Quote Originally Posted by keith3267 View Post
Not completely true. All other things being equal, the 80 gallon water heater will cost slightly more to operate. The reason is that to hold 80 gallons, the exterior surface area of the water heater will be larger and that means more area to radiate heat from, that is to lose heat from.

But, the cost to heat that water is exactly the same. If this is a well insulated water heater located in a heated space, the heat loss for storage will not be very high, $2-3 per month. The biggest cost is in the hot water used.

But all things are not usually equal. For two people without a jacuzzi. a 40 gallon water heater would be more than enough. With a shower head limited to 2.5 gal/min, you would be a prune before the water got cold.

The jacuzzi kind of changes things, and it doesn't matter whether there are only two of you or not or if it is seldom used or not. Jacuzzi's need a lot of hot water. If you use it at all, you may need anywhere for 80-120 gallons of hot water just to fill it.

This is where the 80 gal could actually be cheaper. To have enough hot water to fill the jacuzzi with a 40 or 50 gallon water heater, you would have to maintain a tank temperature of around 150-160F. The higher the storage temperature, the greater the storage losses. I based my estimate on a storage temperature of around 130-140F, the higher the storage temp, the faster the storage costs go up.

With an 80 gallon water heater, you could drop the storage temperature to 120F and still fill that jacuzzi, but since you rarely use it, your overall storage costs will be lower. The lower temperature has added benefits as well, the lower temperature slows down the reaction of the metal parts of the water heater with the water. It will last much longer. So will the heating elements.

BTW, we have an adult son living with us right now so three adults in the house. 2.5 baths but no jacuzzi, a 50 gallon electric water heater set to 120F and we do not run out of hot water.
Ok so since it does not cost anymore to heat a 80 gal vs a 50gal I guess the 80 would be ok. If I decide (or ever have time to wait for the jacuzzi to fill up) I will have the extra 30 gals at my disposal. Right? He is quoting me around $400 for the Bradford White tank. Is that a good brand?