08-05-2007, 03:20 AM
You have two different topics so I think I will do two posts.
First Gas vs. Electric Stored Hot Water.
Sticking with storage tank type water heaters, you will find that electric water heaters have better insulation than gas. An example you can check online is the Sears Power Miser 6 in electric has R16 insulation but the gas model has R8. If you infrequently use hot water and the water spends a lot of time sitting in the tank, then more of the energy used to heat the water escapes into the air around the tank with a gas heater than a electric (wasted). The other consideration is that a lot of the heat from burning the propane will go up the flue as uncaptured heat, whereas the electric heating rod is 100% efficient (though electricity is more expensive expensive because you are taking heat, converting it to electricity and then back to heat).
Electric water heater can be a good choice as a boost heater for solar hot water heating. The tank becomes part of the hot water storage system and the superior insulation make it a better choice than gas. There are cheap electric heater with poor insulation so do some checking. Consider solar hot water heating instead of switching to on-demand if your location has plenty of sun.
One of the ways you can make any storage tank type water heater more efficient is to put foam insulation around the hot water pipe. Make the insulation extra thick closest to the tank. Also make sure you do not have a thermal siphon on the hot water line. Hot water less dense than cold water and will rise so you don't want the hot water pipe to rise straight up for any distance from the water tank.
Larry
First Gas vs. Electric Stored Hot Water.
Sticking with storage tank type water heaters, you will find that electric water heaters have better insulation than gas. An example you can check online is the Sears Power Miser 6 in electric has R16 insulation but the gas model has R8. If you infrequently use hot water and the water spends a lot of time sitting in the tank, then more of the energy used to heat the water escapes into the air around the tank with a gas heater than a electric (wasted). The other consideration is that a lot of the heat from burning the propane will go up the flue as uncaptured heat, whereas the electric heating rod is 100% efficient (though electricity is more expensive expensive because you are taking heat, converting it to electricity and then back to heat).
Electric water heater can be a good choice as a boost heater for solar hot water heating. The tank becomes part of the hot water storage system and the superior insulation make it a better choice than gas. There are cheap electric heater with poor insulation so do some checking. Consider solar hot water heating instead of switching to on-demand if your location has plenty of sun.
One of the ways you can make any storage tank type water heater more efficient is to put foam insulation around the hot water pipe. Make the insulation extra thick closest to the tank. Also make sure you do not have a thermal siphon on the hot water line. Hot water less dense than cold water and will rise so you don't want the hot water pipe to rise straight up for any distance from the water tank.
Larry
Larry