How Many Btu's Are Needed To Get Grilling Temp To 1800 Degrees?

1800 Degrees will create charcoal, not a perfect steak.  If you need to grill at this temperature, try a blow torch.  Most Ruth's Chris Steak Houses use grills burning at approx. 400 degrees.  The signature 'crust' is a combination of higher heat cooking and thicker cuts of meat.

Try this tip from Vice President of Culinary and Purchasing for Ruth's Chris Steak House, Jim Cannon;

Steaks
- Start with high quality steaks, choice grade or better. Choose a center cut, like a fillet, rib eye or strip steak.
- Choose a cut with great marbling, the white ribbons of fat running through the beef. The fat will turn to liquid during cooking, keeping the meat moist and flavorful.
- Think thick. Ruth's Chris' signature is the flavorful crust on the outside of their steaks. A steak less than 1.5" thick will cook through before the outside is crispy.
- Season your meat with sea salt and fresh black pepper, drizzle with extra virgin olive oil and let it marinate for 10 minutes at room temperature.
- Let your pan or grill pan get very, very hot before cooking. If using a grill pan, sear for one and a half minutes on each side, transfer to a cast iron pan and cook in a 400 F oven 12 minutes for medium rare meat. The internal temperature of the beef should be 130 F. Or just do the whole thing in a cast iron pan and save time on cleanup

You probaly r not going to get a bbq grill that hot with out insulating the grill with bricks around the outside of the grill charcoal would be best alot of it