Emergency Generator sizing

[jrpascucci]

I'm somewhat convinced that the power grid is growing weaker than it has been in past years for various reasons, and wouldn't find it surprising at all if we had a major outage this year, so I've decided I want to purchase a emergency (that is, non-whole-house) generator for such exigencies. This the last 'prepping' sort of thing I feel really strongly about getting sorted, but since I'm not yet out of my mind, I want to spend responsibly.

Let's say that I'm torn between something at around 4400 watts like this and something around 9.5kw like this.

Questions:
1) Do larger generators use significantly more fuel than smaller ones under light loads? Or is it reasonably constant fuel usage per kw in either case?

2) Sizing - my primary concern is to permit the oil heat (steam boiler) to run periodically (which needs the pump and ignition circuit to have power), and light-duty charging duties, maybe some ham stuff.
On a gut check, without sitting down and doing the calculation, it seems to me like it should be coverable by something on the lower end of the spectrum.
(I realize this doesn't take into account refrigeration, but I'm content to lose the contents of the fridge or move it outside if it's cold. I have other food, water.)

3) How much fuel am I looking at stocking? (I'd buy dual fuel unit, and want to keep some of each kind of hand)
I haven't found great information, I've found one site that says 1.2G propane or 1G gas an hour will power 6kw.
So, that might be 4hours/day*14 days = 55 gals? Maybe 5 20lb tanks (which should hold 20 gals of propane), and 6 5-gal cans?
Does that sound reasonable, or am I missing something?
(Side question: how good is gas stabilizer? With it, do I still need to rotate/refresh these at some interval, or do they stay usable for a relatively long time)

Thanks, and I'm looking forward to the good answers and any good additional thoughts you might have.

 

[one-eyed Jack]

I have a "big" one for whole house and a little one that is set up to run the heating system and sump pump only. For extended outages and limited gas I would have heat and a dry basement. Quite the not- to - code switching arrangement, however. Jack.

 

[Enzo]

My portable generator is a 5500/7000 watt inverter that I connect to an interlock and power my entire house (2,500 sq ft).
Having said that, my heat, hot water, cooking and dryer are all natural gas. Everything is 120v and all of my lighting is LED or florescent and if the generator is running there’s an understanding that not everything can be on at once (hairdryers, toaster/toaster oven, cloths iron, microwave (which all use 1000-1500 watts and can add up quickly).
For fuel I keep 15 gallons of gasoline on-hand at all times and fuel in the generator and extra gas cans if needed. If I know there’s severe weather coming I also make sure the vehicles have full gas tanks, about another 35 or so gallons of gas and a siphoning system (would still leave all vehicles with a 1/2 tank full or empty depending if you’re an optimist or pessimist….). I rotate the 15 gallons of gas, pouring a 5 gallon gas can into one of the vehicles (usually mine) every week or two.

 

[Cphobes]

My portable generator is a 5500/7000 watt inverter that I connect to an interlock and power my entire house (2,500 sq ft).
Having said that, my heat, hot water, cooking and dryer are all natural gas. Everything is 120v and all of my lighting is LED or florescent and if the generator is running there’s an understanding that not everything can be on at once (hairdryers, toaster/toaster oven, cloths iron, microwave (which all use 1000-1500 watts and can add up quickly).
For fuel I keep 15 gallons of gasoline on-hand at all times and fuel in the generator and extra gas cans if needed. If I know there’s severe weather coming I also make sure the vehicles have full gas tanks, about another 35 or so gallons of gas and a siphoning system (would still leave all vehicles with a 1/2 tank full or empty depending if you’re an optimist or pessimist….). I rotate the 15 gallons of gas, pouring a 5 gallon gas can into one of the vehicles (usually mine) every week or two.

Exactly the same, can't run the central AC but otherwise I'm good. Switching to gas appliances helped.

Gasoline can last longer than a week or two but I cycle it in to the truck no later than two months.

I get about 8-9hrs on my generator with 5gal of fuel it's an older one.

Only thing I'd do different is get a propane generator instead. Propane doesn't go bad and it's easier to store.

 

[Alien]

I do not have a direct answer to your questions. But I would like to share my recent experience with the last storm. Our family has owned this house for 55 years. In that time the power had never gone off for more than a few hours. This last storm our power was out for three days. I have one of those 2000 W inverter generators this one is manufactured by Wen. We also have gas hot water and heat. I used the 2000 W inverter generator to run the fridge, the heat, a few lights and a TV using an antenna, and to charge phones flashlights etc.

