The whole essence of spending time in an RV is unplugging and driving to beautiful campsites to enjoy nature. If you desire to be off-grid for long, you will need a reliable power source to keep your basic house electronics.
While solar and an upgraded alternator are an excellent way to put renewable or unobtrusive power into your house batteries, there are times when they are not enough.
Your upgraded alternator won’t charge your batteries well if you stay parked for a week or drive up and down mountain roads at low speeds. The solar panels won’t make enough electricity in winter.
Your only solution is getting a backup generator. The question is, how big of a backup generator is enough for my RV or off-grid motor home?
How Big of a Generator Do I Need for an RV: Quick Answer
The ultimate size depends on your budget and how you want to use the generator. If it is a backup for when off grid or your battery bank is low, sizing something cheap and efficient will help you power critical loads as you charge up the batteries. 3000 to 4000 watts will be enough.
If you want the generator as a full-time backup that can power everything in your RV, you will have to do the math as explained below and figure out the ideal power you need to run your rig as if it were plugged into a mains power supply.
It Depends on Your RV Size and Installed Electronics
Your RVs power consumption will determine how big of a generator you need. An excellent way to estimate expected power consumption is by determining your RV’s size. Logically, bigger RVs have more prominent spaces and more accessories, meaning they need more power.
Using RV Size to Estimate Power Consumption
Here is a quick estimate using RV size. Remember, it is not very accurate since RV specs change.
- Class B Van with an AC unit: 2000 to 3000 watts
- Class C RV with a single AC unit: 2800 to 4000 watts
- Class A RV with two AC units (30k BTUs total) 5500 to 8000 watts
- Fifth wheel with two AC units: 5500 to 7000 watts
What Appliances Will You Be Running?
Regardless of your RV size, the equipment you choose to run when off-grid determines how big of a generator you need.
While most RVs have AC systems, not everyone runs their air conditioning when not plugged in. If you are on a tight budget, you could decide to make trade-offs on power-hungry devices so that you can power your motor home on a smaller generator.
Some of the most common power-hungry devices in an RV are:
- The air conditioning
- The fridge
- An induction cooktop
- Electric hot plate
- A space heater
- Laundry machine or dishwasher
- The coffee maker
- A toaster
- A blender
- The fridge
- A hairdryer
Each of the above accessories can easily pull over 1000 Watts depending on the size and type.
Having just one of them could force you to get an RV generator that can supply 30% more power than the most power-hungry device in your house.
ProTip: Appliances with motors and compressors like the fridge and laundry machine might have a high surge current when starting. This will task the generator more.
Don’t Estimate: Use a Meter.
Getting an AC meter or borrowing one is a great way to estimate the maximum power you can ever draw on your system.
Plug the meter before connecting the mains power cord to your RV and use it to identify the highest power draw ever when running all appliances. This will give you the ideal figure of how big a generator you need to run your RV.
The power rating of your offshore power connector can also help you estimate the max power your RV was designed to handle. If it is still stuck without any modifications, you can use the figure to determine how many watts your RV draws.
If it is a 240V outlet rated at 50 Amps, your RV is (use formula Power = Volts x Current)
240 x 50 = 12000 watts
If it is rate 30 amps on a 120V outlet, you can do with 120 x 30 = 3600 Watts and above generator.
What size generator do I need for a 30 Amp RV?
From the calculations above, 3600 watts is the maximum your RV can take unless you’ve modified it. Anything around that power output will be more than enough.
What size generator do I need for a 50 Amp RV?
A 50 Amp RV can draw up to 12000 watts. They do this by using a 240W outlet or two 120V outlets, each pushing 50 Amps.
Theoretically speaking, you can max out your 50 Amp RV by getting a 12000 Watt generator. In reality, this is way more power than you need on a mobile home – unless you have it parked at a permanent spot and run other power tools off it.
You could still use a 3000 Watt Generac generator on such a massive RV as long as you remember you have less power at your disposal and avoid running power-hungry appliances.
Generators are Expensive, Make Trade-Offs
The ideal generator size for your RV might be more than you can afford. Moreover, chances are you might never push your rig to maximum power consumption under normal circumstances.
For instance, it would be against the off-grid living philosophy to run your AC with the laundry machine, dishwasher, coffee maker, and hairdryer running. The ideal way is to run different equipment at different times.
You could appropriate power use to avoid running power-hungry devices all at a go. This will bring the generator size to just a smidge above most power-hungry devices.
Are You Complementing Your House Batteries?
If you already have a well-sized solar and house battery system, chances are you are looking for a generator to compliment your battery bank on cloudy days.
In this case, you can go with a small silent generator that only kicks up when the batteries drop below a set value. The generator will provide power for basic amenities as it charges up the batteries.
