Home Backup Power (Portable Option)

Michael Sharpe
12 min readNov 6, 2021


Last February, our home lost power for five days during a winter storm. Never in my life have I been so cold. The only defense my family had was to cover up in layers of clothes, blankets, and other bedding. Even the cat and the dog needed help. It reached 7F on the night we lost power. Before that, I would estimate that every 18 months, my home has lost electricity for a day or more due to bad luck, I guess. We lost power for well over a week during the aftermath of hurricane Ike. The largest immediate cost to long power loss is all the food in the refrigerator and freezer is ruined. That can cost several hundred dollars.

Like many others, we investigated a whole home backup generator for the house. At the cost of $15k to $25k, it was hard to stomach. Many who ordered backup generators are still waiting for installation. My biggest issue with a whole home backup generator was that it became an asset attached to the house. An asset we would likely not get full value from once we sell the house. Instead, we investigated a solution based on a portable generator. Indeed, a few generators are suitable for home backup to varying degrees, all of which can be taken with you when you sell the house. Depending on your future plans, using portable generators can be very appealing.

Suppose you plan to downsize when you move. In that case, portable generators become more attractive. In the next house, the generator is going to be better sized to the house. Alternatively, if an RV is in your future, a generator is essential for RV life. If you want to build a cabin in the woods, then a generator is also crucial. A portable generator can be a valuable investment for the future for some.

An alternative form of power independence is solar. However, still today, whole-home solar systems are costly. It is not clear if a solar system ever really pays for itself, and it can hinder selling later.

For our 4800sq ft house with 3 ACs (2 ton, 3 ton, and 5 ton), it was estimated that we would need 18kW to 22kW of backup generation power. These estimates assume you want to be running all ACs and refrigerators while cooking a roast, making coffee, and doing your washing all at the same time. In an emergency, this is unlikely. It’s important to set your expectations. It is very possible to ration which appliances are used such that they are not all on at the same time. Freezers and refrigerators can be sustained with little full-time power, particularly, if you have some frozen water bottles in them (and during a hurricane, you should freeze your bottled water ahead of time in the freezer just in case power is lost). A freezer with a lot of ice in it can sustain itself for a few days if it is kept closed. Outside the major appliances, it’s only ACs that draw a lot of power. Everything else uses minimal power in general. Without ACs and a little rationing, it is possible to power a house with only a few thousand kilowatts of generated electricity. The next important thing is that you have an environment in the house that is comfortable. This will vary family by family to some extent. Ideally, you want some places in your home where you can maintain a comfortable temperature. This will provide for a comfortable place to sleep at the very least. You will often want to be able to run internet equipment, as many data centers and equipment huts have backup power. The internet can both entertain and relieve boredom whilst you wait for services to return. Also important is the ability to keep cell phones charged.

It is possible to get decent portable generators for home backup for as little as $2k. However, there is a lot more to it than just getting a generator. The rest of this article will describe everything required for getting a backup generator for the house.

Generator Types

Firstly, let’s consider generators. There are two types of generators to consider, a regular generator or an inverter generator. A regular generator will typically produce power, but it generally is not necessarily clean power. Running computer equipment off a generator which does not produce the higher quality power can easily damage it. Many generators which claim to produce clean power (less than 5% THD) only do that when the generator has warmed up and is running normally. At other times, for example, when it starts up, when it runs out of fuel, when a large load kicks in, it can produce dirty power that can damage electronics. Inverter generators solve this issue; these generators always produce clean power, the inverter will simply stop outputting power if necessary to protect the line. In general, inverter generators produce less power than regular generators. Until recently, inverter generators did not produce enough power for a home. It is easy to find regular generators that produce 12kW-17.5kW of power for between $2k to $4k. However, a few companies recently started making larger inverter generators, which produce 9500kw peak power and 7600kw regular power. While this is smaller than the larger regular generators, it is sufficient to power a home if you ration usage well. It is possible to power a small central AC (perhaps with modifications), and most appliances. Inverter generators tend to support “parallel” operation too. That means it is possible to run two generators in parallel and double the power. That means 19000kW peak power and 15.2kW of regular power. That is huge! The price range for a large inverter generator is around $1.8k to $3k.

Which is better? An inverter generator or a larger regular generator. It depends on what you plan to power. Its possible to use a UPS with sensitive electronics to protect them. But if you have smart fridges, washers/dryers, TV etc which you plan to power, you may end up having to buy a lot of UPSes.

