Backup Power from a 6500 Watt Tri-Fuel Generator Running on Natural Gas and Connected to a Transfer Switch Inlet Box.
If you’re looking for a way to power your house during a power outage, public safety power shutoff, or blackout, a generator is a good choice for backup power. Generators produce power from the moment they start and continue until shut off or they run out of fuel or oil. Some generators can power an entire block, neighborhood, or even a small city. Generators for homes start in a more realistic power range of around 6500 watts.
Need to Know: Generator Watts Volts Amps
In order to determine what size generator you need, understanding electrical power and how much your home or individual appliances require is the first step to determining what size generator you should buy.
Watts is a measure of power. Household lights and appliances require different amounts of power. The typical modern house has a minimum 100-Amp electrical service supplied by the local electric utility. Houses use an efficient supply of 120-Volts on two lines. The two lines can work together for 240 volts.
Power in Watts = Volts x Amps
Watts ÷ 1000 = Kilowatts. 6500 Watts = 6.5 Kilowatts, or 6.5kW.
Manufacturers rate generators in watts because the electrical load connected could be a mix of 120 volts or 240 volts. As long as the total load does not exceed 6500 watts, it won’t matter if the loads are 120 volts, 240 volts, or a combination of the two.
6500 Watts ÷ 120 volts = 54.17 Amps
6500 Watts ÷ 240 volts = 27.08 Amps
North American Split-Phase Power
Utilities in North America deliver residential electrical service over Line 1 and Line2. A Neutral serves as the return for any imbalance in the load. It is important to realize that your circuit breaker panel is also divided between lines 1 and 2. The same is true of a generator that provides 120/240 volts.
When connecting the generator to your appliances, balance the load between the two lines. If you have a correctly-wired manual transfer switch, you won’t have to worry about balancing the power.
In the service panel pictured here, we can see the two main copper bus bars that deliver power from Line 1 and Line 2 coming from the transformer outside. The two terminal blocks on the black plastic connect to the circuit neutral (grounded conductor) The two blocks on the far left and far right are ground terminals. The green screw is the Neutral Bonding Screw
What Can a 6500 Watt Generator Run?
Let’s look at a few household appliances that you might consider essential.
| Electrical Load | Watts | Starting Watts |
| Refrigerator | 850 | 2000 |
| Furnace | 700 | 1800 |
| Sump Pump | 1050 | 3200 |
| Microwave | 1000 | |
| CPAP (heated) | 100 | |
| Internet Router & Modem | 20 | |
| Laptop Charging | 90 | |
| Phone Charging | 6 |
Total Watts Required = 3816 Watts
At this point, you might should be asking, what are starting watts? Sometimes called surge watts or max watts, Starting Watts is the power an electric motor requires to start turning and reach running speed. It can vary depending on whether the motor is under load or not when it starts. The refrigerator motor runs at about 800 watts (50 watts for lights, fan, controls, thermostat, etc) but it requires 2000 watts to start turning under load from a complete stop.
Just like motors, generators come with a max watts or surge watts rating for a momentary extra boost of power to get an electric motor running. If the surge of power lasts more than a few seconds and does not quickly taper off, the generator’s circuit breaker trips to prevent the load from damaging the generator.
Typical Surge Watt Rating for a 6500 Watt Generator is about 8000-8100 Watts.
The electrical load running watts must not exceed the generator rated watts, and the starting watts can’t exceed the generator’s maximum rated watts—in this case about 8100 watts.
3816 Watt + 3200 Watts = 7016 Watts
So far, we’re in good shape with our 6500 watt generator.
6500 Watt Generator Limitations
You may have noticed that the table above lacks an air conditioner. Home air conditioners range from 5000 to 28000 BTU Window Units, and 12000 to 60,000 BTU Central Air Conditioners.
The power available from a 6500 Watt Generator would not preclude running a window unit or a 1-Ton to 1.5-Ton Central Air Conditioner Alone, but the larger window units and smallest central A/Cs would overload the generator if they ran with essential loads listed in the table above.
