Your location and the time of year of an EMP event both make a big difference in how much food you need to store. Most people who have thought about this conclude that Spring is the worst time for an Event, since loss of power would interfere with the planting. If you live in the corn belt, then the best time for an Event is right after the harvest, but before the corn is packed and sent off to processing plants out of state. In theory, you wouldn’t have to store much food if you live near a grain silo, especially if the silo has just been filled.
If you live in a big city, no amount of food storage is going to ensure your longterm survival, because eventually it will run out and you’ll have to move to the countryside.
I live in Oregon, where most of the fields are growing grass seed, so for me the least harmful time for the Pulse to occur might be prior to the planting in May. The Pulse would induce farmers to plant more food crops. In my part of Oregon, not much food is stored locally, so storing food to last until the next harvest is important. I figure I should store a year’s worth of food, just in case the Pulse occurs too late in the summer to allow extra food crop plantings. If I store enough food for 8 people for 1 year (8 people-years), and then the Pulse occurs in May (3 months until harvest), then I can instead feed 8 x 12/3 = 32 people with that same amount of food.
No matter where you live, eventually all stored food will run out, and there will be a shift to food planted after the Event. So it may be worth thinking how we can make sure that farms get the seeds, water, and tractor fuel they need to remain productive.