I didn't follow these instructions, but rather offer them in homage to the principle of "do as I say, not as I did" 8-) Begin by deciding: 1. how much to spend 2. what to power and for how long 3. how to supply the required fuel 4. how to distribute the power Step 1 is an attempt to measure worry level, as reducing worry is the only sure benefit. In my case I found a Miller AEAD200LE welder- generator for $700 and wanted to play with it. So $700 was my "no hesitation" budget. It'll turn out $700 is rather low. Step 2 can get rather messy, but it's important for sizing the generator and fuel supply. I'm going to simplify for clarity: I'll power only my fridge and my communications. The comms stuff draws only 50 watts, but runs 24/7. That's 24 hours times .050 kW, or 1.2 kWh per day. The fridge is more complex, consuming about 1 kwH per day, measured with a Kill-A-Watt. It uses about 700 watts briefly to start up, 100 watts to cool and 400 watts to defrost for 20 minutes about once per day. Control is automatic, so it isn't practical to time generator operation to match the fridge. The worst case draw is 700 watts at fridge start plus 50 watts for comms, so a 1kW generator might just barely do the trick. Using .1(load+rating) we'll average .1(.1+1) or .11 gph continuously, or about 2.6 gallons per day for a minimum-size generator run around the clock. The fuel needed is simply runtime mulitplied by no-load fuel consumption _plus_ each load's runtime muliplied by load size times .1 gph for each load. Practically, that means fuel consumption is dominated by the generator size, not the load size. My 4.8kW rated generator can run a toaster, microwave and coffeemaker all at the same time to get a meal made quickly. Each will need 1kW at least, though only for a few minutes. The 5 kW generator will use nearly 10 gallons per day if run continuously, neglecting the energy used for cooking (because it's so brief) just because the generator is bigger. The fuel consumption of comms and fridge are insignificant. I opted to put the continuous small loads on battery- backed inverter-chargers and retain the big generator, running it to supply the cooking appliances, plus what's required to charge the batteries. The charging rate is important; ideally we'd like to complete charging in the same time other loads are powered also. Lithium iron phosphate batteries can charge fully in no more than a couple of hours. In the example here two hours per day of generator time will burn about 1.6 gallons of fuel. Much less than 10, but still quite a lot of fuel.. In the end I settled on cheap inverter-chargers and lithium iron phosphate batteries. The charge time required is about eight hours out of 24, but that is still much better than 24 out of 24 hours. Each battery backup cost about $600, or $1200 for the two required. The convenience was worth it, letting me wait about eight hours before doing anything at all. It's worth noting that when using battery-powered inverters, peak loads like starting surges can cause real difficulty. On paper, my 1.2 kWh battery should run the fridge for a day. Actually, it's only good for about half a day, because at half charge the 700 watt starting surge will trigger an undervoltage shutdown fault, depowering the fridge and causing a restart cycle that makes matters worse. Battery capacity is one case where bigger is always better. These estimates are quite crude, but they do make it clear that fuel supply for a backup generator is a major burden. Most towns limit home gasoline storage to ten gallons without special fire safety arrangments. Folks out in the country with a private bulk propane tank are better off, but propane goes about half again as fast as gasoline. Diesel is maybe 20% better than gasoline and makes sense if you already have it on hand. Limiting peak loads to minimize generator size is the single most important step in ad hoc backup power design. If the generator is oversized like mine, speedy battery charging rates are almost as important. Finally, the inveter-chargers were selected for minimum standby loss, around 10 watts. This is the power consumed when the grid is up, the battery is charged and the inverter is on and ready to pick up the load if the line drops. Other losses are felt only when the system is actively in use, but standby losses are paid 24/7/365. Over a year, I'll pay close to $80 for the insurance of having backup power available. Like generators, standby losses scale with inverter capacity. Step 3, fuel supply, involves the thorniest compromises between convenience, safety and cost. I chose gasoline, simply because a gasoline generator was what I had and gasoline is already on-hand in my car's rather large gas tank. It's possible to adapt gasoline engines to burn propane, but I normally have only ten gallons in reserve, equivalent to about six gallons of gasoline, compared to nearly 30 gallons of gasoline in my car. For those with deep pockets, a piped natural gas connection is the obvious solution. That will cost in the low thousands of dollars unless existing pipes are readily accessible and adequately sized. A 50kBTU per hour barbecue gas port is adequate for only about 2 kW of generator output. Step 4, distribution of the power, will be dictated by whether you want to run hardwired loads like furnaces, built-in lights, pumps and ventilators. If so, a generator interlock is by far the best choice if possible. A transfer switch subpanel is a little more money, but also more flexible by allowing a 120 volt generator to supply arbitrary branch circuits. I'd avoid extension cords unless there's some very specific reason to use them. They're a huge nuisance and suprisingly expensive unless already on hand. I chose cords because of an obsolete service panel. It takes at least half an hour to set them up, they cost (in parts only) about $300. Having the inverter-chargers in place as UPS units takes some of the nuisance away, since I can wait a few hours before it's essential to take action. My $700 generator needed another $300 in power cords plus about $1200 in batteries and inverter-chargers to make a serviceable emergency backup system, roughly three times my "no hesitation" budget. Had I not been an antique car buff with a big car to use as a tanker the cost would have been much higher due to fuel storage costs. The experiment still counts as success, but had the primary goal been power backup I'd have chosen a much smaller generator. 20230815