I ran that little generator nonstop for three days. We were warm. We had food. And could catch the local news on the TV with an antenna. For cooking are used a microwave and had to run that all by itself and disconnecting everything else for 10 minutes at a time. The microwave really was hard on that little generator and it would kick the breaker off occasionally. If I ran the microwave power level seven I had no problems.

in those three days the generator used a gallon of gas about every eight hours. Or only 3 gallons a day. For three days that was 9 gallons. I generally keep 20 gallons of gas on hand and could last a week with the generator without having to go to a gas station. I think if I were to go with a larger generator that will run the whole house I would want to hook it up to natural gas so that the portable fuel is not an issue.

with all that said an outage is not the time to test your equipment. I recommend testing your generator and equipment for a whole day just to make sure everything works as expected. I used to hardwire my heat and run an extension cord to it with the end cut off. I have since installed a little transfer switch so I can just plug a cord in and flip a switch. Everything else is run off of extension cords.

smaller inverter generators are also fairly quiet. In an extended outage I am concerned with vandalism and theft. I am sure after a week of freezing temperatures some neighbors might get a little jealous? Do you have a way to secure your generator so it doesn’t get stolen or vandalized. Walking around my neighborhood you could almost not hear my little generator just a house away. I could hear a couple of my neighbors generators and they are three or four houses away at the minimum. In terms of

 

[Knob Creek]

First remember that Propane does not flow well in cold weather. I’m going with a Honda 5000 this year. With all gas appliances and heat I will be covered. I had my panel updated with new breakers so I could use a Interlock switch for $55 as opposed to a transfer switch for $400. Another things th my electrician told me was to turn off breakers to unused appliances like A/C, washer and dryer etc. Don’t just not use them but shut off the breaker.

 

[SDG]

I have a "big" one for whole house and a little one that is set up to run the heating system and sump pump only. For extended outages and limited gas I would have heat and a dry basement. Quite the not- to - code switching arrangement, however. Jack.

Like Jack said a two pronged approach is best. I have a 7500W Westinghouse that runs the whole house, save the central air, via a 30Amp twist lock to the main panel. This sized gen(7500-9000) and you get to live with most of the amenities you are accustomed to during the outage I also have a 2500W super quiet inverter Gen, which will run my boiler and 1 fridge and freezer. It would be used if there were an event where we were in for an outage that was going to last more than a couple of days. Either way if you want to rely on them in times of trouble you need to test them every once in a while when things are good.

Pro tip... Start with the big one first and get the little one second. Your family or friends will find it more enjoyable to eat home made cookies and watch movies during the next outage than playing cribbage by flashlight and that will encourage them to get behind your next purchase.

 

[appraiser]

here I go again...

Emergency generator, something to keep the basics running on the least amount of fuel possible.

I can stay happy and warm on 1600 watts running, 2000 peak load

I can stay happier on 2 inverters tethered together.

I can run the basic house needs (heat, fridge,TV and internet, basic lighting, microwave or hot plate) on as little as 5 gallons of gas a day

If you are looking to sink a 500 or 1000 gallon propane tank and run the whole house, that is a back up generator.

I have a 5500 watt generator that can power a good part of the house, and the well pump. That gets used sparingly as it sucks down gasoline like a hemi at the drag strip

My normal setup is two EU2000i Honda inverters tethered together

at night I shut one off as all I need is the heat and fridge to run.

 

[natf]

I went the other way from Robin Proctor. I bought a Honda eu2000i about 12 years ago to run the household basics. Oil heat with power exhaust and circulator pumps, fridge, freezer, internet and a couple LED bulbs. It can keep the house warm and the food safe on a gallon of gasoline every 8-10 hours. I planned on stepping up to a larger generator a couple years later to be able to run everything without worrying about the fridge compressor kicking in while the oil burner is running (the eu2000i handles it, but not well) but never did because the fuel efficiency of the little generator was so good. I don't need to keep any extra gas cans on hand, just the 10 to 15 gallons I rotate through the lawn mower, snowblower and other small engines around the house. Those 15 gallons will last almost a week running the eu2000i but barely a day trying to keep a large non inverter generator running.

