RV/Van Life Inverter Sizing Calculator
Created by: Daniel Hayes
Last updated:
Determine the right inverter size for your RV or van based on your AC appliance needs. Calculate continuous and surge power requirements, battery draw, and get cable sizing recommendations.
What is an RV/Van Life Inverter Sizing Calculator?
An RV/Van Life Inverter Sizing Calculator helps you determine the correct inverter capacity for your camper van, RV, or off-grid system. By analyzing your AC appliance needs, the calculator recommends the right continuous wattage, surge capacity, and provides battery draw estimates.
Choosing the right inverter is crucial - too small and it won't power your appliances or may shut down from overload. Too large and you're wasting money and space. This calculator helps you find the sweet spot based on your actual power needs.
Understanding Inverter Sizing
Continuous Watts: Power the inverter can deliver indefinitely (your primary sizing metric)
Surge Watts: Brief power spike capability for motor startup (typically 2x continuous)
Pure Sine Wave: Clean power safe for all electronics (recommended for van life)
Efficiency: Typically 85-95% - factor in losses when calculating battery draw
Idle Draw: Power consumed when inverter is on but no load connected (5-25W typically)
Frequently Asked Questions
What size inverter do I need for my van or RV?
Size your inverter for 25-50% more than your largest single load, plus a margin for simultaneous use. For most van builds, 1000-2000W handles laptops, blenders, and small appliances. For hair dryers or microwaves, you'll need 1500-3000W. Consider future additions when sizing.
What's the difference between pure sine wave and modified sine wave inverters?
Pure sine wave inverters produce clean power identical to grid electricity, safe for all electronics. Modified sine wave is cheaper but can damage sensitive electronics, cause buzzing in audio equipment, and reduce motor efficiency. For van life, pure sine wave is strongly recommended.
How many amps does an inverter draw from my 12V battery?
Divide watts by battery voltage, then add 15-20% for inverter inefficiency. A 1000W load on a 12V system draws about 100A from the battery (1000÷12×1.15=96A). This is why large inverters need thick cables and adequate battery capacity.
Can I run my inverter while driving?
Yes, many van lifers use their inverter while driving since the alternator charges the battery. However, monitor battery voltage and consider an isolator or DC-DC charger. Running large loads while parked can quickly drain batteries without solar or shore power.
What's inverter surge capacity and why does it matter?
Surge capacity handles momentary power spikes when motors start. A fridge compressor might need 3x running watts to start. A 2000W inverter with 4000W surge handles a 1200W fridge starting (1200×3=3600W surge). Look for 2x continuous rating for surge.
Should I get a 12V or 24V inverter?
Match your battery bank voltage. 24V systems are more efficient for larger inverters (2000W+) because they draw half the current of 12V, allowing smaller cables. Most van builds use 12V for simplicity; larger RVs often use 24V or 48V for big inverters.
How do I wire a large inverter to my battery bank?
Large inverters need short, thick cables - typically 2/0 or 4/0 AWG for 2000W+ inverters. Keep cables under 3-4 feet, fuse at the battery with a Class T or ANL fuse rated for the inverter's maximum draw. Follow manufacturer specifications exactly.
What appliances won't work with an inverter?
Most appliances work fine with pure sine wave inverters. However, induction cooktops often have issues, some microwaves may underperform, and high-draw heating elements (space heaters, hair dryers, electric kettles) drain batteries rapidly. Always check wattage before purchasing.
Sources and References
- Victron Energy, "Inverter Selection Guide", victronenergy.com
- Samlex America, "Inverter Sizing and Selection Guide", samlexamerica.com
- AIMS Power, "How to Size a Power Inverter", aimscorp.net