There are really two things - the first is load, how much current is being drawn at a given time - the other is total consumption (which I think is what you're looking for). It is pretty easy to figure out actually. Take whatever the car's pack size is and multiply that by the 40% or so that you're interested in. Most major appliances include energy usage information on them. I was just at home depot and saw a sticker on the inside of a new refrigerator and if I remember correctly it was estimated like 650kw/hr annually, so 54kw/h per month. Take that number you got earlier (let's say its 30kw/h if you're referring to a model 3) and compare it. So charging your car 40% is roughly the equivalent of running your refrigerator 2.5 weeks.
Oh I just saw your latest post about nay-sayers and the ignorant argument that EVs aren't practical because they put too much stress on the grid. I'd start that conversation by asking them what power company they work for... The power companies and grid have a maximum capacity that they can service but demand is not flat. It has peaks and valleys. The high demand times just so happen to be the opposite of when most people charge their cars. So peak capacity is totally irrelevant. A Tesla is the equivalent of running your dryer or air conditioner - except most charging happens at night, when its cooler, and the grid is in a low state of use.
But since all of these people are so concerned about protecting the power grid (which is odd since they don't seem to know anything about it) there's also the potential for electric cars to increase peak capacity by working as reserve banks of energy. Elon has talked about this, as have others, but in a nutshell your electric car plugged in at home or work could be used to power said home or workplace (or even beyond that) during peak hours of depend. Then recharge during off peak times. Effectively working as an overflow capacitor for the grid itself.
If you haven't already you'll run into someone reiterating the flawed argument that EVs just trade "one smoke stack for another" and the electric comes from fossil fuels so there's no difference to the environment. Wrong again - and even if we overlook that fact that electricity doesn't need to come from fossil fuels (while ICE vehicles clearly need them) it simply comes down to efficiency of using those fuels to do useful work. A coal burning power plant is much more efficient at turning fossil fuels into usable energy. Anyone who doubts that should spend a month powering their home with a gas powered generator and report back.