Taller de Trabajo Tecnico del Programa BIEE
24-25 de marzo 2015
UPME
Ciudad de Bogota, Republica de Colombia
Climatic corrections:
methodology and examples
Bruno Lapillonne, Vice President, Enerdata
Outline
1. Heating
2. Air conditioning
Climatic corrections : heating degree days

The number of heating degree days is an indicator of the winter severity, and
thus of the heating requirement.

It is calculated as the sum over each day of the heating period (e.g. October to
April) of the difference between a reference indoor temperature (usually 18°C)
and the average daily temperature: If the average temperature of a day in winter
is 5°C, the number of degree day of that day is 13 degree days (18-5).

The number of degree-days in EU countries is in a range from 700-800 degreedays for Cyprus and Malta to 4000-5000 degree-days in Nordic and Baltic
countries; ( EU average around 2800 degree-days).

The daily outside temperature is measured from various meteorological stations
and averaged to get a national value. This national average should be population
weighted as it is more representative of the heating requirement in the
country.
2 winters much colder than a normal winter (2010 and 1996) and 4 winters much warmer
(2011, 2007, 2000 and 1990)  very strong reduction in number of degree days between
2010 and 2011 (-16%!) and in the actual average consumption per dwelling (-12%).
This shows the importance of analysing energy consumption trends at normal climate (i.e.
with climatic corrections)
Climatic variations in winter : number of heating degree days (EU)
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
3400
3200
3000
2800
2600
2400
2200
2000
Actual
Normal
The
) heating degree days represents the number of degree-days for a normal winter or an
average winter; it is based on a long-term average of degree-days value. Eurostat uses a 25 years
average (1980-2004); some national data are based on a 30 years average.
4
Climatic corrections : methodology
Climatic corrections are done in a linear way on the space heating
consumption on the basis of the ratio normal degree days actual degree
days
 for countries with yearly data: direct correction on space heating
consumption
 for other countries , corrections on the space heating part of the
consumption estimated from an exogenous and constant heating share
Climatic corrections : Methodology
 Countries with heating consumption data)
SH=SHn x (DD/DDn) or SHn= SH x (DDn/DD)
(by fuel)
 Countries without annual space heating consumption data
E = En x (1-K)+ En x K x (DD/DDn)
or En = E x 1/ (1-K x (1-DD/DDn))
with K= heating share for normal year
or K= r x a with r = heating share for normal year and a = share of heating
dependant on degree days (eg 90%)
Climatic corrections: case of EU (heating)
Smoother variation of the household energy consumption per dwelling at
normal climate, with a regular decrease since 2000
Specific consumption per dwelling : actual value vs climatic corrected (EU)
2,0
110
1,9
100
1,6
1,5
95
1,4
90
1,3
1,2
actual values
at normal climate
degree days
85
1,1
1,0
80
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
toe/dwelling
1,7
Normal climate =100
105
1,8
The number of heating degree-days measures the winter severity ; normal climate
(30 years long term average )
7
Climatic corrections: case of France (heating)


In France climatic corrections are done in all official statistics and in the energy
balance for all energies used for space heating (gas , electricity, oil);
For electricity, as electric heating is significant (12% of electricity consumption),
climatic corrections are necessary to get the real trend in electricity use.
Trends in electricity consumption in France
10%
Real
At normal climate
5%
0%
-5%
-10%
2008/2009 2009/2010 2010/2011 2008-2011
•For instance in 2010,
electricity consumption
increased by almost 6%. At
normal climate (i.e. with
climatic corrections), the
growth is only 4%, as 2010
winter was rather cold: thus
the climate explains 2% point
of growth (i.e. one third ).
•In 2011, this is the reverse
phenomenon because of a
mild winter. consumption
dropped by almost 6% but with
climate corrections it only
dropped by 2.4%
Outline
1. Heating
2. Air conditioning
Cooling degree days
 The number of cooling degree days is an indicator of the outside
temperature, in summer or during the period of high temperature and
thus of the cooling requirement.
 It is calculated as the sum over each day of the cooling period of the
difference between the average daily temperature and a reference
temperature.
 The calculation of cooling degree days is common in the US where they
used 65°F (18°C as a reference). This reference may be too low for other
countries and should be adapted taking into account the present comfort
habits and living style; a higher temperature may be more relevant (e.g.
26°C).
Cooling degree days: national values
 The number of cooling degree days correspond to the national average,
calculated from average of different climatic areas, as a population
weighted average.
 In the US, cooling degree-days are published by States and for the whole
country. Temperatures, recorded by weather stations,
are used to calculate State-wide and national degree-day averages
based on resident State population.

