One of the most misunderstood elements of our house is the way that it will be heated. Many people read the quote that it could be heated with two space heaters as it would. Obviously, this led to a great deal of consternation, confusion and derision. Aside from the fact that I don’t think it’s even possible to get approval from the city for something like this, it would be extremely expensive to heat even our house with electricity*.
The difference between gas and electrical resistance heat is large here in Minnesota. Gas is sold in therms, which represent 100,000 BTUs of energy. A therm is 78 cents in Minneapolis. Assuming that the combustion device is 90% efficient, that means you get 90,000 BTUs of useable energy for less than a dollar. Electricity, on the other hand, is measured differently. It’s sold in kilowatt-hours (kWh), at about 10 cents a kWh. A kilowatt-hour of electricity can be completely converted to heat (there’s no ‘waste’ in the process), resulting in 3,413 BTUs.
Put simply, this means that 1,000 BTUs cost less than a penny (.86 cents) if you burn natural gas, but almost 3 cents if you use electricity. Even more simply, electricity costs 3 1/2 times as much to heat with than natural gas.
Cost is not the only reason to heat with something other than electricity. Consider that electricity is very ‘dirty’ in most parts of the country. Why? Because it’s generated by burning coal. Also, while converting the electricity that arrives at your house to heat is 100% efficient, the transfer of power to your house is not. Transmission losses average 7% in the United States, putting electrical efficiency roughly equivalent to a high efficiency gas condensing boiler or water heater.
All of that said, space heaters make for an excellent short term solution until the heating system is installed. Our house is about 60% insulated at this point, which means we have exterior walls with an R-value of about R-35. It’s not quite airtight, as the new front door is not installed and the access panel to the attic has not been sealed. We’re not to where we need to be, but it’s pretty good for a house in progress. A heater on the first and second floor running on low (900 watts draw each) will keep the house in the mid-60s. Not bad.
An example of how easily the house can be heated: this morning I came downstairs to an unheated first floor, after a nighttime low of 15F. The thermostat on one of the heaters sometimes resets to its lowest setting (45F), which is inconvenient. I turned on the heater, and in about 15 minutes, it had warmed almost 1,000 square feet to 62F. I can’t wait to see how the house performs when it’s actually fully insulated, tuned and ready to go.
* Note that when I say heat with electricity, I’m referring to electrical resistance. Air-to-air heat pumps, geothermal ground loops and other technologies technically use electricity to generate heat, but via a completely different mechanism.