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How Long does a Generator Need to Cool Down?

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Typically, the larger and more powerful the generator, the longer it takes to cool. Most portable generators of less than 1,500 watts take about 4 to 7 hours to cool down before being handled or re-fueled (while equipped with a full tank). 

So, how long will a generator take to cool? This will depend upon the size and make of the generator, the environment it is in, duration of use, and capacity. Diesel generators cool faster due to the lower fumes suppression capabilities.

According to most manufacturers’ safety instructions, you must not re-fuel your generator while in use or if it is hot!

Simply walking away from an electric generator for a few minutes, will not do the trick and allow it to cool down. Even a small generator needs some time to cool down. 

The typical cooling down or shutdown time for the typical smaller generator is about 4 to 7 hours. Here is an approximate generator cool down list:

  • 500w generator –  will cool down in about 4 hours.
  • 1,000w generator –  will cool down in about 6 hours.
  • 1,500w – will cool down in about 7 hours.
  • 2,000w – 3,000w  – will cool down in about 10 hours or more.

Sometimes generator cooling time can run as much as 18 hours, depending on the size and outside temperature. This is why if you use a generator all the time, it is a good idea to have pre-charged batteries to back you up during those times.

If you use a generator extensively, such as during and after an emergency, you will want to shut it off for about an hour at certain periods of time (not for refueling) to let it cool down a bit. The size of a generator plays a big role in how fast your generator will cool down.

Very small generators can cool down in about 1-2 hours after being turned off, and they may be serviced almost instantly. Larger generators can take 3-4 hours to cool down, and very large whole-house generators require a much longer cooling time.

Another factor to consider is the generator’s prior run time BEFORE disconnecting and leaving it to cool down.

The longer the run time, the longer will be the cool down time!

Does a generator need to cool down?

Yes, generators require a certain amount of time to cool down before they can be started up again. You should NOT attempt to refuel or start a generator if you only allowed it to rest for a small period of time. Some generators, especially larger ones like standby units, may have problems if started immediately after the previous use.

It will either not work properly or some components may become damaged. Not to mention, that it is a safety hazard issue!  Although it is technically safe to start a standby generator immediately after switching it off, it is still better to allow it some time to cool down before doing so.

Most generators can run between 8 and 24 hours before needing to be refueled or switched off (check your user manual). Some high-end generators will run for longer periods of time, while others may run for shorter periods of time.

Generators used for household or agricultural purposes will require the engine to cool off for several hours before you can continue to use them.

How to cool down a generator?

Overheating is a possibility with all generators and this is why cool-down time is very important! Generators that are run at higher temperatures will have increased stress and wear on components, along with a shorter life span.

Most generators are set to shut down if overheated, but checking the temperature gauge is a good idea once in a while to be on the safe side. Some fuel-powered generators are equipped with high-temperature alarms that can go off (if programmed to do so)  when an engine reaches a certain temperature.

Simply set the temperature of your generator to a certain setting, and the alarm would trigger if the temperature rose to that degree and possibly damage your equipment. The cooling time of the generator also depends on the design of the cooling system.

Before starting a generator it’s a good idea to check the following to avoid overheating:

  • Check the air filter and make sure it’s clean, especially after intense prior usage.
  • Make sure you use top-quality oil and the filter is clean.
  • Keep oil and coolant topped off.
  • Make sure nothing is blocking the exhaust pipe.
  • Keep your generator in a well-ventilated area and away from direct sun.
  • Do NOT overload your generator!

Cooling a generator down is actually vital especially after it’s been running for a long period of time.  If you don’t do this, permanent damage to the generator can occur. When the load on your generator is reduced prior to being turned OFF, it can help with cooling down a little more quickly.

One main tip in conserving generator power and keeping it from running too hot is to:

Watch your power usage and don’t use many power-hungry devices at once.

Be reasonable in your power usage and your generator will cold down much quicker! On a hot summer day, placing a small generator in an air-conditioned room can assist with cooling down as well.

Running the generator at idle and disconnecting it from its load will help you with cooling it down quicker, depending on the model. Maintaining the minimum amount of electrical load significantly decreases the time it takes to cool when shut off.

Here are more things to consider when trying to figure out how long you need to wait before your generator cools down:

  • Generator placement. Generators that are left outside, will cool down faster (if no A/C is available). Sometimes placing a generator in a cold basement will help with cooling-down times.
  • Generator compactness. The more compact the generator, the more time will take for it to cool down. Generators that are compactly designed, will have trouble cooling down even if it is cold outside. If there is more space for air to circulate between the engine components, this type of generator will cool down quicker.
  • Generator size and type. Smaller-sized generators will naturally cool down quicker. Propane generators will cool down much more slowly than gas-powered units. Cooling-down time also depends on the cooling system type (air-cooled vs liquid-cooled).
  • Weather and ambient temperature. Generators will cool down faster in winter and slower in summer.  If you live in a place where it’s ALWAYS hot, be ready to give your generator some time to cool down.
  • Portable (handheld) generators. If the portable generator is made up of a series of lithium-ion batteries, it lacks a combustion engine and it is usually called – “a power station” or “ a solar generator”. Because it is merely a set of batteries, it can be cooled in one to two hours if unplugged.

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