What Size Generator Do I Need to Run My Whole House?

Generators can be a lifesaver – literally and figuratively. Some households rely on 24/7 electricity, such as those with members that require medical support. If you are afraid of the dark (and there’s no shame in that!), blackouts are probably your worst enemy and generators will help you survive these incidents without freaking out.

Choosing the appropriate generator for your home is not really as easy as it seems; you need to consider a lot of aspects. How big is your home? Which of your appliances should run on it when your electricity is out? How long should you use it during blackouts? There just are so many questions.

You need to get the proper size generator for your home at the first try. But how exactly can you do that?

permanent generator

Sizing of Generators

When we talk about an object’s size, we normally think about the physical dimensions. Is it big? Is it small? Is it as heavy as a bowling bowl or is it as light as a feather?

Do you remember your basic science classes, especially those that involve electricity? Do the terms ‘watts’ and ‘kilowatts’ seem awfully familiar? If they do, they are actually something you will encounter a lot when it comes to generators.

Contrary to what you might think, the size of a generator has more to do with the electrical power, particularly the watts and/or kilowatts it can supply, and not its physical characteristics. To give you a clearer picture, what is meant by a big size generator is one that can handle a lot of load in terms of kilowatts or watts, not a generator that is as big as a house.

Getting a small size generator for your needs will mean it will run out much faster than you would like, especially if you use it to power several appliances at home. If you need a lot of power at home during the blackout and yet the power generated by your unit is insufficient, a voltage drop is a real possibility. And when it happens, it can damage both the generator and the appliances connected to it.

But if you get something that is just too big, you’ll end up wasting a lot of resources – they cost more and need more fuel to run, even if you will only be using just a few of your appliances.

Factors to Consider When Choosing the Right Generator

Whether it’s your first time to buy a generator for your home, or you’re looking to upgrade your current one, choosing which one to buy is not a simple task. You always have to consider a lot of things, since you would rely on generators for the long run.

The right generator is important. Bigger generators would not always mean better for your home. You only need a generator that would support the total load of all the appliances you would connect to it and the easiest way to know this is to get a licensed electrician to help you out. But if an electrician is unavailable, you can also list down all the electrical appliances to be connected to it and add up their load. It is as simple as that.

Now that you have a rough idea of the total load, you can now have an easier time choosing which generator is right for your home. To do that, here are some major factors you need to take note of:

  • Size – single-phase and three-phase generators are the two types available in the market, and a single-phase generator is best for residential use. Aside from the estimated total load, one thing you should also consider is if you would require the generator to support electrical equipment running simultaneously or not. If you do, you need one that has higher ratings.
  • Where it will be placed – one thing homeowners should keep in mind is that generators, when operating, will produce harmful fumes that can be considered as toxic. As a result, it needs to be placed in a location that makes it compliant with the local laws and regulations that involve health and safety. However, don’t make the mistake of putting it in your garage.

Another thing to keep in mind in terms of a generator’s location is noise. Some generators operate very quietly, and there are also those that make a lot of noise. While the location can lessen the generator noise you hear, especially if it is stored some distance away, it may not be enough if you are sensitive to noise.

Your generator’s required operating temperature, as well as its altitude, should also be considered. Output derating by 1% is required, particularly for every 100 m that it is found above sea-level. Also consider the required operating temperature of the generator; make sure that the location it will be placed in has a temperature that falls within its operating temperature range. Ventilation is equally important and generators need to have their exhaust systems leading outside.

  • Operational costs and conditions – generators should ideally run at 70 to 80% on average in terms of load, and should never work below 40%. It is also not okay to let it run on overload. This is why it is vital for you to know the total load of the appliances you want the generator to run when needed.

Generators will run on fuel, and you have a number of options to choose from. And the more you use it, the more fuel it will consume. Gasoline prices are known to be unstable, so go for the most economical option for you.

Different generators also have different startup methods. You also need to consider this, as some electric motors would require a running power that is 7 times more than their usual requirement.

  • Maintenance and warranty – like any other appliance, warranty and after-care maintenance are important for generators. These appliances are a costly and the warranty can help cut costs if you encounter issues with your generator. This is why it is vital that your generator has excellent aftercare support and warranty. Don’t go for the ones that are sold at very low prices because they are not covered by warranty.

These factors are important and will help ensure that you get the size generator appropriate for your home. Take them into consideration when choosing your unit.

How Does an Electric Home Generator Work?

Homeowners know that generators are there to be the backup source of electricity whenever you experience power shortages or blackouts. But, do you know how exactly they work? You’re not alone if you have no idea how. After all, this is not something that a lot of homeowners would bother learning about – they are only concerned about if they would work or not.

