If you live in an area that’s prone to severe weather, a portable generator can make life easier to endure – if and when the power goes out. But a small portable generator can’t power everything in your home. Before you purchase a generator, you should have a clear understanding of what you will – and won’t – be able to do with it.

That understanding begins with taking inventory of your power needs – specifically how much wattage your devices require. You’ll find many resources online that will tell you roughly how much wattage a device requires. (This is a particularly good one.) Here are the wattage requirements of some devices that would be handy during an outage:

  • Smartphone charger – 10W
  • Tablet charger – 10W
  • Tablet – 10-20W
  • Television – (LCD, small) 50W
  • Household fan – 50-120W
  • Notebook computer – 20-75W
  • 60W light bulb – 60W
  • 100W light bulb – 100W
  • Desktop computer – 200-400W
  • Refrigerator – 500-750W
  • Washing machine – 500-1000W
  • Microwave – 300-1000W
  • Portable air conditioner – 1300W

If you have a small portable generator with a 2000W capacity, you won’t be able to run all of the above devices at once – let alone the many devices that aren’t on this list. And you may have already noticed that there are no household systems on the above list. There are two reasons for this:

  1. Household systems use more power than a small portable can deliver. A central air system, for example, might need a constant 1500W to run, and potentially as much as 5000W on start-up.
  2. You can’t plug household systems directly into your generator, and you can’t plug your generator directly into your household electrical system.

But don’t worry – you’ve got options.

Many generators that have the capacity to power more household devices, and even entire homes – they’re just more expensive. Generally speaking, if you double the wattage of a generator, you’ll almost double its price. Where a 2000W generator costs a $1000, a 4000W version might cost $1800-$1900. Whole-home generators can cost $3500 or more.

While you can’t connect your generator and your household electrical system directly, you can bridge the gap by having an electrician install an interlock or a transfer switch. These two devices allow you to switch your home between generator power and the power line; they disallow you from using both at the same time, which is an unsafe practice. And – most conveniently – they can provide power to the outlets in your home.

If outages are relatively few and far between, you might opt for a smaller portable, and plug select devices directly into it. If severe weather is more common – or being without household power is not an option – you’ll probably need to choose a whole-house generator along with an interlock or transfer switch.

Now that you have a better idea of what you’ll need to do to maintain a suitable amount of power during an outage, you can weigh needs and wants against costs. You’re one step closer to being ready for whatever challenges the next big storm brings.