Eli5: How do backup generators work?


If I got a generator for my house to be prepared for a power outage (California wildfire country) – how does that work? Do I have to run extension chords from any appliances I want on generator power? Is there a way to connect a generator to the house so that lights work?

In: 3

Speak to your electrician. There are basically two options.

One option is that you plug extension cords into the generator, so the generator is only powering the devices that you plug into it.

The other option is having the generator wired into your electrical panel, using something called a transfer switch. That way when the power goes out, your generator is providing power to all of the plugs in your house via your electrical panel. The transfer switch will automatically disconnect your generator when the power comes back on (which prevents you from backfeeding the grid and possibly electrocuting someone working on the power lines)

There’s two options for this

Portable gas generators are meant for construction, being in the woods, etc but can be used to power appliances in an emergency. They are gas powered and you hook up to them using an extension cord.

A standby generator for your house will typically either be Diesel or natural gas and will be hooked up directly to your fuse panel using a transfer switch.

When it detects that power is out, the generator will start automatically (depending on the model) and once it’s running the transfer switch will cutover to the generator.

The generator will keep running until either the mains come back up, or the generator runs out of fuel.

The downside is there is 30 sec or so of power loss between losing power and how long it takes the generator to spool up and cutover.

In the IT + Medical world this is a massive problem because the equipment we work with can’t loose power. So to hold the equipment we also need a UPS or a battery backup system in addition to the generator.

2 ways:

1) have an electrician wire up a plug that connects to your house so all the plugs in your house work as if you’re on the grid when the generator is plugged into it. I assume they would make up a switch for safety reasons.

2) run a bunch of extension cords and plug in which appliances you want to power when you turn on your generator.

I haven’t done the first one yet but it has its advantages and disadvantages like convenience vs practicality

What you’re talking about is a whole house standby generator. They are installed with an ATS(automatic transfer switch) which automatically starts the generator and switches over when the power from the street goes out. You’ll need to have a fuel source, depending on your location, it could be Natural Gas or Propane. These systems are wired directly into the house so everything comes back on. (Some systems are set up to provide power to essential systems, food storage, some lighting, a few outlets, heat.)

There are also portable generators, which can be connected to the same fuel sources as above, or can run on gasoline. These can also be wired into the whole house, but more often you’ll see extension cords running to the important appliances.

Source – I’m have one of these installed.

As others have said, you can buy either a mobile generator, usually gasoline powered or have an actual permanent “standby generator” installed. Residential standby generators are usually propane or natural gas powered as it’s common for people to have those as a utility or have tanks on site in rural areas.

In the case of a standby generator, they have what’s called an “Automatic Transfer Switch”. It’s a device that you can think of as a Y shape, one leg of the Y connects to the main power grid, the other to your generator. The tail of the Y connects to your house. In the event of a power loss, the ATS “senses” this, and cuts your connection from the grid leg to the generator leg and sends a “turn on” signal to the generator. This usually takes around a minute for the generator to get fully on, so you’ll be without power for a full minute or so, then the lights come back on. That’s pretty much it.

In my case, I have a mobile gas powered generator that isn’t powerful enough to power my whole home, but it it can still do a lot. I don’t have an ATS, my switch is manual.

My generator comes with two sets of outputs, one is just regular 3 pronged outputs for normal devices to plug directly into the generator. The other is a high-voltage plug like you might see on a dryer or washing machine. I had a corresponding plug installed on my home that can receive this cord directly.

That cord feeds to an electrical sub-panel in my basement along with a “manual transfer switch”. The electricians installed this small panel which looks a lot like my main home panel, just much smaller. My main home panel has about 40 breakers which feed my entire home, my subpanel has roughly 1/3 of that.

In the event of a power outage, I have to throw switches that disconnect my home from the power grid and connect it to the generator plug I had installed.

I worked with my electrician to decide which circuits should be fed from the generator (because I couldn’t choose them all, my generator is too small) So in general I’m feed my home heating system, a few lights and outlets per floor, my main appliances, and that’s about it. More than enough to get through a few days of outage.