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How big a battery do you actually need? Enter your appliances below and the calculator does the math — accounting for fridge runtime, inverter losses, depth of discharge, and days of autonomy you want.
The quick formula if you want to do it by hand: add up your daily Wh consumption (watts × hours for each device), divide by 12V, divide by 0.8 (usable DoD for LiFePO4), then multiply by your desired days of autonomy. Example: 700Wh/day ÷ 12 ÷ 0.8 × 3 days = 218Ah → round up to 200Ah or 300Ah.
⚡ Expert tip
Size for your winter consumption, not summer. In winter you run the diesel heater fan, charge more devices (shorter days = more indoor time), and get less solar. A battery that's perfect in June can leave you stranded in December.
Example calculation for your setup
Results based on a typical use case
| Appliance | Power | Usage/day | Wh/day |
|---|---|---|---|
| Compression fridge | 45W | 24h | 1080 |
| LED lighting | 20W | 4h | 80 |
| Water pump | 30W | 0.5h | 15 |
| Phone charging | 15W | 2h | 30 |
| Daily consumption | 1205 Wh | ||
Recommended LiFePO4 battery
126 Ah
(80% depth of discharge)
Recommended AGM battery
201 Ah
(50% depth of discharge)
Adjust these values with the calculator below
VANPOWERCALC PROYOUR ENERGY PROFILE
YOUR ENERGY PROFILE.
This document contains the sizing of your future electrical installation, calculated based on your appliances.
Minimum Daily Consumption
0 WH / DAY
Inventory:
SYSTEM SIZINGPage 2
Battery
To guarantee 0WH without damaging your bank (80% max discharge):
0 AH
LiFePO4 12V
Solar
Minimum power required to recharge your consumption:
0 W
via MPPT
220V AC
Maximum power (with 25% safety margin).
0 W
No Need
Safety & CablingPage 3
12V Cable Sizing Guide
Use this professional reference table to select the correct gauge (mm²) for your cables. For 12V in a van, the maximum tolerated voltage drop is 3%. Always use multi-stranded flexible automotive wire.
| Current (A) | Round trip < 2m | Round trip 4m | Round trip 6m |
|---|---|---|---|
| 5A (LEDs, USB) | 1.5 mm² | 2.5 mm² | 4 mm² |
| 10A (Fridge, Pump) | 2.5 mm² | 4 mm² | 6 mm² |
| 20A (Heater) | 4 mm² | 10 mm² | 10 mm² |
| 50A (DC/DC Booster) | 10 mm² | 16 mm² | 25 mm² |
| 100A (Inverter) | 25 mm² | 35 mm² | 50 mm² |
Fuse Sizing
The fuse protects the wire, not the appliance. Always place it as close to the power source as possible (battery or busbar).
- Wire 1.5 mm² → Max fuse 10A
- Wire 2.5 mm² → Max fuse 20A
- Wire 4 mm² → Max fuse 30A
- Wire 6 mm² → Max fuse 40A
- Wire 10 mm² → Max fuse 60A
SCHÉMA ÉLECTRIQUE
PANNEAUX SOLAIRES
0W
REGULATEUR MPPT
BATTERIE AUXILIAIRE
0 Ah
Lithium LiFePO4
FUSIBLE
FUSIBLE
BOÎTE À FUSIBLES 12V
Pompe, Leds, Frigo...
CONVERTISSEUR 220V
NON REQUI
PRO GEARPage 4
SHOPPING LIST
Where to find this equipment? Here is the community-approved selection.
12V 6-way Fuse Box
Mandatory protection
Digital Multimeter
Test your connections
Heavy Duty Crimping Tool
For perfect lugs
Heat Shrink Tubing
Insulation and safety
GENERATED BY VANPOWERCALC PRO - UNLIMITED.
About this tool
Most vanlifers fall into three consumption brackets. Minimalist (lights + phone + small fan): 150-250Wh/day → 100Ah is plenty. Standard vanlife (fridge + lights + phones + occasional laptop): 500-800Wh/day → 200Ah sweet spot. Digital nomad / heavy user (fridge + all-day laptop + monitor + router + coffee maker): 1,000-1,500Wh/day → 300-400Ah. The calculator on this page handles all the edge cases: inverter efficiency loss (typically 10-15% for AC devices), temperature derating (cold weather reduces effective capacity), and charging source offset (if you drive daily, the DC-DC charger reduces your battery storage needs). One mistake people make: sizing the battery for zero solar or driving. If you have 200W of solar and drive 1-2 hours/day, your effective charging input is 600-1,000Wh — that changes the autonomy equation dramatically.
Frequently asked questions
How do I calculate what battery size I need?▼
Daily Wh ÷ 12V ÷ 0.8 DoD × autonomy days = Ah needed. Example: 700Wh/day ÷ 12 ÷ 0.8 × 3 days = 218Ah. Round to nearest standard size: 200Ah or 300Ah.
100Ah vs 200Ah vs 300Ah — which do I need?▼
100Ah: weekend trips, minimal loads. 200Ah: standard vanlife with fridge. 300Ah: digital nomad, heavy inverter use, or winter camping. When in doubt, go one size up.
Does the calculator account for solar?▼
Yes — enter your solar panel wattage and the tool subtracts estimated daily solar harvest from your consumption. This shows how battery size and solar work together.
Should I size for summer or winter?▼
Winter. Solar production drops 50-70%, diesel heater fan adds load, and you spend more time inside using electricity. A battery sized for winter handles summer easily with surplus.
200Ah LiFePO4 or 400Ah AGM?▼
200Ah LiFePO4 every time. It gives 160Ah usable (at 80% DoD) vs 200Ah usable from 400Ah AGM (at 50% DoD). The LiFePO4 weighs 25kg vs 120kg for the AGM. And lasts 5x as many cycles.