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RV Solar Calculator

Estimate RV panel wattage, battery Ah, controller current, and inverter capacity from explicit energy, reserve, sun, and load inputs.

Methodology reviewed August 25, 2026 by the Solar Calculator HQ editorial team. This is an editorial check, not professional engineering or tax certification. Review our formula, source and limitation standards.

RV Solar Calculator

Calculated battery capacity
800 Ah
Next listed solar size
720 W
Next listed controller step
80 A
Illustrative inverter allowance
1,000 W

What this calculator does

This RV solar calculator produces first-pass estimates for a 12 V, 24 V, or 48 V recreational-vehicle system. It takes daily energy, autonomy, peak sun hours, an array-efficiency assumption, battery chemistry, nominal battery voltage, and peak AC load, then reports battery amp-hours, panel wattage, controller current, and inverter wattage.

The results are energy-balance estimates, not a bill of materials, permit design, or safety certification. They do not check module short-circuit current, cold-corrected open-circuit voltage, conductor ampacity, overcurrent protection, battery/BMS current, fault current, mounting, ventilation, or the rules adopted where the RV is built or used. RVIA lists separate standards for recreational vehicles, low-voltage DC systems, and the NEC; applicability depends on the installation and jurisdiction (RVIA adopted standards).

The four numbers every RV solar build needs

A complete system must match panels, controller, battery, inverter, wiring, and protection. The calculator covers only four headline ratings; use manufacturer instructions and a qualified designer or installer for the electrical design.

1. Battery capacity (Ah)

Battery storage is the foundation. The formula is:

Battery Ah = (Daily Wh × Days of autonomy) ÷ (Battery V × Depth of Discharge)

For a 2,400 Wh daily load on a nominal 12 V lead-acid bank at 50% DoD with two days of reserve: 2,400 × 2 ÷ (12 × 0.50) = 800 Ah.

With the calculator’s 80% LiFePO4 preset, the same inputs give 2,400 × 2 ÷ (12 × 0.80) = 500 Ah. In the calculator’s nominal-Ah model, that is five 100 Ah modules, not two, before any aging or temperature reserve. Real products may use 12.8 V nominal ratings and restrict series/parallel configurations, so convert the selected battery’s published usable watt-hours and follow its installation manual. This formula also omits inverter loss, battery aging, temperature derating, lead-acid rate-capacity effects, and DC loads that bypass the inverter.

2. Solar panel wattage (W)

Panel W = Daily Wh ÷ (Peak Sun Hours × System Efficiency)

The system-efficiency input is one aggregate planning factor. The calculator defaults to 0.80, but that is not a universal or NREL-prescribed RV value. NREL’s current PVWatts model instead uses site weather, array geometry, inverter parameters, and explicit system-loss inputs; use it to refine the sun and loss assumptions (NREL PVWatts V8 API documentation).

For 2,400 Wh/day at the user-entered 4.5 peak sun hours and 0.80 efficiency, the raw result is 2,400 ÷ (4.5 × 0.80) = 666.7 W. The interface rounds that up to its next configured panel step, 720 W. It does not test whether that wattage fits the roof or whether the panel voltage is compatible with a controller. Use monthly, site-specific data when the camping season matters.

3. Charge controller (A)

Controller A = Panel W ÷ Battery V × 1.25

Here, 1.25 is a screening margin applied to the unrounded panel result. It is not a substitute for NEC current calculations or controller-manufacturer sizing. For the default raw result, 666.7 ÷ 12 × 1.25 = 69.4 A, which the interface rounds up to 80 A. At 24 V, the same arithmetic gives 34.7 A and rounds to 40 A.

The controller list stops at 100 A. If the raw calculation exceeds 100 A, the displayed 100 A is only the list ceiling—not an adequate recommendation. Design the array around one or more controllers, then verify each controller’s maximum PV open-circuit voltage at minimum design temperature, input short-circuit current, output-current limit, battery-voltage range, and permitted series/parallel configuration. NEC requirements also depend on the adopted edition and installation context (NFPA 70).

4. Inverter (W)

Inverter W = Peak simultaneous AC running load × 1.25

A 1,830 W simultaneous running load produces 1,830 × 1.25 = 2,287.5 W before choosing an available inverter rating. The factor provides 25% running-load headroom only. It does not model compressor or pump starting current, duration-dependent surge capability, inverter temperature derating, DC cabling, or battery/BMS discharge limits.

Use the waveform and power quality required by every connected appliance. For medical devices and other critical loads, rely on the device and inverter manufacturers’ written compatibility requirements rather than a general waveform claim.

