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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