Appliance Load Calculator
Add every appliance you plan to run to calculate daily power consumption. Include realistic daily usage hours.
Your Appliances
| Appliance | Watts | Hrs/Day | Type | Wh/Day | Actions |
|---|
⚙️ Advanced Preferences
⚡ DC Voltage, AC Mains, Battery Type and Autonomy are set in the bar above — visible from every tab.
Set by location above, or enter manually.
Used to calculate max panel capacity. Typical van: 40–80 sq ft, caravan: 60–120 sq ft.
⚡ Charging Sources (reduces solar / battery requirement)
e.g. Victron Orion 30A. Enter 0 if not used.
AC charger output current. e.g. 30A = 30A × voltage = charge rate. Enter 0 if not used.
Generator charging contribution (50% of output assumed to battery). Enter 0 if not used.
System Sizing Results
Calculated minimums based on your loads and preferences. Always verify with a qualified installer before purchasing.
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Wh / Day
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Peak Watts
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Ah Battery
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Watts Solar
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Inverter (cont.) VA
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Controller (out) A
🔋 Battery Bank
| Total Storage Required | — |
| System Voltage | — |
| Minimum Ah Capacity | — |
| Recommended Ah (incl. 20% buffer) | — |
| Usable at Chosen DoD | — |
| Autonomy (no charge) | — |
| ⏱ Recharge Time (solar only) | — |
| ⏱ Recharge Time (all sources) | — |
| ☁️ Cloudy Day Scenario (50% solar) | — |
| ☁️ Battery SoC after 1 cloudy day | — |
| ⚖️ Est. Battery Weight | — |
☀️ Solar Array
| Required Array Output | — |
| Panel Configuration | — |
| Panels @ 200W each | — |
| Panels @ 400W each | — |
| Roof Area Needed (est.) | — |
| 📐 Max Panels in Your Roof Space | — |
| ☀️ Expected Daily Production | — |
| ⚡ Alternator Contribution/day | — |
| 🔌 Shore/Generator Contribution/day | — |
| 🔋 Net Daily Surplus / Deficit | — |
† Derate factor accounts for temperature loss, wiring resistance, soiling and MPPT losses. Expected production = array W × sun hrs × derate.
⚙️ Charge Controller
| Recommended Type | MPPT |
| Min. Output (Charge) Current | — |
| Suggested Controller Size | — |
| PV Input Voltage Rating | — |
| Battery-Side Wire Gauge | — |
† Output amps = solar W ÷ system V. PV input voltage rating is a fixed controller spec — verify panel string Voc does not exceed controller's rated PV input.
🔄 Inverter
| Continuous Rating Needed | — |
| Surge / Peak Rating Needed | — |
| Recommended Inverter Size | — |
| AC Output Voltage | — |
⚠️ Motors (AC, fridge compressor, pump) draw 2–3× their running watts at startup. Size inverter surge rating to handle the largest motor load's startup current.
🔌 Shore Power / Generator
| Min. Generator Size | — |
| Shore Power Current | — |
† Shore/generator amps are based on peak load. Average draw will be lower. Run generators at 50–80% capacity for efficiency and longevity.
🌦 30-Day Weather Simulation
Real Data
Runs your system against 30 days of actual solar radiation data from Open-Meteo for your selected location. Shows how your battery state-of-charge would have fared day by day.
ℹ️ Select a named location in the Loads tab to enable the simulation.
Component Selector
Select components to build your shopping list. Prices shown are approximate retail estimates in the currency of your selected region (🛒 Shop in the bar above) — verify with the retailer before purchase. Hide options you don't want. Add custom products with a link from any retailer.
🔋 Battery Options Select One or More
☀️ Solar Panels Select One or More
⚙️ Charge Controller Select One
🔄 Inverter / Inverter-Charger Select One or More
🚗 DC-DC Charger (B2B) Optional
Charges your house battery from the vehicle alternator while driving. Essential for any build that moves regularly. Select None if you rely on solar only.
📊 Battery Monitor / Shunt Recommended
Measures real-time state of charge, voltage, current, and time remaining. A shunt-based monitor is far more accurate than voltage-only meters — essential for LiFePO4.
