What Size Generator Do I Need?

Choosing the correct sized generator for your needs can be a confusing decision. This guide will give you everything you need to know to choose the perfect fit for your needs.

The amount of electrical power that a generator is capable of producing is called the Wattage. The more appliances you wish to power from your generator the higher wattage you will need. Generators come in a vast ranges of sizes to suit all needs. These can range from small extremely portable 800 Watt generators all the way up to units producing 40,000+ Watts. Powering a handful for personal devices on the go all the way up to an entire construction site! Yet it can be easy to over or underestimate your needs. Underestimate and you will not have the power required to run all your desired appliances properly. This can be damaging to both the generator and the appliances. Overestimate you may find yourself with a generator that is less fuel efficient, louder and heavier than what you need.

Key aspects to consider

The key to choosing the correct generator is to determine all the appliances you wish to run together. You can easily find your exact needs using our generator calculator tool, but that are some other considerations to be aware of.

Starting Wattage vs Running Wattage

When choosing a generator you will probably notice these two terms come up a lot. The explanation is actually quite simple.

Some appliances have a “Starting Wattage”, this is the initial amount of power needed to be able to get started. These are usually appliances with motors such as air compressors, fans and power tools. These appliances will then only need a fraction of that power to carry on running once started. This is called the “Running Wattage”. For most static appliances the Starting Wattage and Running Wattage will be the same.

Why is this important? When choosing a generator you must ensure it has the power to start and run all the appliances you wish to supply. The calculations needed for this can all be simply achieved using our generator calculator tool.

Do you need to power all appliances at once, probably not…

When sizing up it is important that you consider what your general usage is likely to be. For you home backup you may want to choose a generator capable of running your oven, freezer, furnace and sump pump. But do you really need to run all of these together? The same is true in work or recreational use generators, most of the time you won’t need all of your high power items at the same time. By thinking about the concessions you are willing to make here you can avoid over sizing your generator.

Choosing to oversize for assurance

When you have a rough idea of the range of Watts you are likely to typically need there is no harm in taking this a little bit higher to give yourself some slack. It is important to note that the less elements you have drawing power from your generator the less fuel it will use. However the closer to 100% capacity your generator is the more fuel efficient it will be. So it is much more efficient to have a smaller generator with 80% power drawn than it would be to have a larger generator that is only 20% utilised.

When browsing generators you will notice that some will list the “Automatic idle” feature. This means that the generator will sense the amount of power that is being drawn from it and idle the engine when not in use. This give you added efficiency, reduces noise and prevents wear on the engine.

Adding more power by running generators in parallel

Many modern portable generators also have the option of using a “Parallel-kit” to connect two generators together to get twice the power. Choosing to buy two generators that can run in parallel or independently can offer some great benefits. There will be times when only one is required so you can leave its partner at home for convenience and efficiency. You can split your power production across two areas of your house, camp or work site as required. Then bring them together when the extra power for larger jobs is required.

Generator Calculator tool

Using our Generator Calculator tool you can quickly and accurately determine the Wattage you need for your power production needs. You use the tool you simply need to follow the below steps:

  1. Browser through the list of appliances in Home, Work and Leisure categories
  2. Click on an appliance to add it to your list
  3. If you can find an appliance on the list you can add one manually
  4. Review your total load at the bottom of the page, you can add and remove items at any time
  5. Note the recommended Wattage and click the button at the bottom of the page to be taken to a list of appropriate generators