Electric tank or tank less efficiency?

[Hardware]

I have about a 900 sq ft addition on my house..
Im gettin ready to hookup my radiant and was wondering what would be more efficient? Electric 30 gallon tank or a tank less?

Anybody have any input???

Thanks!

 

[Backlight]

If efficiency is your main goal and electric is your only option your best best is a hybrid unit (heat pump / electric) such as this - http://www.rheem.com/product/water-heating-heat-pump-professional-prestige-series-hybrid-heat-pump

Second on the list would be tankless as you don't have to pay to heat and store water when it is not in use. However there are pro and cons to tankless that need to be considered.

The lowest operating costs (in most cases) would come from a high efficiency natural gas unit, provided you have access to natural gas..

 

[anthony666]

those rheem heat pump units are damn nice, they take ambient air as heat source and are insanely efficient .. the down sides are they require 4 square feet of foot print, and they need tons of air flow to operate correctly .. meaning you cant just jam it in a tiny closet and forget about it .. and as awesome as it is, most folk wouldn't say it checked the right boxes as an architectural feature

i'm assuming you don't have existing radiant to tie into, or the build doesn't have provision to run piping out to the extension ?? i hate to say it, but this is one of the few times an electric wall hung boiler would make sense .. steibel eltron is the go to name for me, they have been doing this stuff in europe for a long time; http://www.stiebel-eltron-usa.com/radiant.html

just make sure it is a boiler and not an on demand water heater .. unless it says 'suitable for space heating' on it it is simply not heavy duty enough for the rigors of extended operation

 

[Highbeam]

Kind of silly to heat a room with a water heater that makes heat by extracting it from the room.

Electric resistance heat is 100% efficient whether it's a tank or on-demand. No reason for a tank really. It doesn't buy you anything and burns up space.

 

[Hardware]

Thanks for the advise.... My tubing is in the concrete slab. The only option I have is electric. Tankless would fit better than a tank. But I Wasn't sure what would save more electric..

 

[finn]

It won't. The tankless will save space and the tank will save purchase $.

Both are 100% efficient at turning electricity into btu output, ie hot water when you factor in the fact that the heat " leaking off" the tank is actually going into heating the room air.

 

[JCByrd24]

highbeam and finn are correct, electric is electric and a heat pump water heater won't work for you.

I can't confirm or deny what anthony says about a boiler vs on demand heater. I'm sure they're very similar inside and in fact heating water from ground temp to hot could in fact be more demanding than keeping radiant water warm and depending on climate and number of bathrooms could in fact see more BTU output throughout it's life. I'd certainly try an on-demand first if it saved $ upfront and was was enough BTU/hr output.

 

[Hardware]

Thanks guys, I'm going the tankless route. Makes sense.