Cayveman, I finally checked back on this thread. It's about thermodynamics and the conservation of energy, so in easy to understand terms when you have energy input (like the voltage and amps going to the heater) and what comes out has to be the same because the energy can't magically increase or be destroyed. It's simpler with electric resistance heaters because inefficiencies that we normally see in motors, pumps, etc. manifest themselves as heat which in this case we want. So the energy (kwh) can be directly converted to Btu's (Btu = Btu/hr average x number of hrs on). The reason I say Btu/hr average is that the heaters thermostat turns the heating element on and off. As for the heat lamp vs a std lamp, if they both draw 100 watts of power, they have the same heat output in Btus to a space. The std lamp would have a higher lumens (measurement of light) per watt but even the light after being absorbed and reflected by surfaces converts to heat. So there is ultimately no difference in the heat added to a room. Other items in your home such as TV's, dishwashers, etc. are not 100% efficient at doing the intended task, but all the input power in them as well converts into heat. So a dishwasher or refrigerator running helps heat your house as well as a portable heater in the winter but adds to the air conditioning load in the summer. Calculating the heat output is easy because all of the inefficiency of the motors and circuits in your appliances result in heat. That is not the case with your electric water heater because much of the heat is dumped down the drain with your bathwater and only a part of the heat stays in your home. Lastly concerning heating of air or water, the equation is the same for sensible heating or cooling (w/o removing moisture like an Air Cond. in the summer). What I think everyone is interested in is heating the space so a thermostat will show a higher temperature in the room. There is radiant heating used in non heated spaces where people have to stand in a line of site of the heater to feel the heat but that is like standing in front of a fireplace to keep warm. The equation for heating air or water is: Btu = mass x heat capacity x Temperature difference The difference is that water has a spec. wt. of about 62.4 pounds per cubic ft (Varies with temperature and can be found on the web.) Air is only about 0.075 pounds per cubic foot. (Varies with temperature and can be found on the web.) Also the heat capacity of water is 1.0 Btu/pound - deg F while that for air is 0.24 Btu/pound - deg F. Example: Small bathroom 5 ft x 9 ft with 8 ft ceilings at 40 degrees F. We want to heat to 80 deg F using a portable electric heater having an input of 1500 watts ( 5,119.5 Btu/hr input = output). Volume = 6 x 9 x 8 = 432 cubic ft Mass = 432 cubic ft x 0.075 pounds/cubic ft = 32.4 pounds Specific Heat of air = .24 Btu required = 32.4 pounds x 0.24 Btu/pound - deg F x (80 - 40) deg F = 311 Btu kWh= 311 Btu x 1 kWh / 3413 Btu = 0.091 kwh Time required to heat the room = 311 Btu x 1 hr / 5119.5 Btu = 0.0608 hr = 3.64 minutes You would actually take more than 3.64 minutes because you would be heating all the fixtures, walls, and if not insulated well other adjacent rooms. I asked my mailman if I could borrow one of his edenpure heaters for a test just to compare what Im describing above, the heating of a small bathroom with two types of heaters just for fun. I have the equipment to measure input energy and the air temperatures would have to be measured in several areas in the room every 30 seconds or so and recorded. There wont be a difference because its impossible but it might be interesting to post the test results. Could be done in the summer but you would have to heat the room to 100 deg F to get good results and preferably before the sun comes up (to eliminate another factor) and at about the same outdoor air temperature. What goes in has to be what comes out. It cant disappear or get larger. Not talking about heat pumps or air conditioners right now as that is a more complex subject and those units have COPs and EERs associated with them where the heat addition to a space is higher than the compressor energy used. They still dont violate the laws of thermodynamics about the creation or destruction of energy. Again this isnt saying everything is 100% efficient. Its just electrical appliances, heaters which wont have 100% efficient motors but the inefficiencies manifest themselves as heat. I used to sell pumps as a sales engineer and our pump curves would show the pump efficiencies which would vary depending on rpm, flow rate, and pressure. What this meant was that the motor and pump when combined might only be 75% efficient and was determined by tests performed by the pump and motor manufacturers that were shown on graphs that engineers used. The efficiency the manufacturer stated was based on the actual power required to pump a given flow and pressure compared to the theoretical power required (based on another engineering formula). All the electric power (watts) into the motor ends up as heat while moving the water. Pumping the water even heats it up slightly. Hope this clarifies things and I havent been too long winded. Even if its stored by being absorbed by a piece of copper it eventually is released into the air. It has to be the same as what's input. The same is true of a 100 watt light bulb no matter what type it is, although a heat lamp having larger diameter wire inside its bulb outputs a smaller percentage of light and more heat

My landlord just put a new GE slide in stove (cooktop and combo oven) as I complained about the old oven blowing hot air out the front and also that it only seemed to be on "convection" even though there wasn't a convection mode on it. Certain foods never came out like they should, such as cracker breads and quiche (I had to overcook the top to make certain the middle of the crust was cooked). But this oven blows hot air, too -- only out the back! I made cracker breads last night which bake on a pizza stone at 450 and the house became an oven, as well. If they have to do this to keep the high tech elements from over heating, then maybe this isn't such a good design. Maybe they should go back to the old designs. And I ask -- how can this be energy efficient? If hot air is blowing into your house in summer, then the air conditioning is running to counter-act it. If unnecessary heat is being expelled from the oven, then how is that efficient because the oven is surely producing more heat than it needsk or is healthy for the electronic components. And now I wonder if it means that air is still blowing around in the oven, giving it a convection mode by default. I'm going to have to experiment with it to see. And one more thing, on this model, as soon as I even put a tea kettle on to boil, cold air blows out the vent in the back. I had to move my pet bird. Why am I thinking that men design these products.

Thanks for the comments! Well, the model that I have is programmable. It has one setting for days Monday-Friday and one for the weekends. You can set a certain temp for "wake", "away", "home", and "sleep" for the weekdays and "wake" and "sleep" during the weekends. You can easily override the temp at any time if your schedule changes. I have no problems with the features of the thermostat, I just want to know if it's efficient. In our house, every penny counts! We live on my husband's income while I go to school and stay at home with my daughter. So money is tight and if we can save more money by spending $50-$150 on another thermostat, so be it. But if it's unnecessary, I'd like to know that as well. I'd ask a professional, but I don't personally know anyone so I feel like I can't really trust their opinion. Even clerks at hardware stores are trying to make a sale so it's hard for me to decide if it's necessary or not.

There have been a lot of advances in building science and construction techniques over the years. Engineers, architects and building trades have worked together to evolve the technology and know-how to significantly enhance energy efficiency. Newer but larger houses properly built provide much greater temperature comfort using substantially less energy than much smaller homes built as recently as 20-40 years ago. Structures older than 20-25 years that haven't had work done to add properly sealing windows and doors, enhance insulation, and seal wall and ceiling passages (like electrical switches and sockets and boxes for ceiling lights) are an energy use nightmare. Such problems can be partially ameliorated with retrofit work to provide what's lacking (better windows and doors, air sealing and insulation) and to replace older energy hog HVAC equipment and appurtenances (like leaky ducts) with the substantially tighter and more efficient equipment that's sold today. So it's not true "the larger the house, the larger the carbon footprint". Rather, it's "the older the house, the larger the carbon footprint". And many will say, "well, that doesn't apply to my house" but if it's older and mostly in "as originally built" condition, it does.