Angle grinder: what is the best power rating?

[LoungeLizard]

I rarely use an angle grinder but need one to cut through some concrete base fence panels (they're 1 foot by 6 foot by 1 inch).

Looking on the market I notice that the power rating varies from about 400 to 2000 watts.

Would anyone with practical experience of angle grinders care to make a suggestion? 

[zmudge]

For that sort of work you will need a 9" angle grinder rated around 2000 watts. Mine is 2300 watts. You will need a supply of 9" stone cutting discs, but if you have a lot to do a 9" diamond stone cutter is much better, quicker and easier but more expensive. Angle grinders are wicked things and kick when you start them and continue running when you switch them off. Therefore have a dry run practice before you start, and particularly plan where you might drop it if things get out of control, although it is better in this event to stand up straight, hold the thing at arms length, switch off and remain still until it has stopped. Goggles, mask, gloves and thick boots are essentials. Under no circumstances should anybody be closer than 10 feet to you whilst you are working. A lot of dust is produced, so plan for that also.