Price of Energy Cost-Comparisons
Gas versus Electric
Potential customers often wonder what the least expensive form of energy is in their area. Should
I use electricity or is natural gas cheaper? We have no way of answering this question broadly.
You will have to contact your local electric and gas utilities and ask what they charge. Electricity
is charged in $ per kilowatt-hour and natural gas is charged in $ per therm or sometimes in $ per
Mcf. Once you have this information, then you can make a comparison. Here are the conversion
1 therm = 29.3 kilowatt-hrs
only 80% efficient. Taking this efficiency factor into effect, the following table provides the
equivalent cost at which alternative fuels would need to be priced:
1 therm =0.097Mcf or 1 Mcf = 10.3 thermHowever, while electric heating is nearly 100% efficient, gas pool and spa heaters are typicallyTABLE
below 1.17 US$/therm. Break-even is however not good enough. At least a 25% savings is
required, to justify the extra capital cost and extra maintenance costs of a gas heater system.
Capital cost for a more elaborate gas heater with the additional digital spa pak can be $1000
The amount of energy used by a 5ft 5in OD cedar hot tub, with an insulated floor, is in the order
of 30 kW-hrs/day during a moderate winter season (similar to NYC or London). At 5 cents/kWhr
this cost you .05 x24 x30 = $45/month, during this season. During the summer the energy
usage is considerably less (~1/3) and during spring and fall it would be about 1/2. If you live in a
warmer climate (such as LA) your usage will be much less in the winter and during the summer
the pump energy can be enough to keep the tub at temperature. Of course if you live in a more
severe winter climate (Montreal) it will be more during winter, fall and spring. During the times
you are in the tub, energy usage will be greater since the cover is off. Larger tubs will also
require more energy to heat, roughly in proportion to the ratio of the surface area of the staves.
If using LPG (propane) a good question is how many gallons I will use and how big should my
tank be. 30 kW-hrs/day equates to 1.07 gal (US)/day of LPG. You should therefore expect to use
30 ? 40 Gal (US)/month during in a moderate winter (such as in NYC). We recommend at least
a 500 pound size tank (called a ?pig? in some areas). LPG has a density of approx 4.5 lbs/ Gal
(US). A 500 lbs tank would therefore hold somewhat more 100 Gal (US) or a 3 ? 4 winter-month
For example if you are being charged 5 cents/kW-hr, natural gas would be cheaper if it is priced more.