Performance of the Extreme Green Retrofit of a 1929 Craftsman era House in Oklahoma City

All BTU figures are for "millions of BTU's".
Project began in August 2005.
2003 electricity usage is estimated based on 2004 usage.
Air conditioning was added in July 2007.
Propane prices from internet sources.
Propane use estimated.
All other data is from utility bills.

AC Note: When we decided to add air conditioning, we bought 3 window units, two 5,000 BTU and one 8,000 BTU. As it turns out, we were generally able to keep the house interior cool with only one 5,000 BTU unit AC. The 8K BTU unit ran for maybe 30 hours total July - September. The other 5K BTU unit ran for about 10 hours total in July and then was not turned on again for the rest of the summer.

Weather note: The Oklahoma City winter of 2006-2007 was significantly colder and cloudier than 2005-2006. Household size increased to 3 for 6 months of 2007. The area experienced prolonged severe cold in conjunction with ice storm and snow (which is to say, 2005-2006 was a winter of "ideal conditions" for passive solar; 2006-2007 and the 2007 half of the winter 2007-2008 was much less "ideal").

The first table is a summary, followed by the details for each of the energy sources used during the 2003-2007 period - electricity, natural gas, propane, and wood. Electric prices per MBTU are an artifact of OGE's billing system, wherein the more you use, the less you pay per kilowatt hour (due to embedded meter and line charges which are the same whether you use 1 kwh or 10,000 kwhs. The household buys all-wind-energy electricity from OGE.



Year Total Annual Energy Use, all sources, (Million btu's) (electricity, wood, propane, natural gas) Total Annual Energy Cost Annual Cost per Million BTU's Estimated Annual Cost if no extreme green retrofit Estimated Annual Savings with extreme green retrofit
2003 181.33 $1,352 $7.45
2004 179.54 $1,364 $7.60
2005 133.21 $1,230 $9.24 $1,663 $433
2006 92.23 $767 $8.31 $1,496 $729
2007 111.55 $1,066 $9.55 $2198 $1,132

2007 rate of return on $14,200 investment: 8% tax free.

Electricity





YEAR

KWH
Electricity
Electricity
BTU's
(millions)
Electricity
Cost
Annual Cost per million BTU's
2003 14500 145.44 $900 $6.19
2004 14571 147.44 $900 $6.10
2005 10521 106.46 $937 $8.80
2006 7093 71.77 $706 $9.84
2007 9628 97.43 $882 $9.04


NATURAL GAS
Natural gas use was discontinued in the fall of 2005.

Year Natural Gas
Dekatherms
BTU's
(millions)
Annual Cost Annual Cost per million BTU's
2003 28.1 28.1 $346 $12.31
2004 24.3 24.3 $335 $13.79
2005 11.8 11.8 $200 $16.95
2006 0 0 $0 0


Wood

Year wood (cords) Wood Btu's (millions)

Wood Annual Cost

Wood Annual Cost per million BTU's
2003
2004
2005 0.5 10
2006 1 20 $50 $3
2007 .5 10 $50 $5



Propane

Year Propane (Gallons) Propane BTU's (millions) Propane Annual Cost Propane Annual Cost per million btu
2003 85 7.79 $106 $14
2004 85 7.79 $129 $17
2005 54 4.95 $93 $19
2006 5 0.46 $11 $23
2007 45 4.13 $135 $33


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