They will cost more. Won't fit where your current water heater is now----New home water heaters are bigger and more expensive

New home water heaters are bigger and more expensive:
"If you need a hot water heater, but aren't looking to spend a lot of money, now might be the time to buy.
New federal regulations that went into effect April 16 require all new water heaters to meet updated standards to promote energy efficiency.
But these changes translate into more expensive — and slightly larger —heaters. 
However, paying a little more now could mean paying less later.
Manufacturers are allowed to sell their remaining stock of old models, but all newly made heaters must meet the new U.S. Department of Energy requirements."