What Size Portable Generator Do I Need

According to market research by Generac, about 12% of Americans own portable generators. Portable generators come in handy, especially if you live in an area with rare power outages, love going for picnics, or working on a construction site. However, to safely power your home with a portable generator, you need to install a manual transfer switch.

While a standby generator can also provide you with power during a power blackout, it’s not portable. As a result, you cannot use it for outdoor purposes such as picnics and remote jobs. So, what size portable generator do you need? The appliances you’ll be plugging into your generator and their power requirements determine the generator’s size to buy. Read on to learn how to size a portable generator for your needs.

How to Calculate the Size of a Generator for Your Needs

Before buying a generator, you need to relate its power output against your power requirements. The power output in generators is measured in watts.

Portable generators used for camping and tailgating activities can produce anywhere from 1000 watts to 3000 watts. Such are light-duty portable generators.  However, for home and construction powering purposes, you’ll need a heavy-duty portable generator, one that can deliver over 10,000 watts. Such a power output is enough to run most appliances at home and various power tools at a job site.

So how do you estimate your power needs?

Step1: Identify the Appliances you Need to Run on the Generator

what size portable generator do I needIf you’re looking for a generator to power your home, draft a list of the essential appliances you want to run during power outages. Some of these appliances include a refrigerator, lighting, air conditioning unit, among others.

If you need the generator for your RV, check the size of your RV AC unit and other appliances you would wish to run.

Step 2: Calculate Your Total Power Requirements

what size portable generator do I needThis step involves getting the starting watts and running watts of every appliance that you will be powering. If your appliances are rated in volts and amperes, multiply the voltage by amperes to get the total watts. For appliances that don’t have an electric motor, for instance, TVs, desktops, and lights, their starting and running wattage are the same.

However, devices with heating elements or electric motors such as microwaves, fridges, AC units, drills, and pumps are different. Their starting power can be thrice their running power. This is because such equipment has motors, compressors, or heating components that require more power to start than to run.

Starting wattage is the temporary power required to create the momentum of an electronic appliance to run. This temporary power is also called a surge or peak wattage. On the other hand, running watts is the amount of power required to keep electronic equipment running. Running wattage is also known as rated watts which is usually lower than the starting watts.

what size portable generator do I needTherefore, it is essential that when shopping for a portable generator, you ensure the generator’s starting power is more than that of your appliance. If the appliances have a greater starting wattage than the generator, the generator won’t run them. This is regardless of whether the generator’s running power matches the running power of your appliances.

If the starting and running watts are not on the equipment’s tag, you can inquire from the manufacturer via their website. Alternatively, you can use a wattage meter to get the information.

Step#3: How Many Appliances Will You be Running Simultaneously?

If you’re interested in running a single appliance at a time, step#2 above will help you settle for the right generator size. For instance, to power, a 10,000 BTU AC unit will need a generator that can deliver 2,200 starting watts and 1,500 running watts. A Honda EU2200i, which delivers a peak wattage of 2200W and 1800 rated watts, can comfortably power such an AC unit.

But what if you want to power multiple appliances at a go? Get the total of the starting wattages and running wattages separately. The total starting watts will reflect the minimum size of the generator that can power the appliances.

However, if some of your appliances don’t have starting power, include their running power into your starting power calculations. If you have appliances with high starting power, start connecting one at a time as you and incrementally add the rest. Doing so will lower the possibility of having power surges.

If a generator cannot produce enough power for your load, the overload circuit breaker will trip. And this will shut down your generator.

Step#4: Go for a Generator that Offers More Power Than What You Need.

After knowing your power requirements, don’t pick a generator with the exact power output. Instead, go for one with extra wattage. Here are reasons you should pick a generator with extra power output;

  • To avoid overload scenarios. Buying a generator with a few hundred extra watts gives you an allowance to run few extra appliances.
  • You will be avoiding a scenario of running a generator at 100% load, which can be noisy.
  • Generators that run at full load tend to have a shorter lifespan.

Choose a portable generator that has 10 to 20% more power output than your power requirements.

