How Big of a Generator Do I Need?

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If you’re tired of relying on candles and a camp stove during a power outage, or if you need power when you’re off the grid, it’s time to look into buying a generator. But before you can settle on the right kind, the first thing you need to ask yourself is How big of a generator I need? It all comes down to how many appliances you want to run during an outage, or how many appliances you need while camping. From there, you can calculate your power requirements and find the right size unit. Here’s a rough guide on generator sizes and the power draw of most common appliances, plus a few more things to take into consideration when shopping for a generator.

Picking the Right Generator Size: The Basics

To figure how big of a generator you need, you need to add up the wattage of all the appliances you want to use off-grid and match that to the wattage listed on your generator. But, of course, you don’t want the unit to run under a max load at all time. So, should plan your wattage needs to come in well under your unit’s maximum output.

How to Pick the Appliances You Need Off-Grid

If you’re looking for back-up power during an outage, you first should take an inventory what appliances you absolutely need to use. For most, these include heating or cooling, depending on your climate, running a well pump and hot water heater, keeping the lights on, and charging your phone so you can stay connected. Hunters and anglers may also want to consider keeping a freezer or multiple freezers going during an outage. For myself, I can rough it through a power outage with my woodstove and battery-powered lanterns, but I need to keep my freezers and my well pump going. Campers and tailgaters typically need less from a generator. Their needs might be running a fan, a string of LED lights, and a portable refrigerator. Generally, campers like to use smaller units that also tend to be more quiet.

Understanding Min, Max, and Surge Power

A power crews works to to repair an electrical line after winter snowstorm

Before you can add up the power your appliances will consume, you need to be familiar with minimum, maximum, and surge power. The minimum is the lowest amount of power an appliance will consume measured in watts. The maximum is the most. The surge is the amount of watts an appliance needs to start up. This is usually the most power an appliance will use, and once it’s running, it will settle into to maximum and minimum power. When selecting how big of a generator you need, you need to factor in the surge power of your appliances. Otherwise, this can knock out other appliances, damage your unit, or trip a breaker if you’re trying to use too many things at once.

High Draw vs Low Draw Appliances

The best way to figure out the draw of your appliances is to look at a chart. There are tons of power-draw charts available online, but here are some examples of common high- and low-draw appliances. And remember, you need to account for the surge power when adding up wattages to avoid maxing out your generator.

High Draw Appliances (measured in watts)

Central Air Conditioner (Min: 2000, Max: 10,000, Surge: 11,250)
Window Air Conditioner (Min: 1,000, Max: 1,500, Surge: 2,000-2,200)
Electric Clothes Dryer (Min: 1,800, Max: 5,400, Surge: 6,750)
Sump-Pump (Min: 600, Max: 1,050, Surge: 1,300-2,150)
Well Pump (Min/Max: 700, Surge: 0)
Electric Stove (Min: 2,100, Max: 4,500, Surge: 0)
Toaster Oven (Min/Max: 1,225, Surge 0)
Electric Water Heater (Min/Max: 5,000, Surge: 0)
Electric Heat (Min: 1,125, Max: 1,500, Surge: 0)

Low Draw Appliances (measured in watts)

Electric Clock (Min/Max: 3, Surge: 0)
Laptop Computer (Min: 200, Max: 250, Surge: 0)
Phone Charger (Min/Max: 20, Surge: 0)
Fan (Min: 10, Max: 150, Surge: 30-450)
Engine Block Heater (Min: 150, Max: 1,000, Surge: 0)
CF Lightbulb (Min/Max: 25, Surge: 0)
Television (Min: 65, Max: 340, Surge: 0)
Refrigerator (Min: 132, Max: 192, Surge: 1,200)

Traditional Generators vs. Inverter Generators

Another consideration you need to make is whether you want a traditional generator or an inverter generator. Traditional units deliver a constant supply of power once they’ve been started. They are generally cheaper than inverter generators, and they consume more fuel. Inverter generators will throttle depending on the power load. They tend to be quieter and burn less fuel. They’re also more expensive. If you’re looking to save money in the long run and noise is an issue, go with an inverter model. If you who want to save some money upfront, look at a traditional generator.

Generator Size Catagories

Generators come in all shapes and sizes for all kinds of uses. Unit size is broken down by wattage. A good rule of thumb is that you will likely pay $1 per watt. Whichever model you choose, it’s a good idea to have a professional electrician install some way to tap it into your home’s electrical panel should you need it during an outage. It is possible and safe to run one or two appliances from extension cords to a generator, but tapping into your home electrical panel yourself can be dangerous. Let a pro do it. The following categories should cover most models you’ll encounter when you’re shopping.

Small/Recreational Generators (2000 watts)

Portable recreational generators are great for those who need to power a campsite or a tailgate party. They can be used in a pinch during an outage to power one or two appliances and keep the lights on, but are too small for running heat and air conditioning. The best thing about small recreational units is how portable and quiet they are.

Best Uses

Some backup power for the home
Camping
Tailgating