Everything you need to know about generator safety, what your generator can actually power, and how to connect it to your home the right way.
Inside this guide
A free guide from Backup Power Pro
backuppowerpro.com
It is hard to know how much your generator can really handle until you see it laid out. Here is a straightforward breakdown.
Running watts is the steady power an appliance uses while it is on. Starting watts is the extra surge some appliances need for the first second or two when they kick on. Anything with a motor (fridge, well pump, A/C) draws 2 to 3 times more watts to start than to run. Your generator needs to handle both.
| Appliance | Running Watts | Starting Watts |
|---|---|---|
| Refrigerator | 200 W | 1,200 W |
| Chest Freezer | 75 W | 800 W |
| Sump Pump (1/3 HP) | 800 W | 1,300 W |
| Well Pump (1/2 HP) | 1,000 W | 2,100 W |
| Window A/C (10,000 BTU) | 1,200 W | 3,600 W |
| Furnace Blower (gas furnace) | 700 W | 2,000 W |
| Garage Door Opener (1/2 HP) | 725 W | 1,400 W |
| Washing Machine | 1,150 W | 2,250 W |
| Ceiling Fan | 70 W | 140 W |
| Electric Water Heater | 4,500 W | n/a |
| Microwave (1,000 W cooking) | 1,500 W | n/a |
| Coffee Maker | 1,000 W | n/a |
| Space Heater | 1,500 W | n/a |
| TV (55 inch LED) | 100 W | n/a |
| LED Lights (per room, 4 to 6 bulbs) | 40 to 60 W | n/a |
| WiFi Router + Modem | 20 W | n/a |
| Security System + Cameras | 100 W | n/a |
| Phone Charger | 10 W | n/a |
Common estimates. Actual wattage varies by brand and model, check your appliance label or owner's manual for exact figures. Gas appliances (gas dryer, gas water heater, gas stove) use much less electricity since the gas does the heating, they may only need 300 to 600 W for controls and fans.
Your generator's nameplate shows its maximum output. Plan your total running load at about 75% of that number to leave headroom for starting watts. A 7,500-watt generator should run about 5,600 watts of steady load comfortably.
These are the most common, and most dangerous, things homeowners get wrong with portable generators.
Carbon monoxide from a generator can kill in minutes. Over 80 people die from generator CO poisoning every year in the U.S. The only safe location is outside, at least 20 feet from any window, door, or vent. A cracked garage door is not enough.
This sends power backward through your panel and out onto the utility lines. It can electrocute a lineman working to restore your power. It is illegal in every state. Some homeowners do this without realizing the danger.
Running more watts than your generator can handle does not just trip a breaker. It can damage the generator, damage your appliances, or cause overheating. Know your wattage limits (see page 2).
Water and electricity do not mix. A generator sitting in a puddle is a shock hazard. If you run it in rain, use a manufacturer-rated canopy. A tarp duct-taped to a frame does not count.
Running six cords through a cracked window is the most common "plan," and the least safe. Cords get pinched, overheat, get rained on, and create trip hazards. They also mean you cannot power anything hardwired, your furnace, well pump, sump pump, ceiling lights, or water heater. If it does not have a plug, an extension cord cannot reach it.
Four out of five of these problems are solved by how you connect your generator, not by the generator itself.
Here is what changes when you stop running cords through your windows.
An inlet box is a weatherproof plug mounted on the outside of your house. An interlock kit is a small mechanical device on your breaker panel that prevents your main breaker and generator breaker from being on at the same time, which is what prevents backfeeding. Together they give you a safe, permanent, code-compliant way to connect your portable generator to your home.
Here is exactly what happens when the power goes out, step by step.
You walk to your generator, wherever you store it (garage, shed, carport). Roll or carry it to the inlet box on the side of your house.
Connect the generator cord to the weatherproof inlet box on your exterior wall. One cord, one connection.
Fire it up and let it warm up for about 60 seconds before connecting any load.
Go to your panel inside. Switch the interlock to the generator position, this automatically disconnects you from the grid (that is the safety mechanism). Then flip on the circuits you want: refrigerator, lights, furnace, well pump, whatever you chose.
Reverse the process. Flip breakers off, switch the interlock back, unplug the cord, turn off the generator. Done.
The whole process takes about 3 minutes once you have done it once. Most people say it becomes second nature after the first outage.
Central air conditioners draw 3,000 to 6,000 starting watts, more than most portable generators can handle. A device called a soft start can cut that surge by up to 70%. An HVAC technician installs it on your A/C unit (not the generator), letting the compressor ramp up gradually. With a soft start, many homeowners can run their A/C on a mid-size portable generator. Ask your HVAC tech about it.
Standard generators produce rougher power with voltage fluctuations. That is fine for fridges, lights, pumps, and furnace blowers. Sensitive electronics like computers and medical equipment do better with an inverter generator, which produces clean, stable power. For a typical outage running the essentials, a regular generator through an inlet and interlock works great.
The 240-volt outlet on your generator decides how it connects to your home. There are two common ones.
Round, twist-lock. Up to 7,200 W at 240V. The most common outlet on 5,000 to 8,000-watt generators. Plenty to run a home's essentials: fridge, furnace, well pump, sump pump, lights, and outlets.
Larger, 4 prongs. Up to 12,000 W at 240V. Found on bigger 9,000-watt and up generators. Lets you run more at the same time, including larger loads.
Add up the running watts of what you want on during an outage (use the table on page 2 and the worksheet on page 7). To run the essentials comfortably, a 30-amp connection on a 5,000 to 8,000-watt generator is plenty. Step up to 50-amp if you have a larger generator or want to run more circuits at once. Either way, with an interlock you control each circuit with its own breaker, so you turn things on and off as needed.
To connect to your home, your generator needs one of these two 240-volt outlets. If yours has either, you qualify. When you get your exact price from us, we confirm your outlet type and size the connection to it. If your generator does not have a 240-volt outlet, that is the one thing to upgrade before a home connection.
Fill this out and keep it with your generator. When the power goes out, you will already know exactly what to do.
That is okay, it just means you will manage which circuits are on at the same time. With an interlock this is easy. You control each circuit with its own breaker switch, so you turn things on and off as needed.
A generator that sits unused for two years and will not start when you need it is not backup power. It is a paperweight.
That is all it takes to make sure your generator starts when it matters. About 50 cents in gas buys you peace of mind that your backup power actually works.
If you have read this far, you already know extension cords are not the answer. An inlet and interlock kit gives you a safe, permanent, code-compliant way to connect the generator you already own to your home's electrical panel. No video call, no salesperson at your door. Just text us and we will get you a price.
Your name, your generator's outlet (30A or 50A), and your address. Two minutes from your phone.
Not an estimate. The actual all-in number, hardware, permit, inspection, and cord included.
Permitted, inspected, and done right. Most installs are completed in a single visit.
or text (864) 863-7800