Heating Costs

Tessa Hill and Dennis Odin Johnson
Bear Creek Dome – North Branch, Minnesota

  • Model: 1800 mid profile, 49′ diam. dome home
  • Location: North Branch, Minnesota. Department of Energy Zone 7A (severe cold-moist) 9000 heating degree days.
  • House size: 3200 SF; slab on grade. Main floor 2100 sf, upper floor 1100 sf.
  • Specifications: 18″ thick dome walls and dome roof, 16″ fiberglass insulation (R-Value=57 in triangles, R-Value=62 in riser walls), vented dome shell; slab has 2″ styrofoam under and 11″ styrofoam on edge of slab. Blower door test was .06 ACH
  • Heating system: Radiant floor in 4″ concrete slab using 1500 lf of PEX tubing circulating water. Heating unit is 14 KW Seisco Electric “instant on” boiler with a secondary natural gas “Munchkin” boiler that you can switch to manually. Electric rate is off-peak interruptible rate of 4.2¢ /KW. * Note: Rate increase to 4.8¢ /KW in Feb. 2008 (14% increase).
  • Built: 2007, moved into November 2007.
  • Heating costs: See below.(Electric billings run from the 7th of each month. Natural gas billings are from the 17th).
  • Air conditioning costs: The Summers of 2008, 2009 and 2010 had zero A.C. costs. The outside temps were 90°-95° F many days, yet the highest inside temps were 72°-74° F.

Winter 2007-2008 Radiant Floor Heating

Month Cost KW Used
July 07  $0 None
August 07 $0 None
September 07 $0 None
October 07 $71 1680 kw
November 07  $153  3640 kw
December 07  $156 3720 kw
January 08 $165  3940 kw
February 08  $143* 2980 kw
March 08 $97 2020 kw
April 08 $73 1520 kw
May 08  $16  340 kw
June 08  —-  —-
Total: $765 16,660 KW

 

Winter 2008-2009 Radiant Floor Heating

January, 2009, was extremely cold, the 4th coldest January on record. All of the days were below 32° (0° C) with some periods of 4-5 days where it never was warmer than 0° (-18° C). Instantaneous hot water gas heater
Month Electric Heat 4.8¢ /kw KW Used Natural gas base monthly fee Actual gas used
July 08 $0 None $8 $4.01
August 08 $0 None $8 $4.73
September 08 $11 220 kw $8 $3.82
October 08 $55 1140 kw $8 $1.59
November 08 $152 3160 kw $8 $5.10
December 08 $216 4500 kw $8 $3.86
January 09 $244 5080 kw $8 $6.04
February 09 $150 3120 kw $8 $3.64
March 09 $140 2160 kw $8 $3.21
April 09 $30 620 kw $8 $4.21
May 09 $8 180 kw $8 $2.51
June 09 $8 $3.96
Total: $871 16,840 KW Total $96 $46.68 ($3.89)

 

Winter 2009-2010 Radiant Floor Heating

Instantaneous Hot Water Gas Heater

Month Electric Heat 4.8¢ /kw KW Used Natural gas base monthly fee Actual gas used
July 09 $0 None $8 $226
August 09 $0 None $8 $1.71
September 09 $25 520 kw $8 $2.11
October 09 $97 2020 kw $8 $4.28
November 09 $115 2400 kw $8 $4.62
December 09 $223 4640 kw $8 $3.07
January 10 $188 3920 kw $8 $5.00
February 10 $153 3200 kw $8 $3.88
March 10 $8 $5.96
April 10 $8
May 10 $8
June 10 $8
Total: $801 16,700 KW Total $96 $32.89 ($3.65)

