Tuesday, May 3, 2011

Dryer deathmatch - electric vs. natural gas

In our home, the electric clothes dryer is by far the greatest consumer of electricity. So naturally, in any energy audit, we target the largest consumer of energy first, because usually it offers the best return on investment, the biggest opportunity to save, and the biggest impact on the bottom line.

Before we can determine which energy source is better and by how much, we need to first figure out how much energy does it take to dry a typical load of laundry? We can't use a plug-in type meter on a dryer because there aren't any for 220V loads, but we don't need one because the Hydro web portal gives us that information.

Let's take another look at a laundry day in the graph. On this particular day, my wife starts the dryer just before taking the kids to school. Then again later in the afternoon at 2pm, and finally in the evening around 7pm. Notice here is that it takes about 4kWh to dry a load of laundry. Your consumption per load might vary depending on things like the ability of the washer to extract water from clothes, the size of the dryer, the amount and type of clothes dried per load, how plugged the lint filter and dryer vent are, etc. It's going to take more energy to dry a load of towels and jeans than it would for some socks and t-shirts. Regardless, the outcome of this exercise will allow us to see the order of magnitude of savings, and then consider the cost of procuring and installing a gas dryer over the electric one currently in service.

To make this fair, a spreadsheet was used to break out the true cost of energy and exclude the fixed monthly customer charge from each utility, since that amount is not affected by the amount of energy consumed. The spreadsheet allows us to run various scenarios depending on how many loads are dried in a week. The average TOU line gives a rough idea of what it would cost to dry clothes if dryer use is somewhat random during waking hours.

The results aren't even close. Gas wins by a wide margin. In this scenario, a gas dryer handling six loads a week would save $143 to $188 annually. On the other hand, a single person running one load a week would only save $20 to $31 annually.

Now let's consider the cost of a new gas dryer, supposing the old one has reached it's end of life and a new one must be purchased anyway. Most gas dryers carry a $50 cost premium over the electric model. A 120V receptacle needs to be installed for the gas dryer, since the electric one uses 240V. An electrician can do this work for something in the order of $200 unless you are able to do it yourself or there is a spare receptacle nearby. And a gas fitter must run a new gas line to the dryer location. Count on $350 to $500 for this work depending on length and difficulty to install. Let's assume your venting is already metal and suitable to vent the lint, moisture, and products of combustion. So total cost premium for gas is in the order of $550 to 750. At a savings of $143 to $188 mentioned above, payback for this is three to five years. This payback will decline rapidly if electricity prices continue to rise rapidly, or you can get the work done cheaply.

So the bottom line is that gas wins, but only if there is a lot of dirty laundry. With smaller laundry demands, electricity, despite the painfully difficult to swallow electricity prices, may still be the better option for you.

Or just put up a clothesline and fight the relentless rain and birds. Hmmm. Maybe $200+ a year to dry clothes worth thousands of dollars isn't such a bad idea after all.

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