RV Solar Panels: Guide to Sizing, Installing, and Getting It Right

If you’re researching RV solar panels, you’ve probably realized two things: there’s a lot of recycled information online, and most of it either oversimplifies the process or makes it sound more complicated than it really is.

We’ve helped hundreds of customers size and source RV solar systems, and we’ve also done the hands-on installs ourselves. The truth is this: RV solar isn’t hard — but it does require planning. The biggest mistakes happen when people guess at sizing, underestimate their usage, or buy equipment that doesn’t work well together.

This guide breaks down everything that actually matters: how to size your system, which panels make sense on an RV roof, inverter and battery options, common mistakes, and how to avoid wasting money.

Why RV Solar Panels Make Sense

RV solar panels let you camp longer without running a generator, reduce fuel costs, eliminate noise, and maintain battery charge automatically. For some RVers, solar is about convenience. For others, it’s about true off-grid capability.

The key question isn’t “Should I install solar?”
It’s “How much solar do I really need?”

Everything starts with usage.

How to Size an RV Solar Panel System

Most people start by shopping for panels. That’s backwards. You start with your daily power consumption.

First, calculate daily watt-hours. Add up everything you plan to run: fridge, lights, water pump, Starlink, laptop, CPAP, TV, microwave. Multiply the wattage by hours used per day.

A small setup might use 800–1,200 watt-hours per day. A more realistic off-grid setup often lands between 1,500–2,500 watt-hours per day. Running air conditioning pushes you far beyond that.

Once you know your daily watt-hours, divide by average sun hours (typically 4–5 in most of the U.S.). That gives you the minimum solar wattage required. Then add 25–40% buffer for cloudy days, imperfect angles, and system inefficiencies.

How Does Air Conditioning Affect Power Estimates?

Air conditioning is the single biggest variable in RV solar system design. Without AC, most RV power estimates are predictable and manageable. Once AC enters the picture, daily energy usage can double, triple, or even quadruple.

Here’s how it impacts your system planning in real terms.

AC Dramatically Increases Daily Watt-Hour Usage

• Most 40-ft RVs without air conditioning use roughly: 1,500–3,000 watt-hours (Wh) per day (fridge, lights, devices, water pump, TV, etc.)
• A typical rooftop AC unit draws: 1,300–1,800 watts while running

Now look at the math:

• AC running 2 hours → ~3,000 Wh added

• AC running 4 hours → ~6,000 Wh added

• AC running 8 hours → ~12,000 Wh added

Add your baseline load (2,000 Wh average), and your daily usage becomes:

• ~5,000 Wh/day with light AC use

• ~8,000 Wh/day with moderate AC use

• ~14,000 Wh/day with heavy AC use

That’s why a system that works great in spring can feel undersized in peak summer.

AC Changes Inverter Requirements

Air conditioners don’t just consume energy — they demand high output.

Most rooftop units require:

• 3,000W inverter minimum (recommended)

• High surge capacity for startup

Without a soft-start device, AC startup spikes can trip undersized inverters instantly. Many RV solar builds fail here because inverter sizing was based on average loads instead of peak loads.

AC Demands Much Larger Battery Banks

Batteries determine how long you can run AC without shore power or a generator.

Running a 1,500W AC unit for 4 hours requires: 6,000 Wh of battery capacity.

At 12V, that’s roughly: 500Ah of lithium (usable capacity).

And that’s just for AC — not counting your other loads.

This is why serious AC-capable solar systems often move toward:

• 24V systems for efficiency

• 400–800Ah lithium banks

• Hybrid solar + generator strategies

Choosing the Right RV Solar Panels

Panel selection depends on roof space, weight considerations, and how serious you are about off-grid capability.

For most modern RV builds, high-watt residential-style panels offer the best value and performance.

Philadelphia 450W Nexus Panels are an excellent balance of footprint and output. Instead of installing four or five smaller panels, one 450W panel delivers serious production with fewer mounting points and cleaner wiring. These are ideal for travel trailers and mid-sized motorhomes where roof space allows.

Runergy 450W Panels are another strong option when building a 900–1,300W system using two or three panels. They offer strong efficiency and cost-per-watt performance, making them ideal for full-time RVers who want dependable output.

If you have a large Class A motorhome or a custom van build with significant roof area, the Axitec 550W AXIpremium panel provides maximum production per panel. The footprint is larger, so layout planning is critical, but the power density is impressive for high-demand systems.

The biggest mistake we see is choosing panels based on price alone. Roof layout, voltage specs, and expansion plans matter more than saving a few dollars upfront.