I still say I'll eventually buy a larger generator but I absolutely will get an inverter based generator (Honda EU7000iS appears to be the gold standard, there are probably other brands worth checking out these days) because of how quiet and fuel efficient they are. Being able to drop the engine RPM when not under full load helps tremendously.

 

[wilson911]

Only thing I'd do different is get a propane generator instead. Propane doesn't go bad and it's easier to store.

My neighbor runs propane but only for his generator. He does not heat or cook with it. During outages, it is difficult for him to get propane delivered as he is not a steady customer. I would think that gasoline is preferred for preppers, as it is readily available almost everywhere, no?

 

[PaulR]

As above.
Big one for whole house, little ones for little items.
Redundancy. Two is one, one is none.
Sink 500 gallons of propane.
Keep non ethanol gas stores with stabil and rotate.
propane and gas.
Google Tri-fuel.
Solar with batteries too.
Can never have enough power!

 

[daekken]

This is a good thread. I'm hoping to purchase a generator and get wired/hooked up for it before this winter. I keep putting it off but I am ready to move on it now, the hardest part has been determining which generator to buy and "how much" I need.

My goal is basically to prevent the pipes from freezing (via having heat) and running the well so that I have water. Fridge/hot water would be nice as well.

Would something like this be sufficient?

Generac GP Series 6500 W 120/240 V Portable Gas Generator - Ace Hardware Mfr# 7680 - Ace Hardware

Generac's GP6500 portable generator with CO-Sense Technology provides tons of power while protecting you and your home from carbon monoxide (CO) poisoning. If you inadvertently use the GP6500 in an enclosed area, CO-Sense will automatically shut off your unit when increased levels of CO are...

www.acehardware.com

When I try to run the numbers, I come up with roughly 2635 running watts and 6600 starting, but obviously some fudge factor would be nice.

 

[xtry51]

I agree with the above posts. A 9500W gen is going need a lot of fuel and if your concern is grid down, you should do a real energy audit of what you NEED, not what you want.

If you are in possession of a money tree, go with the 9500W standby and bury a few huge propane tanks.

If money is an issue, strongly consider looking at the 2 Honda 2000W setups and really have a detailed family discussion about what you NEED versus what you want.

Water and Heat are paramount. The rest are all conveniences.

I have a 4500W gen to run my house if we lose power. Ran it three days once. Used 20 gal of gas. It runs half the house though. So we're using TVs, computers, lights and everything.

If you have oil heat, strongly consider a diesel gen and add more 250gal storage tanks in basement or outside in a shed.

We also have a 2200W Ryobi and a 800W Earthquake as easily portable power. The 800W is amazingly useful, quiet, and sips gas.

 

[appraiser]

and how are you going to fuel that 6500W monster during a snow storm where the roads are impassable, or worse an ice storm where there is no gasoline for 40 miles and it will be 5 days before you can get more?

trust me eight 5 gallon gas cans can keep a inverter running for a long time

at 50% load you are going to burn 16 gallons of gas a day, that number goes up the more load you put on it

"The GP6500 can operate for around 10.5 hours at 50% load with a full tank (fuel consumption around 0.66 GPH), due to its fuel capacity of 6.9 gallons"

5 days, 16 gallons a day, 80 gallons of gas

My longest run on inverters is 11 days after an ice storm

 

[Kevin_NH]

If you're using propane or NG for heat, might consider a gas-fired "direct vent gravity wall furnace" to heat the most important room(s), these can run without electric hookup, no generator needed to avoid freezing, just a gas supply.

1) Do larger generators use significantly more fuel than smaller ones under light loads? Or is it reasonably constant fuel usage per kw in either case?

Yes, however it isn't linear. Also with diesel, you run into "wet stacking" if it trundles along at or near idle all the time, you want a load that will give it some real work, at least part of the time.

One way to work around the idle load/efficiency/etc issues is to go with a battery-backup where the generator recharges the backups then you can shut it down and run off battery (Think diesel-electric submarine).

First remember that Propane does not flow well in cold weather. I’m going with a Honda 5000 this year. With all gas appliances and heat I will be covered.

For the temperatures we experience here in N.NE, it is rarely cold enough to really stop propane flowing, but it does get cold enough that a smaller, above-ground tank, might not provide sufficient vapor pressure on the coldest night.

