Water Heating - Advice Needed

11 years ago

My home has a 50 gallon electric water heater that is only 3 years old. However, we have a jetted tub that needs more hot water than the tank can handle. It also goes cold at the end of a 20 minute shower. So, we were planning to upgrade. Our electricity costs $0.06 cents per kw/h, so its rather affordable. We have a large propane tank.

My dilemma, what to upgrade to:

My first thought was to get a mid size Rinnai LP tankless unit and connect it inline with our electric tank. That way we could continue to use the electric tank but when the water cooled down, the LP tankless would kick in and keep heating. Another benefit is that when or if the electricity was out, the LP heater would continued to heat the water (we do have a generator, but not powerful enough to heat the water in the tank). A local plumber (we live in a rural community) told my wife no, that wouldn't work. However, I'm not sure he understood, or really listened.

The plumber suggested that we install two mid size rinnai heaters and get rid of the electric unit altogether. He says we would save a lot of money, but based on my calculations I'm not sure that is true. Additionally, the cost of the TWO tankless and installation would be like $5000 and I don't think I would every save enough money to make it worth it.

The other thing he said that I wasn't sure about was that because it gets windy where I live that he would have to place an outdoor unit somewhere that was shielded from the wind and rain to protect it. I can't find that anywhere online and don't understand why that may be. Placing it indoors would make venting expensive and challenging considering where the current unit is.

We do have a large and well ventilated crawl space (its at least 12 feet high in most placed. Would it be bad to install an outdoor unit in that area? Is that crazy?

Finally, the last idea is to just install a larger electric tank.

I'd love to hand "endless" hot water but I don't want to break the bank either.

What do you all think? Thanks for your time. I'm clueless in this regards, and appreciate your input.

Comment (1)

zver11
11 years ago
Electric is quite cheap in your area especially if that is a delivered price(most utilities now price generation and delivery separately--the relevant cost is the sum of the two) Generally electric much less efficient at heating water than propane. Modern propane units would vent through a side wall with a PVC pipe. Need to locate unit in location which can run two PVC pipes to reach outside wall. If you can run plumbing to the crawl space, you probably can run vent line down there and then out to side of house (long runs require a slightly higher diameter pipe--not a big deal.)

Cheapest way to increase hot water capacity: If hot water heater not cranked up to 140, raise temperature and add hot water extender valve to output of hot water heater (mixes in cold water to blend down to target temperature.) This can boost total hot water capacity a little--the hotter the temperature increase the tank can take, the greater the increase. Probably enough to solve shower problem. May not be enough for tub.

In line heater as addon is interesting in that avoids some of the downside of inline heaters (lag turning on and not turn on if too low flow). Not sure why you would want two inline units--seems like a waste.
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