Electricity Saving Tips For Homes And Offices

Street lighting and General Illumination options for residential complexes: HPSV, LED, Fluorescent and Solar

By on April 26, 2018

Street lighting and general illumination is very important for security in all residential complexes. Parking lots and pathways should be lit uniformly as it provides a sense of security. Although lighting may be a small portion of a residential complex’s electricity bills but it is a very important aspect for the well being of the residents. Lately with rising electricity bills, management committees of various residential complexes have started thinking about various ways of cutting down the electricity bills and interestingly their first target is lighting. So we thought of giving some idea about various options that are available for street lighting at various places.

Specifications of effective street lighting or general illumination system

Bureau of Indian Standards (BIS) has set specific standards for street lighting at various locations (can be accessed through http://www.standardsbis.in/Gemini/home/Home.action). But here are the general things that one should consider while setting up a lighting system:

  1. High Lamp Efficiency: Try to get more lumens (or brightness) per watt of energy.
  2. Cost Effectiveness: Low operating costs.
  3. Life of the system: More the life is better.
  4. Good Color Rendering: Helps object appear more natural and pleasing.
  5. Proper light distribution: Provides light in the right areas.
  6. Proper aesthetics: Blends with the surroundings.

Retrofitting an existing system and various types of lighting options available

The builders build most residential complexes and we hope that they follow the standards from BIS. The real challenge starts when a society takes over which becomes responsible for payment of electricity bills and maintenance of the system. In some cases lack of information makes them pick up wrong choices. So first let us look at various options that are available:

  1. Halogen (Mercury Vapor) Lamps: These are most commonly used lamps for pole lighting and street lighting. They provide very less brightness per watt and thus a higher wattage bulb is required. Most common streetlights use about 150-180 Watts Mercury Vapor lamps. They also have less lamp life of about 10000 hrs.
  2. Sodium Vapor lamps: These are the energy efficient options for halogen lamps as they provide double the amount of brightness for the same amount of wattage. These are also ideal for pole lighting. They have a few drawbacks though: a) their brightness is highest in the center (just below the pole) and is lesser on the outside. b) they are mostly yellow or orange in color. Still if a Halogen is replaced with Sodium Vapor lamp, 20-25% savings can be achieved. It also has high lamp life of 18000-24000 hrs.
  3. Metal Halide lamps: These bulbs are as energy efficient as Sodium Vapor lamps and also come with whiter lights but their life is less (8000-12000 hrs).
  4. Fluorescent Lamps: At many places tubelights are used for lighting and general lamination. Tubelights in general are available in lower wattages and they cannot produce the same kind of brightness as a Halogen or Sodium Vapor lamp. So they should not be used to replace Halogen lamps, as they cannot produce the same amount of brightness. But if any complex has existing lighting system using old T12 or T8 tubelights, then it can benefit by replacing it with T5 tubelights. Please note that CFLs should not be used for larger areas, as their brightness per watts is less than tubelights. T12 or T8 tubelights have a life of 5000-10000 hrs but that of T5 tubelights is 15000-20000 hrs.
  5. CFLs: These should be used only for lighting small areas. They are replacement for incandescent bulbs and not of tubelights.
  6. LEDs:  These are the latest and most energy efficient options available in the market for street lighting. Their brightness is much more uniform and can give up to 50% savings over Sodium Vapor lamps. But they are very expensive to buy with longer paybacks.They also produce less glare and can reduce visual fatigue for drivers and pedestrians. LEDs are also available with solar option that can be an attractive and cost saving (but again one has to evaluate the payback period and should be ready for the same). Typically they are rated to last for about 25 years, but as per feedback from some of our readers it needs to be protected from rust and insects to last longer.

Retrofitting ideas

For Pole Lights:

If pole lights have halogens (150-180 W) then the most ideal replacement for them is a High Pressure Sodium Vapor lamp (70 W) or a similar wattage Metal Halide lamp. This can give up to 25% savings ( electricity is consumed by ballasts also) which can be up to 16 units a month for 12 hours of use per day which roughly converts to Rs 100-150 saving per light per month at average cost of electricity in India. If LEDs are used as replacements then a 48W LED panel is ideal for replacement of a 150-180 W Halogen. CFLs should not be used for replacement on pole lights.

For Old Tubelights:

Wherever old tubelights are there in the complex, they should be replaced with a 28 W T5 tubelight. It gives straightaway 40% savings (or 4-8 units per month for 12 hours use per day which roughly converts to Rs 30-80 saving per month per tubelight at average electricity rates in India). This gets paid back within a year of use.

Parking Areas:

T5 tubelights are again better for parking areas. Halogens or HPSV lamps are too bright for parking areas and T5 tubelights can provide better options. A T5 tubelight is good to cover about 300 sq ft of area.

For other common areas like floor lighting etc

If the areas are big, T5 tubelights can be good. If areas are small (less than 200 sq ft), 20W or less CFLs can be considered.

Using Solar Street Lighting

Solar street lighting is a very promising street lighting option that is coming up these days. Using solar one can completely avoid using electricity from grid for a few months in a year. To find out how much you pay for a streetlight you can use this simple calculation:

If there is a 180 W halogen lamp that is kept on for 12 hours in a day then the cost of using it is:

Units per day = (180 x 12)/1000 = 2.16

Units per month = 2.16 x 30 = 64.8 units

Most residential societies get electricity at the highest tariffs, as their overall consumption is high. Highest tariff rates vary from Rs 6 to Rs 10 across the country. So the monthly cost of using a streetlight is:

64.8 x 6 = Rs 389 to 64.8 x 10 = Rs 648

If a solar replacement can be used for 10 months then it can reduce Rs 3890 to Rs 6480 per year. Looking at the cost of solar streetlights, they come with about 4-6 years of payback period (at current rates).  But the rates of electricity are increasing every year and thus it may come down to 2-3 years after a few years of use.

Most solar LED systems last for 25 years if maintained well. One just has to make sure that the batteries are replaced on time (batteries may last for 2-5 years) and panels are clean.







About the Author:
Abhishek Jain is an Alumnus of IIT Bombay with almost 10 years of experience in corporate before starting Bijli Bachao in 2012. His passion for solving problems moved him towards Energy Sector and he is keen to learn about customer behavior towards Energy and find ways to influence the same towards Sustainability. .

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