Solution is to tandem a couple of moderately large tank, or bury a single +500 gallon tank.

 

[qqac]

A larger generator does use more fuel than a smaller one. Regardless of a light or heavy load, a generator generally needs to keep a constant 3600 rpm to provide 60 hz power. Some generators now can throttle down when demand is low. A large generator supporting a light load is just a waste of energy.

Like Jack, I have a larger and smaller generator. The larger one is when I anticipate a short outage and want to keep the whole house running like normal. The smaller one is put in service for hunkering down for extended outages, and power usage is kept to more essential litems. In actual usage, the 8500 w one runs about 2.5-3 hours on a gal.

An oil fired boiler does not take much. Motors, like a well pump or freezer compressor, suck a lot of energy on startup. With a single fridge, LED lights, and oil burner, you could probably get away with a 3500 w.

Regarding old gas, the conventional wisdom is to rotate and use Stabil. However, for what it's worth, I have successfully used 10 year-old gas recovered from an old 2 stroke power boat I bought. I put fresh gas in the boat, since I did not want to get stranded or damage the engine. I used the old gas in less mission-critical things like my chainsaw and weed wacker without a noticeable loss of power.

 

[xtry51]

Another consideration should be having a woodstove if you live in North. Remove the need for electricity for basic heat, even if you just install it and never use it for primary heat. We use woodstove as primary heat. So our only need is well pump electricity and freezer/fridge power. Beyond that we run our oil furnace for hot water, but I consider that a luxury if the goal is fuel conservation.

 

[Night_solstice]

I'm setup with a Interlock setup, so can run the whole house in the event we need to from my Champion dual fuel (thus far since being setup, I think we've used it twice, max for an hour (a few times, by the time I gleefully ran out to connect, the power came back.) Heat is natural gas (forced hotwater furnace) so would like to get that setup so I can run just that on the small EU2000i I have as well since during the overnight if needed, since all we really need is heat (worst case, I could run an extension over to the fridge) during the overnight period, but don't see any easy way I can setup the furnace so that I can power it either by the panel (fed by the main power and interlock), OR my EU2000i.

 

[Alien]

this is an easy way to set up your heat or another single circuit item that you would like to runoff an extension cord using a small inverter generator. I just installed mine that I’ve had for a couple of years after the last outage.

kind of expensive but for those that don’t want to open up electrical boxes or tie live into a panel this is a fairly inexpensive solution which is very easy to use.

 

[qqac]

I'm setup with a Interlock setup, so can run the whole house in the event we need to from my Champion dual fuel (thus far since being setup, I think we've used it twice, max for an hour (a few times, by the time I gleefully ran out to connect, the power came back.) Heat is natural gas (forced hotwater furnace) so would like to get that setup so I can run just that on the small EU2000i I have as well since during the overnight if needed, since all we really need is heat (worst case, I could run an extension over to the fridge) during the overnight period, but don't see any easy way I can setup the furnace so that I can power it either by the panel (fed by the main power and interlock), OR my EU2000i.

Why not just plug the small inverter into the power inlet box instead of the Champion when you only want to run the furnace? Just switch all the other breakers off so you don't overload the inverter. Alternatively, you could get a transfer switch with a limited number of circuits and wire the furnace and inverter through that.

 

[SDG]

This is a good thread. I'm hoping to purchase a generator and get wired/hooked up for it before this winter. I keep putting it off but I am ready to move on it now, the hardest part has been determining which generator to buy and "how much" I need.

My goal is basically to prevent the pipes from freezing (via having heat) and running the well so that I have water. Fridge/hot water would be nice as well.

Would something like this be sufficient?

Generac GP Series 6500 W 120/240 V Portable Gas Generator - Ace Hardware Mfr# 7680 - Ace Hardware

Generac's GP6500 portable generator with CO-Sense Technology provides tons of power while protecting you and your home from carbon monoxide (CO) poisoning. If you inadvertently use the GP6500 in an enclosed area, CO-Sense will automatically shut off your unit when increased levels of CO are...

www.acehardware.com

When I try to run the numbers, I come up with roughly 2635 running watts and 6600 starting, but obviously some fudge factor would be nice.

You almost never will hit your starting watts, since you will normally turn stuff on gradually and once its on compressors and/or motors will go on and off intermittency and almost never at the same times. The exception to this is if you have a standby gen with ATS(automatic Transfer Switch) then you may hit the starting watts when you transfer over.

