Off-Grid AC Calculator: Can Your Solar Setup Handle the Heat?
Off-Grid AC Calculator: Can Your Solar Setup Handle the Heat?
The number one question we get at ShockTrail is: “Can I run an AC in my van?” The answer is yes, but the physics are brutal. If you underestimate the BTUs, you sweat.
If you underestimate the power draw, you destroy your battery bank. This tool solves both problems.
The Calculator: BTU & Power Audit
Enter your room dimensions and insulation quality below to find out exactly what size AC you need and, crucially, how much power it will consume.
Off-Grid AC Estimator
Cooling Logic by ShockTrail0 BTU
0 W
0 W
⚠️ This is continuous load. You need a battery bank that can sustain this amperage. Check our Wire Calculator.
Understanding the Results: BTU vs. Watts
Most calculators only tell you the BTUs (British Thermal Units). That is useless for solar. You need to know the Watts.
An air conditioner moves heat. A highly efficient unit (like a 20 SEER Mini Split) moves more heat with less electricity than a cheap rooftop RV unit.
The “ShockTrail Rule” for Solar Cooling
Based on our field tests, here is the reality of running AC off-grid:
- Rooftop RV Units (13.5k BTU): These are power hogs. They draw 1500W+. You cannot run these easily on solar.
- Portable “Hose” Units: Very inefficient. Avoid if possible.
- Mini-Splits (12V/24V or 120V): The gold standard. A 120V Mini-Split can run on as little as 600W once the room is cool.
Insulation: The Secret Variable
You can buy more batteries, or you can buy better insulation. Insulation is cheaper. As shown in the calculator above, upgrading from “Poor” (bare metal/glass) to “Spray Foam” cuts your power requirement in half.
Recommended Battery Banks for AC
| AC Runtime Desired | Required Lithium Battery (12V) | Est. Cost |
|---|---|---|
| 2 Hours (Cool down before bed) | 200 Ah | $600 – $900 |
| 4-6 Hours (Afternoon sun) | 400 – 600 Ah | $1,500 – $2,500 |
| 8+ Hours (All Night) | 800 Ah + Massive Solar | $4,000+ |
3 Tips to Run AC Without Going Broke
1. Park in the Shade
This sounds obvious, but direct sun on a vehicle roof raises the surface temperature to 160°F. Parking in the shade reduces your cooling load by 40%. Use portable solar panels if you need to charge.
2. Soft Start is Mandatory
If you use an inverter, the initial startup spike of an AC compressor can trip it. Install a “Soft Start” capacitor to reduce that spike by 70%. See our inverter sizing guide for more.
3. Don’t cool the whole house
If you are in a van or cabin, use a curtain to partition off the sleeping area. Cooling 50 sq ft is easy. Cooling 200 sq ft is hard.
Frequently Asked Questions (FAQ)
What is SEER rating?
Seasonal Energy Efficiency Ratio. Higher is better. A 20 SEER unit uses half the electricity of a 10 SEER unit. For off-grid, never buy below SEER 18.
Can I use a 12V Air Conditioner?
Yes, brands like Velit or Dometic make DC air conditioners. They are efficient because they skip the inverter loss, but they are expensive upfront. Check ShockTrail reviews for models.
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