Electrical generators can either be portable ones that can power up a few appliances temporarily, such as those used in camping, or permanent ones that can support an entire house. But no matter the size, they generally work the same way.

To learn how electric home generators work, you should first learn about their main components, which are the following:

  • Frame or Main Assembly – considered as the generator’s body and holds all of its components together
  • Engine – a generator will depend on its engine in terms of the amount of electricity it can produce, since engines are their source of energy
  • Battery Charger – even though generators run on fuel, they still need batteries to start up. Generators have battery chargers that will automatically run to make sure the batteries would work whenever you need to use your generator
  • Alternator – also referred to as the ‘genhead,’ its main role is to convert mechanical energy in order to produce electricity
  • Control Panel – considered as the ‘brain;’ covers not just operational controls but everything involving a generator’s operation from start to finish. Some generators also come with an Automatic Transfer Switch, or ATS, that can sense electrical drops and blackouts. It would automatically trigger the control panel to run the generator. They also come with gauges for the generator itself and the engine
  • Voltage Regulator – capable of converting the produced electricity from AC to DC, as well as control the voltage of the electrical output
  • Lubrication System – generators consist of multiple small components to function. To protect them and make sure they work as smoothly as possible, they need to be well-lubricated. Generators come with indicators to let you know their current lubrication level. Make sure to check it for every 8 hours that it is in operation.
  • Cooling and Exhaust Systems – ventilation is important for generators, since they generate heat and fumes. To prevent overheating, they come with their own cooling systems. And to address fumes produced during operation, they are equipped with their own exhaust systems as well.
  • Fuel System – generators need fuel to run and produce electricity. This is why each generator comes with its own fuel system that normally consists of a pipe that connects the engine and tank, a return pipe, a fuel pump, an injector, a fuel filter, and a fuel tank.

These parts work together to convert electrical energy from chemical or mechanical energy; conversion, not creation, is what generators do. Think of them as electrical motors – only, they work in the opposite direction. The modern generators also take inspiration from the principle of electromagnetic induction developed by Michael Faraday.

Instead of using up electricity as the components move, generators will instead produce electricity through the movement of its parts. In particular, the movement is captured and the electrons present in the energy that is produced by the fuel source will pass through the generator’s electrical circuit. This will then generate the electrical energy.

Fuel Source, Cooling, and Exhaust

We briefly mentioned that generators require fuel to work. Fortunately, you can now choose among generators that require different types of fuel, such as diesel, propane, natural gas, gasoline, or bi-fuel (can run using both diesel and gasoline). For residential generators, propane and natural gas are the most common options. Depending on the size, the fuel tanks may be built-in or separate from the generator and externally placed.

These machines also come with their own cooling system, which can either be hydrogen, water, fans, or radiators. For home generators, they make use of the fan-radiator combination, while industrial generators normally use water or hydrogen for their cooling system.

If you own a car, you know that it releases exhaust fumes whenever the engine is running. The same is true for generators as well and their fumes are also toxic. To minimize its effects, the exhaust pipes of generators are connected to their engines and will direct the movement of the fumes upwards and away from the generators. This is why it is vital that your exhaust system leads outwards.

Laws are in place to monitor emissions coming from generators, especially if the fumes produced are one or more of the following: Hydrocarbons, Nitrogen Oxide or NOx, Particulate Matter, or Carbon Monoxide or CO. Generators that are permanently installed used to be monitored regularly, as mandated by law due to their emissions, but the modern ones are no longer subjected to it because their emissions are generally way below the maximum thresholds set.


Your electric home generator also needs some good old TLC to run as efficiently as possible. You don’t want your generator to suddenly give up on you in the middle of a blackout because it ran out of fuel, the parts are damaged, or for any other reason. To make sure it runs efficiently, make it a habit to do regular maintenance that involves the following:

  • Making sure that the fuel and coolant levels are within acceptable levels
  • Replacing worn or damaged parts asap
  • Doing a load bank test on your generator and testing its automatic transfer switch
  • Regular cleaning and inspection of its battery
  • Replacement of filters for both fuel and air
  • Inspecting the control panel to see if it gives accurate readings
  • Adding engine oil for lubrication whenever necessary
  • Checking the efficiency of the cooling and exhaust systems

If you are uncomfortable at the idea of doing these maintenance activities by yourself, get a professional to do it for you. You need to remember that all appliances, including generators, need to be properly taken care of. A well-maintained generator is sure to last decades.

Power Usage Calculation: How Many Watt Generator Do You Need?

To know what size generator is necessary for your home, you need to learn how much power your household consumes. And if you plan to only run a select number of appliances on your generator, you should also know the energy cost of each of these appliances.

