A while back, I mentioned in a post that I sometimes get frustrated by burn bans where I live. My shop is heated by a woodstove, and when air quality gets low, I cannot burn wood. My neighbor can, but I cannot.
The only utilities available out of town where I live are electricity and land line phones. Installing a propane or natural gas or oil heater would require some expensive infrastructure installation. I don’t really care to have large fuel tanks on the property, nor loose much shop space to an inside heating unit. This summer, I had an electrician install an electric heater in the shop. I only have a 60-amp sub panel feeding the shop, so I was limited to a 40-amp load. (Upgrading to a 100-amp sub panel was cost prohibitive considering the distances involved.) That resulted in a 7500-watt heater mounted high up on the wall.
I also installed a ceiling fan to help move the rising hot air down to the lower levels of the shop. The shop walls are 12 feet high, and the center peak is at 16 feet. Hot air rises and it gets pretty hot up there even when it is still cold on the floor. The fan runs backwards to pull colder air up and displace the hot air at the top. So far, it is helping distribute the hot air very well.
I also have a Jet air filter on the wall that moves a lot of air, so it also helps move the hot air. It is an energy hog compared to the ceiling fan, though.
Additionally, I have a “milkhouse heater” that plugs into a 110 V AC outlet. It is a 1500-watt heater. This little milkhouse heater sits on my workbench and blows directly on my hands as I use the scroll saw. It helps a lot. I have used this heater for years in addition to the wood stove, at least until the shop warms up enough.
If I am restricted from burning wood, I have roughly 9000 watts of electric heat I can call on in my sort of insulated shop. That does not sound like much, does it? Just for comparison, the electric central heater in my well insulated house puts out 17,500 watts of electric heat.
Let’s convert the shop heaters to BTU’s. To do that, we multiply by 3.4. So, 9000 watts for an hour (9 kWh) is equivalent to roughly 30,600 BTU’s.
Monetarily, 1 kWh of electricity is costing .14448. If I run my electric heaters for 10 hours for a day, it is costing me (9) x (10) x .14448, which is $13.00.
Now, let’s look at wood heat. When the stove is burning, I typically throw in two pieces of firewood every couple of hours. If that is a cubic foot of wood, I am burning .5 cubic feet per hour. Notice that I have my scroll saw fairly close to the wood stove.
1 cord of firewood is 4 feet x 4 feet x 8 feet, or 128 cubic feet. My last load of delivered firewood was $300 for western larch, colloquially known as “tamarack” even though it is not true tamarack.
So, $300 divided by 128 cubic feet gives $2.34 per cubic foot. For the same 10 hours as above, it is costing $11.71 to heat the shop. Pretty much the same cost, right?!?
Well, wait a minute. How much heat is in that firewood? Most of the common cheap pines, spruce, fir, cottonwood, alder, etc., have about 15,000,000 to 18,000,000 BTUs per cord. The western larch sells for a premium price because it has 23,000,000 BTUs per cord. Depending on your source, these numbers jump around quite a bit. A good hardwood is even better, but hard to get in this part of the country.
23,000,000 BTUs per cord, divided by 128 cubic feet gives roughly 180,000 BTUs per cubic foot. If I am burning 1/2 cubic foot per hour, that is 90,000 BTUs. It becomes apparent that the electric heat is way more expensive than the wood heat, being almost 4x the cost per BTU. Additionally, the shop is not necessarily well insulated, so the losses can be significant. If it is less than about 20 degrees outside, the wood stove barely heats enough to work. I historically have not tried puzzle cutting if it is that cold outside. The electric heat by itself does not have a chance on a cold day. I have improved insulation in the shop over the last four years. As built, the walls have fiberglass insulation sandwiched between the outside sheet metal and fiberboard on the inside. The ceiling has 2″ thick fiberglass insulation under the sheet metal roof. The peaks were uninsulated as was the roll up door. My kids helped me install foam insulation board on the peaks, and a garage door company insulated the roll up door. But it is still basically just a pole barn at heart.
Going forward, on a really cold day, I will use both heat sources, which will give about 120,000 BTU’s an hour. We are hitting our first cold spell of the season tonight. It has been unseasonably warm so far. We will be in the low teens this weekend. I will be running both forms of heat and see how it works. That will add up to $25 for a ten-hour day. If the puzzle I am cutting takes 10 hours to cut, you can guess that will be factored into the price! However, in my last 100 puzzles, only seventeen of them hit or surpassed the 10-hour mark. Most are under five hours.
Just some “cold” economic facts to consider when pricing puzzles for sale!
Happy Puzzling!
Bob