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Watts vs. Volts: What's the Difference and Why It Matters

26 May 2024
Watts vs. Volts

When it comes to understanding electricity and power, the terms "watts" and "volts" are often used interchangeably, but they actually represent different aspects of electrical systems. Whether you're a homeowner, an electrician, or simply someone interested in learning more about electricity, understanding the difference between watts and volts is crucial.

In this article, we'll delve into the meanings of watts and volts, their relationship, and why knowing the distinction is essential for various applications.

Watts vs. Volts: What Do They Mean?

Watts and volts are both units of measurement used in the context of electricity, but they measure different things. Let's break down each term:


Volts (V) measure the electrical potential difference or voltage. In simple terms, voltage is the force that pushes electric current through a conductor. It's akin to the pressure in a water pipe – the higher the voltage, the more "push" there is behind the electrical current. In most homes, electrical outlets supply voltage at around 120 volts in the United States and 230 volts in many other parts of the world.


Watts (W) measure power, which is the rate at which energy is transferred or converted. In the context of electrical devices, watts indicate how much energy is used or produced per second. For instance, a 100-watt light bulb consumes 100 watts of power when it's turned on. In the case of electrical appliances, the wattage typically indicates the amount of electricity needed to operate the device.

Understanding the Relationship:

Watts and volts are related through the concept of electrical power. The relationship between volts, watts, and amps is defined by the formula: Watts = Volts x Amps. This formula, known as Ohm's Law, illustrates how voltage, current (measured in amperes), and power are interrelated in an electrical circuit. By understanding this relationship, it becomes clear how changes in voltage can affect the power consumption of devices.

Why It Matters:

Understanding the distinction between watts and volts is crucial for several reasons:

1. Safety: Knowing the voltage of electrical systems is crucial for safety, as working with high voltages can be dangerous. Understanding the power consumption of devices helps in selecting appropriate wiring and circuit protection.

2. Energy Efficiency: By understanding the power consumption of appliances in watts, individuals can make informed decisions about energy-efficient devices, ultimately reducing energy costs and environmental impact.

3.Appliance Compatibility: Some electrical devices require specific voltage inputs to function properly. Understanding voltage requirements can help prevent damage to sensitive electronics and appliances.

Understanding Watt Multiples and their Significance

Watts are measured in multiples of 1,000, and it's essential to comprehend these multiples in the context of power. Here's a breakdown of the common watt multiples and their implications:

1. Milliwatts (mW): This is the smallest measurement, representing 1/1000th of a watt. It is frequently used in small circuitry such as computers and phones, where power is measured in milliwatts.

2. Kilowatts (kW): A kilowatt equals 1,000 watts of electrical power and is a globally recognized standard for measuring electricity. Your home’s energy usage or power consumption is often rated in kilowatts on your electric bill.

3. Megawatts (MW): A megawatt is equivalent to 1,000 kilowatts of power (1,000,000 watts). Generators can be rated in megawatts, kilowatts, or watts based on their size and capacity.

When considering electrical equipment in your home, their usage or consumption is typically rated in watts or kilowatts. For instance, a light bulb might be rated at 60 watts, while a microwave is rated at 750 watts.

Certain appliances have dual ratings. For example, a household refrigerator may have a start (or surge) rating and a running rating, reflecting the varying wattage required when the appliance starts up versus when it is running normally.

Measuring Watts

To calculate the number of watts provided by a power source, you can use a simple equation involving amps and volts, which are measured using a multimeter:

Watts = Amps x Volts (W = A x V)

Alternatively, you might encounter the equation as Power = Amps x Volts (P = I * V), which is a more formal version of the formula. Understanding this equation is particularly helpful in RV and marine applications.

High Wattage vs Low Wattage

High wattage signifies greater power consumption and is often associated with appliances that convert electricity into heat. It's important to note that high wattage can lead to increased heat generation, potential circuit overloads, and the risk of blowing a fuse or tripping a circuit breaker.

Conversely, low wattage applications require less power to operate and charge. Examples include cell phone chargers, smartphones, tablets, and LED light bulbs. It's crucial to remember that regardless of whether an application uses 12 volts or 220 volts, watts remain constant—the voltage does not affect the power consumption of a device.

Power Supply Capacity Explained

A power supply serves the crucial function of providing power to connected devices or appliances. Therefore, it follows that devices or appliances requiring more power will necessitate a higher wattage from the power supply.

In essence, higher wattage equals more power.