Energy Cost

To know the energy cost, you need to take note of how long you use an appliance in a day. To be precise, the average hours of use each day is needed together with the appliance’s wattage. Electrical appliances normally have labels that indicate the wattage of an appliance but if they don’t, you can use a device that measures it.

To help you out, here’s a list released by the Environmental Protection Agency of common household appliances with their respective wattage level ranges:

  • Laptop – 50 watts
  • 19” to 36” Television – 65 to 133 watts
  • Ceiling Fan – 65 to 175 watts
  • Iron – 100 to 1800 watts
  • Computer Tower – 120 watts
  • Computer Monitor – 150 watts
  • 53” to 61” Television – 170 watts
  • Washer – 350 to 500 watts
  • Microwave – 750 to 1100 watts
  • Toaster – 800 to 1400 watts
  • Coffee maker – 900 to 1200 watts
  • Hair Dryer – 1200 to 1875 watts
  • Dishwasher – 1200 to 2400 watts

For you to know any appliance’s energy cost, here’s how you can compute it:

  1. Get its watts per day by multiplying the wattage of an appliance by the number of hours you use it in a day.
  1. Convert the number, which is known as the ‘watt-hours’, into kilowatts by dividing it by 1000.
  1. Compute for the monthly usage by multiplying it by 30. This is now your monthly usage.
  1. Using your electric bill as reference, get the electric rate and multiply it by the said appliance’s monthly usage.

To give you a better idea, here’s an example:

If you have an appliance that has a wattage of 100 and you use it for 3 hours a day, it has 300 watt-hours each day. Once converted to kilowatts, it becomes 0.3 kWh. Multiply this number by 30, so you’ll get a monthly usage of 9 kWh. And if your electric rate is only $0.20, multiply this rate by your monthly usage. For this particular appliance, using it costs roughly $1.8 each month.

Getting the Right Size Generator

To know what size generator would work for you, you need to first identify which of your appliances would be connected to it; it can be all or it can just be the important ones. It’s also important for you to take note of the starting and running wattages of these appliances. Do note that these two are different.

Starting wattages, which are the ones required by any appliance during startup only, are higher than running wattages. They are often two to three times the wattage used by an appliance while it is in operation. If the actual starting wattage is not stated for your device, you can use this guide as reference.

Once you have made a list of the appliances, including their respective starting and running wattages, you need to add them up to get the total wattage. You will use this as your reference in choosing the right size generator. Make sure to get the total of the starting and running wattages separately. The higher total wattage is the number you need to use.

Here’s what the list would look like for a household that decides to only connect a select number of appliances to a generator:

  • Refrigerator – starting wattage of 1200 and running wattage of 150
  • Hot water heater – starting and running wattages of 4000 each
  • Lights – total starting and running wattages of 300 each
  • – starting wattage of 2000 and running wattage of 1300

The total starting wattages of all 4 appliances is 7500, while the total running wattage is 5750. From these figures, this particular household is safe with getting an 8kW generator, since 7500 watts is the approximate maximum total load for all those appliances that will be connected to it.

For a household that wants to use a generator to power up their whole home during blackouts, the same procedure will follow but their list would be obviously longer and the size generator would be bigger. To give you an idea, here’s a sample list:

  • – starting wattage of 1400 and running wattage of 650
  • Refrigerator – starting wattage of 2000 and running wattage of 400
  • Washing machine – starting wattage of 1000 and running wattage of 1200
  • Lights – total starting and running wattages of 1800 each
  • Clothes dryer – starting wattage of 6500 and running wattage of 5250
  • Electric range/stove – starting and running wattages of 2100 each
  • Hot water heater – starting and running wattages of 4000 each
  • Air conditioning unit – starting wattage of 2400 and running wattage of 1750
  • Television – total starting and running wattages of 525 each
  • Computer – total starting and running wattages of 1400 each
  • ½ hp – starting wattage of 2000 and running wattage of 1050
  • Alarm systems – total starting and running wattages of 500 each
  • 650w microwave oven – starting and running wattages of 1000 each

The total starting wattage of this particular household is 26,625 and its total running wattage is 21,625. With an approximate maximum load of 26,625 watts, the right size generator for this household is a 27kW generator.

Do note that the figures in the examples may or may not be the exact wattages of the appliances listed. These figures we used here are to just give you a better idea on how the computations are done.

DIY computations of the wattages of the appliances you have at home are always just rough estimates. It is always better for a professional to do the computations for you. This will assure you that the numbers are as close as they can be to the actual wattages and as a result, you can get the most appropriate size generator for your home.

Home Generators: Why You Should Go for Permanent Generators

If you think of generators, the portable ones would likely come to mind first. They are a favorite of many households because they can be easily moved from one place to another. A major drawback, however, is that their portability limits the number of appliances it can handle.

