Each level is allowed to draw more power than the level below, G1 aims at 16-bit memory bus devices, while the G7 rating applies to devices with 192-bit or higher memory buses. Oddly enough, part of the regulation focuses on maximum memory bandwidth, rather than something more logical like "performance per Watt".
Nordic Hardware studied the documents and claims video cards classified under the G7 category will be required to have a maximum memory bandwidth of 320GB/s, meaning they can have a 384-bit memory with 6667MHz memory or a 512-bit bus with 5001MHz memory. Graphics cards that do not adhere to these specifications will face a sales ban in the EU, and Nordic Hardware reports AMD is quite worried that these new energy standards will prevent them from selling their next-gen high-end graphics cards in the EU.
The site also adds that Lot 3 will require higher energy efficiency, the exact details are still unknown, but a high-level source at AMD told Nordic Hardware that the company's current graphics card don't meet the requirements:
According to data NordicHardware has seen from a high level employee at AMD, current graphics cards are unable to meet with these requirements. This includes "GPUs like Cape Verde and Tahiti", that is used in the HD 7700 and HD 7900 series, and can't meet with the new guidelines, the same goes for the older "Caicos" that is used in the HD 6500/6600 and HD 7500/7600 series. Also "Oland" is mentioned, which is a future performance circuit from AMD, that according to rumors will be used in the future HD 8800 series. What worries AMD the most is how this will affect future graphics cards since the changes in Lot 3 will go into effect soon. The changes will of course affect Nvidia as much as it will AMD.The first Lot 3 requirements are expected to go into effect in 2013 or 2014, with further restrictions to follow in 2015.