When performing home upgrades or buying new appliances such as heaters, volts, watts, and BTUs should be factors to consider.  Some of you may have noticed that the outlet used to plug in your desk lamp may not be the same as the outlet behind your refrigerator, and without understanding volts, watts, and BTUs, you could be stuck with a heater that doesn't produce enough heat to warm your area, or worse yet, you may find yourself with a heater that won't fit in your standard two-pronged outlet. 

Voltage

Voltage is measured as the root mean squared value between two slots or holes in an electric outlet of the sort typically mounted in a wall, and the purpose of an electrical outlet is to provide an area for you to plug in electrical appliances.  Most standard power outlets in the United States are of the 120 volt variety which have spots for two plugs and are rated for 15 amps.  Therefore, for these standard outlets, you will be able to use any of the standard 120 volt electric space heaters.  However, do not exceed these ratings, as the outlet could be damaged and start a fire.  In addition, if your outlet is only rated for 15 amps, you cannot have a 14 amp heater and other appliances running at the same time on the same circuit. 

With that in mind, larger appliances, including garage and industrial heaters, are powered through 240 volt plugs, and cannot be powered through standard plugs.  If they were fed by a 120 volt supply, they would need more than 20 amps of current running through the wires.  In other words, the voltage from one hot wire to the other (called line to line voltage) is 240 volts, and the voltage from either wire to the neutral center-tap (called line to neutral voltage) is half that, or of the 120 volt variety as discussed above.  These 240 volt outlets can also be found in garages, building sites, and other industrial areas. 

Here are examples of a 120 volt plug and a 240 volt plug:

Although a 240 volt electric garage heater is significantly more efficient and powerful than a 120 volt space heater, a garage heater may not be necessary for your home.  Most space heaters are 120 volts, but some wall heaters designed for home use are rated at 240 volts and are just as powerful as garage heaters. 

Watts

On the other hand, a watt is a unit of power equal to one joule of energy per second.  In terms of wattage, almost all 120 volt space heaters are rated up to 1500 watts at the maximum setting, and there is a 10/1 ratio of watts to square feet heated.  Therefore, a 1500 watt space heater (120 volts) will be able to heat an area of 150 square feet, and a garage heater rated at 5,000 watts should be able to comfortably heat an area over 400 square feet.  Therefore, if you want to heat your 450 square foot living room, you would need to purchase three space heaters for adequate heating. 

BTUs

A BTU is a unit of energy that is used globally in heating and air conditioning industries, but is not commonly used elsewhere.  Nonetheless, in North America, the term BTU is used to describe the power of heating and cooling systems such as heaters and air conditioners.  When used as unit of power, BTUs per hour is the commonly used term, and this refers to the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit.  To convert watts to BTUs and vice versa, here are the conversion ratios:

1 watt = approximately 3.41 Btu/hour

1000 Btus/hour is approximately 293 watts

See 120 Volt Heaters

See 240 Volt Heaters

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