Benefits of Choosing the Right Size Portable Generator

  • Your appliances will not shut down unexpectedly due to overloading.
  • It increases the lifespan of your generator, which will also lower the maintenance costs. Generators running on an overload capacity have a short lifespan.
  • Your appliances will be safe since there will be minimal power surges caused by overloading a generator.
  • The generator will give you an excellent performance.

Other Factors to Consider When Sizing a Portable Generator

Noise level

what size portable generator do I needDifferent portable generator brands operate at different noise levels. Portable non-inverter generators are noisier than inverter generators. Suppose you are buying a portable generator for your construction project. In that case, a noisy generator may not be of concern to you. However, if you buy one for tailgating, RVing, and camping, go for a small portable generator with low noise production. Inverter generators are best for operating with minimal noise output.

Fuel Consumption

A 10,000 watts generator will consume more fuel than a 2,200 watts generator. If you don’t need high power output and are concerned about fuel consumption, choose a generator with low power output.

  • Single fuel or dual-fuel source

Single fuel generators are small in size and power output compared to dual fuel generators. So if you’re interested in a dual fuel generator, be ready for a big generator in size and power output.

How to Keep Portable Generators in Top Shape

It feels nice to have a performing generator whenever you need it to meet your power demands. However, this requires proper care and maintenance. Check out the pointers below;

what size portable generator do I needInvest in a cover: Even though generators must be used in the open air, exposing them to harsh environmental conditions is not wise. Direct water pour on your generator’s internal components can lead to malfunctioning; this is likely to happen when it rains. You can void this by investing in a generator enclosure.

Do not allow the generator to run out of fuel: Ensure that your portable generator has adequate fuel whenever it is running. Mechanically, generators produce electricity by continuously spinning magnetic coils alongside each other. When the fuel runs out, the magnetic coils stop generating electricity. But the plugged-in appliances continue drawing power from the coils, which demagnetizes the coils. It’s expensive to return such coils to their best state. You can void such repair costs by ensuring that the generator has sufficient fuel whenever it is running.

Do not use overstayed fuel: Fresh fuel is suitable for your generator’s engine. However, using stale fuel can cause clogging in your engine, leading to the generator’s malfunction and lowering its lifespan. You can avoid this by regularly running your portable generator for a few hours, even when using it.

Regular servicing: Like how you would service your car after a specific period, schedule regular generator servicing. You should plan on servicing the generator at least once in four months. It will keep it at its best state.

Frequently Asked Questions

What Size of a Generator do I Need to Run the Entire House?

Most household appliances can run on a generator producing 5,000 to 7,000 running watts. However, you can be precise on the size of the generator by checking the actual wattage of your household appliances. For example, a 7,500 running watts generator can power a refrigerator and freezer, well pump, and lighting circuits at once.

Is it okay to Power my Sensitive Electronics with a Portable Generator?

It is only okay if the portable generator produces clean power, less than 3% THD (Total Harmonic Distortion). The power supplied by the municipal or state grid is clean and stable, with less than 3%. Unfortunately, most heavy-duty portable generators produce unstable power with over 3% THD. It makes them unfit for powering sensitive electronics, including laptops, flat-screen TVs, and other modern electronics.

However, a portable inverter generator can power your vulnerable electronics with no risk of damaging them. This is because inverter generators are mechanically designed to produce clean and stable output power with less than 3% THD.

Final Thought

So, what size portable generator do you need? It will depend on the devices you will be plugging in. There are different generators in the market with varying power outputs. To pick the right one for your needs, you must know how to estimate your power needs. First, get to know the appliances you want to run and their total power requirements. Next, identify the appliances that you’ll be running concurrently and then choose a generator that has more power output than your total power requirements.






About Steve Stuart

Steve Stuart is an electrical engineer who developed interest on generators during his school years. After school, he became a generator enthusiast. This is after encountering power supply problems at the area of residence where he lived. Power would be on and off and so food would go bad and the room heater would go off especially during winter. After trying the different generator brands for several years, Steve now provides information on the available brands and products in the market today. Based on his experience, he gives the do’s and the don’ts when it comes to generator use.

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