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What Size Propane Tank for 20 KW Generator

Let’s talk about propane gas and why you need it for a generator. Specifically, let’s get clear on what size propane tank for a 20 KW generator. I was so confused when I had to make this important and expensive decision for myself. We’ve been doing many cabin updates, including reglazing our windows and installing new fireclay tile. While that’s the pretty stuff, making system upgrades is just as necessary so that in the event of a power outage, we can rest assured that our cabin can be powered safely to be enjoyed all year long and nothing is making me feel more at ease than knowing that we have a 18-20KW Generac generator and sufficient propane tanks to power it for weeks at a time.

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Here’s the truth: Having a whole-house generator does little good if you don’t have enough fuel to power it. That’s why we ended up getting a 500-gallon tank. Although we ended up going with an 18kW generator purely based on size, it is more than enough for the 1,000 sq ft space, and if we decide to upgrade to a 20kW model in the future, we certainly can.

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So what is the simple answer to what size propane tank for 20 KW generator should you buy? In most situations, a 500-gallon tank will be more than enough. However, depending on your situation, you can get away with a significantly smaller tank. Still, I don’t think the price and hassle of running out in a remote area and paying Sur-charges on delivery during peak rain or fire seasons is worth it. You can just go for the 500-gallon tank. It will last you almost two whole weeks, which is almost always enough time for power to be restored. Note that most forced outages last up to 7 days in Northern CA. What to know more? Here are a few more details for those who want to know more: you can find the right tank for your home.

Fuel Consumption – Why it Matters for What Size Propane Tank for 20 KW Generator

Simply put, fuel consumption is how much fuel a generator uses during a specific time. This will vary, depending on a few different factors such as efficiency and generator load. However, understanding how fuel consumption works is very important if you’re trying to figure out what size propane tank for 20 KW generator you’ll need.

What Size Propane Tank for a 20 KW Generator?
Photo via Dwell

One thing I do want to note before we start: in this article, I’m assuming you’re using a propane generator to provide a temporary solution to the lack of electrical services in your area. Liquid propane (LP) is a popular choice, but it’s not the only choice. You can use a similar process to determine your fueling needs, even if you’re using natural gas or an alternative option.

With that out of the way, let’s get into the nitty-gritty.

How Fuel Consumption Works

Propane Tank Size Options

When fuel burns, it generates energy that can then be converted into electricity. Although propane doesn’t have as high of an energy density as gasoline, it’s still fairly efficient, making it a great way to power your generator.

Fuel consumption itself can be measured in gallons per hour (GPH) or liters per hour (LPH). This number tells you how much propane the generator will consume in a given time frame. Using that number, you can determine what size propane tank you will need.

Sadly, it’s not quite that simple. There are a couple of other factors to consider as well. After all, running your entire home will require much more energy than turning on a simple lamp.

Factors to Consider

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There are four main factors to consider when trying to figure out what size propane tank for 20 KW generator you’ll need. The first one is load, AKA the amount of energy you’ll need. Essentially, the more household gadgets you’re trying to run, the more electricity—or, higher load—you’ll have.

The second one is efficiency. For example, while a 20 kW Generac might be able to efficiently produce energy, a cheaper model may not produce energy as efficiently. This costs you more in the long run, as a less efficient model will require more fuel to produce the same amount of energy as an efficient model.

Another thing to consider is operating conditions. Like other machines that run on fuel, generators can be affected by the environment around them. Things like temperature and altitude can actually reduce a generator’s efficiency, resulting in higher fuel usage.

Lastly, you can never underestimate the importance of routine maintenance. Without proper maintenance, a generator won’t be able to run at peak efficiency. Similar to bad operating conditions, this will have a negative effect on the overall efficiency.

Determining the Perfect Propane Tank Size

what size propane tank for 20 KW generator bedroom
Design via Hammer & Spear

Alright, so now you know what fuel efficiency is and which factors can affect it. What’s next? Well, you should never assume that your generator will run at peak efficiency all the time. I usually recommend leaving a bit of “wiggle room” to ensure that you’ll be left with reliable power systems.

While it’s unlikely that your ​standby power unit will be constantly in use, you still want to ensure that your automatic standby generator will meet your needs at the moment. That said, figuring out the ideal tank capacity shouldn’t be too hard if you follow the next few steps.

What Size Propane Tank for 20 KW Generator – Find Your Ideal Fuel Consumption

Interior design - Furniture what size propane tank for 20 KW generator
Cabin via Floyd Home

The process of figuring out what size propane tank for 20 KW generator you need starts with determining your generator’s fuel consumption. You can find that out using one of these three approaches:

  • Looking at your generator’s specs
  • Running tests yourself, or
  • Using an online fuel consumption calculator

You can usually find your generator’s specs with the paperwork that came with the machine. It should include fuel consumption and efficiency data. If not, this is often available online as well.

Alternatively, you can run a few tests yourself. Use a specific load, run for a specific time frame, and record how much propane the machine has used.

Lastly, if you’re fine with just a rough estimate, there are plenty of online calculators that you can use to calculate the expected fuel consumption. However, do note that you’ll still need to know how much load you anticipate putting on the generator if you want to find the right size propane tank.

Comparing Consumption to Demand – What Size Propane Tank for 20 KW Generator

what size propane tank for 20 KW generator

With consumption and load data in hand, figuring out the rest should be fairly easy! Just do some basic math to figure it out. For example, let’s say your generator uses 2 gallons of propane per hour. We’re assuming this is at full load (which it likely won’t be most of the time).

