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Everyone wants AC in their van until they see the power numbers. A 12V rooftop AC unit (Dometic RTX 2000, Rigid HTPX) draws 30-50A continuously — that's 360-600W. Running it for 4 hours on a hot afternoon eats 1,440-2,400Wh. Your entire 200Ah battery. In one afternoon.
Let's do the math: a Dometic RTX 2000 draws ~40A average at 12V = 480W. Four hours of afternoon cooling: 1,920Wh = 160Ah from your battery. A 200Ah LiFePO4 with 80% DoD gives you 160Ah usable — the AC alone empties it. You'd need 400Ah minimum to run AC for 4 hours and still have power for everything else.
⚡ Expert tip
If you run a 12V AC unit, wire it directly to the battery bus bar with 50mm² cable and its own 60A fuse — NOT through your fuse box. The sustained 40A+ draw would overheat blade fuse contacts. Treat it like a second inverter in terms of wiring.
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)
Recommended solar panels
302 Wc
4h average sun hours
Recommended inverter
No 220V appliances — no inverter needed
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
This is why 12V AC in a van is either a shore-power luxury or requires a massive system. The builds that actually work run 400-600Ah LiFePO4 ($1,600-3,000) with 600-800W of solar ($600-800). That's $2,200-3,800 just in battery and solar to support AC for a few hours a day in summer. For most vanlifers, the alternatives are more practical: MaxxFan for airflow (30W vs 480W), parking in shade, reflective window covers, and timing your day around the heat. I lived in Spain for two summers without AC — the MaxxFan on intake mode plus reflective covers on all windows kept the van under 32°C even when it was 40°C outside. Not comfortable, but livable. If you absolutely need AC, consider a diesel-powered unit (Webasto Cool Top) — it runs off fuel, not battery. Or accept that AC is a shore-power feature and camp at powered sites during heat waves.
Frequently asked questions
How much battery for 12V air conditioning in a van?▼
400Ah LiFePO4 minimum for 4 hours of use per day. A typical rooftop 12V AC draws 35-50A (420-600W). Four hours = 1,680-2,400Wh. With other loads, you need 400Ah to get through one hot day. 600Ah for consecutive hot days.
Can solar power run van AC?▼
Partially. 600W of solar produces ~2,500Wh/day in summer — enough to cover 4-5 hours of AC. But the timing doesn't align: peak cooling need is 2-6 PM, peak solar is 10 AM-2 PM. You need battery buffer. Solar helps recharge but can't power AC directly in real-time.
What alternatives to AC work in a hot van?▼
MaxxFan on intake (30W vs 480W), reflective window covers (drop interior temp 5-8°C), parking in shade, wet towel over the MaxxFan intake (ghetto evaporative cooling), and scheduling your day to be out of the van during peak heat.
Dometic RTX 2000 vs Rigid HTPX?▼
Dometic RTX 2000: 2kW cooling, ~40A at 12V, $1,200-1,500, well-proven. Rigid HTPX: similar performance, ~$900-1,100, newer to market. Both are rooftop units that require a roof cutout similar to a MaxxFan. Neither is cheap to buy or to run.
Is a diesel AC unit better than 12V electric?▼
For battery independence, yes. A diesel-powered AC (Webasto Cool Top) uses fuel instead of battery — 0.3-0.5L/h of diesel. It keeps your electrical system free for other loads. The downside: higher purchase price ($2,000+) and more complex installation.