Appliance Starting Watts: Typical Surge Draws

Running watts vs. starting watts

A generator spec sheet lists two numbers: running watts (continuous capacity) and starting watts (surge capacity). Starting watts matter because induction motors draw several times their running current momentarily when they spin up. This surge lasts only a second or two, but if the generator cannot supply it, the motor stalls, the generator bogs down, or a breaker trips.

The difference is easy to underestimate on paper. A appliance that runs smoothly on 600 watts might demand 1,800 watts for the first few seconds. If you size a generator for the running watts alone, the motor may not start at all.

• Resistive loads like incandescent bulbs, toasters, and space heaters have no surge; starting watts equal running watts.
• Inductive loads like motors, compressors, and pumps can draw 3 to 7 times their running watts on startup for a fraction of a second.
• Some electronics and battery chargers have inrush current, but it is brief and usually small compared to motor loads.

Typical starting wattage ranges for common appliances

The ranges below are broad, engineering-style estimates for sizing purposes; they are not exact figures from any maker's label. Your actual numbers depend on the model, age, and condition of each appliance. Check the nameplate on the appliance or the manufacturer's documentation for the locked-rotor amps or starting watts if you want a precise figure.

Use these ranges as a planning tool. When in doubt, assume the larger surge figure and add headroom.

How to estimate your total surge requirement

Start by listing everything you will run at the same time. Assign a running watt figure to each item, and note the starting watts for motor-driven items. Add the running watts of all items together. Then, instead of adding every surge, add the largest single starting watt figure over its running watts to the running total. This reflects reality: motors rarely start all at once, and the generator's surge capacity is limited to a few seconds, enough to handle one large start.

For example, a refrigerator (300 running, 1,200 starting), a few lights (100 running), and a sump pump (600 running, 1,400 starting) would have a running total of about 1,000 watts. The largest surge increment is the pump at 800 watts over running, giving an estimated requirement of about 1,800 watts. A generator rated around 2,000 starting watts would handle that comfortably.

If you plan to start a central air conditioner along with other loads, the surge can climb quickly. A 3 ton unit might need 6,000 to 10,000 starting watts on its own. That is why over 9000 watt machines exist.

Why leave headroom beyond the estimate

Starting watts on a generator label are often a best-case figure at the outlet, delivered for a short window. Ambient temperature, altitude, fuel quality, and the age of the generator all reduce real-world surge capacity. Running a generator at maximum surge frequently also makes the engine work harder and shortens service life. A sensible target is to keep your estimated requirement at or below 80 percent of the generator's starting watts and below 90 percent of its running watts.

Voltage drops during a motor start are larger when the generator is already carrying other loads. Leaving headroom keeps voltage stable enough to protect sensitive electronics connected to the same circuit.

When in doubt, pick the next size up. The cost of an underpowered generator is downtime and possible damage to appliances; an overbuilt one simply runs at partial load. See our generator wattage margin guide for a deeper look at headroom.

Matching the requirement to a generator size

Once you have an estimated surge figure, you can match it to a generator class. A small camping or tailgating generator, typically below 3,000 watts, will run lights, a laptop, and maybe a small refrigerator but not a well pump or a central air conditioner. For those larger motor loads, you need a machine in the 3,000 to 5,000 watt class or higher.

If your house has a deep well pump, a large air conditioner, or an electric water heater, the surge requirement quickly enters the multi-kilowatt range. Consider a home standby unit with a transfer switch rather than a portable model, since standby units are sized for the whole electrical panel.

Compare the specification sheets of different units before buying, and note whether the maker lists both running and starting watts on the label. Some small inverters list only running watts on the main spec but have a separate surge figure; check the owner's manual. Our best 3000 to 5000 W generators and best 5001-9000 watt generators pages list figures for many models.

Starting watts for power tools and workshop gear

Power tools with universal motors, such as circular saws and angle grinders, have a surge but it is short and moderate, often about double the running watts. Stationary tools with induction motors, like table saws, planers, and air compressors, have the largest starting draws and can be the limiting load on a portable generator.

When running tools, remember the generator also powers the lights and maybe a vacuum or a radio. Add the tool's starting watts to the running watts of everything else. A 1 hp air compressor with a 3,000 watt starting surge will overwhelm a small 1,800 watt generator even though its running draw is modest. For serious workshop use, a dual-fuel machine in the 5,000 watt range gives flexibility in fuel choice and extra surge headroom.

Power tools are intermittent, so you may not need to run all of them at once. Plan around the single largest start and time your cuts to avoid starting the compressor while the saw is spinning up.

Safety while loading the generator

Running a generator near the edge of its surge capacity creates voltage and frequency dips that can damage motors and electronics. Never use the generator indoors; CO from a generator is deadly and can build up quickly, so only operate it outside well away from windows, doors, and vents.

Use a properly rated extension cord or connect the generator to the home panel through a transfer switch. Never backfeed through an outlet. If you are unsure, see generator safety checklist and how to size a transfer switch.

What to pick for your load

Questions

Why do some appliances have a surge and others do not?

Appliance starting surge comes from the inrush current of electric motors. When a motor starts, it needs a short burst of extra current to build its magnetic field and overcome inertia. Resistive loads, like light bulbs and electric heaters, have no motor and therefore no meaningful surge.

How many watts does a fridge need to start?

A typical domestic refrigerator might run at 150 to 700 watts, and its starting surge is commonly in the range of 600 to 2,200 watts depending on size, age, and compressor type. Larger or older units tend to fall at the high end. If you have the manual, look for the locked-rotor amps to get a more precise figure.

Can I run my generator at maximum starting watts for a long time?

No. Starting watts are only available for a few seconds to cover the motor's inrush. Continuous output comes from the running watt rating. If you exceed the running watts for more than a short period, the generator may trip breakers, overheat, or under-voltage your equipment. Keep continuous loads within the rated running watts.

Should I add the surge of every appliance I will run?

No. The practical way is to add the running watts of everything you plan to run simultaneously, and then add the largest single surge increment (that appliance's starting watts minus its running watts). This accounts for the fact that appliances rarely start at the exact same moment.

Is there a way to reduce a motor's starting surge?

Yes. Some air conditioners and well pumps can use a soft starter or a variable-speed drive that limits inrush current. For refrigeration, newer inverter compressors start more gently than conventional ones. When attaching a generator, also consider an electric-start model with a battery, since pulling a recoil cord on a heavily loaded generator is harder and the surge is more likely to happen on a cold engine.

What if I have a dual fuel generator: does surge change on propane?

Many dual-fuel generators produce slightly lower maximum power on propane than on gasoline. However, the generator's surge rating is usually a specification of its alternator and engine combination, and the same surge percentage typically applies. Check the spec sheet for the propane starting watts if the maker lists it separately. If the numbers are different on the two fuels, plan your load for the lower one.

Why does my generator's wattage meter show less than the starting watts?

The wattage meter on the generator shows continuous power drawn by the loads. Starting surge lasts only a fraction of a second, and most built-in meters do not capture fast peaks. The meter is useful to see your running load, but it will not tell you whether you have adequate surge capacity.

Is it better to oversize the generator to handle future needs?

Within reason, yes. It is easier to add loads than to buy a larger generator later. Oversizing by one class also gives you more headroom for the surge draw of a new refrigerator or an added tool. But an excessively large generator running far below its rating can be inefficient and can build up carbon deposits. Use the starting wattage table plus a modest headroom factor to pick a size that fits both current and near-term needs.