News for hackers. Stuff that matters.

A comment on The humble water heater could be the savior of our energy infrastructure woes. Parent comment

Re:The humble water heater could be the savior of our energy... by toomuchtodo on Tuesday July 06, 2021 @09:17PM (#27756304)
Yeah, timer or grid controlled water heaters are old and busted (especially with bacteria concerns due to a lack of in tank convection). New hotness are heat pump water heaters that are very efficient and can even add cool air to a conditioned spaces by their inherent operation. Electric vehicle charging orchestrated as large aggregate loads are what replaces “the humble water heater.”

Tankless heaters are great if you’re burning gas, but electric versions are wildly inefficient versus a heat pump and require very large circuits and service entrances on the load center/breaker panel.

[ Parent | on HN ]
Re:The humble water heater could be the savior of our energy... by jhgb on Tuesday July 06, 2021 @11:24PM (#27756999)
> timer or grid controlled water heaters are old and busted (especially with bacteria concerns due to a lack of in tank convection)

This is literally the first time I'm hearing of this as a concern. Our local recommendations are to keep tank temperature above 70C and you should be fine.

[ Parent | on HN ]
Re:The humble water heater could be the savior of our energy... by ttwwmm on Wednesday July 07, 2021 @04:21PM (#27765356)
My heat pump water heater is at 140F all the time, maximizing the banked energy. There's an outboard mixing valve to reduce this to a safe temperature in the house.
[ Parent | on HN ]
Re:The humble water heater could be the savior of our energy... by toomuchtodo on Tuesday July 06, 2021 @11:30PM (#27757029)
https://patents.justia.com/patent/20180290899 provides background on the topic. Keeping your hot water tank at or above 50-55C constantly is a reasonable mitigation, anything hotter can cause scalding.
[ Parent | on HN ]
Re:The humble water heater could be the savior of our energy... by jhgb on Tuesday July 06, 2021 @11:51PM (#27757146)
You can't scald yourself with mixed water from the faucet unless you set the faucet lever wrong, so I've never had that issue. In addition to that, the recommended high temperature setting (I believe the recommended default setting on my tank is 60 C?) increases the amount of mixed water that you can use before depleting the tank, so even a smaller tank suffices for a person.
[ Parent | on HN ]
Re:The humble water heater could be the savior of our energy... by ip26 on Tuesday July 06, 2021 @09:23PM (#27756334)
Heat pump water heaters do seem promising... But many water heaters live in cold basements...

Classic tanked electric is so cheap to make & operate, I have come to think they may always be with us. (Though certainly a heat pump water heater is an easy choice in the right climate)

[ Parent | on HN ]
Re:The humble water heater could be the savior of our energy... by otterley on Tuesday July 06, 2021 @09:37PM (#27756414)
"Cold" basements rarely fall below 50 degrees Fahrenheit/10C. There's plenty of thermal headroom below that for heat pumps to work. Heat pumps already work outdoors at below freezing. I don't think there's anything to worry about.
[ Parent | on HN ]
Re:The humble water heater could be the savior of our energy... by s0rce on Tuesday July 06, 2021 @10:03PM (#27756584)
More of a problem is when your water heater is within your conditioned space envelope and in the cold months when you are heating your space the hot water heater takes that heat. Its not a huge issue but you do run the heater extra for the heat that's going into your hot water. If you've got an air source heat pump outside then its just an extra step.
[ Parent | on HN ]
Re:The humble water heater could be the savior of our energy... by anonymousisme on Wednesday July 07, 2021 @12:23AM (#27757346)
I was thinking the same thing. You don't get something for nothing. Assuming the water heater is in the conditioned space, it will just make the central heater work harder (and consume more fuel) during the winter months. Maybe this is offset during summer months when it can help the AC cool the space.

None of this applies if the water heater is not in a conditioned space, but that's not feasible in (common) environments with cold winters.

[ Parent | on HN ]
Re:The humble water heater could be the savior of our energy... by ttwwmm on Wednesday July 07, 2021 @04:26PM (#27765393)
Heat pump models usually have a resistive element for use when the heat pump can't keep up, or when the climate doesn't cooperate. Then you benefit from the efficiency whenever possible. (Here in coastal CA I have mine set to only ever use the heat pump since the climate is so mild.)

The up-front cost of a heat pump is definitely an issue. IMO we should be doing instant rebates to even out the cost between the two so that it's an easy decision.

[ Parent | on HN ]
Re:The humble water heater could be the savior of our energy... by caf on Tuesday July 06, 2021 @10:37PM (#27756786)
There are split system heat pump hot water heaters which allows you to exchange heat with the outside environment, eg. https://reclaimenergy.com.au/products/residential/
[ Parent | on HN ]
Re:The humble water heater could be the savior of our energy... by ttwwmm on Wednesday July 07, 2021 @04:22PM (#27765362)
The all-in-one units can also be installed with ducting.
[ Parent | on HN ]