I still haven’t resolved my dryer issue. One technical detail has been annoying me for a while, until I finally worked on it tonight, is whether I should buy (another) gas dryer, or go with an electric.
Conventional wisdom is a gas dryer will be cheaper to operate in the “long-term,” whatever that means. Unfortunately, gas dryers cost $50 more to purchase. To quote Consumer Reports:
Consider gas. Both gas and electric dryers perform comparably, our years of testing show. Gas dryers cost about $50 more than comparable electric models, but the likely savings in fuel costs should more than make up the difference in the long run.
I’ve emphasized “likely savings,” because I have yet to see someone do actual math. Today, I will do that math. Mwuahahaha.
My utility bill is broken out into gas and electricity components. For the last three years, the gas portion has been substantially higher than the electric. From my power company’s view, it’s doubtful it will improve:
PSE expects the near-term market price for gas to be about 17 percent higher than what is reflected in customers’ current electric rates.
The only things consuming natural gas in my home are the furnace, water heater, and dryer.
Since we keep the furnace set to 66°F during the daytime, 55°F at night, and my bill peaks in January when it’s cold, dark, and rainy, it’s obvious the heater is a big chunk of that. (We turn it off completely from June through mid-October.) I don’t know how much the hot water heater and dryer use, except it’s a lot less than the furnace.
The first challenge is to determine how much gas and electricity actually cost per fomplicatron, the standard, unintuitive units of drive-by, comparative measurement.
Gas service is broken out into several different kinds of charges:
What the hell is a therm, you might wonder. It’s yet another obfuscated calculation equal to one hundred cubic feet of gas multiplied by the heat content of the natural gas, also known as the “BTU factor.” The “BTU factor” is 1.056, no units are provided.
According to a handy conversion chart I found online, 1 therm equals 100,000 BTUs.
The cost of gas per therm is $0.98655.
Electricity is much easier to grok. The basic unit is kilowatt-hour, equivalent to running ten 100-watt light bulbs for one hour.
The cost of one kWh of electricity is thus $0.051687 for the first six hundred kWh, $0.06872 for each additional kWh. (Unless your appliance and the electric company are both enrolled in the Friends and Appliances program…)
For simplicity, we’ll assume the household has both sources available and therefore pays both Customer Charges. Since an electric dryer would shift the equation, we’ll use the higher electricity rate. For the sake of argument, we’ll also assume that the spot the dryer’s in is plumbed for gas. (If it wasn’t, as was the case when I moved in, expect to spend about $10/foot for a gas line.) We’ll also assume a dryer works its magic in the same time, regardless of fuel source.
I looked up the specs for the electric GE Profile DPSB620EC and its evil gas-heated twin, the DPSB620GC. The E has a 5,600 Watt heating element. The G uses a 22,000 BTU/hour heating element. A standard power connection is needed to turn the drum. It appears to be a 1/3 horsepower motor drawing approximately 6 Amps at 120 Volts. That being said, we’re going to simplify life by ignoring the drum motor and assuming each dryer dries equally. Waving my hands, I calculate the per-load cost as:
Electric dryer: 5,600 w/hr * 0.06872 = $0.384832 per load
(If we used the lower rate, it’s only $0.289447 per load)
Gas dryer: 22,000 BTU * 1 therm / 100,000 BTU * $0.98655/therm = $0.217041 per load.
Based on this, gas is cheaper to operate. Now, let’s figure out what the breakeven is. The cost difference is universally $50 for gas versus electric. (I think this is mostly marketing, the same way as premium unleaded is always $0.20/gallon more than regular unleaded.) The cost difference per load is: $0.384832 – $0.217041 = $0.168/load.
The number of loads we need to do to break even (save $50) is:
($50 + sales tax) / $0.168/load =
($50 + $4.3) / $0.168/load = 323 loads
In an average week, we do eight loads of clothes. A gas dryer would pay for itself in about ten months. Since the average lifetime of a dryer is at least five years, conventional wisdom is seems correct.
However… If I was single, it’s likely I would still be in the lower band for electricity cost. Thus the number of loads until break-even would be 750:
($0.289447 – $0.217041) = $0.072406/load
($50 + $4.3) / $0.072406/load = 750 loads
My eight loads per week assumes a family of four. For someone living alone, this might be closer to three loads per week. Assuming they’re in the lower incremental electric rate, the break-even period is 4.8 years, barely less than the average lifetime of a dryer.