When evaluating the capacity of your power supply, it's essential to remember a fundamental rule: it's better to have more power than you need, as running a power supply at 100% capacity is not advisable.

For instance, if you intend to operate a device that requires 100 watts, using a 100-watt power supply would be ill-advised. Why? As mentioned earlier, it's important not to operate the power supply at full capacity. Ideally, in this scenario, you would want a power supply with a wattage higher than 100.

If you employ a 250-watt power supply to operate a 100-watt appliance, the power supply will only deliver the necessary 100 watts required by the appliance. Essentially, the power supply will not "overpower" the appliance.

Significance of Watts in RVs & Boats

In the context of traveling in an RV or on a boat, the measurement of watts is crucial as it allows for the calculation of daily power requirements. For marine applications, understanding the power needed for the size of the boat's motor is beneficial. In RVs, it's important to ascertain the appliances that can be powered and whether multiple appliances can be powered simultaneously.

For instance, RVs often utilize generators. If a generator provides 4,000 watts of power, it is likely capable of running the RV's air conditioner, microwave, and several small appliances, albeit not all at the same time.

Determining Wattage for Solar Systems

When contemplating the installation of a solar system on your boat or RV, it's essential to calculate the amount of power (in watts) consumed over a 24-hour period. This calculation aids in understanding the number of solar panels required, based on their wattage, to sustain daily usage. Further details on how to perform this calculation will be provided later.

Application of Watts in RVs & Boats

RVs and boats encompass numerous applications that demand power, ranging from lighting to device chargers, fans, and refrigerators. Understanding the wattage consumed daily and devising methods to recharge batteries to store additional energy for the following day is imperative.

Power Conservation

Prioritizing the use of lower-wattage devices, particularly when not connected to shore power (i.e., living off-grid), is crucial. To illustrate the variance in power consumption, consider the example of lighting.

Remember, watts equal power!

An incandescent light bulb providing 450 lumens consumes 40 watts, while an LED light emitting the same level of illumination utilizes only 4-5 watts. If you are primarily reliant on solar power while living off-grid, the preferred choice for your rig or boat would be the LED bulb, which consumes significantly fewer watts.


When dealing with appliances that require higher wattage, an inverter is likely necessary to operate them. Inverters convert DC current into AC current to power specific appliances and devices.

Understanding the wattage (both starting and running) of the appliances you intend to power is crucial in determining the appropriate inverter. Once again, the importance of watts becomes evident.


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Related reading: What Size Inverter Do I Need?

Generators & Solar Panels

Suppose you are considering acquiring a portable generator to enhance your off-grid experiences. In this case, the generator must be capable of delivering sufficient wattage to start and run the devices or appliances you intend to power. This principle applies to all items you wish to operate.

Similarly, if you are contemplating investing in solar panels to harness solar energy, it is essential to calculate the amount of solar energy required to sustain your off-grid lifestyle. The quantity of solar energy needed is contingent upon the wattage of solar energy consumed.

Distinguishing Between Watts & Watt-Hours

Differentiating between watts and watt-hours is relatively straightforward. Watts measure the rate of power at a specific moment, while watt-hours gauge the rate of power over a defined period, typically one hour.

Calculating Solar Panel Requirements

To exemplify the significance of watts and watt-hours, consider the process of determining the number of solar panels needed to power an RV or boat off-grid.

Begin by compiling a list of all electrical devices you intend to operate. Note down the wattage of each device and the intended duration of operation. Next, sum the wattage of all devices and the total running time.

Finally, multiply these two totals together (total wattage x total projected running time). The resulting figure indicates the number of watt-hours required to power all electrical devices with solar panels.

For instance, if you plan to operate all devices for 24 hours and possess a single solar panel rated at 250 watts, the panel could generate 6,000 watt-hours (or 6 kilowatt-hours) of power during that period (250 x 24 = 6,000). If the total watt-hour requirement for all devices over 24 hours exceeds 6,000, multiple solar panels would be necessary to meet your power needs.

While the above method provides a simplified approach to calculating solar needs, it's important to note that numerous other factors influence solar requirements. For a more accurate understanding of solar needs for an RV, Mortons on the Move has published an in-depth article explaining additional considerations.

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In conclusion, watts and volts are fundamental concepts in the realm of electricity, each representing distinct aspects of electrical systems. Understanding the difference between watts and volts is essential for safety, energy efficiency, and the proper functioning of electrical devices. Whether you're a homeowner or a professional in the electrical industry, having a grasp of these concepts is invaluable for making informed decisions about electrical systems and devices.

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