Question 1

How do you convert kWh to therms?

Accepted Answer

Divide kilowatt-hours by 29.3. One therm is 100,000 BTU and one kWh is 3,412.14 BTU, so 100,000 ÷ 3,412.14 = 29.3 kWh per therm. Example: 293 kWh is exactly 10 therms of energy content.

Question 2

Does one therm really replace 29.3 kWh of electricity?

Accepted Answer

Not in practice. That figure compares energy content, not useful heat. A standard 80% AFUE furnace turns a therm into about 23.4 kWh of room heat, and a heat pump at COP 3.0 delivers three kWh of heat for every kWh drawn. So the electricity needed to match one therm of gas heat is closer to 8 kWh through a heat pump than 29.3, which is why the comparison above prices delivered heat rather than raw energy.

Question 3

Is gas or electric heat cheaper?

Accepted Answer

It depends on your two prices and your equipment efficiency, which is why both are inputs here. As a rule of thumb, gas usually wins against resistance electric heat, and a heat pump usually wins against gas wherever electricity is not several times more expensive per unit of energy. Cold snaps narrow the heat pump's advantage because its COP falls as outdoor temperature drops.

Question 4

What is a ccf and how does it relate to a therm?

Accepted Answer

A ccf is one hundred cubic feet of gas: a volume, whereas a therm is energy. US pipeline gas averages about 1,037 BTU per cubic foot, so one ccf is roughly 1.037 therms. Utilities meter volume in ccf and then convert to therms using an actual heat-content factor for the month, which is why the two figures on a bill never match exactly.

kWh to Therms Calculator

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