How Century Saras put sunshine to best use

Century Saras apartment's story of moving to solar power can be a guide to others who want to beat power hikes and save the environment

For the third time in the past five months, ESCOMs (electricity supply companies) in the state have sought an increase in power tariff,  to make up for a revenue gap of Rs 3,556 crore. 

The hike will be a double whammy, as the BWSSB (Bangalore Water Supply and Sewerage Board) has said that a hike in water charges will be inevitable (BWSSB spends Rs 70-80 crore of its Rs 115 crore revenue on electricity charges).

While the power hike pinches one and all, it is particularly so for apartment complexes. Besides personal consumption, residents in apartment complexes also share the cost of common area assets such as lifts, lighting, Water Treatment Plants, etc.

Besides the “inevitability” of higher tariffs, the likelihood of a change in policy post-March — which could burden consumers further — is driving apartments in Bengaluru to tap an alternate source of power, solar energy. Those who have already made the switch vouch that rooftop solar systems have led to huge savings in their maintenance costs, offsetting any rise in power tariffs.

Read more: Bengaluru apartments rush to install rooftop solar panels ahead of likely policy change

Century Saras, an apartment situated in North of Bengaluru is a recent entrant to the rooftop solar club. A Bangalore Apartments’ Federation member,  the Century Saras Apartment Association went about this sustainable solution in a systematic manner — from involving experts among the residents, collecting data, computing it, choosing a vendor and installing it — all in a matter of a year and a half. The installation was commissioned on World Environment Day, 5 June, 2020.

The Association went one step ahead to make it a world-class project. They got an audit done by UL (Underwriter’s Laboratory), making Century Saras the only apartment project in India to do so, and also meet IEC 62446-1 standard.

Citizen Matters interviewed Satish Mallya, General Secretary, Century Saras, on how their apartment association went about installing the system, why it makes sense for others to follow suit and what problems to look out for.

Excerpts from the interview:

You are one of the early implementers of  Rooftop Solar, what factors propelled you to do it? 

There are many factors. To start with, a renewable source of energy is free and infinite. We are contributing to the environment. We are reducing our carbon emission by 73 tonnes per year. 

There is a cost saving too. The initial investment is high but after a payback period of less than 5 years the power generated is almost free. The apartment’s maintenance cost will reduce by 20% due to reduced electricity expenses.

Also, the rooftop solar power plant itself is very low maintenance. What’s more, its major component — solar PV modules —  come with a warranty of 25 years. 

What are the factors that need to be looked into while deciding on going the solar way?

Our motto was “Let the sunshine be put to the best use”. The factors, in terms of area and surroundings, that require consideration are: 

  • 1 kWp solar power plant needs approximately 100 square feet of shadow-free area on the roof. Accordingly, for 50 kWp, about 5000 square feet space on the rooftop is needed.
  • 1 kWp solar power plant needs approx 100 square feet of shadow-free area on the roof. Accordingly, for 50 kWp,  about 5000 square feet space on the rooftop is needed.
  • Shadow causing objects on the rooftop like lift rooms, staircase rooms, etc. need to be checked. 
  • In dense urban areas, any shadows from nearby buildings or constructions also need to be checked.

Asset creation in an apartment complex is a complicated process, can you take us through how you went about it?

In October 2018, when the new managing committee took over, they created a  solar project group, a team of technical and financial experts from amongst the residents. They had brainstorming meetings every Sunday on data to be collected and evaluated the technologies available in the market. 

Data on average monthly energy consumption for the common area for the past one year including all amenities was collected. Energy requirements for the common areas including amenities were calculated. Cost projections — budget, payback period — were made. 

The Century Saras solar implementation team (left to right): Kiran Kumar, Sidharth Nayak, Shivanand Prabhu, Satish Mallya, Amit Gaitonde, Ramachandra Allipur, Hemant Pai, and Shashi Kumar

What was the methodology followed in collating information for the feasibility report?

The first step was data collection from internal and external sources.

  1. Internal data collection and sources were BESCOM electricity bills for the 12 months; nameplate ratings of existing electrical equipment or loads for common areas and utility loads; and electrical single-line diagrams of apartments. 
  2. Data on BESCOM infrastructure: This involved identification of main power supply source from BESCOM and understanding the same; HT, transformer and main LT ratings and characteristics; and BESCOM metering of apartments for payments to BESCOM and areas of measurement for each meter.
  3. Measurements
    • Identification of loads in common areas and utility for RYB (Red, Yellow, Blue) status for phase to phase and phase to neutral.
    • Measurements of earthing load in common areas and utility. 
    • Measurements of space available on the roof.
    • Observations of various loads, ratings, earth and preventive actions for possible safe-guarding of equipment life.
    • Feasibility of solar and energy generation potential.        

What was the evaluation criteria?

The feasibility report is based on BESCOM’s policy. 

  • BESCOM policy: We have to first look at solar systems approved by the Government of Karnataka through KERC (Karnataka Electricity Regulatory Authority) and BESCOM guidelines and rules for interfacing with the grid under rooftop grid tied systems.

    These are grid connected systems with no batteries.

    The solar grid connected system works only when BESCOM grid is available and not during power cuts. During power cuts, for safety reasons, solar plants go to sleep mode, and whenever grid supply is back, it again synchronizes with the grid and starts working automatically.

