I'm looking for a recommendation on the best course to update our hot water heating system.Some background: When we moved into our upstate NY, 2200 sq. ft. home five years ago, the home was heated exclusively by Weil-McClain 68 Boiler using heating oil. We have since updated most of the home to minisplit heat pumps. The boiler is now used to heat a small family room in the basement (but only when we have guests) and our hot water. We do not have a hot water tank. We now use about 400 gallons of oil/year.

The problem is that a) I don't feel like using oil is efficient (but could be wrong) and b) when bathing or showering, the hot water doesn't stay very hot for long.

My question is: What would be the best way to heat our hot water moving forward? I have included a picture of the boiler's current space if that's helpful.

Boiler Information Boiler Setup

  • I know nothing about boilers... When filling a bathtub, where does the 30 gallons of hot water come from? Is there a tank? How large is the tank?
    – JPhi1618
    Commented Jan 22, 2020 at 21:43
  • 1
    Domestic water is heated by a coil in the boiler water jacket. The water comes from the cold water supply. The boiler fires to heat the (sealed) water in the heating system which heats the domestic water....
    – Ecnerwal
    Commented Jan 22, 2020 at 23:03
  • I had that same boiler in my last home. I upgraded in stages (long story) from propane to natural gas. There are tradeoffs for each method of heating your water. The most certain issue you have is generally mineral buildup which acts as insulation, reducing the effectiveness of your hot water heating coil in the furnace.
    – noybman
    Commented Jan 23, 2020 at 3:56

1 Answer 1


This veers towards being "a matter of opinion" but you would seem to be of a mindset where a "heat pump waterheater" and perhaps "yet another minisplit for the family room" would be most suited to your direction of progress.

An oil boiler which is not heating much of anything but your hot water has a lot of "standby losses" - i.e. keeping itself warm while doing nothing. The heat exchanger coil that heats your hot water may be suffering from mineral deposits, and if so could be improved by cleaning or replacement, but if that's pretty much all your boiler is doing, it's a sledgehammer being used to drive tacks.

Various other alternatives are options, and the choice of "best" really comes down to your opinions/preferences - change to an oil-fired water heater (probably with tank - very few "tankless" units seem to exist in the market) and perhaps use a heat exchanger off that to provide the limited heat when needed to the family room - a system sized far closer to your actual needs than an old boiler that used to heat the whole house.

If you happen to have natural gas available at your house, it's generally a better cost than oil per unit of heat, and tankless water heaters are commonly available. Of course, if you do, it's nutty to have an oil rather than a gas boiler, but I've seen that sort of nutty...

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