Decoding RV Generator Sizes: How Much Power Do You Really Need?

Decoding RV Generator Sizes: How Much Power Do You Really Need?

One of the greatest freedoms of RV travel is the ability to explore off the beaten path, away from campgrounds with electric hookups. But enjoying that freedom requires a reliable source of power for lights, appliances, and climate control. For many RVers, that source is a generator. However, choosing the right size generator can feel like navigating a technical maze. Too small, and you won’t be able to run your essential appliances. Too large, and you’ve wasted money, are hauling unnecessary weight, and might be dealing with excessive noise and fuel consumption.

So, how do you decode the jargon and figure out exactly how much power you really need? It all comes down to understanding your power requirements and the specifications of your RV’s electrical demands.

Why Sizing Matters: The Pitfalls of Too Much or Too Little

Imagine you’re boondocking on a hot summer day, ready to kick back and run your air conditioner, only to find your generator trips a breaker the moment the AC tries to start. Or perhaps you buy an oversized generator, only to realize it takes up half your storage space, burns through fuel even on light loads, and is so loud your neighbors complain from two campsites over.

• Undersized Generator: Cannot handle the starting surge of motor-driven appliances (like AC or microwave), struggles with running multiple items simultaneously, can lead to damaged appliances or generator due to overload, leaves you without essential power when you need it most.
• Oversized Generator: Higher purchase cost, heavier to transport, consumes more fuel even when not fully loaded, often noisier (though this varies by type), takes up more storage space.

Getting the size right ensures your comfort and convenience without unnecessary expense or hassle.

Understanding the Language of Power: Watts, Amps, and Volts

Before you can calculate your needs, you need to understand the basic units of electrical power relevant to generators:

1. Volts (V): This is the "pressure" or "force" of the electrical current. Standard household and RV power is typically 120 volts AC (Alternating Current).
2. Amps (A): This is the "flow" or "volume" of electrical current. It indicates how much current an appliance draws.
3. Watts (W): This is the total power consumed or produced. It’s the most common unit used for generator sizing. The relationship is simple: *Watts = Volts Amps**.

Most appliances list their power consumption in watts or amps. If an appliance only lists amps, and you know the voltage is 120V, you can easily calculate the watts (Watts = 120 * Amps).

Running Watts vs. Starting Watts: A Crucial Distinction

This is arguably the most critical concept in generator sizing, and it’s where many people get confused.

• Running Watts (or Rated Watts): This is the continuous power an appliance needs to operate once it’s running. It’s the steady draw.
• Starting Watts (or Surge Watts): This is the extra burst of power needed for a fraction of a second to start motor-driven appliances. Things like air conditioners, refrigerators (compressor types), microwaves, and pumps have high starting watt requirements because they need a significant jolt to get their motors going. The starting wattage can be two, three, or even more times higher than the running wattage.

A generator’s rating will typically list both its continuous (running) wattage and its peak (starting or surge) wattage. You need a generator with enough running watts to power everything you want to use simultaneously and enough starting watts to handle the surge of the largest single appliance you might start while other things are already running.

The Calculation: How to Figure Out Your Needs

Ready to crunch some numbers? Here’s a step-by-step process to estimate your RV’s power requirements:

Step 1: List Every Electrical Appliance in Your RV
Think about everything you might potentially plug in or turn on, including:

• Roof Air Conditioner(s)
• Microwave Oven
• Electric or Propane Refrigerator (if using the electric element)
• Converter (for charging your RV batteries – this can draw significant power)
• Electric Water Heater Element
• Coffee Maker / Keurig
• Toaster
• Hair Dryer / Curling Iron
• Television(s)
• DVD/Blu-ray player
• Satellite Receiver
• Lights (especially if not all LED)
• Fans
• Chargers (phones, laptops, etc.)
• Medical Equipment (CPAP machines, etc.)
• Any outdoor appliances you might use (griddle, lights, etc.)

Step 2: Find the Running Wattage for Each Appliance
Look for labels on the appliance itself, check the owner’s manual, or search online for the specific model number. Record the running watts for everything on your list. If you only find amps, multiply by 120 (Watts = Amps 120). Note: These are often maximum ratings; actual usage might be lower.*

Step 3: Identify High Starting Wattage Appliances
Go through your list and mark the items with motors (AC, microwave, fridge, power tools, etc.). Find their starting wattage. This is harder to find than running watts. Sometimes it’s listed on the appliance; other times, you’ll need to search online forums or use typical estimates (e.g., a 13,500 BTU AC might surge to 2500-3000+ watts).

