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What Size Generator to Power a House

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Beyond camping and construction, one of the most popular uses for a generator to power a home. Whether you are using it for backup powering during power outages or are engineering an off-grid lifestyle, having a generator to power your home can be a significant source of freedom and security.

When shopping for a home backup generator, one of the most common questions is “what size generator do I need to run a house?” Choosing a properly sized generator will mean the difference between a solid investment and costly frustration. If you are trying to decide what size generator to power a house is necessary, here is what you need to know.

First, Some Technical Aspects

Answering the question “what size generator do I need to power my house” requires first knowing some terminology. Luckily, there are only a few points you need to know, and the terms are simple.

What’s a Watt?

The output of a generator, and input required to run your home, is measured in watts. A watt is simply a unit of power, just like the horsepower in your car. Watts, or wattage, is calculated by multiplying the voltage of the electricity by the amperage of the power.

In the United States, the electricity flowing from your wall is delivered at around 120 volts. Thus, a generator’s wattage is determined by multiplying the amperage of the unit by 120, and the “watt rating” is the result. The smallest models of generators, often called “suitcase” generators, produce about 1,000-watts.

In contrast, larger models can produce 12,000-watts or even more. You may see a generator’s output listed as “kilowatts” or “kW.” This is simply a shorthand method of reporting the unit’s capacity, wherein 1kW = 1,000-watts.

Surge vs. Continuous

When looking at the specifications of a generator, you may see two separate outputs listed. The higher number will be a “peak” or “surge” output, whereas the smaller number will be a continuous output. In the same way that you can walk for a longer distance than you can sprint, generators have a peak output that they can only output for a brief moment. To understand the need for these two measurements, it is important to understand a concept known as “inductive load.”

Certain devices in your home, such as an air conditioner, fan, or a refrigerator, are powered by electrical motors. The process of getting an electric motor moving requires significantly more power than the electricity needs to keep it moving. Because of this, any device with an electric motor will have an “inductive spike”, wherein it requires more power in the moments after it is turned on. Let’s consider an example.

A medium-sized refrigerator will typically have a running wattage of around 800 watts. However, the spike required to start the motor will be about twice that, or 1,600 watts. Thus, although a generator rated at 1,000-watts of continuous power could run this hypothetical refrigerator, the generator would need to be rated for at least a 1,600-watt peak output to allow the fridge to cycle normally.

When tallying the load of various appliances or utilities in your home, you will need to keep this spike in mind. Even if a generator has enough output to keep an appliance running, it is of little use if it can’t provide enough juice to get the motor started. If you cannot find the surge requirements listed for a specific device, simply doubling the continuous rating is generally a good estimate.

Is an Inverter Generator Worth the Expense?

Inverter generators are a new category of generator that has become extremely popular in recent years. Inverter generators use a slightly different method of generating power that makes these models cleaner, more efficient, and lighter. The tradeoff for this efficiency is the increased expense. Depending on the specific model, an inverter generator can often cost twice as much as an equivalent traditional unit.

So, is it worth shelling out the extra cash? It depends. The electricity generated by a traditional generator is fairly unregulated. The voltage can vary significantly, and the frequency can be inconsistent. As the name would suggest, inverter generators use an inverter to generate the 120-volt electricity used to power your gear. The energy created by an inverter generator is much more consistent and similar to the power that normally comes out of your wall.

For powering some devices, this can make a significant difference. Sensitive electronics typically require or strongly prefer the power created by an inverter generator. The inconsistent power output of a traditional unit can damage laptops, TVs, or other gadgets. Thus, if you intend to run a lot of delicate electronics, an inverter generator may be worth the additional expense.

In contrast, less complex items such as lights, power tools, or air conditioners will typically be indifferent to the source of power. For this reason, many users opt to purchase two generators. One large traditional model for powering high-draw items, and one smaller inverter unit for power electronics.

Your Needs Will Depend on Your Home and Your Expectations

There is no single answer to the question “what size generator to power a house.” As with many considerations, the final answer will depend a lot upon your circumstances and expectations. Here are the key considerations.

Is it a Permanent or a Temporary Solution?

The size of the generator you need to power a house can vary greatly depending on whether you view the generator as a permanent or temporary source of power. For a quick power outage where you simply need to run an extension cord to your fridge and a lamp or two, a much smaller generator may suffice. However, if you intend to permanently run all of the equipment in your home from the generator, then you should consider a much larger model.

If you are in the former camp and simply running a few extension cords, you are bypassing a lot of the electrical demands of a typical home. Because air conditioners, water heaters, and furnaces are generally hard-wired into your home’s electrical system, a temporary generator will not need to run these demanding appliances.