There are some other things to consider with a generator. Just about all generators require gasoline. Some will also work using propane and are often called dual fuel generators. Few will work with natural gas too, called tri-fuel generators. There are conversion kits available for most generators too, so it’s possible to fuel a generator with anything you want. In general, gasoline produces the most power. Propane stores better than gasoline, but produces less power, and natural gas generators need to tap into your natural gas line somewhere. Dual fuel generators are common and useful for many needs with reasonable preparation. Keep in mind, gasoline generators need gasoline, this needs to be purchased before the need arises and needs to be stored. Gasoline goes bad after a short period without additional additives. Having some extra gallons of gasoline around can be useful even if the generator isn’t needed during a hurricane. To power a propane generator for an extended period requires a large amount of propane too. A simple gas grill tank will not produce all that much run time. Gas grill tanks are typically 20lbs. It’s possible to get 40lbs and 100lbs tanks pretty easily and they are manageable, even if you need a propane delivery service. Having extra propane around in an emergency is also useful. This is one reason dual fuel generators are useful. Having some spare propane and spare gasoline is always good. Natural gas means you have unlimited fuel, assuming gas is running.

Another consideration is that inverter generators can run more efficiently than regular generators when lesser loads are required. With smaller loads, less fuel to will be used. For example, it may be that only fridges/freezers are running at night, maybe a small AC and a light or two. An inverter generator will run slower and only produce the electricity demanded.

For our house, we ended up acquiring two inverter generators and a parallel kit. For the rest of this article, this decision is not important. Everything else described below is what you need to ensure a functional solution using the portable generators you decide to buy.

Fuel and Fuel Storage

Most portable generators run on gasoline and/or propane. A lesser number will run on natural gas. Some generators can be converted to work on propane or natural gas too. In general, gasoline will produce the most power. Propane is an attractive alternative as it is easier to store propane. A dual fuel gas/propane generator will give you more options. Most portable generators will not run for 24 hours on a single tank at full speed. Much of the time, the generator will likely not be running at full load. Inverter generators are often far more efficient when running lesser loads, 25% or 50% loads can increase the run time significantly. Conventional generators typically run 100% regardless of the load on the generator. Generators can be powered down when nobody is home too. Fridges/Freezers can sustain themselves for a few hours. Putting some frozen water bottles in the refrigerator when you leave helps.

In times of an emergency, you will need to have a fuel supply on hand. It may not be possible to get fuel during or immediately after the emergency condition. It is likely best to have enough fuel to ensure a couple of days of run time.

You will need good quality gas tanks to store gasoline, and likely a 40lbs or a 100lbs propane tank to store propane. Keep in mind, gasoline goes bad after it has been sitting for a while. You will need to use some sort of fuel stabilizer, or rotate the fuel regularly. The easiest way to rotate the fuel is to put it in your car if you can, periodically. There are many brands of fuel stabilizers around which will allow the gasoline to be stored for a year or more.

Cables and House Hookup

A generator must never be run in or near the house due to the risk of Carbon Monoxide poisoning. The generator needs to be in an open area away from windows ideally. With this in mind, you will need to run cables from the generator to the house to use the power it produces.

The power panel of a generator will have several sockets on it. Some sockets look precisely like the sockets in your house and will produce 120 volts at 15 amps (120V@15A). There are often two to four sockets like this. You will likely find a 3 pin 120V@30A socket and a 4 pin 120V/240V socket at 30A. The three-pin socket is often useful for connecting a 3–4 socket extension cable to it. This will allow you to run a single cable to the house, and from there, it will accept 3–4 regular household plugs. The 4 pin socket is used to plug into an RV or a home. Some generators will also have a 4pin 240V@50A socket, which is used to connect to RVs and houses.

To connect a cable from the generator to the house will require your house electrical panel is modified to allow a generator hookup. There will be a socket for the cable and switching technology to enable the generator to be hooked into the home circuits. When connecting power to the house from a non-mains source (generator or solar), isolating the house from the grid is important. The simplest way to do this is with an interlock modification. An interlock is simply a mechanical mechanism that only allows the main switch to be on or the generator switch to be on at any time. It is also the cheapest option, $500–$750. More complex mechanisms are available, called transfer switches. Most are useful for permanent home backup generators, as the transfer logic will also turn the generator on. It is even more complex with solar, as there are times you want to sell the power back to the grid. For portable generators, a simple interlock is all that is required.

Even with a full house hookup, it’s helpful to have the 3pin 120V/30A cable, which you can run from the generator into the house. It allows you to help a friend in need, for example.

The longer the run of cable, the thicker and heavier the cable will be. Longer runs require a heavier gauge cable to run the power without overheating/melting the cable safely. This is another reason you do not simply want to hook a number of household extension cords together.


