FHB Logo Facebook LinkedIn Email Pinterest Twitter X Instagram Tiktok YouTube Plus Icon Close Icon Navigation Search Icon Navigation Search Icon Arrow Down Icon Video Guide Icon Article Guide Icon Modal Close Icon Guide Search Icon Skip to content
Subscribe
Log In
  • How-To
  • Design
  • Tools & Materials
  • Restoration
  • Videos
  • Blogs
  • Forum
  • Magazine
  • Members
  • FHB House
  • Podcast
Log In

Discussion Forum

Discussion Forum

New heat pump water heaters

wegotrocks | Posted in Energy, Heating & Insulation on February 28, 2010 05:14am

I’ve watched the “Ask This Old House” episode, where one of these heat pump water heaters is installed, twice now and something has been eating at me each time. 

I’d consider installing one (when the price [hopefully] comes down) – but right now, Lowes wants $1599 for the GE model.

Here’s what’s eating me:  If you install one of these units, the heat pump will extract heat from the space it’s installed in; for example your basement.  That’d be fine when the unit first starts up.  But as it runs for a while the air coming out of the heat pump will be pretty cold – the same as an HVAC heat pump works.  So … after it’s been running for a while, your basement will get colder and colder.  Not only will it, sooner or later, and especially in the winter, get pretty damn cold in your basement, but at that point there’ll be less and less heat for the heat pump to extract from the air in the room, so that it can heat your water. 

Wouldn’t the unit be less and less efficient the longer it runs?  Obviously, if the air in your basement is 70 degrees, after the heat pump has been running for a while, the basement temp might be down to 60 degrees.  Then if it keeps running (like in a high demand period), because it still needs more heat to transfer into the water, it would seem to me that it would keep running longer-and-longer each cycle to get the heat it needs out of the colder-and-colder air.

Anybody installed one of these yet?

Reply
  • X
  • facebook
  • linkedin
  • pinterest
  • email
  • add to favorites Log in or Sign up to save your favorite articles

Replies

  1. User avater
    MarkH | Feb 28, 2010 06:16pm | #1

    I like the idea of the heat pump water heater.  A couple of my concerns are the maintence requirements such as fan replacement, electronic controls, compressor, and the payback period.

    I'm going to say that you are right about the issue of cold environments reducing the efficiency of the heat pump.  I also assume the heat pump will only operate at suitable temperatures, so it probably is not a really big concern unless you live in a heating environment. 

    Where is the heat going to come from in the winter?  Your heating plant. If your heating plant consumes electricity for fuel, I don't see where the heat pump water heater would be more efficient than resistance heaters.

    I believe the heat pump water heater excells in warm environments.  It reduces air coinditioning load, while substantially reducing energy used to heat water.  All the while dehumidifying the air, which is a plus in humid environments.

    I doubt that they can compare to my utility costs using natural gas though.

  2. User avater
    wegotrocks | Feb 28, 2010 09:28pm | #2

    The way I understand it, if the compressor can't deliver the amount of heat needed to bring the water to the set temp, or to deliver the water in the required period of time, the electric back-up elements kick in.

    I DO live in a heating environment, and I've only installed one heating register in the basement to keep everything at a reasonable temp during the winter.  If I'd run one of the heat pump units, I'm assuming that within a couple of cycles, my basement would be at about 40 degrees, instead of the 58 - 60 that I keep it at now.  I know from my air-to-air unit outside, that somewhere around 34-35 degrees it starts losing efficiency pretty quickly.  I can only figure the water heater unit would do the same thing.

    You're right about the furnace or other main heat source producing the heat to run this thing - I can't decide if that's a good thing or not.

    It seems like the heat pump compressor would only function like a pre-heater in colder climates - definitely not worth $1600 for me!  Maybe if they come way down in price. 

    During a web search, I did find a couple of companies that make an external unit that works with your existing water tank.  I'm sure it would function the same way, though (cooling the basement).

    1. pixburd | Mar 01, 2010 08:24am | #4

      Wego, you are right about the basement getting colder.  HPWH's are much better suited to the Gulf Coast climates which can take advantage of the cooling and dehumidifying.  When the manufacturer makes claims to a certain Coefficient Of Performance, he is basing it on certain prescribed ambient conditions of temperature, humidity and room size.  Your COP will change based on how your conditions change.  Obviously the hotter the enveronment, the better it will perform.

      To deal with this problem, I saw a website where the guy added louvers for summer / winter operation.  In the winter he vented outside.

      1. User avater
        wegotrocks | Mar 02, 2010 10:21am | #10

        Yeah - the more I learn about these units, the less I think I'd be able to use one here in northern WV.  Maybe if the price came w-a-y down, I'd consider making some modifications to install one.  As it is, I like the temp of my basement just the way it is in both summer and winter, and I don't think I'd want to cut any of the foundation block out just to run some sort of ducting or louvering system to the outside.  I rarely have to use any air conditioning since I live at around 2000 feet.  Maybe once or twice in the summer do we flip our current air-to-air heat pump on to A/C.