⚡ Transfer Switch (ATS) If using shore power
Automatically switches between shore/generator power and inverter output. Required whenever both sources connect to the same AC circuit. Skip if your inverter-charger includes a built-in ATS.
📋 Shopping List
ℹ️ Select components above to generate your shopping list.
Wiring Guide
Step-by-step installation guidance. Consult a licensed electrician for all AC wiring.
📐 ABYC Wire Sizing Calculator
Sizes each cable segment per ABYC E-11 standards — the same spec used by marine and RV electrical professionals. Enter the one-way run length for each segment; the calculator determines the correct AWG from both ampacity and voltage drop, then applies derating for your installation conditions.
Derating Conditions (apply to all segments)
| Segment | Amps | Run (one-way) | VDrop % | Ampacity AWG | VDrop AWG | Use AWG ✓ | Fuse |
|---|
† AWG determined by the worse of ampacity or voltage drop constraint. Fuse = next standard size above 125% of load amps. Always verify against your exact component datasheets and have installation checked by a qualified electrician.
Installation Sequence
⚠️ Safety Rules
🚫 NEVER connect solar directly to batteries without a charge controller.
🚫 NEVER work on live circuits — disconnect battery negative first.
⚡ Fuse every positive wire within 18" (45cm) of the battery terminal.
🔥 Use tinned marine-grade stranded copper wire throughout.
✅ Torque all battery terminals to manufacturer spec.
✅ Label wires: RED=+, BLACK=−, WHITE=AC neutral, GREEN/YELLOW=AC earth.
ℹ️ All 240V AC wiring must be performed by a licensed electrician in most jurisdictions.
System Diagram
Visual overview of your RV power system. Values update live as you change your loads.
Power Flow Legend
━━ DC Power
━━ AC Power
━━ Solar Input
━━ Shore/Gen
🔋 Solar Generator Finder
Should you buy an all-in-one solar generator or build a custom system? Based on your load profile.
📦 Matched Solar Generators
Sorted by best fit for your daily energy requirement. Affiliate links help support this free tool.
⚖️ Solar Generator vs DIY Build
Saved Systems
Save your current build, load a previous design, or compare systems side-by-side.
Your Saved Systems
Learn the Basics
RV electrical fundamentals from first principles. Full help guide →
🔑 Key Concepts
Power Triangle — Ohm's Law
Power (Watts) = Voltage × Current. A 12V system drawing 10A = 120W. Batteries store energy as watt-hours (Wh) — a 100Ah 12V battery holds 1,200Wh total.
W = V × A | A = W ÷ V | Wh = W × hours
System Voltage — 12V vs 24V vs 48V
| Feature | 12V | 24V | 48V |
|---|---|---|---|
| Best for | Van, small RV | Medium RV, boat | Large RV, home |
| Wire gauge | Heavy (high amps) | Medium | Light (low amps) |
| Efficiency | Good | Better | Best |
| Component cost | Lowest | Mid | Higher |
| Max practical solar | ~800W | ~2,000W | 10,000W+ |
Battery Chemistry
| Feature | Lead-Acid / AGM | LiFePO4 |
|---|---|---|
| Recommended DoD | ~50% | ~80–90% |
| Cycle life | 400–800 (AGM) | 2,000–5,000+ |
| Weight (100Ah 12V) | ~55–65 lbs | ~24–28 lbs |
| Cold weather | Good | Needs heating <0°C/32°F |
| 10-year cost | Higher (replacements) | Lower |
PWM vs MPPT Charge Controllers
PWM: Simpler and cheaper. Economical only where panel Vmp closely matches battery voltage. Efficiency drops significantly when panel voltage exceeds battery voltage.
MPPT: Tracks the panel's maximum power point and steps voltage down efficiently — typically 20–30% more energy than PWM. Required for any 24V/48V system or array over ~200W.
Inverter Surge vs Continuous Rating
Every inverter has a continuous rating (sustained load) and a surge/peak rating (brief spikes, typically 2× continuous for 1–5 seconds). Motors — air conditioners, fridge compressors, water pumps — draw 2–3× their running wattage at startup. Always verify your inverter's surge rating exceeds the largest motor's startup draw.