How Much Solar Power Do I Need For My RV?

As the world moves away from non-renewable energy sources, mainly fossil fuel-based fuels, it is incumbent for everyone to look at their contribution to saving the planet. We take for granted that electricity is available at the flick of a switch. Still, behind that switch is a network of legacy power suppliers draining the planets’ ability to cope.

The measure of power that an RV uses is measured in watts. The number of watts a system needs can be calculated by assessing which components draw the most power and are used simultaneously. The average  RV will use between 4KWH – 15kWh a day.

Sizing the type of solar power system required for an RV Is not difficult. It’s essential to balance the power you anticipate your RV equipment needs while ensuring you don’t produce more than you need, which isn’t used and is a waste of capital.

How Much Solar Power Does My RV Need

You very rarely need to run the high draw appliances simultaneously. Your needs and budget will dictate the size of your solar power system.

When you work out how much power, there are two ways you can measure it.

Method One to Assess The Electrical Draw

Identify each appliance and the electrical draw it takes. You then need to group these, matching those that simultaneously draw power (switched on).

To calculate the draw of each appliance, you need to work out the kilowatt-hours the device uses. The formula to work this out is watts = amps X volts.

If you know the amperes of the device and the voltage it requires. For example

A 120-volt waffle maker draws 9 amps. Plugging these variables into the formula results in 120 volts x 9 amps = 1,080 watts. The watt result is divided by 1,000, resulting in 1.08 kilowatt-hours.

Devices used in a typical motorhome RV draw the following approximate power

ConsumerWattsNumber of Hours Used per DayDaily Consumption
Fridge4024960
Microwave8000.5400
Television2004800
Cell Phone Chargers542108
Lights805400
Computers30041200
Coffee Makers10000.15150
Water Purifier60160
Toaster5000.150
Water Heater14400.5720
Total Watts Per Day  4,848

The Second Method To Identify Your RVs Electrical Draw

The second method is to install a wattmeter into the RV’s circuit and measure the kilowatt-hours displayed by the wattmeter as you switch on each device. The maximum wattage required by the solar system will be the measurement you take when all the devices (which you will conceivably run simultaneously) are switched on.

Remember, some appliances need to draw significantly more power at startup; this is called the starting watts requirement. Typically, the starting Watts required by a fridge are between 800 – 1200 watts. Even though it is only needed for seconds, this factor must appear in your calculation.

How Much Power Is Required By An RV Solar System

There are a few other variables that you will bring into the calculation, but they are simple, and you don’t need to be a mathematical genius to get a result.

You need to find out the useable “peak sun hours” in the state through which you are traveling. Peak sun hours are the number of hours when the sunlight averages  1 kW per square meter (roughly 10.5 feet).

Peak sun hours differ by state; for example, this figure is 3.5 to 4 peak hours in Alabama. In Colorado, peak sun hours are 5 to 6.5, Pennsylvania is 3, and New Mexico is 6 to 7 peak hours.

You then need to work out the electricity used by the system per day when the highest consumers are running together.

We will assume you intend to purchase 300-watt solar panels.

Using Pennsylvania’s peak sun hours for this example and inputting the numbers into the following formula calculates the solar panels you need.

Electrical usage (watts per kWh)/ daily peak sun hours *1000

4.8 ÷ 3 = 1.6 x 1000 = 1,600 watts

Divide consumption (1600)  by the solar panel watts (300) = 5.34 panels. Using this example, you will need to install 6 * 300-watt solar panels.

Remember, you need to allow for the starting watts of devices as they run through the day. If your RV’s fridge draws 900 watts, on face value, six * 300-watt panels (1,800 watts total)  would be sufficient; however, in the example above,  the regular consumption is 1,600 watts per hour for all the other consumers switched on at the same time.

If you want no disruption, you will need to add solar panels, which will produce enough power for the regular 1,600 watts per hour plus the startup consumption of 900 watts which equals 2,500 watts. In this example, you will need 10 solar panels.

You can reduce the total number of solar panels by installing an MPPT controller-equipped inverter and batteries. Adding batteries to store excess electricity, which the system can draw from to cover shortfalls from the panels, means that you don’t have to size the system for the maximum possible draw.

The inverter will take unused electrical power and store it in the batteries. If the system needs to provide starting watts for a device,  the sun disappears, or at nighttime, the system will draw the excess current from the batteries.

What Is The Optimum Solar Panel Installation In An RV?

Before deciding on the optimum installation, you need to determine what you will use the Solar Installation in your RV for.

The cost to install Solar systems is very high. To achieve the “best bang for your buck,” it is essential to size the system at the design stage. We have discussed how to work out the system’s power (watts) requirement; the next step is to decide on the availability of the electricity.

Many RV solar installations only use the current generated from the solar panels installed on the RV. Although this is the lower cost solution; the downside is that if the sun is not available to generate sufficient current because:

  1. The RV Motorhome is in the shade.
  2. It is nighttime.
  3. The weather is overcast.
  4. The RV is traveling.

There is no access to power.

There are two solutions to this situation.

  1. You can store excess electrical current for later use.
  2. You can use a gasoline generator for the RV.

Both are viable solutions; however, each has its advantages and disadvantages.

We discuss the advantages of using solar batteries or a gas generator in the following section.

