Author: Kapiel Dongle, Business Head, Fourth Partner Energy Pvt. Ltd.

Residential Rooftop Solar Overview

Energy costs for residential buildings are telescopic in nature. As the energy consumption increases, tariff increases in corresponding slabs.

While commercial and industrial entities have adopted solar quite early, adoption of residential solar has picked up lately – Rising power costs and Government of India’s push towards solar adoption has played an important role. Residential Solar is expected to catapult from 130 MWp currently to over 10X in the next 5-7 years. **

In the long term, every rooftop is a generator of solar power. In countries such as Germany, rooftop solar on residential premises has been very successful. In 2014, solar energy covered approximately 7% of Germany’s net electricity consumption.

Evaluating the case for Rooftop Solar Photo-Voltaic System (SPV)

To help evaluate whether a residential rooftop solar system will work for a customer, the customer needs to consider several factors.

Firstly, availability of Sunlight – Is sufficient sunlight available for most of the day, throughout the year? India has one of the highest solar irradiation levels in the world and plenty of sunlight.

Secondly, availability of rooftop space for the system size needed – Is there sufficient shadow-free area on the rooftop? Typically, a 1 kWp system requires 100 sq. ft of shadow-free area on the rooftop.

Additionally, economics of the investment – Are the savings worth the investment? Savings depend on the customer’s cost of power and effective savings.

Lastly, the local permits required – What are the approvals/permits required from local bodies ? For an off-grid rooftop solar system, no approvals are required from any regulatory body. For grid-connected rooftop solar system, a No-objection certificate (NOC) is required from the DISCOM (power utility player) for the installation of Net Meter. Typically, the solar installer / RESCO (Renewable Energy Services Company) assists the customer in the process.

For typical residential houses, a system size ranging from 1-5 KWp single phase (according to the requirements) can be a suitable rooftop solar solution.

For residential societies / apartment complexes, a larger system is more suitable as the energy consumption is higher. The size of system depends on the available rooftop space – can be 10 kWp – 500 kWp. A 10 kWp system can support intermittent lift load, pumping load, common hall AC load, and lighting load during day time.


Key phases in the lifecycle of installation of Rooftop Solar Power Plant include System Design & Engineering, Construction of the Plant, Quality Check, Commissioning, Handover to Customer, and Post-installation O&M Services.

Components of Rooftop Solar System include Solar PV Module, Battery Bank (optional, for backup), Inverters (for AC Loads), Charge Controller, Wires and other accessories, Netmeter  (for grid-connected system)

Net Metering

In a grid-connected solar system, any excess solar power generated (units generated – units consumed from DISCOM) can be fed back to the grid.

Net metering framework is offered by a state under which the power provider (DISCOM) essentially pays you the retail price (as decided by the DISCOM) for the electricity you feed back into the grid.

So far, 25 states and union territories have put in place net-metering guidelines (draft and approved) for rooftop solar installations.**

Economics of a Residential Rooftop Solar System

The customer saves money through the generation of solar power. Other than the upfront cost of the rooftop solar system, there is minimal maintenance cost involved. The maintenance typically involves regular cleaning of the panels and ensuring no obstructions to the panels. The lifetime of a rooftop solar system is approximately 25 years.

A customer’s savings can be calculated using the following formula:

Electricity bill savings / year = (units generated / year) * (cost of power).

For example, a residential customer with a 3 kWp rooftop solar system and a residential power cost of Rs 5 / unit will save approximately Rs 21,600 per year.
(Also note that the power costs are continuously rising !)

Residential Solar – A Key Component of Smart Cities

The launch of Smart Cities Mission – under which the government plans to implement 100 smart cities and Atal Mission for Rejuvenation and Urban Transformation (AMRUT) – which is an urban rejuvenation programme for 500 towns, will trigger the process of urban transformation of India to enable better living.

Sustainable Environment is an important objective of both missions. Residential Rooftop Solar will act as an important agent in the urban transformation by harnessing the renewable energy source (solar) and reducing the emission of greenhouse gases such as COx, SOx and NOx.

Installing a 3 kWp solar system reduces the emission of COx (greenhouse gas) by 3700 kgs and is equivalent to planting 170 mature trees.


Adoption of Residential Solar is poised to grow significantly over the next few years – rising power costs and focus on sustainable development are enhancing the case.

It makes a good business case for Residential Buildings and Societies to go for Rooftop Solar. As the rooftop has zero opportunity cost it could be utilized to generate power and meet their electricity requirements – thereby using an idle asset.

In countries such as USA and Germany, solar plus storage solutions offerings have picked up significantly. Storage solutions (batteries) will play an important role in the adoption of residential solar in India.

New breakthroughs in Lithium-ion batteries and other battery technologies are enabling higher and more efficient energy storage. These batteries can be used to store solar energy generated from the rooftop – allowing for load shifting and providing back-up power – and in theory, enabling people to go entirely “off the grid.”

About Fourth Partner Energy (4PEL)

Fourth Partner Energy Pvt. Ltd. (4PEL) aims to build, develop and manage a large operating portfolio of de-centralized solar power assets in India and is positioned as a leading RESCO (Renewable Energy Services Company).

4PEL has completed over 400 solar installations across the country with several marquee clients. Customers range from a variety of industries such as educational institutions, corporates, hospitals, banks, industrial clients, and non-profit organizations.

Fourth Partner Energy (4PEL) started in 2010 with a focus on decentralised/ rooftop solar energy market. The company has a pan-India presence with offices in Hyderabad, Pune, Gurgaon, Chennai, Rajkot and Jaipur.

Web – Fourth Partner Energy

** Source: Bridge-to-India Report