This is not ideal if you want a generator that can power up your home during blackouts. In these scenarios, automatic generators are better. Unlike portable ones, they will immediately run as soon as they detect that the power in your home has gone out and they will power up your electrical appliances connected to it for a much longer period.

The only major disadvantage of a permanent generator is that once it has been installed somewhere in your home, it should never be moved elsewhere unless you’re already getting rid of it. As for the benefits, here are some that can convince you why they are the best choice for your home:

  • Less operational cost – since a permanent automatic generator is connected to the liquid propane or natural gas supply of your home, the fuel expense is minimized. You don’t need to get a separate fuel source such as diesel or gasoline, which is more expensive.
  • It produces less fumes – you might think the smaller portable generators give off less fumes than permanent ones, but the opposite is true. Portable generators actually produce more toxic fumes than permanent units. And since permanent generators are installed outside, the fumes it produces will not be easily inhaled by anyone.
  • They run automatically when needed – if you’ve ever owned a portable generator, you probably experienced moving it around in your home to connect it to the appliance you want to run during a blackout, then returning it to your shed when the power comes back on. Tiring, right? This is no longer the case for permanent generators, as they will immediately power up your home whenever it detects a blackout. All you need to do is wait.
  • Permanent generators will run longer – it’s a given that portable generators can only run for hours on average. Permanent generators, however, can run for several days. It’s not unusual to experience blackouts for days, especially after natural disasters. With permanent generators, you hardly have to worry about food spoiling in your fridge or necessary medical apparatus shutting off because there is no electricity to power them up.

Given their permanency, these generators come with some requirements before they can be installed in your home. Unlike portable generators that anyone can use as soon as they are purchased, permanent generators require a bit of time before they can be used. Ordering a unit and having it installed can take up to 3 to 4 weeks, or even longer due to the weather conditions. Installing a generator will only take up to two days at maximum.

Local governments may also require permits and licenses before a permanent generator can be installed in any home. In most cases, these permits will be acquired by the installer. But to be on the safe side, always confirm with the installer if he or she will be the one to get the permit on your behalf or not.

Just because permanent generators should be installed outside doesn’t mean it can be placed anywhere; there are still some things to be considered, location-wise. To save up on costs, it should be placed close to your home’s fuel source and electrical panels where it would be connected to. Some distance from your home itself is necessary to prevent its fumes from getting inside.

If you experience flooding or don’t want to ruin your beautiful landscaping, you can still have a permanent generator installed. All you need to do is have your generator elevated to a height above the usual level of floodwaters. You can also have your unit installed in a trench and use plants to hide it from plain sight, making sure that its exhaust system will still function properly. Take note that generators should have a base made up of either concrete, gravel, or plastic that can fully support its weight.

Cost to Install a Generator

Getting permanent generators installed can be quite costly, but you can think of them as investments for your home. After all, you will use them for a very long time. And because installing permanent generators is a complicated task, it is common for professionals to charge high rates. The cost of a generator itself is separate.

To give you an idea of how much you can expect to shell out, you first need to know how much permanent generators cost:

  • Small size, 7 to 10 kW – from $1850 to $4000. Enough to provide power to a few appliances
  • Mid-size, 12 to 20 kW – from $4000 to $10000. Can power up a number of appliances and a heating or cooling system
  • Large size, 22 to 45 kW – from $9000 and up. Can produce enough electricity for an entire home

Depending on your arrangement with the installers and other professionals, the price of getting a permanent generator installed in your home can range from $500 to $3000. Here’s a breakdown of what the entire installation process generally consists of:

  • Initial assessment – is normally free and part of the installation
  • Processing of permits and other documents – charge is for every permit and it ranges from $50 to $200 each
  • Electrical works, particularly a new electrical panel, wirings, and transfer switch – electrician rate is per hour, which ranges from $65 to $85
  • Crafting of the generator’s base and preparation of the site – charge is per square foot, ranging from $50 to $75
  • Tools, equipment, and other materials – from $300 to $2000
  • Installing a new connection or fuel tank to utility lines already present – a natural gas or propane provider will also charge an hourly rate of $50 to $100

To save on installation costs, you can opt not to avail of some of these services, especially if they are redundant or unnecessary. If you already have a concrete surface that can support your unit and your electrical panel is fully compatible with the generator, your installer may advise you not to change them and just work with it, saving you a few hundred dollars.

Reducing installation costs of a generator doesn’t mean trying it out the DIY way. Permanent home generators should always only be installed by a professional. Wrong installation is not only dangerous but it can even prove fatal. You should never risk it.

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