Winter 2010-2011 Radiant floor heating

Instantaneous hot water gas heater

Month (Dates) Electric Heat 4.8¢ /kw KW Used Gas Heating Cost Heating Therms Used Avg.
Temp.
(F)
Natural gas base monthly fee Actual gas used
7/9/10 – 8/8/10  —- None 76  $8 $5.64
8/8/10 – 9/8/10  —- None 78 $8 $3.45
9/8/10 – 10/8/10 $22 460 kw 69 $8 $3.94
10/8/10 – 11/7/10  $69 1440 kw 60 $8 $3.84
11/7/10 – 12/9/10  $175 3640 kw 47 $8 $3.69
12/9/10 – 1/10/11 $229 4780 kw 21 $8 $3.67
1/10/11 – 2/7/11 $145 3020 kw 16 $8   $6.96
1/18/11 – 2/18/11 $65 73  8 $8 $4.50
2/19/11 – 3/20/11  $96 108 27 $8 $4.50
3/20/11 – 4/18/11 $60 62 42 $8 $4.50
4/18/11 – 5/19/11 $32 33 52 $9 $4.50
5/19/11 – 6/19/11 $5 5 68 $9 $4.50
Total: $640 13,340 KW $258 281 Th. $98 $54
We switched from an electric boiler to a natural gas boiler during Jan. 2011. There were some “system adjustments” to the gas boiler during January so there were overlaps with the electric boiler. We calculate that if we were using the gas boiler for the radiant heating during all of the 2010 / 2011 heating season, the total gas bill would have been about $550 – $600 for the year. The temperature on the thermostat was set on a very comfortable 70°F (22°C) for the entire winter. 2010 / 2011 was a very cold Minnesota winter.

Winter 2011-2012 Radiant Floor Heating – Bear Creek Dome

Instantaneous Hot Water Gas Heater (Used for baths, laundry, kitchen, etc.)

Month
(Dates)
Electric Heat 4.8¢ /kw KW Used Gas Heating Cost  Heating Therms Used
(adjusted)
Avg.
Temp
F (C)
Base monthly fee Actual gas used
6/19/11 – 7/19/11 —- None 76 (24) $9 $3.63
7/19/11 – 8/16/11  —- None 78 (25) $9 $5.18
8/16/11 – 9/15/11 —- None 71 (22) $9 $3.55
9/15/11 – 10/16/11 —- None 62 (16) $9 $5.60
10/16/11 – 11/14/11  —- None $36 46 47 (9) $9 $4.50
11/14/11 – 12/15/11 —- None $89 115 32 (0) $9 $4.50
12/15/11 – 1/18/12 —- None $112   150 29 (-2) $9 $4.50
1/18/12 – 2/16/12 —- None $92 128 25 (-4) $9 $4.50
2/16/12 – 3/18/12 —- None $68  94 39 (4) $9 $4.50
3/18/12 – 4-17-12 —- None $25 38 53 (12)  $9 $4.50
4-17-12 – 5-16-12 —- None $7 11 58 (14)   $9  $4.50
5-16-12 – 6-17-12 —- None $13 22   70 (21)  $9 $4.50
Yearly Total: $—- None $442 604 Th. 53.3 (12) $108 $54
73¢ / therm
Average temperature for heating season 10-15 to 4-17 37.5 (3)

Winter 2012-2013 Radiant Floor Heating – Bear Creek Dome

Instantaneous hot water gas heater
(used for baths, laundry, kitchen, etc.)

Month
(Dates)
Electric Heat
4.8¢ /kw
KW Used Gas Heating Cost Heating Therms Used
(adjusted)
Avg.
Temp
F (C)
Base monthly fee Actual hot
water cost
6/17/12 – 7/17/12 —- None 80 (27) $9 $5.63
7/17/12 – 8/15/12  —- None 76 (24) $9 $4.14
8/15/12 – 9/16/12 —- None $6 9 72 (22)   $9 $5.88
9/16/12 – 10/16/12  —-  None $14 22 54 (12) $9 $6.00
10/16/12 – 11/13/12 —- None $60 90 44 (7) $9 $6.00
11/13/11 – 12/16/12 —-   None $84 119  35 (2) $9 $6.00
12/16/12 – 1/17/13 —- None $121  177 20 (-7) $9 $6.00
1/17/13 – 2/17/13 —- None  $120 178 17 (-8) $9 $6.00
2/17/13 – 3-18-13 Heat
6.1¢ /kw
None $75 111 26 (-3) $9 $6.00
3/18/13 – 4/17/13  —- None $69  102 35 (2)  $9 $6.00
4/17/13 – 5/16/13 —- None $30 41 52 (11) $9  $6.00
5/16/13 – 6/17/13 —- None $6 9 64 (20)  $9 $6.00
Yearly Total: $—- None $585 849 Th.  47.9 (9) $108 $72
69¢ / therm
Average temperature for heating season 10-16 to 4-17  29.5 (-2)

Winter 2013-2014 Radiant Floor Heating – Bear Creek Dome

Instantaneous hot water gas heater
(used for baths, laundry, kitchen, etc.)

