My 30 gallon electric water heater has a yearly usage label of $500 @ 4700 kWh:
$500 yearly = $42 month, a total use of 4700kwh = 392kwh monthly (which is less than my total monthly electric usage) 392kwh /30 days = 13kwh daily and is equal to 44,000 btus and the equivalence of raising 100 gallons of water by 50 degrees per day. Mine actually uses only $6 a month in electricity.
Here is the US Energy website and their recommendations - they say to touch the tank to see if it feels warm, but is not a good indication of heat loss because any metal colder than your body (98.6F) will feel cool to the touch. I used digital thermometers taped to the tank about 3/4 up.
http://www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=13070
$500 yearly = $42 month, a total use of 4700kwh = 392kwh monthly (which is less than my total monthly electric usage) 392kwh /30 days = 13kwh daily and is equal to 44,000 btus and the equivalence of raising 100 gallons of water by 50 degrees per day. Mine actually uses only $6 a month in electricity.
Here is the US Energy website and their recommendations - they say to touch the tank to see if it feels warm, but is not a good indication of heat loss because any metal colder than your body (98.6F) will feel cool to the touch. I used digital thermometers taped to the tank about 3/4 up.
http://www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=13070