[Greenbuilding] Opinions on electric tankless HW heaters?

[Nick Pyner]

I submit that you need to look more closely at this.

Last choice depends very much on where you are and how you are being
supplied with electricity.

Both standard electric HW storage tanks and instant electrics are banned for
new residential construction in most states of Australia. In  the 21st
century, nobody would ever use a tankless electric unless there was very
good reason for doing so, and the main reason is that they are replacing one
that was there before.

Most supply authorities have off-peak rates or some sort of smart metering.
Consumers are unlikely to be able to take advantage of this with a tankless
heater. In short, it can cost serious money to take a shower when you want
one, rather than when the supplier thinks it is a good idea.

All other things being equal, a storage heater is probably a cheaper way to
heat water simply because a tankless is essentially devoid of insulation. If
you live in a place with foul weather and heat losses from a tank worry you,
they can probably be rectified in a sensible manner and a lot better than
resorting to tankless. Yes, I recognise that stored water is usually hotter
than instant water but I don't think there is much in that.

Again, all other things being equal, it takes the same ergs to heat the
water no matter which way. A tank is not heated all the time, it is heated
only for as long as the 3600 watt heater takes to heat the water, and
provided the timer is on.  The biggest residential heater I know of is 3.6
kW, most are 2.4.  The smallest instant I know of is 13kW and many are twice
that.

If you are on uniform rates, i.e. no off-peak rates, and supplied by
limitless nuclear or hydro power, then maybe tankless electric is more of a
proposition. If you are on coal-power generators, we had better not talk
about it, This is a green building forum.

Nick Pyner

Dee Why   NSW

  -----Original Message-----
  From: greenbuilding-bounces at lists.bioenergylists.org
[mailto:greenbuilding-bounces at lists.bioenergylists.org]On Behalf Of Matt
Dirksen
  Sent: Tuesday, 19 April 2011 10:53 AM
  To: Green Building
  Subject: Re: [Greenbuilding] Opinions on electric tankless HW heaters?


  Thanks Nick


  "Last" choice is a standard electric hw tank. HP heater would not work
because of the size and sound issues. Due to the client's schedule, the
on-demand kw blast would never come close to a hw tank heating water all the
time.


  I'll look into Stiebel Eltron.



  Matt




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