As I was listening to the How to Inspect Water Heater course I heard the instructors Ben and Kenton in more than one occasion say that the water heater cover is not needed and that it would void the warranty of the water heater. My question is: Would that apply in cold weather states as well and if so, should I remove the cover from my water heater or will I be losing some of the water temperature during the winter months?
Yes! They are worthless…
The heater already comes with all the insulation it needs.
You should remove a cover from your water heater, if you have one covering it. They are worthless…The heater already comes with all the insulation it needs. 
Like it or not it has been proven.
Adding a blanket to some brands of water heaters will actually void the warranty.
Just joking around, Roy. I luv ya brother! 
(I removed it.)
You to Brother Larry !
The analogy that works best for most people is the Thermos. You can think of your water heater as a giant Thermos. When you put your hot coffee/soup in the Thermos the outside remains cool to the touch as there is enough insulation to prevent heat loss/transfer. The same is true of your water heater.
Thanks everyone for all the answers.
Bert,
as the article says, “if you have an older hot water tank”. It is not necessary or a good idea for newer tanks. I will usually put in my report to budget for hot water tank replacement on tanks over 12 years old.
Where is this article on this?
David,
Go back to Bert Hulls post. He has a link to the article.
Yes, I agree. I don’t like the covers, myself. It makes it harder to inspect the tank, and often the data plate is covered. Like you, I also write a comment about budgeting for replacement soon when there is an older hot water tank.
I was looking for the publications on why insulation is not needed and voids warranty.
I can see the Mfg voiding a warranty (many do for not following installation requirements), but I can not agree with statements like “Added insulation is not needed.”
We talk about insulation in crawlspaces here in Tn where HVAC air ducts are located in the space. This is the same as a water heater. Depends where it is installed".
Rate of heat loss; Q = U * A * Delta-T.
A heater located inside the house is not the same as one out in the garage in Minnesota.
The “U” is not sufficient when there is a huge Delta-T.
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David, you are correct that a water heater in a un-conditioned space perhaps in Minnesota is not the same as one in a conditioned space. In my area of NE Ohio, most are in conditioned spaces. IMO, adding blanket insulation to a newer hot water tank that is located in a conditioned space is not needed and not worth voiding some manufacturers warranty. Also, most I see with blankets on them are installed incorrectly (the blankets).
( I always enjoy your posts, you are a wealth of information!)
Thanks Joseph!
Yes, I agree with you.
I have never come across this water heater conversation. Don’t see many used around here.
There is a point where insulation costs do not meet expected return on investment. So from that perspective I understand and agree. Just interested in other perspectives, not that I would agree with it… 
Yes, Joseph, David tells it like it is…good stuff. 
I installed large number of water tanks in my plumbing days and multiple times I had to explain that loosing heat inside your own house in the cold Montreal’s climate is not any loose during the long winter and it is insignificant during the summer (the electricity here is cheap).
The other water-tank pointless addition is a pan, non-connected to drain. Why the hell you need that pan if you can’t use it for drainage?!?
I recently did a commercial inspection where the hot water tanks were in a storage area on the second floor. All had pans but with non-connected drains!
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