GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Should I go with a ground-source heat pump or PV-powered electric boiler?

Kevin Dingle | Posted in Mechanicals on

I have a 1940’s Cape Cod (1200Sq Ft) along the shoreline in Connecticut (Last bill was 294KWH cost $64.09). I want to ditch oil and swap to a new boiler for my hot water cast iron radiators. The overall plan is to add a functional 2nd floor and become a colonial style home, and make vast improvements to the insulation, windows, and air sealing in that process. I’ll be demolishing the chimney as a part of adding on the second floor so I need to get a good heating plan in place before I start executing the building/insulation/windows plan rolling. So am I better off building a bigger PV system and getting the electric boiler(I want a PV system either way sooner and bigger if I go with the Electric boiler option), or spend more money upfront and get ground source heat pump (Duct work and all, ditch the radiators) with a more modestly size PV array whenever I get around to it. Currently heating my domestic Hot water with a GE geospring. Thanks for any input or new ideas.

Replies

  1. GBA Editor
    Martin Holladay | | #1

    Kevin,
    The two options you propose are not your only two options.

    If you want to switch from oil heat to electric heat, the most economical approach is to heat your house with ductless minisplits or ducted minisplits. These appliances make much more sense than a ground-source heat pump.

    You can, of course, install as big a PV system as you want (or can afford).

  2. Kevin Dingle | | #2

    Wife is against minisplits, including the nice art-deco ones.

  3. Expert Member
    Dana Dorsett | | #3

    At 22 cents/kwh in an electric boiler vs.$4/gallon oil in an 85% efficiency boiler, it's slightly cheaper to heat with oil.

    At 22cent/kwh and a pretty good ductless mini-split it will cut the cost of heating by more than half, and you'll have high effciency air conditioning to boot.

    A typical reasonably-tight modestly insulated 2x4 framed 1200' Cape with clear-glass double panes or tight storms over wood sash double hungs will have a heat load of about 17-20,000 BTU/hr @ +10F (your 99% outside design temp is probably close to +10F, if you're near the shore. See: http://www.energystar.gov/ia/partners/bldrs_lenders_raters/downloads/Outdoor_Design_Conditions_508.pdf ) That is within the output range of a Mitsubishi MSZ-FH15NA, which would cost about $4500 installed, as compared to about $25,000 for a 2- ton ground source heat pump.

    When adding the second story it won't double the heat load- it will probably even increase it by less than 50%, but you have some control over that, since you can specify the window U-factors and wall/attic R-values, etc.

    In the new design, keep the roof lines simple (no dormers or valleys) , and use a gabled roof with an east-west ridge so you can maximize the available area & output of the solar.

    With a ZIP code (for weather data), the date & volume of a mid to late-winter oil-fill up and the date of the previous fill up it's easy to get a pretty good handle on the current heat load as a sanity check.

    If the missus can't stand mini-splits, there are mini-duct cassette versions that would work almost as efficiently in your location. The SUZ/SEZ-KA18NA or SUZ/SEZ-KA15NA would probably cut it, at a seasonal COP of about 3 (instead of 3.3 for the -FH15.)

    http://usa.mylinkdrive.com/uploads/documents/4297/document/17_8_SEZ_Ducted_Heat_Pump_Systems.pdf

  4. GBA Editor
    Martin Holladay | | #4

    Kevin,
    You may be able to convince your wife that ducted minisplits are acceptable. Ducted systems have diffusers or registers, and no lumps on the wall.

  5. Kevin Dingle | | #5

    This is the best place on the internet, thank you everyone for your guidance.

Log in or create an account to post an answer.

Community

Recent Questions and Replies

  • |
  • |
  • |
  • |