Civil Engineering Reference
In-Depth Information
The conversion factor for propane is:
• 1gallon[U.S.]ofLPG=95,500BTU
Our example of propane consumption in gallons for January 2014 was 40 gallons.
So, to convert that to BTUs we must multiply 40 times 95,500.
• 4gallons 95 5
0
×
,
00
=
3 82
,
0 000
,
BTU
The conversion factor for fuel oil is:
• 1gallon[U.S.]of#2fueloil=138,874.15823BTU
Our fuel oil consumption example in gallons for January 2014 was 36 gallons. So,
to convert that to BTUs we must multiply 36 times 138,874.15823.
• 36 gallons 138 874 15823
×
,
.
=
4 999 469 696 BTU
,
,
.
You may notice that these BTU values are very large. It would be cumbersome to
use these values to compare our energy consumption from one month to another.
The energy index we create will be a much smaller and more meaningful number
since it normalizes the consumption with respect to temperature extremes and the
size of our homes.
4.2
Calculating the Energy Indexes
The energy index describes the energy consumption for each utility service in such
a way as to make it meaningful no matter how cold or hot it is or how large or small
our homes. So, let's calculate the energy index for each of the utility services we
now have BTU values for. Remember the formula for the energy index is:
• EI=BTU/DDSF
In Chap. 3 we found that the degree days value for January 2014 at our example
location was 1300.9. In our example home the living area is the same for all utility
services, 2253 ft
2
. Here is how to calculate the EIs for each utility service for Janu-
ary 2014.
•
ElectricEI426 326 946282 BTU139DD 2253 SF
(
)
=
=
,
0
,
.
/
00
.
×
137
.
(
)
=
•
GasEI2874
=
0
,
,
000
BTU139DD 2253 SF 712
/
00
.
×
.
(
)
=
•
Propane EI 382 TU 13 9DD 2253 SF
=
,
0 000
,
/
00
.
×
13
.
0
(
)
=
• Fuel OilEI4999 469 696 BTU139DD 2253 SF
=
,
,
.
/
00
.
×
171
.
You can see that these EI values are much smaller than the BTU values and will
be much easier to compare month to month. They should vary only a small amount
from month to month. These values are also very consistent from home to home.