Month
(Dates)
Electric Heat
6.1¢ /kw
KW Used Gas Heating Cost Heating Therms Used
(adjusted)
Avg.
Temp
F (C)
 Base monthly fee Actual hot
water cost
6/17/13 – 7/17/13  —- None 78 (26) $9 $8
 7/17/13 – 8/15/13 —- None $2  2  71 (22) $9 $8
8/15/13 – 9/16/13 —- None $3 4 76 (24) $9 $8
9/16/13 – 10/15/13 —- None $11 16 62 (17) $9 $8
10/15/13 – 11/13/13 —- None $59 92 41 (5) $9 $8
11/13/13 – 12/16/13 —- None $128 188 23 (-5) $9 $8
12/16/13 – 1/19/14 —- None $160 224 13 (-9) $9 $8
1/19/14 – 2/18/14 —- None $158 200 7 (-14) $9 $8
2/18/14 – 3/19/14 —- None $139 144 19 (-8) $9 $8
3/19/14 – 4/17/14 —- None $80 91 37 (3) $9 $8
4/17/14 – 5/18/14 —- None $37 49 51 (11) $9 $8
5/18/14 – 6/17/14 —- None 68 (20) $9 $8
2013-2014
Yearly Total:
$—- None $777 1010 Th.  45.5 $108 $96
77¢ / therm
Average temperature for heating season 10-15 to 4-17 23.3 (-6)

Winter 2014-2015 Radiant Floor Heating – Bear Creek Dome

Instantaneous hot water gas heater
(used for baths, laundry, kitchen, etc.)

Month
(Dates)
Electric Heat
6.1¢ /kw
KW Used Gas Heating Cost Heating Therms Used
(adjusted)
Avg.
Temp
F (C)
 Base monthly fee Actual hot
water cost
6/17/14 – 7/17/14 —- None 72 (22) $9 $6
7/17/14 – 8/17/14 —- None 75 (24) $9 $4
8/17/14 – 9/16/14 —- None $2 2  68 (20) $9 $7
9/16/14 – 10/15/14 —- None $25 34 57 (14) $9 $6
10/15/14 – 11/13/14 —- None $58 75 44 (6) $9 $6
11/13/14 – 12/16/14 —- None $137 167  23 (-5) $9 $6
12/16/14 – 1/19/15 —- None $166 207 18 (-8) $9 $6
1/19/15 – 2/18/15 —- None $126 165  20 (-6) $9 $6
2/18/15 – 3/19/15 —- None $99 129 27 (-2) $9 $6
3/19/15 – 4/19/15 —- None $40 61 45 (7) $9 $6
4/19/15 – 5/18/15 —- None $15 27 55 (13) $9 $6
5/18/15 – 6/17/15 —- None $4 8 65 (18) $9 $6
2014-2015
Yearly Total:
$—- None $672 875 Th. 47.4 (8) $108 $71
77¢ / therm
Average temperature for heating season 10-15 to 4-19  29.5 (-1)

2015-2016 Radiant floor heating – Bear Creek Dome

Instantaneous hot water gas heater (used for baths, laundry, kitchen, etc.)

Month
(Dates)
Electric Heat
6.1¢ /kw
KW Used Gas Heating Cost Heating Therms Used
(adjusted)
Avg.
Temp
F (C)
Base monthly fee Actual hot
water cost
June 2015 —- None $5 15 65 (18) $9 $6
July 2015 —- None $1 7 72 (22) $9 $4
August 2015 —- None $0 6 75 (24) $9 $7
September 2015 —- None $0 6 69 (20) $9 $6
October 2015 —- None $10 25 60
(15)
$9 $6
November 2015 —- None $36 68 49
(9)
$9 $6
December 2015 —- None $67 118 35
(2)
$9 $6
January 2016 —- None $121 202 18
(-8)
$9 $6
February 2016 —- None $100 169 22
(-5)
$9 $6
March 2016 —- None $55 101 39
(4)
$9 $6
April 2016 —- None $34 75 44
(7)
$9 $6
May 2016 —- None $10 30 54 (12) $9 $6
2015-2016
Yearly Total:
$—- None $439 822 Th. 50 (10) $108 $71
$.54/therm
Average temperature for heating season October 2015 – April 2016 38 (3)

2016-2017 Radiant floor heating – Bear Creek Dome

Instantaneous hot water gas heater (used for baths, laundry, kitchen, etc.)