        Maybe I'll look into solar water heating, although the way this winter's been going, I'm not sure I'd recognize the sun if it came out!

        Thanks for the input, guys.

  3. DanH | Mar 01, 2010 08:01am | #3

    The unit doesn't get less efficient as it runs longer, but, as it runs longer, the area where it's sited goes into a larger and larger "heat debt".  Sooner or later you can't make the payments and foreclosure is required.

    The units really only make sense where heat is free (the south) or cheap (heating with nat gas), or where the cold can be used for some purpose (eg, the first units of this sort were sold to dairies -- the heat was needed for cleaning and the cold to chill the milk).

    1. pixburd | Mar 01, 2010 08:33am | #5

      Any heat pump is exactly that -- a heat pump.  It does not create heat, but rather pumps it from one place to another, in this case from the room air to the tank water.

      The performance will always be dependent on temperature differentials.  Maximum performance will occur when the water in the tank is coldest, and the utility room air is the hottest.  As the utility room air drops, and the water temperature in the tank rises, the Coefficient of Performance will continually deteriorate.  The same thing happens to a whole house heat pump in Minnesota -- it just can't "pump" across a temperature differential which is too great..

  4. Scott | Mar 01, 2010 01:41pm | #6

    What DanH said. If you're already paying to move heat out of your house, you might as well move it into your domestic hot water.

    Otherwise, you'll pay once to take the heat out of your interior air, then you'll pay again to put heat back into it. These units would never be feasible in our climate.

    1. gfretwell | Mar 01, 2010 09:47pm | #8

      If you are payingh to get heat out of your house (the AC is on) why not just get the heat recovery uint made for the purpose that takes heat from the HVAC condenser? That is pretty cheap compared to the price of a heat pump water heater..

  5. GaryGary | Mar 01, 2010 09:29pm | #7

    Hi, You might take a look at the info here:

    http://www.builditsolar.com/Projects/Wat...

    The last one "Wiinter use of Heat Pump Water Heater" describes a setup that helps with the issue of the heat pump water heater fighting with your furnace in the winter.  It involves a little ductwork, and you have seasonally change a damper, but it seems workable to me.

      The part on the heat pump water heater is a ways down in the document.

    The video from Tom Gocze on installing a heat pump water heater is interesting and fun.

    Gary

    1. DanH | Mar 02, 2010 08:28am | #9

      Probably a reasonable solution farther south, but I'm guessing that the HPWH doesn't operate too well on the 0-30F air they'd get from a crawl (if there was one) around here.

      1. GaryGary | Mar 03, 2010 11:06am | #11

        Hi,

        That's a mighty cold crawl space -- I'm in Montana and mind runs in the 40 to 50F area all winter.

        Gary

Log in or create an account to post a comment.

Sign up Log in

Become a member and get full access to FineHomebuilding.com

Video Shorts

Categories

  • Business
  • Code Questions
  • Construction Techniques
  • Energy, Heating & Insulation
  • General Discussion
  • Help/Work Wanted
  • Photo Gallery
  • Reader Classified
  • Tools for Home Building

Discussion Forum

Recent Posts and Replies

  • |
  • |
  • |
  • |
  • |
  • |
View More Create Post

Up Next

Video Shorts

Featured Story

A Practical Perfect Wall

Getting the details right for a wall assembly with the control layers to the exterior and lots of drying potential.

Featured Video

How to Install Cable Rail Around Wood-Post Corners

Use these tips to keep cables tight and straight for a professional-looking deck-railing job.

Related Stories

  • Podcast Episode 695: Saving Bricks, Cut-and-Cobble Insulation, and Waterproofing Foundations
  • FHB Podcast Segment: Waterproofing Below-Grade Foundation Walls
  • Midcentury Home for a Modern Family
  • The New Old Colonial

Highlights

Fine Homebuilding All Access
Fine Homebuilding Podcast
Tool Tech
Plus, get an extra 20% off with code GIFT20

"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.

Get home building tips, offers, and expert advice in your inbox

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters

Fine Homebuilding Magazine

  • Issue 333 - August/September 2025
    • A Practical Perfect Wall
    • Landscape Lighting Essentials
    • Repairing a Modern Window Sash
  • Issue 332 - July 2025
    • Custom Built-ins With Job-Site Tools
    • Fight House Fires Through Design
    • Making the Move to Multifamily
  • Issue 331 - June 2025
    • A More Resilient Roof
    • Tool Test: You Need a Drywall Sander
    • Ducted vs. Ductless Heat Pumps
  • Issue 330 - April/May 2025
    • Deck Details for Durability
    • FAQs on HPWHs
    • 10 Tips for a Long-Lasting Paint Job
  • Issue 329 - Feb/Mar 2025
    • Smart Foundation for a Small Addition
    • A Kominka Comes West
    • Making Small Kitchens Work

Fine Home Building

Newsletter Sign-up

  • Fine Homebuilding

    Home building tips, offers, and expert advice in your inbox.

  • Green Building Advisor

    Building science and energy efficiency advice, plus special offers, in your inbox.