This means you can still provide the surge power for power-hungry components through a well-sized inverter while the generator focuses on charging up the batteries.
Bigger Generators Could be Noisy and Sometimes Less Power Efficient
While you might be tempted to get the biggest generator possible, this might not be a good idea, especially if you value frugal living and already have solar power or an alternator driving power system.
Going for a cheap, high-quality, 3000-watt generator inverter is better than paying double for a 6000-watt inverter. You can power down heavy appliances, let the generator charge batteries for 2 or 3 hours before turning them on.
Skipping on spending a fortune on the generator will save you money for more batteries and solar panels. This is a plus if you are keen on eco-friendly living.
ProTip: The more power a generator produces, the heavier it gets. You are adding dead weight to your RV, especially if you already have a sizeable lithium battery bank might not be a perfect idea.
Should I Get a Conventional Generator or an Inverter Generator?
Once you’ve figured out your power requirements, you have to decide between buying a conventional generator and an inverter generator.
A conventional generator feeds the power created by spinning the generation circuit straight to the outlets. While there are circuit breakers and some form of voltage regulation, it isn’t often accurate.
The generator uses RPMs to produce the right frequency and voltage power. Precise mechanical is tough. Most mechanical generators tend to surge now and then. The very expensive with high outputs will be more stable and have a power conditioner. Don’t expect this from a cheap Target or Amazon generator.
Inverter generators are a more refined alternative. The difference between a conventional generator and an inverter generator is that the inverter-based unit adds extra solid-state circuitry to provide a stable voltage and frequency sine wave for your appliances.
- The generator’s surging AC is converted to DC power
- The power goes through a DC to AC inverter to generate a stable AC power supply
The result is cleaner power with less distortion similar to or even better than your main’s power supply. They’re perfect if you want to run delicate equipment like computers, smart home appliances, and chargers off the power.
ProTip: Though slightly expensive, inverter generators tend to be better engineered and have better sound insulation making them less noisy than conventional units.
Here are some other notable differences between conventional and inverter generators
- You can get high watts output for the price of a conventional generator. Inverter generators are more expensive due to the extra circuitry
- Inverter generators are more efficient since the additional circuitry ensures the unit only produces as much power as drawn out of it. This is good for your fuel
- Inverter generators tend to be compact and more portable than conventional units of around the same power
- Invertor generators run at a steady low RPM compared to traditional units that surge with power demand. The low RPM naturally makes the inverter generator less noisy
- Some manufacturers program in some intelligence to let you parallel multiple inverter generators. You can get the extra punch by running two generators or going for fuel efficiency and running one when you need the extra power. You can’t do this with a conventional generator.
What Fuel Type Generator Should I Choose?
Choosing the fuel type depends on a couple of factors. First, you have to understand the pros and cons of different fuel types.
Propane/ LPG Generators
Propane generators run cleaner since propane combusts better than gasoline or diesel. Even though they give you fewer emissions, they pack less punch since propane has less energy per unit than gasoline or diesel.
Additionally, propane is cheaper than gas in most countries. You might save some money running yours on propane.
This could be a good idea if you already have big propane bottles to run your heat, fridge, and cooker. You won’t have to go out of the way to purchase independent fuel just for one need.
Gasoline generators are the most common market, especially when shopping for low 1000 to 8000 watts.
They are easy to use and run. Moreover, they are light and more compact than their diesel counterparts. However, they have to run at higher RPMs to hit their rated power unit. (This is normal, gasoline engines, even in cars, achieve max power at a higher RPM than diesel)
Due to the higher RPMs, they might be noisier than a diesel of the same output. Moreover, this makes them not suitable for long hours on end since they heat up fast.
Gasoline generators are perfect if your RV runs on gasoline and not looking for high output units. Sticking to the same fuel as your RV makes it faster to fuel.
Diesel generators are sturdier, heavier, and more efficient. Diesel engines are known for their torque, even in vehicles.
As such, you can get more power from the generator at lower RPMs than gasoline and propane. This means the generator will be quieter and can produce way more power. This is why most big and commercial generators are all diesel-driven.
The diesel engine’s low RPM, efficiency, and tenacity mean diesel generators can run days on end without any problem.
Check this too: Onan Generator How to & Troubleshooting Guide
The generator will consume less fuel thanks to diesel engine efficiency. Even though they are more durable and require less maintenance, you might have some trouble during cold weather starts.
If you want high output (above 5000 watts), go for a diesel generator, or your RV runs on diesel. This way, you can plump the generator straight to the main fuel tank and won’t have to worry about buying fuel for your generator too. Just one refill is enough to run your vehicle and the generator.
Most big RVs come with a pre-installed diesel generator plumbed into the fuel supply and wired into the house electricals. Manufacturers know diesel is the best way to go if you need reliability and high wattage.