RV Air Conditioner Size Calculator

Calculate required BTU cooling capacity for optimal RV climate control

RV Length (feet)

RV Width (feet)

RV Type

Ceiling Height (feet)

Insulation Quality

Typical Climate Zone

Window Area (% of wall space)

Standard RV: 15-20%, High glass: 30%+

Number of Occupants

Each person adds ~600 BTU/hr

Electrical Service

What Is an RV Air Conditioner Size Calculator?

An RV air conditioner size calculator estimates how many BTUs (British Thermal Units per hour) your RV needs to stay cool.

BTU measures cooling capacity. The higher the BTU rating, the more heat the unit can remove from the air.

The calculator uses key inputs like:

RV length
RV width
Ceiling height
RV type
Insulation quality
Climate zone
Window area
Number of occupants
Electrical service (20A, 30A, or 50A)

It then calculates:

Total cooling load (BTU/hr)
Recommended AC unit size (13,500 BTU or 15,000 BTU)
Number of units needed
Electrical demand
Installation guidance

Why Correct RV AC Sizing Matters

Proper RV AC sizing affects:

Cooling performance
Energy efficiency
Electrical safety
Equipment lifespan
Comfort in extreme heat

A unit that is too small will:

Run constantly
Struggle in high humidity
Wear out faster

A unit that is too large will:

Short cycle (turn on and off often)
Waste power
Increase upfront cost

Getting the BTU calculation right helps avoid all of this.

How the RV Air Conditioner Size Calculator Works

The calculator uses a structured formula based on RV volume and environmental factors.

Step 1: Calculate RV Volume

The basic formula is:

Length × Width × Height = Cubic Feet

Example:

32 ft length
8 ft width
7 ft ceiling height

32 × 8 × 7 = 1,792 cubic feet

The base cooling load is:

Volume × 3 BTU per cubic foot

So:
1,792 × 3 = 5,376 BTU (base load before adjustments)

Step 2: Apply RV Type Factor

Different RV types have different cooling demands.

Each type adjusts airflow and heat retention:

Travel Trailer → Standard factor (1.0)
Fifth Wheel → Slight increase (1.05)
Class A Motorhome → Higher factor (1.1)
Class C Motorhome → Moderate increase (1.05)
Camper Van (Class B) → Reduced factor (0.85)
Truck Camper → Reduced factor (0.9)
Pop-Up Camper → Lowest factor (0.7)

High ceilings and large windshield areas increase cooling demand.

Step 3: Adjust for Insulation Quality

Insulation makes a big difference.

Excellent (R-15, double-pane windows)
Good (modern standard RV)
Average
Poor (older RV, single-pane glass)

Better insulation lowers the BTU requirement. Poor insulation increases it.

If your RV is older, expect higher cooling needs.

Step 4: Factor in Climate Zone

Your typical camping temperature changes everything.

Mild (85°F max)
Moderate (95°F max)
Hot (105°F max)
Extreme (115°F desert conditions)

If you travel through Arizona or Nevada in summer, you need significantly more BTU than someone camping in Michigan.

Step 5: Window Area Percentage

Windows add heat.

Standard RV window coverage: 15–20%
High-glass RV: 30% or more

More glass means:

More solar heat gain
Higher BTU requirement

Reflective shades or thermal curtains help reduce this load.

Step 6: Occupant Heat Load

People generate heat.

Each person adds about:

600 BTU per hour

So a family of four adds 2,400 BTU to the cooling load.

This matters more than most people think.

Standard RV AC Sizes

Most RV roof air conditioners come in two sizes:

13,500 BTU
15,000 BTU

The calculator determines whether you need:

One 13.5k unit
One 15k unit
Two units
Multiple units for large Class A motorhomes

When Do You Need Two RV Air Conditioners?

Generally:

Under 12,000 BTU load → One 13.5k unit
12,000–14,000 BTU → One 15k unit
14,000–24,000 BTU → Two 13.5k units
24,000–28,000 BTU → Two 15k units
Above 28,000 BTU → Multiple units required

Large fifth wheels and Class A motorhomes often require dual AC systems.

Electrical Service and Power Limits

Your electrical hookup matters just as much as BTU size.

20 Amp Service

Cannot properly run a standard RV AC
Only suitable for small DC or low-draw units

30 Amp Service

Supports one AC unit
Typical running draw:
- 13.5k → ~14 amps
- 15k → ~16 amps
Startup surge can reach 35–40 amps

50 Amp Service

Supports dual AC units
Ideal for larger RVs
May require soft-start kits

If you try to run two AC units on 30A service, you will trip breakers.

Installation Tips Based on Unit Count

Single Unit Setup

Install near center or slightly forward
Ensure 14-inch roof clearance
Use insulated ducting

Dual Unit Setup

One front, one rear
Avoid placing both on same electrical leg
Sync thermostats for zone control

Extreme Heat Setup

Add 20% safety margin
Park with awning side facing the sun
Use reflective roof coating
Install roof vent fans

Small changes can reduce your cooling load by thousands of BTUs.

Example Calculation

Let’s say you have:

35 ft Class A motorhome
8.5 ft width
7.5 ft ceiling
Average insulation
Hot climate (105°F)
25% window area
4 occupants
50A electrical service

The calculator may return:

~24,000–26,000 BTU requirement
Recommendation: Two 15,000 BTU units
Total capacity: 30,000 BTU
Capacity ratio: Optimal

This ensures strong cooling even in peak summer heat.

Signs Your RV AC Is Undersized

Runs nonstop during the day
Interior never reaches set temperature
High humidity inside
Warm rear bedroom area

If this sounds familiar, you likely need more BTU capacity.

Signs Your RV AC Is Oversized

Short cycling
Loud compressor start/stop
Higher upfront cost
Uneven cooling

Bigger is not always better.

Frequently Asked Questions

How many BTU do I need for a 30 ft RV?

Most 30 ft RVs require between 13,500 and 15,000 BTU, depending on insulation and climate.

Is 15,000 BTU better than 13,500 BTU?

It provides more cooling capacity, but only if your RV requires it. Otherwise, it increases cost and power draw unnecessarily.

Can I run two AC units on 30 amp service?

No. A 30A connection typically supports only one standard RV air conditioner.

Does ceiling height affect BTU needs?

Yes. Higher ceilings increase cubic footage, which increases cooling demand.