Alternatively, if your generator will be wired into your home as a permanent back-up source, you will need a fairly sizable generator. There are two reasons for this. First, a generator running a complete home will be tasked with running many “background” systems that you may not even think about, like a security system or random attic lights you forgot to switch off.

Secondly, a permanent home backup generator will not have the benefit of timing or control. In a temporary setup, it is easy to make sure you never turn your microwave on at the same time as your blender. In contrast, a whole-home generator may have to cope with the simultaneous demands of an HVAC system turning on at the same time as a water heater. These individual loads can add up quickly.

HVAC is a Huge Draw

One of the most common reasons to want a generator to power a home is so that your HVAC system, be it air conditioning or electric heat, can continue running in the face of a power outage. Unfortunately, HVAC systems are also some of the most electrically demanding appliances in a typical home. If you anticipate running air conditioning, you will need at least 4,000-watts of capacity for a typical central AC system, and around 1,500-watts for a window unit. Heat is similarly demanding, with even the smallest space heater requiring almost 2,000-watts.

Consider Your Appliances

The details of your appliances can greatly impact how large a generator you may need to power your home. To answer “what size generator do I need for my home”, you need to consider the style of appliances your home contains. Many appliances in a home can be purchased in either electric or gas (be it propane or natural gas) configurations. Logically, the gas versions of appliances will be significantly less demanding on a generator than their electrical equivalents.

Generating heat using electricity is a fairly inefficient process. Thus, if your stove, furnace, or water heater are electric, you will need a significantly higher capacity generator to satisfy your power demands.

Time to Take a Tour of Your Own Home

The most accurate way to answer “what generator do I need for my house?” is to take a quick tour of your home with a pen and pad in hand. Think about a typical day and consider every appliance, gadget, light, or utility you may need.

Often, the power draw for an appliance will be written on the unit near the plug. Look on your laptop, for example, and you are likely to see “65Watts” or similar written. By adding up all of the individual devices you will need the generator to power, you can establish an accurate idea of how large a generator you will need.

If you would rather not take the time to research the power demands of each specific appliance in your home, here is a rough idea of many common items.

  • Window Air Conditioner – 1,500 Watts (Peak)
  • Central Air Conditioner – 4,000 Watts (Peak)
  • Standard Refrigerator – 1,500 Watts (Peak)
  • Dorm Fridge – 600 Watts (Peak)
  • Microwave – 1,500 Watts
  • Coffee Maker – 1,000 Watts
  • Space Heater – 1,800 Watts
  • Flat Screen Television – 100 Watts
  • Laptop – 65 Watts
  • Standard Light Bulb – 65 Watts
  • LED Light Bulb – 8 Watts
  • Ceiling Fan – 50 Watts (Peak)

Let’s Look at Some Averages

Determining the exact power capacity of your home can be an admittedly time-intensive experience. Thus, having some helpful rules of thumb can make the process more straight forward. Here are some general outlines of what generators of various common sizes can support.

What Can a 2,000-Watt Generator Power

Small 2kW generators are a popular option because they are compact and efficient. However, they can be fairly limited in the context of powering a home. For a generator this size, it should be possible to power an average fridge, 2 or 3 lamps, and a TV or laptop. However, much beyond this will push the limits of a smaller generator.

What Can a 5,000-Watt Generator Power

This is a popular generator size for RVs and construction sites. With over twice the capacity of the smaller units, a 5,000-watt generator can typically run a fairly large air conditioner, a fridge, and several lights and electronics. It is important to be careful to not exceed the peak capacity, however.

What Can a 10,000-Watt Generator Power

This is a common size for home-backup generators. A 10kW generator is typically the smallest generator that would be installed as a permanent home-backup unit. Although a generator of this size can be costly, it will have enough capacity to run most homes completely with little interruption to your normal routine. If you are trying to decide “what kind of generator do I need for my house” and you want to run all of the bells and whistles, look for a model with at least 10kW of continuous output.

Conclusion

As you can see, although “what size generator do I need?” may seem like a simple question, the answer can require some investigation. Thankfully, a little research can guarantee that you end up selecting a generator that can power your home properly while meeting your expectations and budget.

In the world of powering a home from a generator, the simple maxim of “more is better” often applies. When adding up the individual demands across a common home, the amount of power required can become surprisingly high.

Luckily, there is a truly impressive selection of high-quality, affordable, and large-capacity generators on the market to perfectly suit your needs.

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