    As per recent circular from the Ministry of New and Renewable Energy (MNRE), apartments are eligible for up to 20% subsidy for systems above 10kW under consideration of use of ‘made in India’ panels as per norms and on commissioning of the solar power plant.

    DG Sync if done, is to be with the approval of BESCOM and generally not allowed unless protections are in place (and generally in manual changeover mode with reverse protections relays in place). If done, drawing approvals are also required from BESCOM.

    In case of the solar system only, if solar system size is higher than 50 kW DC, evacuation has to be done at HT viz via a transformer at 11 KV level and metering done at 11 KV HT.
  • Approval by BESCOM can be sought under two categories: Gross metering or net metering (see box). We preferred net metering because the savings on retail tariff is higher as daytime solar generation is used directly. We also recommend net metering from the perspective of long-term cost-saving. 

Gross Metering

  • One new additional uni-directional meter for solar is installed and the total solar units generated is measured and exported to the grid only. It cannot be used by customers during day-time.
  • At the end of the month, the main existing retail meter reading is taken and billed separately as usual.
  • Solar units measured under (a) above are credited separately at prevailing KERC tariff, which is presently for FY 2019-20 at Rs 3.07 per unit for capacity above 10 kW (without subsidy) and Rs 2.32 per unit (with subsidy) Only made-in-India solar panels can claim the subsidy. The bill dues are generally settled within 45-60 days by BESCOM.
  • PPA period is for 25 years as per KERC policy 2019-20.

Net Metering

  • One new bi-directional meter replacing the existing customer unidirectional retail meter under LT is installed. 
  • Additionally, either, a new solar generation meter uni-directional type is calibrated and fixed by BESCOM and a sealed or existing retail unidirectional meter is re-used, to measure solar generation. This is decided during the inspection by BESCOM.
  • The NEW bi-directional main meter records both retail consumption as well as solar export. Solar generation as available can be used for daytime loads in this. So, only the surplus gets exported.
  • At the end of the month, net-off reading (as the meter rotates both directions to record grid power as well as solar export) is billed at retail tariff. In case solar units are more, these are generally settled by BESCOM within 45-60 days at prevailing KERC tariff, which is for FY 2019- 20 at Rs 3.07 per unit for capacity above 10 kW (without subsidy) and Rs 2.32 per unit (with subsidy).

Once the feasibility study was done, the next step was to get a buy-in from the owners. So, we scheduled a special general body meeting where we presented our findings and got approval for utilising the corpus fund towards the project.

Solar is a 25 year purchase and clients need their vendors to provide service for this period, so it is very important to choose a solar vendor who has the financial strength and scale to survive in the market in the long term. It’s important to come out with a well defined Request for Quotation RFQ on technical specifications, after sales service, performance guarantees and company’s financial strengths. 

Cost considerations are an impediment to most projects of this scale. How did you overcome this?

  • The common amenities constituted 20-25% of the total maintenance charges.
  • To encourage people to go in for SRTPV, BESCOM had come up with a scheme which allows net metering under a PPA for 25 years.
  • The scheme would mean that our investment will result in a recovery of fewer than 5 years. Thereafter, the savings in electrical charges would directly result in a reduction of maintenance charges for the apartment.
Power expense 80-83% can be saved from 50 kWp Solar plant.

How effective is this on cloudy days, of which Bengaluru has a good share?

From the existing installations in Bengaluru, it is noted that a 1 kWp of solar power plant can generate 1350 kWh – 1500 Kwh (units) per year. There will be variations in solar generation across the summers, monsoon, and winter seasons but this annual average can be very reliably reached in Bengaluru’s climate.

Summers in Bengaluru (from March to June) produce the greatest amount of energy and this can be attributed to longer daily sunlight hours. Monsoons (from July to October) have lower generations due to intermittent rainfall and lower intensity sunlight due to cloud cover. Contrary to popular belief, solar generation in the low temperatures of winters (from November to February) works well.

Read more: Did Bengaluru really get excess rains in 2020?

The conclusion is weather-wise and irradiation-wise, Bengaluru is one of the most ideal cities for solar rooftop installation. This is backed by data from different solar rooftop installations in the city.

Underwriters Laboratory is a global safety and quality certification company headquartered in Northbrook, Illinois, with offices in 46 countries. A third party audit by UL was done for Century Saras solar plant as per IEC standard 62446-1 category 1. The system safety verification involved:

  • Basic system documentation and design review
  • Field inspection of the PV system components
  • Field testing of the PV system components

Also read:


  1. Suresh A Pai says:

    Team Century Saras deserves full credit for implementing Roof top Solar project involving substantial initial investment. The general reaction from any Resident Association is not to take any risk involving such huge amount . But the determination of the Managing committee of Saras needs to be applauded for installing the project , getting UL certification and seeing benefits in the initial months itself. This roof top solar project should be a role model for other apartments in Bangalore . Citizen matters should give good publicity for such cost and environment friendly projects !

  2. Madhukar Olety says:

    Nice to know the dedicated team work of century Sara to implement use of solar energy.
    I am very much interested to know the name of the firm that has installed the solar energy and also reviewe the working

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