Remember we have a base load of 3816 Watts and to that we must add an air conditioner.
An 18000 BTU AC requires 2100 Watts + 4800 Starting Watts.
3816 Watts + 2100 Watts = 5916 Watts
3816 Watts + 4800 Watts = 8616 Watts.
From this we have determined that with the other essential loads connected, an 18000 BTU Central or Window Air Conditioner adds too much load.
A 12000 BTU A/C requires 1700 watts and 3900 Starting Watts
3816 Watts + 3900 Starting Watts = 7716 Watts.
The generator has enough power to start and run the 12000 BTU A/C in addition to the other connected loads.
However, remember that the current coming into the house is split between two lines, and that from a 6500 watt generator, each line has a capacity of about 27 amps. The 12000 BTU air conditioner requires about 14. Balancing the load is essential to prevent the generator circuit breaker from tripping. Go over the 27 amps on either side of the supply and the generator’s circuit breaker will probably trip.
Be Realistic. You Won’t Power This Beautiful Home with a 6500 Watt Generator.
Photo Credit: Memory Catcher
Can a 6500 Watt Generator Run a House?
The careful, qualified answer is yes it can. Qualified because it is unlikely that the 6500 watt generator can power everything at once.
If you have an electric range, electric water heater, and electric dryer, those three appliances alone require more than 10,000 watts. If you’re running your house on a 6500 watt generator, you won’t be able to run those appliances.
On the other hand, if you have a small home with natural gas or propane appliances and perhaps one or two 5000 BTU window air conditioners, most likely, you can run a house on a 6500 watt generator.
Air conditioners, well pumps, furnace fans, and other hard-wired appliances require a manual transfer switch. The generator plugs into the transfer switch inlet box to make a single, fast and safe connection to the house. Circuits chosen at the time of installation receive power from the generator.
A generator is like any other machine. The harder you work it, the more wear and tear it sustains. Push a generator to the limit all the time and it will wear out sooner than a machine that runs at 70-80 percent capacity. When buying a generator, give it some breathing room so it doesn’t work so hard. That also provides the extra power you might need for a short while. For a 6500 watt generator, this means plan for a running load to 4550 to 5200 watts. That’s enough breathing room to plug in an extra refrigerator or small window AC.
What Can a 6500 Watt Generator Run at the Same Time?
Standby Generators made specifically for home backup can do the job more efficiently than a portable. They are automatic and run whenever the power goes out. A standby generator uses municipal natural gas or propane from an onsite storage tank which eliminates refueling multiple times a day. An automatic transfer switch makes a permanent connection to your home’s electrical system and keeps the generator isolated from utility power.
The smallest home standby generator produces 7500 watts on propane, and 6500 watts on natural gas. With the included automatic transfer switch, it can power up to eight 120-volt circuits, or a smaller number of 120-volt and 240-volt circuits (each 240 volt circuit breaker uses two circuit positions.)
In our example above, we chose eight appliances that many homeowners would consider essential and determined that a 6500 watt generator could power all of them at the same time. We then explored the possibility of running an air conditioner and found ourselves limited to all but small to medium window air conditioners and small central air conditioners.
With careful power management, it would be possible to run a larger air conditioner. Just remember that your central air unit probably relies on your furnace fan to distribute the cool air through your home. You can’t shut off the fan and expect the A/C to work.
Maybe you don’t need the sump pump or microwave on a hot August night while you’re trying to sleep. In that case, you might have enough power to run a larger air conditioner.
Read your appliance tags. They have the information you need to make important decisions about what size generator to buy. Armed with that information, you’ll know whether or not a 6500 Watt Generator Can Run a Home.
About MJ Logan
MJ Logan began his writing career in third grade creating small booklets with a construction paper cover and two or three sheets of white typing paper, carefully folded in half and glued to the construction paper. His career led from electrical engineering and electronic test to network management, independent software development, and finally back to writing.