You install solar batteries to store the excess current generated by the solar panels for later use. In this example, a typical RV installation would consist of:

  1. Solar Panels
  2. A Battery Bank
  3. A 12-volt  output. Most RVs need to draw a combination of Direct Current (DC) and Alternating Current (AC). Unlike home-based solar systems, which exclusively convert the current to AC, an RV system must generate both types of electrical power.
  4. Solar panels produce Direct Current (DC). To convert the DC to Alternating Current (AC) for systems, such as microwaves, air conditioners, and TV, you will need to install a sufficiently sized inverter.

Advantages Of Solar Batteries

Solar technology offers many advantages over other systems as follows

Solar Batteries Provide Instant Power

Electricity stored and distributed by a solar battery is instantaneously available at the click of a switch.

There Is No Maintenance Required

Solar systems require no maintenance. Once the initial purchase and installation costs have been spent, there are minimal additional costs. Depending on the type of battery, you will only need to replace it after 5 to 20 years.

Solar Systems Are Silent

Solar systems, and therefore batteries, are virtually silent. If an inverter is installed, the cooling fan will make a humming noise which increases with the degree of load on the system. Soundproofing the compartment in which the inverter is installed reduces this problem.

Solar Systems Are Classed As Renewable Energy

Solar systems are classed as renewable power sources and do not release pollutants into the atmosphere.

Solar Systems Are Reducing In Cost

Each year solar systems are becoming more capable and affordable. In 1965 Gordon Moore stated that the number of transistors in integrated circuits doubles every 24 months. This rate of advance seems to apply to solar systems. Each year there are tremendous advances in solar generation and battery technology which increase capacity reduce the size, weight, and cost of systems.

Although Solar systems can already be considered a good investment, this will continue to be improved.

Disadvantages Of Solar Batteries

Every technology has its disadvantages, and this is true of solar power.

Solar Systems Need The Sun

Batteries have a finite storage capacity, and if the sun is not available for an extended period, the RV will run out of power.

Large Consumers Will Discharge The Battey Vey Fast

If you run hefty power consumers (e.g., air conditioners) when there is no sunlight, the batteries will discharge quickly. It will be high, resulting in a fast discharge of the battery.

If you are going to run items like an air conditioner, we recommend that this is separated from the RV’s solar circuitry and is connected to the RV park’s main power supply.

Batteries Don’t Last Forever.

Lead Acid RV batteries, AGM RV batteries, or Gel Cell RV Batteries are heavier and require replacement after 5 – 7 years.

Lead Acid Batteries Need Maintenance

Lead Acid batteries need regular maintenance and cleaning to ensure no corrosion on the terminals or spillage in the battery compartment, damaging the RV.

Lithium Batteries Are Expensive

Lithium-ion batteries last for 20 years and are lightweight; however, they cost significantly more than gas generators or the other battery types.

Solar Batteries Are Heavy

Solar batteries are hefty (Lithium-ion is the lightest). You need to make sure that the weight of the batteries is within the capability of your RV motorhome.

The Advantages Of A Gas Generator

The advantages of Gas Generators are.

Gas Generators Don’t Need The Sun.

Gas generators work irrespective of the availability of sunlight. You can park in the shade and in whatever position you want to orientate the vehicle without experiencing any loss of power.

Gas Generators Are Flexible

You can turn Gas generators on and off at any time when you need the power.

Disadvantages Of A Gas Generator

There are some disadvantages of gas generators as follows.

Gas Generators Are Noisy

Having a gas generator means putting up with the noise it generates every day and possibly all day; this is not optimum for a peaceful holiday.

Gas Generators Need Maintenance

Gas generators require ongoing costs to run them. You need to make sure they have sufficient oil and gas, but you also need to keep them maintained, which costs money.

Gas Generators Use Non-Renewable Fuel

Gas generators use fossils fuels to run and, therefore, cannot be considered eco-friendly. As the planet is under severe attack from pollutants, this is an issue that is becoming more and more important.

Gas Generators Are Not Automatic

Unless you have a more advanced gas generator, you must manually start it each time you need the current. Power is not instantaneously available.

How Do You Position The Solar Panels?

Assuming you settle on six panels 300-watt panels, the total power produced will be 1,800 watts (1.8kw)

The reality is that the boxy shape of a Motorhome RV makes it challenging to install the panels optimally, and therefore power created will not be optimum.

The loss based on the installation of the panels is:

  1. Installing the panels flat on the RV roof will result in a 10% – 15% loss of power; this means that 1,800-watt panels will only generate 1,530-watts.
  2. If you install three panels on each side of the Motorhome, there will be an automatic reduction in power developed of 25% – 30%. The panels installed on the sides will only be able to generate 1,260-watts.
  3. Installing half the panels on one side and the other half on the other means that only one side will over-optimally face the sun.

Installing the panels on the sides of the Motorhome RV is not a good idea, and installation should be restricted to the roof and portable units, which can be erected on the ground at the side of the Motorhome.

Conclusion

Installing a solar system on your Motorhome RV is a great idea and is much more efficient than a generator-driven system.

Calculate the power requirements of your RV, and if possible, include an inverter and batteries as part of the installation.

Good luck, and happy camping!

Check out our article on: Best Portable Solar Panels For RVs With Kits

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