The mean cooling degree days , also called normal degree days
represents the number of degree-days for a normal summer; it is based
on a long-term average of degree-days value (e.g.30 years in the US) ((see
table below)..
http://www.eia.gov/totalenergy/data/annual/index.cfm#summary
Cooling degree days: calculation as a population
weighted national average: case of the US
New
Middle
Year England Atlantic
362
587
2009
657
997
2010
Norm
al
441
665
East
West
North
North
South East South West South
Pacific United
Central Central Atlantic
Central
Central
Mountain
States
547
720
2 025
1 497
2 570
1 504
884 1 229
975 1 123
2 267
2 004
2 750
1 450
655 1 457
731
949
1 982
1 564
2 477
1 308
755
1 242
Climatic corrections for cooling : methodology

Linear correction of the air conditioning consumption on the basis of
the ratio normal degree days actual degree days

Corrections on the cooling part of the consumption estimated from an
exogenous and constant share for a normal year

E = En x (1-K)+ En x K x (CDD/CDDn)  En = E x 1/ (1-K x (1CDD/CDDn))
with E actual electricity consumption
En electricity consumption at normal climate
K= share of cooling in power consumption for a normal year (e.g. 20%
for households in the US)
CDD: actual number of cooling degree days
CDDn: number of cooling degree days for a normal year
Climatic corrections: are they necessary? Case of
the electricity consumption in the USA for cooling
 A climatic correction is only useful if the need for cooling can change a lot
from one year to the other and explains variations in the electricity
consumption from one year to the other
 Climatic correction: for 2010: En = E x 1/ (1-K x (1-CDD/CDDn))
= 1418*1/(1-0.2*(1-1457/1242))= 1418/1.034= 1371
Year
Cooling
degree days
(US
Average)
Climatic
index
(cooling)
Electricity
consumption
(TWh)
Electricity
consumption
(TWh) at normal
year (summer)
Normal
2009
2010
Variation
2009/2010
1242
1 229
1 457
100
99
117
1362
1418
1365
1371
+19%
-19%
+4.1%
+0.4%
In the USA climatic correction is also necessary for heating but less important
(9% of electricity consumption
Electricity consumption at real and normal climate:
impact of climatic variations
Climatic corrections on electricity specific consumption depend on the weight/share of
electricity in AC and depend on climate
Specific electricity consumption per household and cooling climatic index (kWh/household):
Case study of Panama
2600
150
130
2200
2000
110
1800
90
1600
1400
Climatic Index
kWH/household
2400
70
1200
50
1000
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012
kWh/dwelling (at real climate)
kWh/dwelling (at normal climate)
climatic index (air conditioning)
15
Climatic corrections: case study of Panama
Trends in electricity consumption with and without climatic corrections (%/year)
5%
4%
3%
2%
1%
0%
2000-2007
Real
2007-2012
At normal climate
2000-2012
Combined climatic correction of electricity consumption
for heating and cooling
Climatic corrections on electricity specific consumption depend on the weight/share of
electricity in space heating and AC (for instance 10% each in this example), and depend
on climate (for instance moderate climate in winter and summer)
kWh/dwelling (at real climate)
kWh/dwelling (at normal climate)
climatic index (space heating)
climatic index (air conditioning)
2010
2009
2008
2007
2006
2005
2004
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
1991
1990
Specific consumption per household and space heating climatic index (kWh/household) (Country X)
5000
150
4500
140
4000
130
3500
120
3000
110
2500
100
2000
90
1500
80
1000
70
500
0
60
17