I bought a Generator from SAMIVA Limited at Adjiringanor / East Legon (closer to Boundary Road).
To your questions:
1. They can certainly come and survey your place and recommend required size of Generator, I am not sure if their might be a charge on this service though.
2. For their prices, I did look around a bit but could not find a better offer, this was the ultimate reason to buy from SAMIVA (besides the warm reception at their office).
3. Their Generators run on diesel, it depends what size of generator you purchase but each generator has a max. and min. fuel consumption rating.
4. They also offer generators for rent. You must pay for transportation of the generating set and you must pay for fuel.
I must add, that I experience an outstanding sales service and maintenance, both in price and quality.
They also have stabilizers and UPS to protect Fridge / Freezer. They also cater professional equipment to TV Stations, Radio Stations, Banks, Hospitals and Communication Providers.
Just google SAMIVA for their website or visit directly samivaltd.com
Hope this helps ^^