In this thread http://www.greenbuildingweb.com/Forums/tabid/53/view/topic/forumid/4/postid/72123/Default.aspx I discuss my energy usage from about 11/22 to 12/22/2009. My best estimate is that the load on the heat pump was about 1.25 Btu/HDD (not energy input into the pump) and that all other electrical use added about .75 Btu/HDD for a total heat load for the house of about 2 Btu/HDD.

Does your figure of 2 Btu/HDD include electricity usage? Keep in mind that over 90% of the electricity that enters the home gets converted to heat. A high electrical load will reduce the heating system load. In an ordinary stick house the ratio between heating and all other electrical is great enough that it's ignored. In an ICF house the other usage is a significant contributor. Comparing my September power bill, when there was very little if any cooling load and no heating load, against the December bill I estimated that 55% of the my electrical usage in December was other than the heat pump and contributed about 38% of the heat requirement.

Your $0.48/therm gas cost is incredible, I think. The last I looked at their website Intermountain Gas residential rate in Idaho is $0.77/therm. That's way down from a year ago.

Hi Clark,

I'd love to compare, but I have no way to separate my heating load/cost from my regular household electric usage.  My electric bill for Dec, 14 - Jan 14 was $304.76 for 2198 kWh.  Weather data for the area says that period had 1,442 HDD (@ base 65F).

That figure includes everything... heating, ERV, cooking, clothes and dishwashing, clothes drying, and well water, in addition to all the usual household loads for a family of 5.  Electric bills in our previous house was ~$200.  That did not include cooking, heating, ERV, chest freezer, or water (we had city water).  In short, I think we are doing pretty darn well. 

Regards,
Ed

 

No, dmaceld, the 2 BTU/SF/HDD does not include any heat from electrical equipment or other sources. The house is, as yet, unoccupied, so that would not be a big adder. I consumed 491 KWH of electricity over the same period, and about half of that went to the RV parked outside. From what you're saying, I can expect a somewhat lower gas bill once we move in. Still, it appears that your house is more energy efficient than mine. What do you attribute that to? Are you better insulated? Could it be due to higher solar gain? Here in northern Illinois we don't enjoy as many sunny days as you do in SW Idaho.

BTW, dmaceld, the price of natural gas that I quoted ($0.48/therm) didn't include the cost of delivery and the various taxes.  When those costs are added in, the total comes to $0.74/therm, a lot closer to the $0.77 figure you would pay.

Ed, it appears that you, too, are living in a northern state.   Why did you chose to heat your home with electricity?  Are heat pumps so efficient now that it's becoming a viable option in cold climates?

Yes, I am located in Douglas, Massachusetts.  Annual HDD is ~6990.  I have Ground Source heat pumps (aka geothermal), not air source (which I assume is what you are referring to).  I cycle 50F ground (well) water through the heat pumps, extract heat, and return that water back to the same well.  This is also known as a standing column well.  We also use the same well for domestic purposes.  Works great.  While I have not measured, COP should be in the 4-5 range given water temp and primarily single state operation.

Everything is located within the house.  Here is what my two units look like.  One is an all-in-one, the other is a split.  The water tank is simply used to store any hot water made by the geo units.  The tank is not powered/fueled in any way.

Ed

Very well could be. Winter time solar gain seems to be pretty good, both through the windows and through the walls and roof. The south side of the house is warmer than the north side, and that's with air circulating full time.

I've got Andersen 400 double pane windows and around 10" of Icynene on the underside of the roof.

"The south side of the house is warmer than the north side, and that's with air circulating full time.

I've got Andersen 400 double pane windows and around 10" of Icynene on the underside of the roof."

Interesting, but perhaps concerning...  Even on a bright sunny day (winter or summer), my interior wall surfaces are the same temp on the north and south side of the house.  If you are getting "warmth" through the walls and roof during the winter months, how much additional heat are you going to gain in the summer?  Yikes!

Ed    

I was thinking this morning I should put a temp probe on the wall surfaces to see just what variation is, if any. The room air temp difference north to south, around 2°F, surprised me. I really noticed the solar gain this past fall when the outdoor temp was warm enough, 45F or so, that the heat pump didn't need to come on during the afternoon. The living room, with the most window exposure, would get up to 78 or 80F while the north side master bath and bedroom would stay around 74F. Summer window solar gain isn't as much an issue as the windows are almost fully shaded by the overhang. But the house warms up more than the garage does, and the garage has a little less insulation on the roof than does the house. It has, comparatively, less south and west facing roof surface than does the house. That's what leads me to think that even with R40 foam some heat does travel through. Only makes sense.

Part of the issue of temp difference very well could be the lesser number of floor registers and ceiling return grills, per 100 sq ft of floor, in the bath and bedroom than in the rest of the house. I may not be getting as much volume of air flow as I need to keep the temp more uniform.

i guess i should be very happy with my january (12/7-1/7) electric bill....
2200 sf under air, plus 1000 sf garage/shop/storage

2009 - 955 kwh    $90.00
2010 - 1382 kwh  $135.00 .... remember, we had a record cold period...

icf house with second floor and roofs 12" insuldeck, all utilities electric, 3 adults, no basement (florida), single laminated glass hurricane proof aluminum windows and sliders, lots of glass on the south side for passive solar gain, but large cantelever overhangs for summer shade, all rooms 12'+ ceilings...

largest electric bill last summer (acually in october) with a/c at 78 degrees was $167.00, lowest is usually in april at about $83.00

but, with no hurricane insurance needed (by my own choice, even though i am only 15' from the intracoastal, at 5'6" base elevation) i think i can make a strong case for icf construction and energy efficiency....

solar and wind power would allow me to be selling power back to the utility, but the investment is still pricey....

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