At that rate, your generator will use roughly 48 gallons of propane per 24-hour period. If you only needed a day or so worth of power then a 100-gallon tank would be more than enough. However, if you anticipated outages lasting multiple days, you’d definitely want to go with a larger tank.

Essentially, you just want your backup generator to have enough fuel to power it for the allotted time frame, and then some. Like I said before, never assume peak efficiency at all times. As long as you have enough (plus a bit to spare), then your generator should be well-equipped to meet your power needs.

Other Things to Think About

what size propane tank for 20 KW generator stove

You’ve figured out what size propane tank for 20 KW generator you’ll need. Is there anything else? Well, there are a few other things you might want to take into consideration. Don’t worry, though, as we’re almost done.

How Often You’ll Use Your Generator

Cabin inspo what size propane tank for 20 KW generator

You should really have a solid idea of how often you’ll use your 2 kW generator. Obviously, your power demands will be much lower if you only need to charge a few tools or turn on a light if the power goes out for a few hours. 

However, for long-term outages, routine things like cooking or using the water heater could become an issue. Appliances tend to draw quite a bit of power, so don’t forget to factor these into your calculations.

Essentially, figure out what the main purpose of your generator is. Is it for the occasional outage, or do you need it as a reliable source of backup power? The role it plays will have a great influence on the size of the tank you actually need.

How Much Space You Have

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You might not have thought about this part yet, but propane tanks can get quite large. Are you sure you have enough space? If not, then you might have to deal with refueling a smaller tank more often. If you’re lucky, though, using underground tanks might help you overcome this obstacle.

It’s also important to make sure the tank can be easily refilled. Depending on where you place it in the property, you may need to move a few things around to ensure easy refills.

Aside from physical limitations, regulatory issues like property size or zoning limitations can also pose problems. Even local building codes might give you issues. Make sure to cover all of your bases before purchasing a new tank.

Where You Live


I touched upon it briefly up above, but don’t forget to consider where you live. Things like lower temperatures can definitely affect efficiency, but extremely hot or cold weather can actually damage your tanks if you don’t prepare for them properly. Consider going for a larger tank if you live in a particularly frigid climate.

Aside from that, how’s the weather around there? Is your area prone to natural disasters, or even frequent storms? You’ll certainly want a plan for dealing with weather-related issues, so make sure to factor that into your planning as well.

What Size Propane Tank for 20 KW Generator: A Quick Reference Guide

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To help you quickly figure out what size propane tank for 20 KW generator you might need, I’ve written a quick overview of the most popular sizes below. You certainly don’t want to be left with only a small candle to light your home. Fortunately, this quick reference sheet should help you get an idea of what you’ll need.

Tank SizeCommon UseWeightRuntime
100 gallonsResidential340 lbs.Short
250 gallonsSmall homes850 lbs.Medium
500 gallonsLarge Homes1,700 lbs.Long
1,000 gallonsCommercial3,400 lbs.Extended

Closing Thoughts

Kelly Sikkema FZirmwarM0E Unsplash

Picking out the right gallon LP tank isn’t overly complicated, but it is an important decision. In the event of a power outage, you don’t want to be left worrying “did I get a large enough tank”? Hopefully, by now, you have figured out what size propane tank for 20 KW generator you’re going to need for your home.

One more thing though. The installation of a new generator is never something you should attempt by yourself. Your local propane company or gas company is the perfect service provider for this. I’d shop around a bit for the best pricing, but ultimately, don’t try to save with DIY. Safety is key, especially when dealing with the potential danger of flammable gases.

Well, we’re perfectly happy with our 18 kW generator, 500-gallon setup, and we hope you’ll be happy with yours too. Whether you decide on something bigger, smaller, or the same, let me know in the comments below.

I’m always interested in your household improvements, and I hope you’ve enjoyed reading about mine. Until next time!


How long will a 500 gallon propane tank run a 20kw generator?

Well, your 500 gallon propane tank won’t actually hold 500 gallons of propane. Propane tanks are only filled up to 80% for safety reasons, so you’d actually be working with 400 gallons of propane. Keeping that in mind and averaging going through about 3.44 gallons per hour, you could expect to get about four days and twenty hours worth of power.

How many gallons of propane does a 20kw generator use?

The exact number will vary depending on the factors described above. Still, as a quick reference to help you find the propane tank size, you can generally expect a 20-kilowatt generator to go through about 3.44 gallons per hour.

How long will a 100 lb propane tank last on a generator?

The actual run time you get will depend largely on the wattage of the generator you’re using. While a 7-kilowatt generator could be powered for up to 65 hours by such a small tank, a 20 kW generator would likely last for less than seven hours.

Does a 100 lb propane tank have more pressure than a 20 lb tank?

Assuming both tanks are stored in the same environmental conditions, the smaller tank should have the same amount of internal pressure as the bigger tank.

Does a 100lb propane tank need a regulator?

Yes, but you should always make sure you have the right regulator for the job. While the size of the propane tank does play a factor in regulator selection, so does the task you’re using it for.

How many gallons of propane will a 100 lb tank hold?

You can expect a 100-lb tank to offer a roughly 23 gal tank, which is suitable for short-term cooking or heating.

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