correct generator sizing

The size of your generator is directly related to how well it accommodates your home. When you are learning how to choose a generator size, there are multiple factors to consider. With the correct generator sizing, you can power everything that you need to remain safe and comfortable during a power outage.

Why You Need to learn How to Choose a Generator Size Properly

With correct generator sizing, you reap a number of benefits.

The following are benefits that come with using a generator of the proper size for your home:

  • Unexpected system failures are unlikely
  • The generator will last longer
  • Maintenance is easier to perform
  • The correct size is safer to operate
  • You will not have to deal with capacity overload
  • The generator will work at an optimal performance level
  • Considerably smaller risk of damage to the generator’s components

Correct generator sizing ensures that your generator can handle the capacity that you need. If you pick one that is too small, this can make the generator dangerous to use. Ensure that you are specific when you work to determine generator size for safety.

How to Determine Generator Size

Before working to ensure correct generator sizing for your home, you want to know exactly how to calculate the proper size. Generator manufacturers use kilowatts (kW) or watts (W) to provide a size for their generators. The size refers to how much electrical power the generator provides.

If you choose a generator that is too small for the capacity that you need, damage to your generator and electrical items can occur. This is due to the potential for a voltage drop.

If you choose a generator that is too big, this will not cause issues with damage or voltage. However, you will be paying far more than you need to power your home.

Correct generator sizing saves you money and ensures that your electrical items are safe when you are using your generator. You will need to do some math and explore your home’s electrical panel to ensure that you pick the right size. Overall, the process is relatively simple. However, it is a good idea to have a professional double check your math and information before installation so that you get the most benefit from your generator.

1) Determine the Average Power Outage Frequency

How often power outages occur in your area is something to consider when you are working to determine correct generator sizing. There are three levels of power outage frequency to explore to help you pick the size of generator that will keep you in power during outage times.

Frequent Power Outages

If you live in an area where weather gets harsh at certain times during the year, such as a place where heavy snow or hurricanes occur, you should consider a generator that is ideal for frequent power outages. Ideally, the generator should also be effective for prolonged outages too.

The following generators are a good choice:

Both of these generators are capable of powering your whole home as long as you choose the right wattage. You can connect them to the circuit breaker panel in your home so that the generator comes on automatically when a power outage is detected.

These two types of generators are capable of running the largest electrical components of your home, including your air conditioning and heating system, major appliances and sump or well pumps.

Another option is a portable generator. These come in a variety of sizes. However, they are not connected to your home’s circuit breaker. The only possible drawback with this option is that they are often not powerful enough for heating and air conditioning systems.

Occasional Power Outages

A portable generator or a large inverter generator are ideal for areas with occasional power outages. For example, if you only lose power for short periods of time once or twice a year, these are generators that are a good choice. For the larger inverter generator, you might consider a transfer switch so that the generator kicks on and off automatically when an outage occurs.

Rare Power Outages

If you experience power outages less than once a year, they are considered rare for your area. A recreational inverter generator or a midsized inverter generator are good choices.

To run more items, consider the midsized inverter. With this type of generator, you can run a window air conditioning unit, small electrical heater and a few large appliances so that you have comfort when the power is out.

A recreational inverter is smaller and meant to run a few key items at a time. You can switch out which items you are running based on your needs.

2) Picking the Right Wattage

Correct generator sizing is mostly related to the wattage that you need to power your appliances and the other electrical components of your home. There is a three-step process to ensure that you calculate the needed wattage properly.

Step One

Make note of the electrical components, such as your appliances and small electronics, that you need to keep running when the power goes out.

Step Two

Look at the running and starting wattage of each of these items. You can usually find this information somewhere on the actual item or in the owner’s manual.

Step Three

Add up the total wattage that you need to keep these running to get the wattage number necessary for your generator.

Ideally, your generator needs to be able to handle a little more than your total wattage for safety. For example, if the total wattage for the items that you need to run is 10,000 watts, consider a generator that can handle a minimum of 12,000 watts. Ideally, you should take your total wattage and multiply by two. This will make sure you have a generator that can power everything you need.

