Electric water or Indirect water heater?

edwardpitzul

We have a small adu 720 sq, trying to choose between which water heaters to go with? We already have radiant flooring running off a gas boiler and could go with indirect water heater but the cost is triple.. We were considering Electric water heater because of the cost of the unit and efficiency. Would the monthly cost be cheaper if we did indirect? Please help, thank you!

bburd

The question of which is less costly to run depends on your utility rates, but in most places the indirect off a gas boiler will cost much less to operate than an electric resistance water heater; and a heat pump water heater may not be practical in an ADU due to the noise and the fact that there is usually no basement.

However, the first cost of the indirect water heater will be higher as you have seen.

ADUs generally don't use much hot water due to low occupancy.

RascalOrnery

Anyone care to offer some comparison between lifetimes of hot water heaters vs indirects?

hot_rod

7-10 years for a glass lined tank.

Life expectancy comes down to how much water you run through the tank. How hard you water is, and the temperature.

Is it a full time dwelling? One bath and kitchen? Wash machine?

Jamie Hall

https://forum.heatinghelp.com/discussion/comment/1839859#Comment_1839859

They're both tanks. Given similar construction and maintenance, they will be similar. The "similar construction" is the kicker: very often electric water heaters are built to a price point, and thus may not be as robust. Lifetimes? Hard to say. 10 years for quality examples? 15 with good quality water? My direct oil fired ones — I have several — seem to last around 20 years.

edwardpitzul

@hot_rod yes to all your questions.

edwardpitzul

@hot_rod we are running on a well water.

edwardpitzul

are both the heaters indirect and electric as well insulated inside and keep the water warm longer periods?

hot_rod

electric tanks seem to last longer than gas fired, since there is no fire under the tank.

It us tough to guesstimate dhw water usage, it varies widely from family to family Rarely do you hear someone complain about too much hot water

All tanks now have good insulation to meet the energy standard, most are spray foamed no more thin fiberglass wraps

edwardpitzul

@hot_rod thank you. Same insulation for indirect tanks?

Larry Weingarten

Hi, If you take time to do simple maintenance on a glass-lined tank, you can expect 40-50 years from it. It's just making sure the maintenance happens, along with controlling water chemistry somewhat and water pressure.

Yours, Larry

ethicalpaul

I'd pick a heat pump water heater, second choice would be a resistive electric water heater (which I am quite sure will last a lot longer than 7-10 years), third choice would be an indirect which has so much installation cost and makes you keep running your boiler all year just to heat a few gallons of water per day, it's a solution that only a plumber could love.

Kaos

Typical ADU is space limited. Since you only have one bath, one of the smaller tankless (gas or electric) unit would also work and take up less space.

Otherwise, a lowboy resistance tank with a big element hidden somewhere would be the next best option. Under stairs, above washer or in the corner cabinet if L shaped kitchen so it doesn't take up floor space.