What Are Watts and Why Do They Matter?
The power consumption of an RV refrigerator, an LED light bulb, or a conventional halogen light bulb? How much solar power is needed to run a boat fan all night?
As we sleep, watts affect us. But what are these abstract things called “watts,” and why are they important? Well, follow us! In this article, we’ll tell you why understanding watts is important.
What Are Watts In Simple Terms?
In electrical power, watts represent one unit of power. When we use the term “watt”, we are referring to the rate at which energy is produced or consumed by an object.
If we think of watts as measuring electrical flow, then we can think of any device or appliance as needing either a large or a small electrical flow. It is possible to think of a 100-watt bulb as needing a greater flow of energy if you compare it to a 60-watt bulb.
It takes much more energy to run a 750-watt microwave oven – 750, in fact!
Similarly, if you have solar panels on your RV’s roof, the solar energy flowing into your RV is measured in watts.
Common Watt Multiples and What They Mean
In terms of power, watts are measured in multiples of 1,000. Let’s examine what these multiples mean.
Microwatts, or 1/1000th of a watt, are commonly used in small circuitry, such as computers and smartphones.
These tiny wires carry only milliwatts of power.
On your electric bill, you may notice that your home’s energy consumption is shown in kilowatts. A kilowatt is equal to 1,000 watts of electricity.
Generators can be rated in megawatts, kilowatts, or watts, depending on their size.
In your home, any electrical equipment that runs on electricity is rated in watts or kilowatts. For example, a light bulb might be rated at 60 watts while a microwave might be rated at 750 watts.
There are some appliances that have two different ratings. Your household refrigerator, for instance, is an appliance that has a start (or surge) rating and a running rating. As a result, the refrigerator’s wattage will differ when it first starts up than when it has been running for a while.
Assuming a refrigerator has a 1,200 watt start rating and an 800 watt running capacity, it needs 1,200 watts when it starts (when the compressor kicks on), but 800 watts when it’s running normally.
Learn how to measure watts. It’s easier than you think!
How Do You Measure Watts?
To be able to calculate the number of watts provided by a power source, you will need to know the number of amps and volts in that power source. Amps and volts are measured using a multimeter.
For a DC circuit, the calculation is simple:
Watts = Amps x Volts (or W = A x V).
Therefore, if the current is 5 amps and the voltage is 110 volts, then 5 x 110 = 550 watts.
It’s also often written Power = Amps x Volts (or P = I + V), which is a more formal or technical version of the equation.
You’ll be fine with DC circuits as long as you remember watts = amps x volts.
Let’s take a look at the difference between high and low wattage first, before we discuss why knowing this formula is so useful in RV and marine applications.
High Wattage vs Low Wattage
As a result, we tend to build and use appliances with lower wattages and use lower wattages because high wattage means more power is consumed. However, higher wattages are useful when electricity needs to be converted into heat. Heaters with higher wattages are hotter.
In the context of your specific application, you need to account for the fact that high wattage can cause high heat. When powering a high wattage appliance, more heat is generated. Additionally, high wattage appliances can cause a circuit overload, resulting in a fuse or circuit breaker tripping.
Low-wattage applications, such as cell phone chargers, smartphones and tablets, and LED light bulbs, require less power to operate or charge.
The voltage does not matter here. A 12-volt device does not use less power because it is a 12-volt device. Watts are watts.
Power Supply Capacity
A power supply provides power to the connected device or appliance, so it makes sense that the more power a device or appliance requires, the higher the wattage that the power supply will need.
You should always have more power than you need when considering the capacity of your power supply. You shouldn’t run your power supply at 100% capacity.
You would not use a 100-watt power supply to power a 100-watt device. Why? Because you don’t want to run your power supply at full capacity. Ideally, you’d want your power supply to have a power higher than 100.
In other words, if you have a 250 watt power supply and you use it to run an appliance requiring 100 watts, the power supply will not “overpower” the appliance.
Why Do Watts Matter in RVs & Boats?
In an RV or boat, watts are important because you need to be able to calculate the amount of power you need on a daily basis. When it comes to marine applications, you should know how powerful your motor needs to be based on your boat’s size. In RVs, you’ll need to know which appliances can be powered and whether more than one can be powered simultaneously.
If your generator puts out 4,000 watts of power, you might be able to run your RV’s air conditioner, microwave, and several small appliances simultaneously, although maybe not all at once.
You need to be able to calculate how much power you use in 24 hours if you are planning to install solar panels on your boat or RV. You will then be able to calculate how many solar panels you need (based on their wattage) in order to sustain your daily usage.
Where Will You See Watts In RVs & Boats?
There are many applications on RVs and boats that require power, from lights to chargers to fans and refrigerators. Understand how many watts you will consume each day, and how you will recharge your batteries.
Power Conservation
As an example, let’s use lights to illustrate how power consumption varies when not connected to shore power (e.g. living off-grid).
Remember, watts = power!
A 40 watt incandescent light bulb will illuminate at 450 lumens, whereas an LED light that illuminates at the same level will only use 4-5 watts. It is likely that you worry about your power consumption if you live off-grid, mainly on solar power. Therefore, which light bulb would you prefer to have on your boat or in your rig? A few watts LED bulb, of course!
Inverters
It is likely that you will need an inverter to run appliances and devices that consume a lot of energy. Inverters convert DC current into AC current.
Direct current, or DC current, is the type of electricity that comes from a battery (think RV power). Alternating current, or AC current, is the type of electricity you receive from a power station.
Therefore, you must know the wattage (starting and running) of the appliances you want to power in order to determine what inverter you need.
In this article, we used the refrigerator example. A 750-watt inverter would not be sufficient to run a refrigerator that starts at 1,200 watts and runs at 800 watts. Instead, you’d prefer an inverter with a larger capacity, like 1,500 watts.
Inverters are also rated in VA, which means they are rated in volt amps. There is something called power factor in AC circuits that causes the power to appear higher than the load to the generator or source. To account for this, it is typically best to add 20% more to your loads to get an accurate estimate of power consumed.
Generators & Solar Panels
Let’s say you’re interested in boosting the power of your off-grid adventures with a portable generator. You’ll need a generator that can deliver enough wattage to start and run an air conditioner in the summer heat if you want to run that AC unit. The same goes for everything else.
The last thing you need to know if you’re considering investing in solar panels to harness the power of the sun is how many watts of solar energy you will need. Based on how much solar energy you use, you will need to determine the amount of solar power you need.
Distinction Between Watts & Watt-Hours
It’s quite easy to understand the difference between watts and watt-hours. You might remember that electrical power is measured in watts. Watts measure the rate at which power is applied.
Watt-hours measure the amount of power consumed over a specific period of time.
A watt-hour is equal to one watt of power flow over one hour, so a 5-watt LED light bulb left on for one hour has consumed 5 watt-hours.
How Many Watts of Solar Do You Need?
We can illustrate the significance of watts and watt-hours by calculating how many watts you would need to power your RV or boat off-grid.
Write down the wattage of each electrical device as well as how long you intend to run each of them. Total the wattage of all the devices by adding them all together, then add the running time of all the devices.
Finally, multiply those two totals (total wattage x total projected running time) to determine how many watt-hours are needed to power all of your electrical devices.
If you plan to run all of your devices for 24 hours, a 250-watt solar panel can generate 6,000 watt-hours (or 6 kilowatt-hours) of power (250 x 24 = 6,000). Therefore, to meet your power needs, you need more than one solar panel if you calculate that your total watt-hour usage for all your devices is more than 6,000 over a 24-hour period.