Interpretation of energy efficiency indicators from BIEE

Bruno Lapillonne, Vice President, Enerdata

Reunión Técnica de Trabajo del Proyecto BIEE24 – 26 de febrero, 2014, San José, Costa Rica

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BIEE indicators are aggregate indicators that enable to monitor energy consumption and energy efficiency trends.

They are statistical indicators relating the energy consumption, total or by sector, to indicators of activity so called “top-down indicators”;

They are expressed in monetary units (energy intensity per unit of GDP or value added) and physical units (indicators of specific consumption);

Other energy efficiency indicators relate to data collected at a micro level, at the levle of buildings factories or transport companies from reporting of large consumers or surveys; they are referred to as “bottom-up” indicators;

Both types of indicators will often be expressed in the same unit: for instance kWh/m2 for buildings only their scope and interpretation will differ.

BIEE indicators: what are they ?

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Change in BIEE indicators can be used to assess energy savings.

The more detailed the indicator, the more accurate will be the evaluation;

Anyway, even with detailed indicators, the calculated savings will not reflect the impact of EE policies alone, but the effect of different factors, of which EE policies (autonomous trends, energy prices, other effects).

Bottom-up indicators are more relevant to assess the impact of a specific energy efficiency programme or measure but require a specific data collection and are thus more costly to develop.

This is why at European level, the EU Commission has left the choice for national government to report their energy savings with top-down indicators, such as BIEE ones or with bottom –up evaluation.

BIEE indicators: what are they used for ?

1. Instead of showing annual trends with multiple fluctuations that are always difficult to explain, summarize trends by homogenous period

20002001

20022003

20042005

20062007

20082009

20100.00

0.05

0.10

0.15

0.20

0.25

0.30

How to analyze trend in energy efficiency indicators?

2000-2004 2004-2010-5%-4%-3%-2%-1%0%1%2%3%

Summarise trends by homogenous periodAvoid showing too many yearly variations

0.150.160.170.180.190.200.210.220.230.240.25

2. To identify the periods, show as much as possible on a same graph the trends in the different factors (e.g. economic growth, price trends , …) :

i. In index as they are expressed in different units

How to analyze trend in energy efficiency indicators?

19901992

19941996

19982000

20022004

20062008

2010100

120

140

160

180

200

220

consumption GDP

1990

=100

3. Pay attention to the scale: this affects the vision of the real change

20002001

20022003

20042005

20062007

20082009

20100.10

0.15

0.20

0.25

0.30

How to analyze trend in energy efficiency indicators?

Smooth the yearly variations by well selecting the scale on the vertical axis : well balance the space above and below the curve

20002001

20022003

20042005

20062007

20082009

20100.150.160.170.180.190.200.210.220.230.240.25yes no

Variations over time of energy efficiency indicators are usually expressed in average annual growth per year (%/yr) over a period.

The average annual growth rate (agr) for energy indicator I between year m and n (% per year) should be calculated as follows: agr= ((In/Im)* (1/(n-m) – 1)*100

as In= Im (1+agr) n-m (with)

Trends in energy indicator (%/year)

1990-1995 1995-1998 1998-2004 2004-2010-5%-4%-3%-2%-1%0%1%2%3%4%