12V vs 24V RV Solar Systems

Smaller RV systems can run comfortably at 12V. But once you cross 800W of solar or start building larger battery banks, 24V systems reduce wire size requirements and improve efficiency.

For serious off-grid builds, especially those using high-watt panels like 450W or 550W modules, 24V systems often make more technical sense.

Inverters: What Actually Matters

Your inverter determines what you can run — not your panels.

For dependable, straightforward systems, Samlex inverters are a strong option. They provide reliable pure sine wave output and are well suited for mid-sized RV builds.

For advanced monitoring, expansion flexibility, and premium performance, Victron inverter/chargers are widely considered the gold standard. Victron systems allow you to integrate solar, shore power, and generators seamlessly while providing Bluetooth monitoring and system diagnostics.

The most common inverter mistake is undersizing. If you plan to run a microwave, coffee maker, or air conditioner, make sure your inverter can handle both continuous and surge loads.

Batteries for RV Solar Systems

Battery choice will define your experience more than panel selection.

Today, lithium iron phosphate (LiFePO4) batteries are the standard for RV solar. They provide:

• More usable capacity
• Faster charging
• Longer lifespan
• Lighter weight
• Deeper discharge capability

Look for batteries with built-in battery management systems (BMS), low-temperature protection, and heated options if you travel in cold climates.

For moderate RV usage, 200Ah of lithium is a common starting point. For serious off-grid builds, 400Ah or more is typical. If running air conditioning from batteries, you’re entering the 400–600Ah range minimum.

Weight and mounting location also matter in RV builds. Lithium helps reduce overall system weight compared to AGM or flooded lead-acid batteries.

Mounting Considerations for RV Solar

Proper mounting is just as important as panel choice. A well-sized system can still underperform — or cause long-term roof damage — if mounting is rushed or poorly planned. In RV solar, you’re working with limited roof space, curved surfaces, vibration, wind load, and weather exposure. Mounting isn’t just about attaching panels — it’s about building something that lasts.

Choose the Right Mounting Hardware

Use high-quality aluminum brackets or RV-specific mounting feet designed for mobile applications. RV roofs flex while driving, so mounts must allow for slight movement without stressing the panel frame.

Common options include:

• Z-brackets for simple flat installs

• Tilt mounts for seasonal optimization

• Rail-based systems for larger, high-watt panels

• Low-profile mounts for minimizing wind resistance

If you’re installing larger residential-style panels like 450W or 550W modules, rail systems often provide better load distribution than basic corner brackets.

Avoid mixing hardware types unless you’ve planned the load paths properly.

Seal Roof Penetrations Correctly

Every roof penetration must be sealed carefully. This is non-negotiable.

Best practices include:

• Pre-drilling properly sized pilot holes

• Using stainless hardware

• Applying compatible RV roof sealant (Dicor for rubber roofs, appropriate sealants for fiberglass or aluminum)

• Inspecting seals annually

Water intrusion is one of the most expensive RV mistakes — and almost always avoidable with proper sealing.

Maintain Airflow Under Panels

Solar panels lose efficiency as they heat up. Mounting panels flush against the roof traps heat and reduces output.

Leave space beneath panels to allow airflow. Even a small gap helps improve cooling and long-term performance. Rail-mounted systems naturally create better airflow than low-profile adhesive mounts.

The Biggest RV Solar Mistakes

The most common issues we see include:

• Undersizing the system. Buying too small and upgrading later costs more.
• Ignoring voltage compatibility. High-watt panels must match charge controller specs.
• Using undersized wiring. Voltage drop reduces real-world performance.
• Not leaving expansion room. Future-proofing saves headaches.
• Overestimating what 100W panels can do. They’re fine for maintenance charging — not full off-grid living.

Need Help With RV Solar? Reach Out to US Solar Supplier

RV solar panels are one of the best upgrades you can make — if you size the system correctly the first time.

We consistently recommend slightly oversizing both panels and battery storage. It prevents frustration, reduces generator use, and allows you to grow into your system instead of rebuilding it.

If you’re evaluating RV solar panels and aren’t sure how to size your setup, our team at US Solar Supplier can help you match panels, inverters, batteries, and charge controllers so everything works together properly.

Building it right the first time saves money, time, and a lot of avoidable frustration — and makes off-grid RV life quieter, simpler, and far more reliable.

👉 Contact US Solar Supplier for personalized guidance on solar equipment, design services, and homeowner-focused solar planning.