Step 4: Calculate Your "Maximum Likely Simultaneous Running Load"
This is your continuous power requirement for your typical worst-case scenario of simultaneous use. Think about what you would realistically have running at the same time.

• Example Scenario: AC running + Microwave heating something + Lights on + TV on + Converter charging batteries.
  Add up the running watts for all the appliances you would have running simultaneously in that scenario. This sum is your minimum running watt requirement.

Step 5: Calculate Your "Maximum Likely Starting Load"
This is your surge power requirement.

• Identify the single appliance on your list with the highest starting wattage.
• Add that appliance’s starting wattage to the running watts of all other appliances that would already be running when you start that specific high-surge appliance.
• Example based on Step 4 Scenario: You have the AC running (1500W running), lights on (200W running), TV on (150W running), Converter charging (500W running). You want to start the microwave (1500W running, 2500W starting). Your surge requirement for this moment is: 2500W (Microwave Starting) + 1500W (AC Running) + 200W (Lights Running) + 150W (TV Running) + 500W (Converter Running) = 4850 Watts.
• Now consider starting the AC instead. You have Microwave (1500W running), Lights (200W running), TV (150W running), Converter (500W running) already on. Your AC needs 2800W to start and runs at 1500W. Surge requirement: 2800W (AC Starting) + 1500W (Microwave Running) + 200W (Lights Running) + 150W (TV Running) + 500W (Converter Running) = 5150 Watts.
  Your maximum likely starting load is the highest of these surge calculations (5150 Watts in this example).

Step 6: Choose Your Generator Size
You need a generator that meets both your maximum likely simultaneous running load (Step 4) and your maximum likely starting load (Step 5).

• The generator’s continuous/running wattage rating must be at least the value from Step 4.
• The generator’s peak/starting wattage rating must be at least the value from Step 5.

Always round up and consider adding a 10-20% buffer for safety, future needs, and variations in appliance draw or generator performance (especially at altitude – see below).

• Based on the example: Running requirement ~2350W, Starting requirement ~5150W. You would look for a generator with a continuous rating of at least 2500W-3000W and a peak rating of at least 5200W-6000W. This might translate to a generator often advertised as a 3000W or 3500W running watt unit with a higher surge rating, or possibly two smaller inverter generators run in parallel.

Typical RV Appliance Wattages (Estimates):

• 13,500 BTU RV AC: 1200 – 1800 Running W, 2500 – 3500+ Starting W
• 15,000 BTU RV AC: 1500 – 2000 Running W, 3000 – 4000+ Starting W
• Microwave (0.7-1.0 cu ft): 800 – 1500 Running W, 1500 – 2500 Starting W
• Refrigerator (Electric Element): 200 – 600 Running W (compressor fridge needs starting watts)
• Converter/Charger: 500 – 1000+ Running W (depends on battery state and charger size)
• Electric Water Heater Element: 1000 – 1500 Running W
• Coffee Maker: 600 – 1000 Running W
• Hair Dryer: 1000 – 1800 Running W
• Television: 50 – 200 Running W
• Lights (LED): Very low, perhaps 10-20 per fixture. Incandescent much higher.

Remember: Check your specific appliance labels!

Factors Beyond the Numbers

• Altitude: Generators lose power output at higher altitudes (roughly 3.5% for every 1000 feet above sea level). If you plan to camp at significant elevations, you’ll need a larger generator to compensate for the power loss.
• Boondocking Frequency: If you rely heavily on your generator for extended periods, investing in a slightly larger, more fuel-efficient, and quieter inverter generator might be worthwhile compared to a conventional generator that just meets the minimum.
• Type of Generator: Inverter generators provide clean, stable power (safer for sensitive electronics), are generally quieter, more fuel-efficient, and often have the ability to be run in parallel with another identical unit to double the power output when needed. Conventional generators are typically louder, less fuel-efficient, but can offer higher raw power for a lower cost.
• Budget: Your budget will influence the brands and types of generators available.
• Noise: Campground rules often have noise limits. Inverter generators are usually the quietest option. Size also impacts noise, as a larger generator working harder will be louder than a smaller one loafing, but a larger generator loafing will be quieter than a smaller one maxed out.