Reproducible default check and larger-load limits

With the en-US defaults—2,400 Wh/day, 12 V lead-acid, 50% DoD, two days of autonomy, 4.5 peak sun hours, 80% system efficiency, and an 800 W peak AC input—the displayed results can be reproduced as follows:

  • Battery: 2,400 × 2 ÷ (12 × 0.50) = 800 Ah.
  • Raw panel requirement: 2,400 ÷ (4.5 × 0.80) = 666.7 W; next configured step = 720 W.
  • Controller screening current: 666.7 ÷ 12 × 1.25 = 69.4 A; next configured step = 80 A.
  • Inverter: 800 × 1.25 = 1,000 W.

For a 5,000 Wh/day, 12 V LiFePO4 scenario with two days of autonomy, the battery result is 1,041.7 Ah (normally displayed as 1,042 Ah), not 500 Ah. For 8,000 Wh/day at 24 V and 80% DoD, it is 833.3 Ah at 24 V, not 600 Ah. The panel-step list also tops out at 1,600 W and the controller-step list at 100 A; if the raw formula exceeds either ceiling, ignore the capped display and obtain a product-level design.

Installation and standards boundary (United States)

No single sentence can determine which edition or standard governs every RV alteration. RVIA’s current standards list distinguishes NFPA 1192 for RVs, ANSI/RVIA A119.5 for park-model RVs, an ANSI/RVIA DC standard for systems at 60 V nominal or less, and the NEC (RVIA adopted standards). Check the RV manufacturer, equipment instructions, insurer, authority having jurisdiction, and a qualified installer before work begins.

  • Size conductors and overcurrent protection from actual equipment ratings, allowable temperature, bundling, termination ratings, and the applicable standard—not from panel watts alone.
  • Verify battery fault-current protection, disconnecting means, polarity, chassis bonding/grounding instructions, and protection against movement and abrasion.
  • Keep life-safety equipment wired exactly as required by the RV and detector manufacturers; this calculator does not determine those circuits.

Limitations and common RV solar mistakes

  • Using annual-average sun for a seasonal trip. Model the location and months you will actually camp with NREL PVWatts.
  • Treating chemistry presets as product specifications. Use the selected battery’s charge profile, usable-energy limit, temperature range, and series/parallel rules.
  • Using the capped controller or panel recommendation above its range. Calculate the raw requirement and obtain a multi-controller or higher-voltage design when necessary.
  • Sizing only by watts. Module Isc/Voc, cold-temperature Voc, battery and controller current limits, cable routing, and protective devices can be binding constraints.
  • Ignoring simultaneous and starting loads. Measure the AC load profile and compare it with both continuous and time-limited inverter ratings.

Sources

Frequently asked questions

How many watts of solar do I need for my RV?
Total the energy used by your own loads in watt-hours per day, then divide by peak sun hours and the efficiency assumption. For example, 2,400 Wh/day ÷ (4.5 h/day × 0.80) = 667 W before rounding. The 0.80 factor is an adjustable planning assumption, not a location-specific production guarantee; NREL PVWatts uses weather, array geometry, and separate loss inputs for a more detailed estimate.
What battery bank size do I need for RV solar?
The calculator uses battery Ah = daily Wh × autonomy days ÷ (nominal battery V × allowed depth of discharge). At 2,400 Wh/day, two days, 12 V, and 50% DoD, the result is 800 Ah. At the calculator's 80% LiFePO4 preset it is 500 Ah—not 200 or 270 Ah. Treat both DoD values as editable design assumptions and verify the battery maker's usable-energy, current, temperature, and configuration limits.
Do I need an MPPT or PWM charge controller for RV solar?
Choose from the controller manufacturer's permitted PV-voltage, battery-voltage, current, and temperature ranges. MPPT can use PV voltage above battery charging voltage, while PWM operation depends more directly on panel and battery voltage matching. There is no universal 200 W cutoff or fixed percentage gain; compare candidate datasheets for the actual array.
How big does the inverter need to be?
Enter the largest simultaneous AC running load. The calculator multiplies it by 1.25 as planning headroom, so 1,800 W becomes 2,250 W. This is not a motor-start calculation or a code-compliance result: separately check the inverter's continuous rating, short-duration surge curve, DC input current, waveform, and every appliance's instructions.
Will RV solar work in the winter or under shade?
Yes, but output depends on location, month, tilt, weather, shading, snow, and system losses. Use a monthly site-specific production model rather than an annual-average sun-hours value if winter or shaded camping matters. NREL PVWatts exposes weather, tilt, azimuth, soiling, shading, snow, and other loss inputs.
What's the difference between rooftop solar and a portable suitcase panel?
A rooftop array is fixed and can produce whenever it is exposed to sun. A portable array can be placed away from a shaded vehicle, but its cable loss, connector rating, controller location, theft risk, and setup time matter. Count both arrays only if their controllers and wiring can safely operate together and you expect both to be deployed.

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