  • Old House Journal

    Repair, renovation, and restoration tips, plus special offers, in your inbox.

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters

Follow

  • Fine Homebuilding

    Dig into cutting-edge approaches and decades of proven solutions with total access to our experts and tradespeople.

    Start Free Trial Now
    • Facebook
    • Instagram
    • X
    • LinkedIn
  • GBA Prime

    Get instant access to the latest developments in green building, research, and reports from the field.

    Start Free Trial Now
    • Facebook
    • YouTube
  • Old House Journal

    Learn how to restore, repair, update, and decorate your home.

    Subscribe Now
    • Facebook
    • Instagram
    • X
  • Fine Homebuilding

    Dig into cutting-edge approaches and decades of proven solutions with total access to our experts and tradespeople.

    Start Free Trial Now
    • Facebook
    • Instagram
    • X
    • LinkedIn
  • GBA Prime

    Get instant access to the latest developments in green building, research, and reports from the field.

    Start Free Trial Now
    • Facebook
    • YouTube
  • Old House Journal

    Learn how to restore, repair, update, and decorate your home.

    Subscribe Now
    • Facebook
    • Instagram
    • X

Membership & Magazine

  • Online Archive
  • Start Free Trial
  • Magazine Subscription
  • Magazine Renewal
  • Gift a Subscription
  • Customer Support
  • Privacy Preferences
  • About
  • Contact
  • Advertise
  • Careers
  • Terms of Use
  • Site Map
  • Do not sell or share my information
  • Privacy Policy
  • Accessibility
  • California Privacy Rights

© 2025 Active Interest Media. All rights reserved.

Fine Homebuilding receives a commission for items purchased through links on this site, including Amazon Associates and other affiliate advertising programs.

  • Home Group
  • Antique Trader
  • Arts & Crafts Homes
  • Bank Note Reporter
  • Cabin Life
  • Cuisine at Home
  • Fine Gardening
  • Fine Woodworking
  • Green Building Advisor
  • Garden Gate
  • Horticulture
  • Keep Craft Alive
  • Log Home Living
  • Military Trader/Vehicles
  • Numismatic News
  • Numismaster
  • Old Cars Weekly
  • Old House Journal
  • Period Homes
  • Popular Woodworking
  • Script
  • ShopNotes
  • Sports Collectors Digest
  • Threads
  • Timber Home Living
  • Traditional Building
  • Woodsmith
  • World Coin News
  • Writer's Digest
Active Interest Media logo
X
X
This is a dialog window which overlays the main content of the page. The modal window is a 'site map' of the most critical areas of the site. Pressing the Escape (ESC) button will close the modal and bring you back to where you were on the page.

Main Menu

  • How-To
  • Design
  • Tools & Materials
  • Video
  • Blogs
  • Forum
  • Project Guides
  • Reader Projects
  • Magazine
  • Members
  • FHB House

Podcasts

  • FHB Podcast
  • ProTalk

Webinars

  • Upcoming and On-Demand

Podcasts

  • FHB Podcast
  • ProTalk

Webinars

  • Upcoming and On-Demand

Popular Topics

  • Kitchens
  • Business
  • Bedrooms
  • Roofs
  • Architecture and Design
  • Green Building
  • Decks
  • Framing
  • Safety
  • Remodeling
  • Bathrooms
  • Windows
  • Tilework
  • Ceilings
  • HVAC

Magazine

  • Current Issue
  • Past Issues
  • Magazine Index
  • Subscribe
  • Online Archive
  • Author Guidelines

All Access

  • Member Home
  • Start Free Trial
  • Gift Membership

Online Learning

  • Courses
  • Project Guides
  • Reader Projects
  • Podcast

More

  • FHB Ambassadors
  • FHB House
  • Customer Support

Account

  • Log In
  • Join

Newsletter

Get home building tips, offers, and expert advice in your inbox

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters

Follow

  • X
  • YouTube
  • instagram
  • facebook
  • pinterest
  • Tiktok

Join All Access

Become a member and get instant access to thousands of videos, how-tos, tool reviews, and design features.

Start Your Free Trial

Subscribe

FHB Magazine

Start your subscription today and save up to 70%

Subscribe

Enjoy unlimited access to Fine Homebuilding. Join Now

Already a member? Log in

We hope you’ve enjoyed your free articles. To keep reading, become a member today.

Get complete site access to expert advice, how-to videos, Code Check, and more, plus the print magazine.

Start your FREE trial

Already a member? Log in

Privacy Policy Update

We use cookies, pixels, script and other tracking technologies to analyze and improve our service, to improve and personalize content, and for advertising to you. We also share information about your use of our site with third-party social media, advertising and analytics partners. You can view our Privacy Policy here and our Terms of Use here.

Cookies

Analytics

These cookies help us track site metrics to improve our sites and provide a better user experience.

Advertising/Social Media

These cookies are used to serve advertisements aligned with your interests.

Essential

These cookies are required to provide basic functions like page navigation and access to secure areas of the website.

Delete My Data

Delete all cookies and associated data