There is no software that can calculate the rooftop surface area in a given city. You will to Google the city of interest and estimate the number of buildings in this city  (residential, commercial, or industrial). You can then multiply this number by an average roof surface area to get the total surface area. I've done that myself using Google search and it is so easy to estimate.

Hope this helps answer your question.

Professor Yehia Khalil, Yale University, USA

Fellow of the University of Oxford, United Kingdom

Dear Dr. Khalil, thank you for your answer it will help me a lot. I will go in this direction.

Best Regards

Ashraf F. Khalil

It depends on whether a 3d model of the city in question is available. If so you could search for, or even write a Grasshopper3d definition to assess it. It would be more precise. 

Kind regards,

Gustavo

I think you may use 'Calculate Geometry dialog box' in ArcMap. This should works smoothly if you have GIS files of the buildings in your city.

I never did that, but I had to used GIS files (shapefiles) to get streets central-lines on order to generate axial lines using Space Syntax approach into GIS. This was for a study of an American city where you can find all layers you need.

Option 2: If you are working for your city 'Benghazi' you may have to convert city's map to CAD files and then you can import them into ArcMap.

Option 3: you may have get DWG files of your city from googleMaps, (kml to dwg). Of course this is no accurate.

Dear Gustavo, Thank you for the answer, all the buildings rooftops are flat.

Dear Hadi, Thank you for your answer. Option 2 and 3 are helpful for me.

Dear José

Thank you for the valuable references. I appreciate your assistance.

Best  Regards

Dear Ashraf, 

At the company I work with I use Google Earth to calculate the roof area or the proposed area "by a tab measure tool" to design a PV system. It gives a decent accuracy to the real measurements. Then based on the measurements, and on different modules sizes,  one can work the total size system that can be fitted in a particular roof or area. 

Hope find this useful 

Regards, 

Tariq 

Dear Tariq,

Thank you very much for your answer. Yes this what we did for the initial assessment.

Best Regards

Ashraf