Conventional coal fired electricity generation systems generate emissions of around 2 pounds of greenhouse gases per kilowatt hour; a solar panel, zero. While it varies depending on local conditions, an entry level system consisting of 1.5kW worth of solar panels (6-8 modules) can avoid around 3.2 tonnes of greenhouse gas emissions per year (compared to brown coal fired power generation).\
A coal-fired power plant uses around 1.5 gallons of water to generate a kilowatt-hour of electricity (source). A solar power plant uses none.
Solar panels can also act as rooftop insulators. The solar panels provide roof shading and helps in reducing the absorption of heat by the building. This in turn reduces consumption of electricity by air conditioning systems. It can be noted that the savings in cooling through a solar panel’s roof shading qualities amounts to a 5% discount on the cost of the modules over their lifetime.
From the point of electricity generation to the point of consumption, the more energy is lost, usually as heat. It’s estimated between 7 – 10% of all electricity generation in India is wasted through line loss; which means millions of tons of coal are burned each year for nothing. Rooftop solar power systems only have to transmit over a very short distance, not miles – and no coal is burned in the process.