That Generac will work fine. I have the Westinghouse listed below. 30A Twist lock to a breaker interlocked in my Main Electrical Panel. She is a beast for sure, but its been through a dozen outages and never had an issue and the wife loves having the whole house lit up. It goes through 5 gallons in 12 hours under 50% load but typically runs closer to 30% loaded. I keep 30ish extra gallons on hand. If we had an event where we were looking at longer than a week. I would switch over to the inverter gen I have.

Amazon product ASIN B07R3RXBF6View: https://www.amazon.com/gp/product/B07R3RXBF6/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=B07R3RXBF6&linkCode=as2&tag=shootingmades-20&linkId=757e421d4cae51a863baa1eb1f0ecd25

From a peppering/grid down / extended outage scenario(or maybe even just not wanting to bother keeping extra fuel on hand) light little and quiet is the way to go. Honda is indeed the gold standard but out of my immediate price range. So my backup is a Ryobi which works fine for what it is.

 

[alpineboard]

Many portable generators are wired with "Neutral bonded to Ground" as they should. You need to change that to a "Floating Neutral" to hook it up to a panel that has "Neutral bonded to Ground. " And if using as a Stand alone again, easy solution is to use plug with Neutral jumped to Ground. Most have Neutral to Ground connection under the end plate of generator, but also use the ground wire as a neutral to the control box, so the idle control/safety controls need to be hooked to neutral in the control box.

 

[Night_solstice]

Why not just plug the small inverter into the power inlet box instead of the Champion when you only want to run the furnace? Just switch all the other breakers off so you don't overload the inverter. Alternatively, you could get a transfer switch with a limited number of circuits and wire the furnace and inverter through that.

Thought about that, but wasn't sure if would work: 110 coming out of the Honda, but feeding 220 at the panel (I know we're keeping just one circuit open for the furnace but I'm still awake of being warned not to use 110 to power the panel (two legs), and not 100% it's on a circuit breaker as I see it's hard wired into the panel, but it has a power shutoff at on the furnace itself, and the outlet on the honda is a standard 3prong, and the input outlet is the twist lock from the big generator. (I know just about enough of house power to: Have respect for it, and know when I'm over my head and left to someone who know, and this project would be over my head )

 

[bfm]

Still need to buy a generator, but I am glad that when I had the service upgraded from 100 to 200 amps I had them add a line for hooking up the generator.

 

[appraiser]

I have a EU2000i "Companion" that is one of the 2 EU's you need to tether to get 26 amps

The Companion has a twist lock connector, and what I did (I am not an electrician so take this advice as if it were from a burger flipper) was I made a cheater cord that goes from the EU to the cable I use for the 5500 watt generator ... that is the cable that feeds the transfer panel... and I only power one leg of the transfer panel, which in my case is the 4 basic circuits Fridge/kitchen, heating plant, family room electrical outlets ( TV, lights, computers, router if it will connect to the Comcrap network) and the master bedroom.

I have a 10 switch panel, the bottom switch/breaker on each side of the transfer switch is to run the well, so when I am on the EU's I don't throw the bottom breaker as it would only power one leg of the well pump and cause all sorts of trouble, and I don't throw the 4 120V circuits on the left side when using the cheater cord.... they would not get any power anyway but I don't throw them

 

[daekken]

You almost never will hit your starting watts, since you will normally turn stuff on gradually and once its on compressors and/or motors will go on and off intermittency and almost never at the same times. The exception to this is if you have a standby gen with ATS(automatic Transfer Switch) then you may hit the starting watts when you transfer over.

That Generac will work fine. I have the Westinghouse listed below. 30A Twist lock to a breaker interlocked in my Main Electrical Panel. She is a beast for sure, but its been through a dozen outages and never had an issue and the wife loves having the whole house lit up. It goes through 5 gallons in 12 hours under 50% load but typically runs closer to 30% loaded. I keep 30ish extra gallons on hand. If we had an event where we were looking at longer than a week. I would switch over to the inverter gen I have.

