Where do I find the wattage of my appliances?
You find appliance wattage on the nameplate label, usually on the back, inside the door or near the power cord, and in the owner manual. If a label lists only volts and amps, multiply the two to get watts. Keep a written list so nothing gets missed.
Walk through the house with a notepad. Include the air conditioner, refrigerator, freezer, well or booster pump if you have one, water heater, microwave, lights and the electronics you rely on. Mark which items you truly need during an outage and which can wait.
In the West Valley the air conditioner is almost always the biggest decision. Summer outages in monsoon season can last long enough that going without cooling is a safety concern, so many homeowners decide early whether the generator should carry the AC.
Why does starting wattage matter more than running wattage?
Starting wattage matters because motors draw a brief surge of power when they kick on, often several times their running load. An air conditioner compressor is the classic example. A generator sized only for running watts can stall or trip when that surge hits.
You do not add every surge together, because motors rarely start at the same instant. The usual method is to total all running loads, then add only the single largest extra surge. That keeps the estimate realistic without oversizing wildly.
Soft start devices on some air conditioners reduce that surge and can let a smaller generator carry the load. That is a design choice worth discussing with a technician before you commit to a unit.
Should I size a generator for the whole house or just essential circuits?
Sizing for essential circuits costs less and runs more efficiently, while whole house sizing keeps everything working as normal. The right choice depends on your budget, fuel supply and how long outages tend to last. Most homeowners start by ranking what they cannot do without.
A transfer switch or automatic transfer switch is what safely connects a generator to your home wiring. It prevents power from backfeeding onto the utility lines, which is dangerous to line workers and can damage your equipment. Never connect a generator to a house outlet with a homemade cord.
Panel capacity also matters. A licensed electrician looks at your service size and breaker layout to confirm that the circuits you chose can be supported together, and flags anything that needs an upgrade.
Why not just choose a generator by square footage?
Choosing by square footage does not work because two homes of the same size can have very different electrical loads. A small house with a pool pump and two air conditioners can need more power than a large house with one unit. Loads decide the size, not floor area.
Online calculators are a decent starting point, but they depend on the numbers you feed them. A site visit catches things a list misses, like older equipment that draws more than its label suggests or circuits shared across rooms.
Undersizing causes overloads and shutdowns. Oversizing wastes fuel and money and can make a machine run lightly loaded for long stretches. A professional load calculation lands between the two and makes sure the unit matches your panel.
More questions: Home Generators: 12 Most Asked Questions Answered