I want to agree with tundrayeti, and I am quite surprised that this article really did not discuss alternative technology (including solar) to the old water tank.
I live in Kansas City and last spring, replaced a very inefficient hot water tank with a tankless system. If you really, truly, like long, hot showers, then get one of these. You will have an unlimited supply of hot water, AND you will be taking those long showers using far less energy to heat the water.
The system is more expensive than a traditional water tank systems, but that is only if you consider the initial cost. The system, now seven months old, that we have is well on its way to paying for itself through natural gas savings alone. We no longer have the chore of draining the tank, sending 40 gallons of water down the sewer system, every six months to keep the sediment out of it, nor do we wake up to ice cold showers because the doggone pilot light went out in the middle of the night (which was the reason we dumped the tank in the first place).
And when you add the energy tax credit I'll get next year, it just makes no sense not to have one of these, particularly with two teenagers in the house. Are you stuck waiting 30 minutes for another tankfull of water to heat up after your teenager has had his 20-minute shower? I'm not.
