Every March, the clocks in the UK are advanced by an hour. It's the start of daylight saving time (DST). The purpose is to save energy by utilising more daylight and correspondingly reduce the use of artificial light. Will this strategy work in India where demand for power exceeds supply?

Since the early 1980s studies have been undertaken to evaluate various time-based measures for energy conservation. These included adoption of DST for six months (April-September), advancing IST by 30 minutes (i.e. GMT+6 hours) during the summer. The possibility of demarcating the country into two time zones was also studied. The difference in sunrise/sunset time between East and West is two hours. Therefore, Zone 1 would comprise northern, western, and southern grids and Zone 2 would comprise eastern and northeastern grids. It was expected that this division would stagger the coincident peak loads of the zones thereby, reducing the aggregate peak capacity requirement in the country.

Studying the impact of energy savings in time zone 1
Studying the impact of daylight saving time in northeastern India
The TERI team undertaking a survey at a village in Varanasi (left) and Meghalaya (right) to determine the impact of time zones in the country

A 1988 TERI study for the Government of India's Advisory Board on Energy had explored these issues only to reveal a nominal saving potential-both in terms of energy and reduction in peak load. The range estimated under different scenarios was less than 1% in peak savings and energy consumption. However, it commended a periodic evaluation of these options taking in to account changes in demand, prices and consumption patterns. In 2010-11 TERI undertook another study to evaluate the energy savings potential for similar time-based measures. The findings of the study are discussed here.

A key measure of evaluating time-based energy conservation lies in quantifying its impact on the lighting load since the latter constitutes 12-17% of morning and evening peak consumption depending on the season (as a 2007 TERI study for the city of Delhi indicated). As sunrise and sunset times differ for any particular place, so does the use of artificial lights. Besides, the usage of artificial lighting load is primarily dependent on individual lifestyle, habits, and building facade (other factors being, availability of daylight, household size, use of curtains, climate, awareness about energy efficient appliances etc). To understand this, survey and stakeholder interviews were conducted across the entire geographical extent of the country.

What did the study indicate?

The analysis of sample data and grid-level load curves showed the following:

  • The addition of half-an-hour to IST does not amount to significant saving of energy. The net energy savings was estimated to be in the range of 1.02-1.10 billion units, which is a mere 0.14-0.15% of total electricity availability (CEA, 2009-10. All India Electricity Statistics). The total yearly energy savings potential during summer evenings due to delay in sunset was estimated to be in the range of 1.81-2.45 billion units. And the total additional lighting load (energy losses) required during winter morning because of late sunrise, was estimated to be 0.79-1.35 billion units.
  • The net savings potential through implementation of DST was estimated to be in the range of 0.69-0.84 billion units.
  • The demarcation of the country into two time zones indicated no significant influence on peak capacity demand. It was estimated that the extra energy consumption at all India level would be in the range of 0.54-0.64 billion units. The energy benefits estimated in Zone 2 (eastern and north-eastern) were 0.26-0.36 billion units. The aggregate losses are caused by extra consumption in Zone 1, which constitutes nearly 74% of India's population.

The reasons why time-based measures are not a viable proposition for energy conservation are:
Month-wise energy savings by adding half-an-hour to IST Figure 1: Month-wise energy saving
potential in India by shifting IST by
Energy consumption at peak hours across India Figure 2: The share of different regions
on all India peak days
The demand for energy reaches its peak well after sunset Figure 3: All India load curve depicting
energy savings and peak capacity
  • During winter months days are shorter. Due to delayed sunrise, there is a surge in lighting load in the mornings which negates the reduced demand in the evenings (Figure 1).
  • Many residential and commercial buildings surveyed were not designed to optimally utilize available sunlight.
  • The usage of curtains in buildings in hotter regions and congested urban areas hindered sunlight penetration and hence increased the usage of powered lights.
  • The survey showed that the use of energy efficient lighting is limited. Besides, with rising incomes, the use of energy intensive appliances like ACs has increased, thus decisively undermining the significance of lightning load as a proportion of the total load.
  • An analysis of the electricity load curves revealed that the evening peak period which stretches for more than an hour, and in some months, occur well after the sunset time. Therefore, a half-an-hour shift in the clock would not significantly impact the capacity requirement to cater to the peak demand (Figure 2).
  • The load curve reveals that the evening peak in most of the months occurs well after sunset (Figure 3) when most people return home but the impact of shifting clocks is limited to half-an-hour past sunset. The savings potential is higher in summer as days are longer and more people have already returned home before sunset (Figure 1) as compared to winters.
  • Two time zones fail to provide positive results as states in the northeast and eastern grids (Zone 2) together constitute a mere 12-13% of the national peak over the year and with a one-hour relative shift with respect to Zone 1 has negligible impact (Figure 2).
  • With a major share of the Indian population being on the left of the IST (with eight of the most populous states lying to the West of IST), IST can be called 'optimally situated' from the point of view of utilization of daylight for the maximum number of people in the country.
  • The study also indicates that many lack awareness and, thus, fail to use artificial lights judiciously.
  • The energy efficiency initiatives on the lighting front like Bachat Lamp Yojana, etc would further bring down the benefits


The TERI study does not find substantial value in investing in any of the identified options - shifting IST, adopting DST or demarcating the country into time zones. However, this study was essentially based on the evaluation of energy consumption and did not factor in wider social dynamics, costs and benefits of deploying these time-related instruments. But prima facie, it appears that the social costs on account of biannual adjustment (DST) and coordination between the two time zones may offset the savings to a large extent.

Duration of the project: 9 months
Key Stakeholder(s)/ Beneficiarie(s): Bureau of Energy Efficiency, Ministry of Power, State Electricity Regulatory Comissions, Electricity Utilities

To evaluate energy savings potential under the following circumstances:

  • Shift in IST i.e. advancement of IST by half-an-hour;
  • Implementation of DST for six months (April-September);
  • Establishment of two time zones in the country based on the existing regional electricity grids. (Zone 1 comprising northern, western and southern grid and Zone 2 comprising Eastern and Northeastern grids).
Findings of the study

To evaluate energy savings potential under the following circumstances:

  • Net energy savings by shifting IST by half-an-hour are estimated to be in the range of 1.02-1.10 billion units, a mere 0.14%-0.15% of total electricity potential.
  • Demarcation of the country into two time zones indicates no significant influence on peak capacity demand. It is estimated that in spite of positive savings in Zone 2 (0.26-0.36 billion units) extra energy consumption would be in the range of 0.54-0.64 billion due to high magnitude of losses in Zone 1 (caused due to extra half-an-hour of evening darkness) which constitutes nearly 74% of the populace.
Other studies that corroborate the findings
  • A 1988 TERI study for the government of India's Advisory Board on Energy estimated that the benefits arising out of introduction of time zones or advancing clocks in the country were small. The range estimated under different scenarios was 0.3-1.0% in peak savings and 0.04-0.7% in energy consumed. The study also pointed out that given the existing transmission infrastructure, the scope for load levelling was unlikely. The study recommended that the potential impact of deploying these options be evaluated periodically. This is because, as demand grows, price change and consumption patterns vary.
  • In 2001, a four-member committee under the ministry of Science and Technology examined the scope of multiple time zones and daylight saving time. It rejected the implementation of DST. It also concluded that countries around the equator have marginal seasonal difference in daylight hours compared to those near the poles.
IST and time zones A map of India showing the major power grids and the distribution of population. 75 degrees East longitude and 90 degrees East longitude, each indicate Zone 1 and Zone 2 respectively. 82.5 degrees East longitude denotes the IST.