Month
(Dates)
Electric Heat
6.1¢ /kw
KW Used Gas Heating Cost Heating Therms Used
(adjusted)
Avg.
Temp
F (C)
Base monthly fee Actual hot
water cost
June 2016 —- None $0 11 69 (21) 9 8
July 2016 —- None $0 8 74 (23) 9 8
August  2016 —- None $0 7 77 (25) 9 8
September 2016 —- None $0 7 69 (21) 9 8
October 2016 —- None $0 9 60 (16) 9 8
November 2016 —- None $26 54 51 (10) 9 8
December 2016 —- None $72 126 33 (0) 9 8
January 2017 —- None $127 202 16 (-9) 9 8
February 2017 —- None $98 155 26 (-3) 9 8
March 2017 —- None $63 111 33 (0) 9 8
April 2017 —- None $39 77 44 (7) 9 8
May 2017 —- None  $24  56  53 (12) 9 8
2016-2017
Yearly Total:
$—- None  $449  823  50 (10)  $108  $96
Average temperature for heating season October 2015 – April 2016

2017-2018 Radiant floor heating – Bear Creek Dome

Instantaneous hot water gas heater (used for baths, laundry, kitchen, etc.)

Month
(Dates)
Electric Heat
6.1¢ /kw
KW Used Gas Heating Cost Heating Therms Used
(adjusted)
Avg.
Temp
F (C)
Base monthly fee Actual hot
water cost
June 2017 —- None $6  25  65 9 8
July 2017 —- None $0  6  72 9 8
August  2017 —- None $0  7  73 9 8
September 2017 —- None 9 8
October 2017 —- None 9 8
November 2017 —- None 9 8
December 2017 —- None 9 8
January 2018 —- None 9 8
February 2018 —- None 9 8
March 2018 —- None 9 8
April 2018 —- None 9 8
May 2018 —- None 9 8
2017-2018
Yearly Total:
$—- None  $108  $96
Average temperature for heating season October 2015 – April 2016

Kim and Steve Long – Perry, Iowa

  • Model: 1500 low profile, 45′ diam. dome home
  • Location: Perry, Iowa. Department of Energy Zone 5A (cold-moist) 6500 heating degree days.
  • House size: 3600 SF total; 1700 SF basement, 1700 SF main floor, 200 SF loft.
  • Specifications: 2×8 dome walls and dome roof. 7″ sprayed-in place foam (R-Value=27), unvented dome shell, no vapor barrier, permanent treated wood foundation walls with 2×8 studs, 7″ sprayed-in-place Icynene “soft” foam (R-Value=27). Basement walls have one side approximately 2/3 out of the ground. Blower door test was .03 ACH
  • Heating system: Radiant floor in basement concrete slab using PEX tubes circulating water and PEX tubes under plywood of main floor with insulation under; heating unit is “Munchkin” natural gas boiler. There is a natural gas burning fireplace on the main floor, however; it is not used for the main heating. It is rated at 42,000 BTU output with 86% efficiency.
  • Built: 2006 (moved in March 2007)
  • Heating costs: See below. Please note that the domestic hot water system is also operating with natural gas. The average usage is based on 30 therms per month and is not in the heating total. *Also note that this dome was not complete until Fall 2008. The insulation under the main floor had not been finished, and the heating costs decreased as the proper insulation was finalized. Billings run from the 10th of each month through August 2009, when they switched to show billings to the 27th of each month.
  • Also note that due to rising energy costs, the cost per therm nearly doubled this past heating season. The price per therm is noted in the chart below.
Month Cost Price per
therm
KW or Therms Used
July 2007 $0 None
August 2007 $0  None
September 2007 $0 None
October 2007  $35 $.60 33 therms *
November 2007  $111 $.73 100 therms *
December 2007 $142  $.74 128 therms *
January 2008  $169 $.77  150 therms *
February 2008 $120 $.86 134 therms *
March 2008 $72 $1.00  80 therms *
April 2008 —-  $1.02  —-
May 2008 —-  $1.12 —-
June 2008 —-  —-
2007-2008
Total:
$649.00*(see note above) 625 Therms