Common Mistakes to Avoid

• Ignoring Starting Watts: This is the most frequent error, leading to generators that can’t start essential appliances like the AC.
• Underestimating Simultaneous Use: Only calculating for one or two items at a time. Think about your actual lifestyle.
• Not Checking Appliance Labels: Relying solely on general estimates can lead to inaccuracies.
• Buying Based Only on AC Needs: While the AC is often the largest draw, you need enough running watts for everything else too.
• Forgetting the Converter: The converter charging your batteries can be a significant continuous load, especially after using lights or fans off-grid.

Conclusion

Choosing the right RV generator size is a critical step towards ensuring comfort and convenience during off-grid adventures. It’s not about guessing; it’s about understanding your appliances’ power needs, distinguishing between running and starting watts, and calculating your likely simultaneous load.

By taking the time to list your appliances, find their power draw, and perform the necessary calculations, you can confidently select a generator that meets your specific requirements. Factor in variables like altitude and generator type, and you’ll be well on your way to enjoying reliable power wherever your RV travels take you, without the frustrations of an undersized or oversized unit. Get the size right, and your RV generator will be a source of freedom, not frustration.

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RV Generator Sizing FAQs

Q1: Can I just buy the biggest generator I can afford to be safe?
A: While it ensures you have enough power, it’s usually not the best approach. Oversizing means paying more upfront, hauling more weight, using more fuel (even on light loads), and dealing with increased noise compared to a properly sized unit. Calculation is better than guessing big.

Q2: My AC is 13,500 BTU. What size generator do I need?
A: You need more than just enough running watts for the AC. A 13,500 BTU AC might run on 1500-1800 watts but could need 2500-3500+ watts to start. You also need enough running watts for everything else you want on while the AC is running (microwave, lights, converter, etc.). Calculate your total running and starting needs as outlined in the article. You’ll likely need a generator with a continuous rating of 2800-3500 watts or more, depending on your other loads.

Q3: What if I only want to run my AC? Do I still need a big generator?
A: Yes, you’ll still need a generator capable of handling the AC’s high starting wattage. While you might get away with a slightly smaller continuous rating if literally nothing else is on, the AC’s surge is the primary driver of generator size for many RVers.

Q4: Can I use two smaller inverter generators instead of one large one?
A: Many inverter generator models are "parallel capable," meaning you can link two identical units together using a special cable to combine their power output. This is a popular option as it offers flexibility (use one for light loads, two for AC), easier lifting/storage of smaller units, and redundancy. Check the generator’s specifications for parallel capability.

Q5: What is a soft starter for an RV AC?
A: A soft starter (like Micro-Air EasyStart) is a device installed on an AC unit that significantly reduces the amount of surge power needed to start the compressor. This can dramatically lower the required starting wattage, often allowing a smaller generator (like a single 2000W inverter) to start and run an RV AC that it otherwise couldn’t. It’s an additional cost but can save money/weight on the generator side.

Q6: Do I need a separate generator for battery charging?
A: Your RV’s built-in converter/charger handles battery charging when connected to shore power or a generator. The converter itself draws power from the generator. While some RVers use very small generators just to "top off" batteries, most use their main generator for charging as part of their overall power needs. Ensure your generator size calculation includes the converter’s draw.

Q7: How accurate do my wattage estimates need to be?
A: Aim for as accurate as possible by checking labels or manuals. Using typical estimates is okay for planning, but it’s wise to add a buffer (10-20%) to your final required wattage. Using a tool to measure actual appliance draw can also be helpful for precise sizing.

Q8: What’s the difference between a 30-amp and 50-amp RV generator connection?
A: RVs have electrical service rated as either 30-amp or 50-amp (at 120V).

• A 30-amp service provides a maximum of 30A * 120V = 3600 Watts.
• A 50-amp service is actually two separate 50A legs at 120V, totaling 100A 120V = 12,000 Watts.
  A generator needs to provide enough total* watts to meet your needs and connect appropriately. A 30-amp generator (typically 3000-3600 running watts) is generally sufficient for 30-amp RVs that don’t run two ACs simultaneously. A 50-amp RV often requires a much larger generator (often 5000-7000+ running watts or paralleled units) to fully utilize its capacity, especially to run two ACs. You can use adapter cords, but the generator can only provide its rated power, regardless of the RV’s service rating.