Most of the time, your portable generators will not be used. It is important to store them appropriately. It is helpful to get some dust covers for them to keep them clean. Ensure there is no gasoline in the generator when you store it. It’s necessary to periodically start the generator and run it for a bit.

When the generators are running, you may want to protect them. Water and electricity rarely mix, during the aftermath of a hurricane, it will often be raining. Some sort of cover to protect them from the rain is useful.

Tools and Maintenance (jugs, oil pans, oil, surge protector, adapters)

Owning generators will require you to perform some basic maintenance. Sure, small motor mechanics can do this for you, but keep in mind that large portable generators are not all that portable. Even though most are on wheels, and its possible to move them from your garage/shed to a run location, they weigh 250lbs or more. Its not an easy matter to pick one up and put it in a truck.

It is helpful to know how to do an oil change, charge/replace the battery, check/clean/replace the spark plug. Most of these tasks are not complicated and will ensure the generator stays healthy. Here is a list of useful tools

  1. tools to remove the generator cover to access oil fill, oil drain, battery and spark plug
  2. tool to remove the oil drain plug (normally a bolt)
  3. spark plug removal wrench
  4. oil drain pan and oil disposal bottles
  5. Cleaning rags and solvents, generators can get oily from the exhaust. Oil allows dust to adhere.

Emergency Appliances

Now that you have a backup power solution, its worth considering if you have the necessary appliances built in or available to exploit the power. Depending on the generator size you go with, it may not be possible to power everything in the house at the same time. There may be times you do not even want to run the household appliances too. For example, instead of running your regular built in oven, you may prefer to run a toaster oven instead to minimize load. It is important to evaluate the appliances in the house against the specs of the generator and decide what you can and can’t run, and then perhaps acquire alternatives. At my home, I have 3 ACs, and whilst I have the power to run them, I am not convinced I have the power to get them to start appropriately. Central ACs are fussy when it comes to power. To power an AC from a generator, it’s likely that a soft start kit will be required (helps reduce starting amps). Further, as ACs age, they often end up needing more power to start. I ended up also getting a couple of portable ACs so that I could be sure it would be possible to be able cool/heat atleast a couple of rooms in the house.

Ensure you have a mechanism to cook, if you have a propane generator, you will have propane on hand, so a propane grill/cooker is a useful backup device. If you have a gas generator, keep in mind that you have a supply of emergency fuel for your car.

Our Setup

This is what we ended up with

  1. Two Duromax XP9000iH inverter generators which run on gasoline and propane (Predator 9500W inverters are a possible alternative)
  2. Duromax XP9000iH parallel kit (allowing for 18000W starting watts, 15200 running watts and 50A output, perfect for full home backup)
  3. High Quality 4 pin, 240V@50A cable to hook up to the house
  4. House hookup + interlock
  5. 8 5-gallon gas tanks, 2 100lbs propane tanks (extra gas and propane in an emergency is useful)
  6. 4 pin at 240V@30A to 4 pin at 240@50A adapter cable. Allows one generator to power the house with 30A, which is fine for most things
  7. Storage covers and all-weather running covers (water and electricity do not mix)
  8. Funnels, tools, oil, magnetic dipsticks, oil change pan, used oil storage can etc
  9. Two portable ACs which cool 500sq/ft each (both will run on one generator)
  10. A table lift rated for 500lbs. These are 250lbs generators, if you need to get them into a trailer, truck or the back of a SUV, you are going to need some assistance.

This setup allows us to run the whole house using both generators in parallel, or most of the house with one generator. At night time, a single generator will run lights, chargers, fridge and two portable AC at about 50% power). This allows for maximal fuel efficiency. In many situations, it allows us to help a friend in need too.

Shopping the right deals, you can get all this for less than $7k, which is about half the price of a permanent backup generator. It is likely worth exploring soft-start kits for the central AC systems too. These would likely be required for a permanent backup generator too.


Using portable generators for home backup power is certainly cheaper than the permanent backup generator solutions. In my case, I spent around $6k. The best quote I could get for a permanent solution was $12k. I know people still waiting to get permanent solutions installed too. The portable route allows you to take the solution with you when you move. That was the most attractive thing for me. My family will soon be considering downsizing when the kids leave home. The idea of acquiring some land off grid or traveling around the country in an RV has been discussed in the past too. Having a generator for those purposes is ideal. Thinking about your investment as more than just a backup solution could help justify the purchase more.

During the winter storm, I was able to borrow a generator. It was small, but it did allow me to power my refrigerator, charge my devices and even power the internet for a while. It certainly is comforting to know that I can manage better now, or help a friend if needed.



Michael Sharpe

Senior Software Architect located in Houston, Texas