and taking longer showers" while exclaiming their gas bill is much lower. These are mutually exclusive. If you increase your overall efficiency from about 70% for a tank water heater to about 85% for a non condensing tankless, you've reduced your bill by about 15% for the identical use. But if you take longer showers you've increased the gas used, so the bill can be higher depending on how much more you use. Very simple concept. Condensing units can be up to 95% efficient.
Here are some rough cost/benefit numbers for a tankless:
Suppose your conventional water heater fails and must be replaced. You can call a plumber or a water heater only type company to pop over and slam a new one in in a couple of hours for about $1,000. or so. Give or take.
Or you can get a qualified plumber to install a tankless correctly for you. Cost of the heater might be $1,500. Cost of a new gas line might be the same, but let's say, $1,000. Various other costs of new vent and condensate line might add several hundred or more. Now we're getting close to $3,000. for a professional installation. Maybe less if your neighbor's friends mailman does it for you. And also less if you do it yourself. But if you only save $30. per month, assuming you do not take longer showers, you'll have a payback of, what, six years or so. If you have to call the plumber back to flush it out once a year, the payback may never work out. Meanwhile you had to spend three times the upfront cost and be without hot water for days instead of a couple of hours. Everyone looks at the costs and characteristics with a different emphasis. High initial cost for possible low operating cost. Green or not. High tech or not. Imagined reliability. Etc. How long are you willing to argue with the manufacturer over a warrantee problem? How long does it take to get a new circuit board if you need one, while having no hot water? It's also a good idea to factor in if the end user likes baths or showers and what size the tub is.
It's just best to go into these decisions with your eyes wide open instead of discounting the actual issues. And especially if your "savings" becomes the budget for the next gun buy. The upfront savings could get you a nice stainless 686, a Model 63 and maybe an LCR thrown in for good measure. Whereas the monthly savings might net you an LCR after waiting 7 or 8 years. I'm glad you put the saving in terms of how many guns it might equal. :laughing:
