I always get this query from first-time RV owners, and I understand their concern. You will also want to know how you can enjoy the comforts and conveniences of modern living whenever you go on an RVing adventure.
Although your RV has an energy system for running your appliances, it requires charging at electric utility pedestals. Unfortunately, the next RV park might be a few hundred miles away. Hence, installing a solar power system makes perfect sense for your off-grid adventures.
So, how much solar power do I need for my RV? Let us find out.
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How Do You Determine Your RV’s Solar Power Requirements?
There are two methods for determining your RV’s solar power requirements. Although the first method is quick and straightforward, it does not give you a very accurate description of your energy needs. On the other hand, the second technique is more complicated yet delivers a more realistic estimate.
Appliance Energy Usage Method
As mentioned, this technique is as straightforward as you can imagine. It only requires a few steps and simple math to estimate your RV’s solar energy requirements.
All electric appliances have an energy rating expressed in watts and amperes. You will want to check each appliance’s watt-hour rating and list them down.
Next, it is crucial to determine how many hours you intend to operate each appliance. For example, you might want to keep your refrigerator running 24/7 while using the air conditioner for only four hours.
Multiply each appliance’s wattage rating by the number of hours it will be in use. For instance, suppose an air conditioner requires 1,000 watts to run for four hours. In that case, your RV’s air conditioning needs 4,000 watt-hours from your solar system.
The last step involves adding all items’ watt-hour results to obtain an estimate of your solar power requirements.
Actual RV Energy Consumption Method
This method is more complicated than the first one, but it offers a more accurate estimate of your RV solar power requirements.
For this method to work, you will need to install a battery monitor to determine your energy consumption when driving the RV. Connect this device to the negative power line between your RV and the battery.
Charge your RV battery until it’s full and switch off the battery charger circuit from the breaker panel. Note the battery monitor’s power level, and use your RV appliances. Check the battery monitor to see if the battery level is near 50%. If it is not, continue using your RV some more until you see 50% on the monitor.
Please note that ordinary lead-acid batteries should not have charge levels lower than 50%. If your RV battery is lithium, you can continue using your vehicle until the battery monitor displays 20%.
Then, read the amp-hours on the battery monitor and multiply it by the battery’s nominal voltage. Lead-acid batteries have a nominal voltage of 12.6 volts, while lithium cells have 13 volts.
For example, suppose the display reads 150 ampere-hours (Ah), and you have a lead-acid battery. In that case, the energy consumption is 1,890 watt-hours (W/h) (150 Ah x 12.6 volts).
It is also essential to note the time it took for the battery level to reach 50% (or 20% for lithium) from 100%. You will need this information to determine your 24-hour solar power requirements. For example, if the 1,890 W/h is only good for 12 hours, you will need 3,780 W/h for 24 hours.
Unfortunately, your calculations do not stop here. Some RV appliances do not run on DC electricity, requiring only AC power. You might also want to install a power meter to determine your RV’s power usage for 24 hours.
How Do You Determine the Number of Solar Panels to Install on the RV Roof?
Knowing how many watts you need to run your RV appliances and other electrical systems will help you answer the question, how many solar panels do I need for my RV?
Solar panels come in varying wattage ratings, ranging from 100 watts to 300 watts. Newer solar cell technologies offer higher efficiency ratings, with some products producing as much as 415 watts per panel.
Unfortunately, answering the question “how many watt solar panel do I need for RV” is a bit complicated. You already know your RV’s solar power requirement. Sadly, you do not know your location’s peak sun hour (PSH) value yet.
Unfortunately, everything depends on the photovoltaic cell’s exposure to sunlight.
If you take your RV to Arizona, you can enjoy seven to eight hours of intense sunlight. Unfortunately, heading north to Oregon might only give you three to five hours of solar energy.
So, suppose you live in California with a PSH value of about six hours (the range is 5 to 7.5), and your daily RV energy requirement is 3,780 watts. In that case, we will multiply these values by 30 to get our monthly figures (113,400 watts or 113.4 kilowatts in electrical usage and 180 sun hours).
Next, let us divide 113.4 kW by 180 hours to get 0.63 kilowatt-hours (kWh). Multiplying this by 1,000 gives us 630 watts. You can also use an RV solar panel size calculator for this.
The last step requires you to divide 630 watts by the wattage rating of the solar panel you want to buy. For example, you will get 3.15 if you use a 200-watt solar panel (630 ÷ 200=3.15). Hence, you will need four 200-watt solar panels for your RV.
How Much Power Can RV Solar Systems Generate?
One thing we know about solar energy is that it is unlimited. Theoretically, you can expect your solar for RV to generate infinite power if you have the correct solar system setup and the ideal environmental conditions.
Unfortunately, nothing is ideal or infinite. You cannot expect the sun to shine over your RV’s solar panels continuously 24/7. There will always be cloudy or rainy days and nights where the solar system cannot produce energy for your RV appliances.
Solar technology also has its limitations. For example, the most efficient solar panel can only produce 415 watts. Most RV solar panels on the market can generate about half that. Hence, you can install ten 200-watt solar panels to generate about two kilowatts.
It should be sufficient for most RV appliances, but not the power-hungry ones, such as water heaters and air conditioners. You can still run these appliances, but only for a few hours, not for extended periods.
Unfortunately, your RV’s roof is not as extensive as your house’s cover. Some RVers can only install six to eight solar panels, severely limiting their RV solar system’s power generating capabilities.
What Factors can Limit an RV Solar System?
Even if you can answer the question how much solar do I need for my van, you may not be able to set up the power system you want. It would be best to learn the different factors impacting solar power systems, such as RV space, solar system weight, and solar system cost.
1. RV Space
Class A motorhomes have average dimensions of 33 x 9 feet, while Class B recreational vehicles have 20 by 8.5-foot sizes. Class C motorhomes sit between Classes A and B, about 28 feet long and 9 feet wide. These are the average vehicle dimensions, which should give you information about the RV’s roof space.
Why does this matter?
The only RV space with direct access to sunlight is the roof. It is the best place to install solar panels. Unfortunately, it is often impossible to occupy the entire roof with solar-generating sections. Hence, the more expansive the RV rooftop, the more solar panels you can install.
It is not only the roof space you must consider when setting up an RV solar power system. You will also decide where to store the batteries, electrical panel, and other electronics.
2. Solar System Weight
Your solar system’s weight is another crucial consideration because it can impact the gross vehicle weight rating (GVWR). This number reflects the maximum weight your RV can safely accommodate.
Residential solar panels can weigh 35 to 50 pounds, while RV solar panels are lighter at 12 to 20 pounds. If you decide to install a flexible, thin-film solar cell, you will only use three to six pounds of your RV’s GVWR per panel.
Hence, ten rigid solar panels can weigh 120 to 200 pounds, while ten flexible solar cells equal 30 to 60 pounds.
Unfortunately, you also need to consider the weight of deep-cycle batteries and other solar system electrical components. A 12-volt deep-cycle battery can weigh 40 to 50 pounds. Two of these power storage units can add 80 to 100 pounds to your RV.
3. Solar System Cost
Solar systems are more expensive than traditional power-generating technologies. Even with recent technological innovations, cost remains a principal consideration of prospective solar power users.
Unfortunately, solar system prices vary depending on the brand, solar panel type, inherent technology, and unique features. For example, you might get a 50 amp RV solar system for less than $500 without the deep-cycle battery. High-end systems can cost you more than $3,000.
Conclusion
You can observe at least two methods for determining how much solar power do I need for my RV.
- Calculating the sum of all appliances’ watt-hour values
- Using a battery monitor to measure actual RV power consumption
Regardless of the method, the information you obtain will help you determine the number of solar panels to install in your recreational vehicle.
I am Stephen Ryan, content director for RV Web. After seven years of working as an interior decorator, I am confident in turning my clients’ dream houses into reality. I find it rewarding to help others make the best of their space and resources.