Month

Cost

Price per

therm

KW or Therms Used

Avg. Temperature

July 2008
August 2008
September 2008
October 2008
November 2008
December 2008
January 2009
February 2009
March 2009
April 2009
May 2009 $5 $.77   7 65
June 2009 —-  —- 74

2008-2009 Total:

$0

July 2009  —-  —- 72
August 2009 —- —- 74
September 2009 —- —- 68
October 2009 $28  $.79 35 51
November 2009 $43 $.86 50 48
December 2009 $122 $.84 146  27
January 2010 $129 $.95 136   17
February 2010 $139 $.94 148 19
March 2010  $63 $.89 71 41
April 2010  $27  $.88 31 58
May 2010 $22 $.88 25 62
June 2010 —- —- 74

2009-2010 Total:

$573.00

642 Therms

50.0

July 2010 —- —- 78
August 2010 —- —- 78
September 2010 —- —- 68
October 2010  $6  $.98 6 60
November 2010 $60 $.86 70 42
December 2010  $109  $.87 125 2
January 2011  $108 $.86 125 19
February 2011  $108 $.87 124 27
March 2011 $64 $.86 125 19
April 2011  $29 $.90 32 50
May 2011 $10  $.97 —- 61
June 2011 —- —- 71
2010-2011
Total:
$494.00 625 Therms  49.7
July 2011 —- —- 80
August 2011 —- —- 78
September 2011 —- —- 66
October 2011  $7 $.99 7 59

Joyce and Rich Peake – Arden Hills, Minnesota

  • Model: 1250 Low Profile 40′ diam dome home
  • Location: Mounds View, Minnesota. Department of Energy Zone 6A (severe cold-moist) 8400 heating degree days.
  • House size: 3200 SF; walk out basement 1350 SF, main floor 1450 SF, loft 450 SF
  • Specifications: 15″ thick dome walls & dome roof, 12″ fiberglass insulation (R-Value = 44), vented dome shell, riser walls 45″ high, 15″ thick with 15″ fiberglass (R-Value=51) Permanent treated wood foundation walls with 2×8 studs, 7 1/4″ fiberglass insulation (R-Value = 27)
    (Lower floor has 2×8 walls 3′ in ground with a walk out patio door on one side.)
  • Heating system: Forced air, natural gas, high efficiency furnace (no wood stove)
  • Built: 1984
  • Heating costs: (Billings run from the 12th of each month.)

Month

Cost

Cost per therm

KW or Therms Used

June 2007 $12.00 $1  4
July 2007 $12.00 $1 4
Aug 2007 $11.00 $1 3
Sept 2007  $12.00 $1 4
Oct 2007  $37.00  96¢  30
Nov 2007 $96.00  $1.10 80
Dec 2007  $112.00  $1.10 92
Jan 2008  $116.00  $1.05 103
Feb 2008 $106.00 $1.15 92**
March 2008 $65.00 $1.12 51
April 2008 $28.00  $1.18 17
May 2008 $8 base charge 0
June 2008  $8 base charge 0
Total: $530.00 398 Therms

Winter 2008-2009

July, 2008  $8  base charge  0
Aug., 2008 $8 base charge  0
Sept., 2008  $8 base charge   0
Oct., 2008 $31 82¢ 28
Nov., 2008  $90 95¢ 86
Dec., 2008 $115  82¢ 130
Jan., 2009 $91 77¢    108
Feb. 2009 $65  63¢ 90
March 2009 $32 53¢ 45
April 2009  $12 50¢ 8
May 2009 $8 base charge 0
June 2009 $8 base charge  0
Total: $476.00 495 Therms

Winter 2009-2010

July 2009 $8   base charge 0
Aug. 2009 $8  base charge  0
Sept. 2009  $12 40¢  10
Oct. 2009  $21  48¢ 27
Nov. 2009 $37 43¢ 67
Dec. 2009  $74  68¢ 109
Jan. 2010  $67  63¢ 93