take a look at heat pump hybrid electric if carbon emissions are a concern. we just had one installed and are loving it. projections suggest it will cost about $10 a month in full heat pump mode, saving us $300-400 annually. we went with electric because we are working on going zero net energy/zero carbon. Eventually we want to replace our gas furnace with a heat pump as well. Our utility offers a $250 rebate, the feds offer a $300 rebate and then assess for a complete solar PV system to net zero our annual consumption, including the car... probably at least year or two down the line. Home depot had this heater on sale for $1,300. The install was easy!
In a warm climate and in the right place in your home the a heat pump water heater can be great but you do need to read up on it and make sure it is the right fit for your home http://www.geappliances.com/heat-pump-hot-water-heater/
. the refresh rate is slow in full heat pump mode but it sips electrons, 500 watts per hour vs 4,500 an hour. the GE hybrid heat pump has three modes, heat pump only, hybrid mode (for higher demand where the resistive coils augment heating during peak use) and full resistive heater mode for very high output times. It also has a vacation setting where it drops the temp to 50 degrees or ambient and the day before you return it goes back up.
We added a Euro pro high performance/low flow shower head and sealed up the shower stall to retain heat and get plenty of long showers out of the hybrid/electric heater we put in. When it's convenient we time our clothes drying with showers and circulate the warm humid air from the dryer into the room with the hybrid heat pump, capturing the waste heat from the dryer... don't know how much this is saving us, but the heat pump is able to keep up with the dryer and it's at least fun.
We have yet to see the electric bill but we expect to be able to drive the leaf about 10,000 miles a year on the energy saved!
the upside of a tankless gas system is that gas prices should be low for a while and your water supply is virtually endless. The downside is that you are still relying on fossil fuel and emitting carbon into the atmosphere.
Gasless: Silver 2012 SL, traded in for Lease on 1/13
Tesla S P85, Gray, pano, carbon fiber, took delivery: 2-9-13... LOVE this car!
9.8 kW PV Solar installed 9/12, http://www.westseattlenaturalenergy.com