Complete RV Solar System Guide 2024: Sizing, Installation & Wiring

Quick Take

Your solar power survey questions are excellent for planning an RV solar installation, but there's no one-size-fits-all answer since optimal configurations depend heavily on your specific RV size, power needs, and camping style. Most successful RV solar setups range from 400-800 watts total, use rigid panels in parallel configuration with MPPT controllers, and require 10-12 AWG wiring. Fixed installations are most popular for full-time RVers, while weekend warriors often prefer portable options for flexibility. The key is matching your daily amp-hour consumption to your solar generation capacity while considering your budget and installation preferences.

Since you're asking about series vs parallel wiring, controller types, and what people would do differently, you're likely planning a system or evaluating an existing one. The most common regret I hear from RV owners is starting too small - many wish they'd installed 200+ watts more capacity initially rather than adding panels later.

Common Causes

The biggest mistake in RV solar planning is underestimating actual power consumption. Many RVers calculate their needs based on ideal conditions but don't account for cloudy days, seasonal sun angle changes, or increased power usage over time. This leads to undersized systems that can't maintain battery charge during extended camping trips.

Poor wire sizing is another frequent issue. Using 14 AWG wire on a 30-amp system creates voltage drop that reduces charging efficiency by 10-15%. Similarly, mixing different panel types or sizes in the same string causes the weakest panel to limit the entire array's output.

Controller mismatches also cause problems. PWM controllers waste significant power compared to MPPT units, especially with higher voltage panels. Many RVers buy cheap PWM controllers to save $100-200 initially, then end up replacing them when they realize the efficiency loss.

Shading issues are often overlooked during planning. Even partial shade on one panel in a series configuration can reduce the entire string's output by 50% or more. This is why parallel wiring with power optimizers or microinverters is becoming more popular despite the higher cost.

Preparation

Start by calculating your actual daily amp-hour consumption using a battery monitor for at least a week of typical camping. Include all devices - lights, fans, water pump, furnace blower, refrigerator (if running on 12V), phone chargers, laptops, and any inverter loads. Most RVers use 50-150 amp-hours daily at 12V DC, with full-timers often reaching 200+ amp-hours.

Measure available roof space and check structural capacity. Standard rigid RV panels are typically 58" x 26" for 100W units and weigh 40-50 pounds each. Your roof should handle 3-4 PSF (pounds per square foot) additional load. Flexible panels save weight (2-5 pounds each) but generate more heat and typically last 5-10 years vs 20-25 years for rigid panels.

Plan your wiring route from panels to controller to batteries. Calculate wire runs and size accordingly - use 10 AWG for runs up to 20 feet on 30-amp systems (keeping voltage drop under 3%), though consider 8 AWG in high-temperature environments, 8 AWG for longer runs. Include costs for MC4 connectors, combiner boxes, breakers, and monitoring equipment.

Research local electrical codes and RV park restrictions. Some parks limit solar installations or require specific mounting methods. If you plan to work on the system yourself, ensure you have proper safety equipment including fall protection for rooftop work.

Repair Steps

System Sizing and Configuration: For most RVs, 400-600 watts provides good balance between cost and capability. Use 100-200W panels - they're easiest to handle and replace. Wire panels in parallel using a combiner box with individual breakers for each panel. This prevents one failed panel from killing the entire array and makes troubleshooting much easier.

Controller Selection: Choose MPPT controllers rated 25-30% above your total array short-circuit current (Isc) with additional margin for safety and future expansion. Victron, Renogy, and AIMS make reliable units. A 40-amp MPPT controller costs $150-250 and handles up to 400-450 watts on a 12V system (allowing for safety margin). Include battery temperature sensors for optimal charging.

Wiring and Installation: Run 10 AWG wire from combiner box to controller, then controller to batteries. Use MC4 connectors rated for outdoor use. Mount rigid panels with adjustable tilt mounts if possible - 15-30 degree tilt increases winter production by 20-30%. Seal all roof penetrations with Dicor or similar RV-approved sealant.

Monitoring and Maintenance: Install a battery monitor like Victron BMV-712 or Renogy BT-2 to track actual consumption and charging performance. Clean panels monthly and check connections twice yearly. Monitor controller settings seasonally - absorption voltage may need adjustment for temperature changes.

When to Get Help

Call a professional if you're uncomfortable working on your RV roof or if your installation requires significant electrical modifications. Many RV service centers now offer solar installation services for $200-400 labor plus parts, which is often worth it for the warranty and proper weatherproofing.

Get professional help for complex installations involving multiple battery banks, inverter integration, or automatic transfer switches. These systems require precise wiring and programming that can damage expensive components if done incorrectly.

Consider professional consultation if your calculated power needs exceed 800-1000 watts. Large systems may require structural reinforcement, upgraded wiring throughout the RV, or lithium battery upgrades that are best handled by experienced technicians.

Most importantly, have a professional inspect any DIY installation before your first major trip. A $100-150 inspection can catch potentially dangerous wiring issues or installation problems that could cause fires or system failures when you're miles from help.