NOTE: You can also use a wattage calculator. Most generator manufactures have a generator wattage calculator. Click Here to access the generator wattage calculator provided by Honda.

Guide to Average Device Wattage

The following shows the average wattage for common items in your home:

  • Laptop or desktop computer: 500 to 2,000 watts
  • Coffee maker: 400 to 800 watts
  • Electric furnace: 5,000 to 25,000 watts
  • Central air conditioning: 2,000 to 4,000 watts
  • Sump pump: 1,500 watts
  • Television: 100 to 350 watts
  • Water heater: 3,000 to 4,000 watts
  • Electric range with an oven: 5,000 watts
  • Table lamp: 150 watts
  • Hair dryer: 1,200 t0 1,500 watts
  • Window air conditioner: 600 to 1,500 watts
  • Microwave: 1,200 watts
  • Water pump: 1,000 to 2,000 watts
  • Garbage disposal: 450 watts
  • Toaster: 850 watts
  • Video game console: 150 watts
  • Freezer: 1,080 to 1,240 watts
  • Curling iron: 150 watts
  • Clock radio: 7 watts
  • Dehumidifier: 280 watts
  • Dishwasher: 1,200 to 1,500 watts
  • Electric can opener: 150 watts
  • Electric water heater: 4,500 watts
  • Fans: 120 to 200 watts
  • Electric dryer: 3,000 watts
  • Washer for clothing: 800 watts
  • Internet modem: 7 watts
  • Mobile device recharge: 6 to 8 watts
  • Vacuum: 1,000 watts
  • Humidifier: 200 watts
  • Chainsaw: 1,000 to 1,800 watts
  • Drills: 250 to 1,200 watts
  • Sanders: 250 to 1,500 watts
  • Leaf blower: 1,000 to 1,400 watts
  • Weed eater: 500 watts
  • Saws: 500 to 2,000 watts
  • Hedge trimmer: 250 watts

Obtain the approximate wattage you need to run and multiply this by two. This provides sufficient guidance regarding the generator wattage that you need. Use this information to narrow down your search for the type of generator that will provide enough power for your needs.

You are now aware of the total power needed by your worksite or home. Now, you can start looking at the generators that provide this level of power.

Using total wattage, here are four categories of generators.

Compact Portable Generators

  • Power: 3,000 to 4,000 watts
  • Price: $400 to $800
  • What It Powers: Use this generator for the basics, such as your television, some lights, your refrigerator and microwave.

A compact portable generator is easily portable since it is lightweight and small enough for most people to carry on their own. You can use this type as a standby generator, but be aware that it will only run the basics to keep you comfortable until the grid power is restored.

Midsize Portable Generators

  • Power: 5,000 to 8,000 watts
  • Price: $550 to $1,200
  • What It Powers: This size is ideal for computers, some types of pumps, certain heaters and basic home appliances, such as your refrigerator and microwave.

Generators of this size function well as a backup generator for your worksite or home. They are generally small in size, allowing you to move them around and prepare them for power emergencies with ease. For example, they are a good choice for a campsite or when you need electricity during a storm.

Large Portable Generators

  • Power: 10,000 watts and higher
  • Price: $2,000 to $3,000
  • What It Powers: You can use this generator to do everything that a midsize one can, plus more. For example, use one for major appliances, your home’s water heater and an air conditioning unit.

While technically portable, these are not easy to move from site to site. These generators are bulky and best when you want to have something to keep your home in power. Should you take one RVing or to a similar environment, the noise level would disturb all of the people who are around you.

Whole House Generators

  • Power: 15,000 to 22,000 watts
  • Price: $3,000 to $6,000
  • What It Powers: It can power all elements of your home, including central air conditioning, sump pumps, water
  • heaters and furnaces.

These generators are not meant to be transported. They are placed and remain in one location on your property much like a central air conditioning unit. You get all of the power that you need to keep your home’s electricity running during a power outage. However, it is imperative that they are placed properly and well-ventilated.

