RV Solar Calculator

Enter your daily energy use to size a solar panel, battery bank, charge controller, and inverter for your RV.

Battery, losses & inverter load

Depth of discharge is 50% for typical AGM/lead-acid batteries and up to 80% for lithium (LiFePO4). System losses cover wiring, inverter conversion, and temperature derating. Peak AC load is the largest combination of appliances you'd run at once, such as a microwave or AC unit.

By · Energy analysts and engineers documenting every formula, source, and limitation behind our calculators.

Published Formula, sources & limitations

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HOW IT WORKS

How does the RV solar calculator work?

The calculator converts your daily energy use into four component sizes — solar panel wattage, battery bank capacity, charge controller amperage, and inverter rating — using standard off-grid sizing math and an NEC 690.8 continuous-duty safety margin.

1

Enter daily use & sun hours

Set your daily energy use in watt-hours and your location's average peak sun hours.

2

Set battery & load details

Choose your system voltage and adjust battery, loss, and peak load defaults if needed.

3

View your component sizes

See recommended panel wattage, battery Ah, controller amps, and inverter watts.

Why system losses are added first

Wiring resistance, charge controller conversion, inverter efficiency, and heat all take a bite out of the energy you generate before it reaches your appliances. Rather than sizing components against your raw daily usage figure, this calculator first inflates it by your system loss percentage — 20% by default, a reasonable planning figure for a wired 12V RV system — so the panel and battery are sized to actually deliver the energy you need, not just generate it.

THE CALCULATIONPanel W = (daily Wh ÷ (1 − loss %)) ÷ peak sun hours

Battery Ah = (adjusted daily Wh × days of autonomy) ÷ (voltage × depth of discharge). Controller A and inverter W each apply a 125% NEC 690.8 continuous-duty margin on top of the array's current and your peak load.

Worked example: a typical weekend RV setup

EXAMPLE

2,000 Wh/day on a 12V system, 4.5 peak sun hours, 1 day of autonomy

Suppose you use 2,000 Wh per day running lights, a fridge, a water pump, and device charging, on a 12V battery bank with 50% depth of discharge, 20% system losses, one day of autonomy, and a 1,500 W peak load for your microwave.

  1. Adjusted daily energy: 2,000 Wh ÷ (1 − 0.20) = 2,500 Wh.
  2. Panel wattage: 2,500 Wh ÷ 4.5 peak sun hours ≈ 556 W.
  3. Battery bank: (2,500 Wh × 1 day) ÷ (12V × 0.50) ≈ 417 Ah (about 5.0 kWh).
  4. Charge controller: (556 W ÷ 12V) × 1.25 ≈ 57.9 A.
  5. Inverter: 1,500 W × 1.25 = 1,875 W.

Result: about a 556 W panel array, a 417 Ah (5.0 kWh) battery bank, a 60 A charge controller, and a 2,000 W inverter after rounding up to standard sizes.

Rounding up to standard component sizes

Real solar panels, controllers, and inverters come in fixed standard sizes, so treat this calculator's output as a minimum to round up from, not an exact spec. Common charge controller ratings are 20A, 30A, 40A, and 60A; common inverter sizes are 1,000W, 1,500W, 2,000W, and 3,000W. Rounding up leaves extra headroom for future load growth, such as adding an appliance later.

Common ways to use this calculator

Planning a new install

Size every major component together before buying panels, a controller, or an inverter.

Checking an existing system

See whether your current panel and battery bank match your actual daily energy use.

Comparing lithium vs. lead-acid

Adjust depth of discharge to see how battery chemistry changes the required bank size.

Budgeting for boondocking

Increase days of autonomy to plan for cloudy stretches or extended off-grid stays.

Privacy and appropriate use

Your inputs are processed directly in your browser and are not sent to a database. This is a planning estimate for component sizing, not an engineering or electrical-code compliance document — have a qualified installer verify wiring, overcurrent protection, and code compliance for your specific system.

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FREQUENTLY ASKED QUESTIONS

Questions about the rv solar calculator.

Clear answers about sizing panels, batteries, controllers, and inverters for RV solar.

How much daily energy does a typical RV use?

Light use — lighting, phone charging, a fridge, and a water pump — often runs 300–800 Wh per day. Adding a laptop, TV, or CPAP machine pushes that toward 1,000–2,000 Wh, and running a microwave or air conditioning regularly can take it well past 3,000 Wh. Add up your actual appliances' watts × hours used per day for the most accurate figure.

What are peak sun hours, and how do I find mine?

Peak sun hours are the equivalent hours per day of full 1,000 W/m² sunlight your location receives — not the same as daylight hours. Most of the continental U.S. averages 3–6 peak sun hours depending on season and region; sunnier southwestern states run higher, and northern or cloudier regions run lower. Search "[your state] peak sun hours map" or use a solar insolation calculator for a location-specific figure.

How is NEC 690.8 used in this calculator?

NEC 690.8 sets a 125% continuous-duty safety margin for sizing photovoltaic circuit conductors and equipment above their calculated maximum current. This calculator applies that same 125% margin to the charge controller amperage and inverter wattage, so the recommended sizes leave headroom above your calculated array output and peak load rather than sitting at the exact edge of their rating.

Should I use 50% or 80% depth of discharge?

Use 50% for flooded, AGM, or gel lead-acid batteries — discharging them further shortens their lifespan significantly. Use 70–80% for lithium (LiFePO4) batteries, which tolerate deeper regular discharge without the same wear. Check your battery manufacturer's spec sheet for their recommended maximum depth of discharge.

How many solar panels do I need for my calculated wattage?

Divide the calculated panel wattage by the wattage of the panels you're considering. For example, a 556 W requirement could be met with two 300 W panels (600 W) or four 150 W panels (600 W), rounding up to the nearest combination your roof space and mounting allow.

Do I need a PWM or MPPT charge controller?

MPPT controllers are more efficient and better suited for larger arrays or panels wired with a higher voltage than your battery bank, typically justifying their higher cost above roughly 200–300 W. PWM controllers are simpler and more affordable for small systems where panel voltage is closely matched to battery voltage. Either way, size the controller's amperage rating at or above this calculator's result.

What size inverter do I actually need?

Size the inverter's continuous rating at or above this calculator's result, then check its surge (peak) rating separately — motors and compressors in appliances like microwaves or air conditioners can draw 2–3× their running wattage for a moment at startup. If your peak load includes such an appliance, confirm the inverter's surge rating covers that startup spike.

Is my data stored?

No. All inputs and calculations run directly in your browser and are not sent to a server or saved in an account. General site usage may be measured through Google Analytics as described in our Privacy Policy.