What is needed to hook up a Propane Gas grill to a natural gas line?

go to the Weber web site and order a conversion kit. Gas appliances come preset for one type of fuel if you change it to a new fuel you only want the manufactures parts to do it as a gas leak could get messy. You need a new burner (the orafices are smaller for nat gas) New line regulator as you will be hooking up typical a short flex whip from a gas cock nearby. but now with a simple change of burner you can go from natural to propane any time you want.

You need to change the burner orifice and the regulator. Call Weber repair ,they probably make a change over kit . It is safer to have them do it for you do it for you .They will test for leaks and assure that it is safe to use . also sears repairs weber grills an they sell parts.

You need to change the orifice and regulator. Some times depending on your area, your natural gas company will do this free obviously so you will use more natural gas.

Burner injectors, aeration, and supply pressure are all factors involved in using gas appliances with different families of gases. Unless you are qualified, it is illegal in UK to carry out such work. Gas is a dangerous product for DIY enthusiasts. Seek professional advice.

you just need Flare fittings and some dish soap to check for leaks when finished, if you kinda know the copper size line then a hardware person should be able to help you (i prefer the help at my local Ace store)

If the gas jets are adjustable, you may be able to just adjust them, if not, you will need new gas jets but they are not expensive.

you will need to change the orifices in the grill

Orifice change and regulator.