New York, Feb 28 (IANS): If you are mulling buying an electric car to cut on travelling costs and save the planet, consider the factor of geography with new research pointing to regional energy sources and climate greatly affecting emissions and driving range.

Even as governments across the globe -- including the Indian government that provided fresh budgetary allocation for electric vehicles recently -- are encouraging the use of electric vehicles to save the environment, researchers have found that emissions and driving range can vary greatly depending on regional energy sources and climate.

Most electric car models can only go about 100 to 160 kilometres on one charge in optimal conditions. The overall vehicle efficiency decreases at cold and hot temperatures.

Based on a study of a commercially available electric car, researchers at the Carnegie Mellon University, at Pittsburgh in the US, developed computer models that incorporated information on vehicle energy consumption, temperature and driving patterns from Nissan LEAF drivers.

Their analysis found that because extreme temperatures affect battery efficiency and the use of air conditioning or heating, the electric car's driving range could fall from 100 kilometres down to 70 kilometres on the most frigid days in cold regions.

Temperatures above 38 degrees Celsius can have a similar effect. Also, regional differences in electricity sources played a role in the vehicle's emissions, they found. The researchers conclude that geographical differences are large enough that they could influence the energy implications of electric vehicles.

The study was published in the journal Environmental Science & Technology.