Essentials-only or whole house? Add up your loads, understand surge, and learn how 100A and 200A panels fit into backup power sizing.
- Decide on essentials-only or whole house first; most outages need essentials.
- Add running watts, then add the biggest surge, then add margin.
- Panel size is the ceiling of your service, not your actual draw.
There is no single wattage for a house. A home running only the fridge, some lights, a furnace fan and phone chargers needs far less than one running an oven, a dryer and air conditioning at once. The right plan starts with deciding what you actually want to keep running.
This guide shows how to build your own number step by step, and how to tell whether a portable power station, a generator or a whole-home system fits.
Essentials-only versus whole house
Most people do not need whole-house power in a short outage. An essentials-only plan covers the items that protect health, safety, food and comfort:
- Refrigerator and possibly a freezer
- A few lights
- Furnace blower (if gas or oil)
- Phone and device charging, internet router
- Medical equipment, if anyone uses it
- Sump pump or well pump if you have them
A whole-house plan adds big loads such as electric ranges, water heaters, dryers and air conditioners. Those draw thousands of watts each and quickly outgrow a portable battery.
Add up your loads
- List every item you want to run.
- Find its running watts on the label, the manual, or with a plug-in watt meter.
- Note which items have motors or compressors, because these have a higher start surge.
- Add the running watts of items that could run at the same time. That is your continuous need.
- Take the single biggest surge and add it to the rest. That is your peak need.
- Add about 20 per cent margin.
You do not have to run everything at once. You can rotate loads, such as using the microwave while the furnace fan is paused. Managing the order of use lowers the size you need.
Energy versus power
Two separate numbers matter. Watts measure how fast you use energy. Watt-hours measure how much you use over time. Your generator or battery must cover the watts at any moment, and the battery must also hold enough watt-hours for the length of the outage. See what size power station do I need for more.
Canada and US panels in plain terms
Your electrical panel has a main breaker that shows the service size in amps, commonly 100 A or 200 A in North America, and many older homes have smaller. Most homes run on 240 V split into two 120 V legs. The rating of your service is the most your house could draw, not what you normally use. Almost no home uses the whole panel capacity at once.
- A bigger panel does not mean you need a bigger backup. Your real draw is what you add up above.
- Older homes with a smaller service tend to have fewer large electric appliances, but check yours.
- Both countries use the same common voltages, though Canadian and US code details differ. A qualified electrician follows the local code where you live.
Choose a type of backup
- Portable power station: quiet and safe indoors, ideal for essentials for hours or a day or two. See options for Canada and options for the US.
- Portable generator: more power for longer, run outdoors only. See sizing a generator.
- Whole-home battery or standby generator: installed by professionals, can cover more of the house. See whole-home battery vs portable power station.
A practical starting point
Write your essentials list tonight, measure the top five loads, and total them. That single page tells you whether a battery, a generator or a professional system makes sense. The outage planner can help you structure this, and our power station hub lets you compare sizes against your total.
Common mistakes
The most common error is sizing from the nameplate of every appliance at once, which produces a number far above real life. The second is ignoring surge, so the unit trips the moment the fridge compressor starts. The third is forgetting runtime: a source that can deliver the watts for ten minutes is not the same as one that can deliver them overnight. Write down the hours you need, not only the watts, and check both numbers against any unit you consider. Revisit the list each winter and summer, because loads change with the season.
Quick answers
Can a portable power station run my whole house?
Usually not. Large loads like electric ranges, dryers and air conditioners exceed typical portable units. Essentials are realistic.
What is the difference between watts and watt-hours?
Watts are how fast energy is used right now. Watt-hours are the total energy used over time, which decides battery runtime.
Do I need an electrician?
For any connection to your home's wiring, yes. A transfer switch or inlet should be installed by a qualified person.