Hot Water Heating Efficiency

Discussions focus on the efficiency of hot water heating systems like heat pumps versus traditional tanks, methods of heating water (resistive or heat pump), and utilizing byproduct or waste heat from appliances, showers, or other sources for domestic hot water or space heating.

📉 Falling 0.3x Hardware
3,310
Comments
19
Years Active
5
Top Authors
#4966
Topic ID

Activity Over Time

2008
3
2009
57
2010
34
2011
38
2012
25
2013
68
2014
87
2015
77
2016
68
2017
105
2018
130
2019
152
2020
227
2021
319
2022
551
2023
618
2024
416
2025
326
2026
9

Keywords

B09V7MDZHF US carbonswitch.com UK amazon.com B08R1HKZ78 DIY renewablesystemstechnology.com system.html water hot water heat hot heater temperature heating pump shower warm

Sample Comments

lutorm Jul 3, 2014 View on HN

The hot water is a byproduct, you don't use the electricity for it.

bitbasher Oct 1, 2024 View on HN

Is this any more efficient than a typical hot water tank in US homes?

1stranger Jul 4, 2022 View on HN

I wonder how the water being heated? Resistive or heat pump?

fuzzythinker Jul 15, 2009 View on HN

I like them to do 1 step further and use the free heated water for warm water needs.

bostonvaulter2 Oct 8, 2020 View on HN

Doesn't that depend on where the electricity for the hot water comes from?

lostlogin Nov 23, 2013 View on HN

A water heater may be better - warming incoming water to save hot water cylinder bills or heat a pool if there is enough heat. Something that needs short bursts of heat would be harder to implement. I know someone who uses a waste water to raise the incoming water temperature 1-2 degrees C and it saves a measurable amount of money on power bills.

nate_meurer Apr 5, 2018 View on HN

Sorry, that should read "domestic water heaters"

kleiba Dec 2, 2023 View on HN

I don't follow. My hot water is heated up about 60cm before the tap, as it runs through. Is that a regional thing? Are you saying that you're keeping a large quantity of water at temperature at all times just in case someone might need it later? Wouldn't that be super inefficient energy-wise?

Gasp0de Jun 14, 2023 View on HN

Why shouldn't you use the heat pump to heat water?

tguvot Nov 6, 2025 View on HN

This is what most (all?) of machines do. Heat water when they need hot water