Van Life Solar Calculator
VanSolarCalc is a free online tool that sizes the solar panels, battery bank, charge controller, wiring, and fuses for a camper van or RV off-grid electrical system — and estimates what it will cost.
Quick start with a profile:
Your daily loads
Add each device with its watts and hours per day.
No loads yet. Add your fridge to start, or pick a profile above.
Solar array
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Add loads to size your array.
Show the math
Battery bank
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Show the math
Charge controller (MPPT)
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Show the math
Inverter
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Show the math
Battery-to-inverter wire & fuse
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Show the math
Estimated cost
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Budget street price → premium brands.
Itemized breakdown
Embed
How to use this calculator
- Add your appliances. Pick each device from the list or add a custom one, then set its watts and hours of use per day. The live daily energy total updates as you type.
- Set your battery and sun. Choose 12V or 24V, LiFePO4 or AGM, how many days of backup you want, and your location so the tool can pull peak sun hours. Toggle winter if you travel in the cold months.
- Read the results. The calculator sizes your solar array, battery bank, MPPT controller, inverter, and the battery-to-inverter wire and fuse — then estimates the cost.
- Download the parts list. Export a printable PDF shopping list, copy a shareable link, or grab an embed snippet for your build blog.
Worked example. A typical van runs a 45 W fridge for 10 hours, 15 W of lights for 4 hours, a 25 W fan for 8 hours, a 65 W laptop for 4 hours, and 10 W of phone charging for 3 hours. That totals 1,000 Wh a day. At 4 peak sun hours that needs 334 W of solar, and two days of LiFePO4 autonomy needs 209 Ah at 12V.
How the math works
Every number here comes from a formula you can check yourself:
- Solar array:
watts = daily Wh ÷ (peak sun hours × 0.75). The 0.75 factor covers wiring, controller, and heat losses. 1,000 Wh at 4 PSH →1000 ÷ 3 = 334 W. - Battery bank:
usable Wh = (daily Wh × days) ÷ depth of discharge, thenAh = Wh ÷ system volts. LiFePO4 uses 0.8, AGM 0.5. 1,000 Wh × 2 days ÷ 0.8 =2,500 Wh → 209 Ahat 12V. - Charge controller:
amps = (array watts ÷ system volts) × 1.25, rounded up to a standard size. 400 W at 12V →41.7 A → 50 A. - Inverter fuse:
amps = (inverter watts ÷ volts ÷ 0.9) × 1.25. A 1,000 W inverter at 12V →116 A → 125 A fuse. - Wire gauge: we take the thicker of two requirements — an ABYC 105°C conductor whose ampacity covers the fuse, and a gauge whose voltage drop stays under 3% over the round-trip cable length.
When you need this
- New build. You have a fridge, fan, lights, laptop, and Starlink on your list and need to know how many watts of solar and how big a battery to buy before you spend $2,000 on an electrical order.
- Retrofit. Your RV has shore and generator power and you want to add solar and lithium — you need panel count, MPPT amperage, and the fuse and wire sizes so nothing is undersized.
- Cold climate. You build for winter trips below freezing and need the cold-weather capacity hit on LiFePO4, plus the hard fact that lithium cannot be charged below 0 °C.
- Budgeting. You are reverse-planning from a budget and want a priced parts list to compare before committing.
Accuracy and sources
The calculations use standard, published methods: a 0.75 system derate for solar sizing, NEC 690.8's 1.25× continuous-current factor for the charge controller and fuses, ABYC E-11 105°C ampacity for the battery-to-inverter cable, and a 3% voltage-drop limit using round-trip cable length. Cold LiFePO4 behavior follows battery-maker guidance. Prices are 2026 planning ranges from budget to premium brands and should be spot-checked before you buy.
These results are planning estimates to get you in the right ballpark, not a substitute for a wiring diagram or a licensed electrician. Verify your final design and local electrical code with a qualified installer before purchasing or wiring anything. See the about page for the full method and sources, or read the solar sizing guide for a deeper walkthrough.
Frequently asked questions
＋ How many solar panels do I need for a camper van?
Divide your daily watt-hours by (peak sun hours × 0.75) to get the array watts, then divide by the panel wattage. A 1,000 Wh/day build at 4 peak sun hours needs about 334 W — roughly two 200 W panels or three 100 W panels. Winter and cloudy regions need more.
＋ What size battery bank do I need for van life?
Take your daily watt-hours, multiply by the days of backup you want, then divide by usable depth of discharge (0.8 for LiFePO4, 0.5 for AGM). For 1,000 Wh/day and two days on LiFePO4 that is 2,500 Wh, or about 209 Ah at 12V.
＋ How much solar do I need for an RV?
The math is identical to a van — size to your daily load and local peak sun hours. RVs often run bigger fridges, larger inverters, and sometimes air conditioning, so daily loads of 2,000–4,000 Wh are common, calling for 600–1,200 W of solar and a 300–600 Ah lithium bank.
＋ Do I need an inverter for van life?
Only if you run 120V AC appliances such as a laptop charger on mains, an induction cooktop, or a microwave. Size continuous watts at 1.25× your largest simultaneous AC load and leave surge headroom for motors. If everything you use is 12V DC, you can skip the inverter entirely.
＋ What size charge controller do I need?
For an MPPT controller, take array watts ÷ system voltage × 1.25, then round up to the next standard size (20, 30, 40, 50, 60, 80, 100 A). A 400 W array at 12V needs about 42 A, so a 50 A controller. Moving to 24V roughly halves the amperage.
＋ Can I charge lithium batteries below freezing?
No. LiFePO4 batteries must not be charged below 0 °C (32 °F) — it causes permanent lithium plating and capacity loss. Discharging is fine, but plan on a self-heating battery or a battery heater, and derate usable winter capacity by about 20%.
＋ LiFePO4 vs AGM — which is better in short?
LiFePO4 gives you roughly 80% usable capacity, thousands of cycles, half the weight, and a lower cost per usable kWh over its life. AGM is cheaper up front but only 50% usable and far fewer cycles. For a full-time build, LiFePO4 almost always wins; AGM suits tight budgets and light use.
＋ How much does a van solar system cost?
A modest 400 W / 200 Ah LiFePO4 system with a 40 A controller, 1,000 W inverter, and cabling runs roughly $900 on budget parts to $2,600 with premium brands like Victron and Battle Born. This calculator itemizes a low-to-high range for your exact build.