Kilowatt hours to therms
One kilowatt hour is 0.034121411565 therms, and this shows the working rather than just the answer. Nothing you type here leaves your browser — it is worked out on your own device, so there is nothing to send and nothing to log.
The factor
One kilowatt hour is 0.034121411565 therms. That is the whole of the conversion: multiply by it, and nothing else happens.
What this page will not claim
It will not call this conversion exact. The factor is right to every figure shown, but at least one of these two units is not defined exactly in terms of the other, so there is a limit to how far the decimals mean anything.
The kilowatt hour is exactly 3.6 million joules. What an electricity bill counts.
The therm is 100,000 ISO BTU — the European therm, which is what a British gas bill means.
The number in your head
Most people use 0.034 for this, which is the factor to two significant figures. It is low by 0.3558% — 3.558 therms too few in every thousand, and 35.58 in every ten thousand.
Going the other way
The reverse is not this sum backwards in your head. It is a different factor, 29.307111111111, and dividing by one is not the same as multiplying by a rounded version of the other.
Rounded, the way back is 29.3, which is low by 0.0243%. So the two roundings do not cancel: go out and back with both and you do not land where you started.
How many of those decimals mean anything
The box above will give you ten decimal places because it can. Whether they mean anything is decided by your measurement, not by the arithmetic.
If you measured to the nearest kilowatt hour, your figure is already uncertain by half of one — so the answer is uncertain by about 0.017061 therms, and every digit past that is decoration. Quoting 0.04212493 when you measured with a tape is claiming a precision the tape never had.
Where these two sit
Kilowatt hours and therms both measure energy, which is why they can be converted at all. A conversion between families — a length into a weight — is not a conversion, it is a question with a missing quantity in it.
The unit converter pairs kilowatt hours with megajoules rather than with therms, because that is the conversion people ask for most. This page exists because a good many ask for this one instead.
Other conversions from kilowatt hours
joules · megajoules · watt hours · kilojoules · BTU · Calories (kcal) · calories · electronvolts