While this is one of the most important aspects of choosing a generator with the right power levels, there are other things to think about. Consider any changes you may make to your home in the future. For example, if you switch from window air conditioning units to a central air system, your generator needs to accommodate this increase in wattage.

Running Wattage vs. Starting Wattage

There are two types of wattage you need to look at when you are doing this calculation. The running wattage and starting wattage can be found in the specifications of your electrical items and your generator.

Running wattage describes how many continuous watts are necessary to ensure that your items continue to run. Starting wattage describes the extra watts that an item needs for about three seconds to get the item’s motor running.

3) Picking The Generator That Meets Your Needs

Now that you know how to determine wattage, the next step in correct generator sizing is to look at the capacity of generators. Generators are typically put into four categories, ranging from small to extra-large.

Small Generator

This category is typically for portable and recreational generators. You get enough wattage to power a few key small items. For example, you can use generators of this size to keep your computer, a small appliance and a lamp going during a power outage. These are not meant to run a whole house or provide power to your larger appliances.

Medium Generator

On average, you get 3,000 to 5,000 watts from a generator of this size. You can use it to run some emergency items during a power outage. On the higher wattage end, you can use it for a fan, refrigerator and a few other key items that will help you to get through a power outage.

Large Generator

Generators in this category average 6,000 to 9,000 watts. You can power most appliances and typical electronics with a generator of this size. A generator with this wattage can keep several rooms in your home in power.

Extra-Large Generator

If you want to power your entire home, this is the generator size that you want. These generators supply 10,000 watts and more. With this size, you can keep even large items going, such as a sump pump and your air conditioning system.

Exploring Fuel Tank Capacity

While this aspect of a generator is not directly related to picking the correct generator sizing, it is important to make sure that your generator can meet your home’s needs. The larger the fuel tank, the longer your generator can run on a full tank.

You can determine the minimum storage capacity by adding the lead-time stock plus the emergency stock. Lead-time stock describes the fuel amount that you need for your generator to work during the lead-time. Emergency stock describes the fuel that you have available to account for delays or the need for more fuel that you initially anticipated.

If you do not experience long power outages or they do not happen often, a fuel tank with a small capacity will usually work for you. If you experience them frequently and you have an average-sized home, you should consider a medium-capacity tank.

For the most part, large-capacity tanks are for commercial use. However, if you have a very large home or your area gets hit with long power outages frequently, a generator with a large fuel tank may be the best choice.

You also want to ensure that you can access the fuel type that your generator uses easily during an outage. Most larger generators use propane or natural gas.

Choosing the Right Transfer Switch

transfer switch

Part of correct generator sizing involves knowing which transfer switch to choose. This device closes off your home’s electrical utility line when you lose power in your home. It then opens up the line to the generator. Essentially, it swaps out the source of power for your home. Then, when the utility power is restored, this switch puts your home back onto the utility power.

A transfer switch is installed close to your home’s breaker panel. It is hard-wired permanently into this. When you have this installed, it prevents backfeeding from happening which can occur if the electricity in your home essentially moves backward to the utility transformer instead of the electricity coming from the transformer to your home.

When you are choosing a transfer switch, you can pick an automatic or a manual type. With an automatic switch, it will kick your generator off and on automatically when the power comes on or goes out. If you choose a manual switch, you will need to flip the switch yourself.

The most important part of choosing a transfer switch is determining the correct amperage. In the United States, the average home would use a 200-amp transfer switch. However, if your home is small, 100 to 150 amps may be what you need.

You will have to look at the circuit breaker panel to determine the proper amperage. Make sure to also check the specifications of your generator to see the amperage that it can work with regarding a transfer switch.

If you are not an electrician, it is imperative to not attempt to install this switch on your own. Improper installation could result in numerous issues from damage to your electrical equipment to an electrical fire. Once it is installed properly, you should have an electrician perform testing and maintenance regularly according to the recommendations in the manufacturer’s manual.