Generally, a portable generator for home use should be a 3KW or larger generator. If you are considering a smaller 3-4KW generator, the maximum power generated can meet the power needs of a refrigerator (or room air conditioner), as well as your lights, TV, computer, and some low-current appliances. If you are using a generator below 5KW, it is not feasible to connect a small generator directly to your home's electrical wiring, and you usually need to use an extension cord. This is because the home's electrical wiring cannot provide enough power. The generator will easily trip when your home power consumption exceeds the output that the generator can provide.
You can connect a portable generator to your home with a transfer switch. This is not as convenient as a standby generator with an automatic transfer switch, but it will still make things much easier. You can buy manual transfer switch kits in various sizes. These will require you to turn the generator on and off yourself. You will also have to manually switch from the mains to the generator and back again. But you can easily use existing electrical outlets and hard-wired lights in your home. If you use an extension cord, you can only use table lamps plugged into the outlet.
You should only consider using a transfer switch for generators with a power of 5KW or more. Even then, you will only be able to use a few lines. You won't be able to power your entire house with a portable generator. Even though the largest portable generators can provide all the power you need. The benefit of using a portable generator as a home backup power source is that you can also use it for other purposes, such as camping.
You can buy a basic transfer switch (Reliance Controls TF151W) for a couple hundred bucks. Although more likely, you'll want a full kit that supplies the auxiliary circuit breaker for the generator. For these higher-end transfer switches, you can expect to pay between $1,600 and $2,500, depending on how many circuits you need. Larger generators will be able to handle more circuits, so a larger transfer switch kit will be required. You'll also need to consider the cost of installation. The kit will likely come with all the necessary plugs and wiring, but you'll still need a qualified electrician to install it for you. Because the transfer switch connects directly to the house wiring, this needs to meet specific regulations.
Camping Portable Generators
If you're camping, you probably don't have a lot of room for a large generator. For basic tent camping, you might consider a really small 1Kw to 2Kw generator. These are usually small and light enough for one person to carry. They also don't require much gas and can fit in the trunk of most cars. You will be limited by what you can do with your generator though. These generators can power a stereo, TV, or similar electronic device, as well as some lights and a stationary fan or small space heater.
If you are using an RV with air conditioning, a 10,000 BTU AC will need at least 3000 watts. You will probably want something larger so you can run more than just your air conditioner on the generator.
Portable Generators for Food Trucks
If you only need to power a point of sale system and a coffee maker (or similar loads), you can get away with a 1-2kw generator for your food truck. In most cases, though, you will probably want to run a few more appliances. Food truck owners seem to prefer 3-4 kW generators. These are small enough to be practical and provide enough power for a small (under-counter) refrigerator, a few appliances, necessary electronics, and lighting.
The size of the generator used for a food truck depends entirely on the size of your truck and what power you need to keep your business running.
Portable Generators for Job Sites
Job site needs vary widely. One thing to consider when using a generator for power tools is that they require high starting wattage (peak load). This will also depend on how many people are working at the same time. Several tools started at the same time will require a high peak load.
For some drills or similar tools, 3KW or so will be fine. Although most construction site generators tend to be 5KW or higher. If you use high-powered tools, such as angle grinders, higher power output will be essential. Even more so if you are using a table saw or air compressor. An air compressor can use anywhere from 3-6kw to start.
Once you have decided on the size and type of generator you need, it becomes easier to narrow down your choices based on the price you can afford. Because there are so many types of generator brands (with different prices), imported brands such as Honda and Yamaha are recommended, and domestic brands such as Shangchai and Weichai are recommended. You can choose a gasoline generator or a diesel generator. Gasoline is more environmentally friendly and diesel is more durable.