Amazon product ASIN B07R3RXBF6View: https://www.amazon.com/gp/product/B07R3RXBF6/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=B07R3RXBF6&linkCode=as2&tag=shootingmades-20&linkId=757e421d4cae51a863baa1eb1f0ecd25

From a peppering/grid down / extended outage scenario(or maybe even just not wanting to bother keeping extra fuel on hand) light little and quiet is the way to go. Honda is indeed the gold standard but out of my immediate price range. So my backup is a Ryobi which works fine for what it is.

That's a really good point about the starting watts, I hadn't thought about how you can flip things on gradually.

I'm thinking interlock, and it would be awesome if I could power the fridge on/off as needed relative to my other needs, but that Westinghouse is beefy enough it might be able to handle well pump, furnace, and fridge. Hot water heater would be awesome as well, but not mandatory.

My use case is 12 hours to 3-4 days; I live in a wooded area and frequently lose power due to trees falling over the lines. I just don't want the pipes to freeze and would like running water for obvious reasons. Typically we get at least one multiday outage per winter. I'm very close to two gas stations so if they are open, refueling shouldn't be an issue and I keep gas cans on hand for snowblower/lawnmower, etc. If it really comes down to it, I do have a siphoning system and could siphon gas from my truck.

 

[Kevin_NH]

I'm thinking interlock, and it would be awesome if I could power the fridge on/off as needed relative to my other needs, but that Westinghouse is beefy enough it might be able to handle well pump, furnace, and fridge. Hot water heater would be awesome as well, but not mandatory.

An electric water heater will need 220V and draws many watts. Well pumps are also often 220, starting current varies by size, depth.

My little tankless gas-fired water heater is such a low draw that it could run from a small battery-backed UPS if necessary.

Thought about that, but wasn't sure if would work: 110 coming out of the Honda, but feeding 220 at the panel (I know we're keeping just one circuit open for the furnace but I'm still awake of being warned not to use 110 to power the panel (two legs), and not 100% it's on a circuit breaker as I see it's hard wired into the panel, but it has a power shutoff at on the furnace itself, and the outlet on the honda is a standard 3prong, and the input outlet is the twist lock from the big generator.

Easiest way to use a 110V generator with an interlock is to make sure all your generator-backed loads are on the same half of the split-phase supply, otherwise you'd need to be sure to turn off any "tied-handle" (double) breakers before switching over to generator.

Cannot directly power a 220V load (like most well pumps, AC compressor, etc) from the little generator.

 

[qqac]

Thought about that, but wasn't sure if would work: 110 coming out of the Honda, but feeding 220 at the panel (I know we're keeping just one circuit open for the furnace but I'm still awake of being warned not to use 110 to power the panel (two legs), and not 100% it's on a circuit breaker as I see it's hard wired into the panel, but it has a power shutoff at on the furnace itself, and the outlet on the honda is a standard 3prong, and the input outlet is the twist lock from the big generator. (I know just about enough of house power to: Have respect for it, and know when I'm over my head and left to someone who know, and this project would be over my head )

You just need to figure out which leg the furnace is on, and then assemble a 3 prong/4 receptacle female (L14-30R) franken-cable accordingly so the 110 from the inverter goes to that leg. Of course, nothing on the other leg will get powered, and nothing 240, so make sure to flip those breakers off.

* Appraiser's post #25 has a pic of such a franken-cable.

 

[Woodstone]

Pretty much what everyone else said...
I've got a 10.5kW peak TroyBilt portable, socket on the side of the house, and an interlock on my panel...
Shut off the breakers and activate the interlock...
Plug in the generator and start...
Turn on only the breakers you need, sans AC, and it'll run the house...
~2300SF and the wife doesn't know how to shut off a light switch...
Full throttle is about 5G every 8 hours...I've never got there...
Pro tip is to run the generator only to heat the house, take showers, recharge the devices, then shut down...
Rinse, repeat...
I keep the generator filled with TruFuel and 15G of the normal stuff in the shed...
I wouldn't run on TruFuel constant but keeping it stored that way and it saves me from draining shit gas out of it every year...
I keep it on a trickle solar charger near the window and fire it up every 6 months to keep it honest...
YMMV.

 

[qqac]

Basic generator care and maintenance includes running it with a load once in a while, like spring and fall. If left sitting and not running for an extended time, it can lose its internal residual magnetism and become unable to produce electricity. Then you will have to try to flash it to restore the magnetism.

Don't leave a load on it after shutting it down.

Start it and let it warm up a bit before loading it.