Whats a Maff rating on a microwave?

I`m not sure if this is the right place for this question but as the title says What`s a Maff rating?

I`m looking for a new microwave and they all seem to have this followed by a letter, if it`s something like energy efficiency which letter is better?

I`m really out of touch as my last microwave has just given up after over 18 years so i hope someone out there is in the know.

I think its the letter rating that they use alongside the wattage.

An 800W microwave is rated E for example. Never fully understood it.

Thanks !

That explains why most of them i`ve been looking at have a rating of E!

Ministry of Agriculture, Food and Fisheries (now DeFRA) power consumption rating for Microwave ovens - A is the lowest rating, E is the most powerful.