Eureka!
OK, so I goofed on a couple of calculations (I had the efficiency calculation backwards) and the assumption of the stove using 9 btus/hour was off by a bit- another source cited the number to be 9000, which makes far more sense. I must have missed the units somewhere...
Electric aggregate cost per kWh: $0.43
According to NYSEG, gas ranges with one 8” burner uses approximately 9 Btu/hour. Another website states that it uses 9000 Btu/hour. I tried both ways, 9000 Btu/hour makes more sense. It takes approximately 0.15 hours to boil 1 L of water with the gas stove.
100,000 Btus = One therm
Our cost per therm, averaged by typical use: $0.25
The hot pot uses 1000 watts. It takes approximately 0.11 hours to boil 1 L of water.
Time started - carafe: 11:18:00 11:27 (9 minutes 10 seconds)
Time started - hot pot: 11:18:00 11:25 (6 minutes 40 seconds)
NB: hours per day assumes water is boiled three times a day.
Appliance Watts x Hours per Day x Days per Year ÷ Convert to kWh x kWh Rate = Cost per Year
Example from website: Window Fan 200 x 4 x 120 ÷ 1,000 x .14 = $13.44
Hot Pot 1000 X 0.33 X 365 ÷ 1000 x .34 $39.94
Appliance Btu/hour x Hours per Day x Days per Year ÷ Convert to therms x Therm Rate = Cost per Year
Gas stove (one burner on) 9,000 x 0.45 x 365 ÷ 100,000 x .25 = $14.78
Another website listed the cost of operating a gas range at $0.08/hour. Multiplied by 0.45 hours/day it comes to $13.14 for the year.
Or, another calculation:
From wikipedia:
where W is the amount of useful work done by the process (in joules), and "energy" is the quantity of energy (again, in joules) used to run the process.
Power output =
• The small calorie or gram calorie approximates the energy needed to increase the temperature of 1 g of water by 1 °C. This is about 4.185 J.
1 gram of water = 1 mL
1 L of water = 1000 g of water.
Tap water = 15* C
Boiling water = 100* C
Difference: 85 * C
85000 calories = 355878 Joules
Power input for gas stove = 9000 btu/hour x 0.15 hours to boil water x 1054.35 = 1422372.5 joules
355878 Joules/ 1422372.5 joules = 0.25 efficiency
Power input for hot pot:
1 watt = 1 joules/second
1000 watts = 1000 joules/second
1000 joules/second x 400 seconds to boil water = 400000 joules
355878 Joules/400000 joules = 0.89 efficiency
Conclusion: The hot pot is far more efficient at heating water, but costs us more to use. I think for smaller amounts of water - one or two cups - the cost difference would decrease, but the carafe is cheaper for heating water for a crowd.
On the environmental impact side, natural gas is not a renewable resource. Our electricity currently comes from 18% hydro power, and we will hopefully be purchasing wind power too soon, to offset the 10% oil, 16% coal, and 29% nuclear power that is used.
Electric aggregate cost per kWh: $0.43
According to NYSEG, gas ranges with one 8” burner uses approximately 9 Btu/hour. Another website states that it uses 9000 Btu/hour. I tried both ways, 9000 Btu/hour makes more sense. It takes approximately 0.15 hours to boil 1 L of water with the gas stove.
100,000 Btus = One therm
Our cost per therm, averaged by typical use: $0.25
The hot pot uses 1000 watts. It takes approximately 0.11 hours to boil 1 L of water.
Time started - carafe: 11:18:00 11:27 (9 minutes 10 seconds)
Time started - hot pot: 11:18:00 11:25 (6 minutes 40 seconds)
NB: hours per day assumes water is boiled three times a day.
Appliance Watts x Hours per Day x Days per Year ÷ Convert to kWh x kWh Rate = Cost per Year
Example from website: Window Fan 200 x 4 x 120 ÷ 1,000 x .14 = $13.44
Hot Pot 1000 X 0.33 X 365 ÷ 1000 x .34 $39.94
Appliance Btu/hour x Hours per Day x Days per Year ÷ Convert to therms x Therm Rate = Cost per Year
Gas stove (one burner on) 9,000 x 0.45 x 365 ÷ 100,000 x .25 = $14.78
Another website listed the cost of operating a gas range at $0.08/hour. Multiplied by 0.45 hours/day it comes to $13.14 for the year.
Or, another calculation:
From wikipedia:
where W is the amount of useful work done by the process (in joules), and "energy" is the quantity of energy (again, in joules) used to run the process.
Power output =
• The small calorie or gram calorie approximates the energy needed to increase the temperature of 1 g of water by 1 °C. This is about 4.185 J.
1 gram of water = 1 mL
1 L of water = 1000 g of water.
Tap water = 15* C
Boiling water = 100* C
Difference: 85 * C
85000 calories = 355878 Joules
Power input for gas stove = 9000 btu/hour x 0.15 hours to boil water x 1054.35 = 1422372.5 joules
355878 Joules/ 1422372.5 joules = 0.25 efficiency
Power input for hot pot:
1 watt = 1 joules/second
1000 watts = 1000 joules/second
1000 joules/second x 400 seconds to boil water = 400000 joules
355878 Joules/400000 joules = 0.89 efficiency
Conclusion: The hot pot is far more efficient at heating water, but costs us more to use. I think for smaller amounts of water - one or two cups - the cost difference would decrease, but the carafe is cheaper for heating water for a crowd.
On the environmental impact side, natural gas is not a renewable resource. Our electricity currently comes from 18% hydro power, and we will hopefully be purchasing wind power too soon, to offset the 10% oil, 16% coal, and 29% nuclear power that is used.