What size generator?

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Brawny

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Every year this time and during hurricane season I realize we need a generator.
We have a 2500 sq ft house, central air, with all the normal appliances.
What size generator do we need to at least keep the heat, fridge, water heater and stove on? Not necessary at the same time.
I know there are calculators for this but just would like real world experience.
I know, as in a lot of things, bigger is better.
Thanks,
Stephen
 
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If you're curious, this article should walk you through the load calculation (link) It's a long link, but its from the International Association of Electrical Inspectors.

When we put one on my parents house, we went with (I think) 20KW. It will run everything but the electric heat strip, however the stove and hot water are propane, not electric. We've had some electrical outages recently and I think it drank about 150 gallons of propane in about 24 hours of operation. It ain't cheap, but it will leave you operating normally.

At my house in High Point, back when I built it in 2003, I wired in a subpanel with circuits that would go to the generator, including some lights, refrigerator and freezer, and the 120Vac for the furnace (gas heat, no AC). I used a 5KW generator and it was oversized.

How big you need sort of depends on what you want to do with it. The amount of fuel it consumes is also somewhat linear with the load you put on it.
 
Here's a good link to check the power consumption of various household appliances (in Watts).

generatorist.com

Power Consumption of Household Appliances & Wattage Chart (2023 UPDATE)

Hey! CLICK HERE ✅ to Discover the Power Consumption of Household Appliances & Wattage Charts on Generatorist.com CLICK HERE NOW!
generatorist.com generatorist.com

An electric water heater can pull 4,000 Watts. The range, of course, will depend on how many of the heating elements you're using. The oven will be about 4,000 W. A surface burner about 1,500 to 2,500 W, depending on the size and power setting.

Something in the 5,000 Watt range will do for most anybody without killing the wallet. These are in the $750 range, give or take. Anything larger will involve more inefficiency, as you'll be using more gas even at lower loadings simply because the generator is larger.

Obviously, the absolute essentials should take precedence with power usage. The fridge and the freezer should take priority over everything else, unless you've got medical equipment that needs powering. Lights, especially these days with extremely low power consumption LED lights available, are a very small load. If you need A/C for some reason, consider a small window unit for under a hundred bucks.
 
Also consider the difference between the newer inverter units and the old "dirty power" type. The newer appliances with circuit boards might not work properly with dirty power. That might extend to the furnace and the water heater too.
 
RetiredUSNChief said:
Here's a good link to check the power consumption of various household appliances (in Watts).

generatorist.com

Power Consumption of Household Appliances & Wattage Chart (2023 UPDATE)

Hey! CLICK HERE ✅ to Discover the Power Consumption of Household Appliances & Wattage Charts on Generatorist.com CLICK HERE NOW!
generatorist.com generatorist.com

An electric water heater can pull 4,000 Watts. The range, of course, will depend on how many of the heating elements you're using. The oven will be about 4,000 W. A surface burner about 1,500 to 2,500 W, depending on the size and power setting.

Something in the 5,000 Watt range will do for most anybody without killing the wallet. These are in the $750 range, give or take. Anything larger will involve more inefficiency, as you'll be using more gas even at lower loadings simply because the generator is larger.

Obviously, the absolute essentials should take precedence with power usage. The fridge and the freezer should take priority over everything else, unless you've got medical equipment that needs powering. Lights, especially these days with extremely low power consumption LED lights available, are a very small load. If you need A/C for some reason, consider a small window unit for under a hundred bucks.
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That's a good point about bigger not necessarily being better.
 
.......I'm guessing 9k ish for electric heat/electric hot water, and fridge. You would probably be able to keep a few lights on, tv, etc.
If you wanted to use the microwave, stove, hair dryer, clothes dryer you will have to turn the heat or hot water or heat off.

Electric Heat, hot water, stove/range, dryer..... they pull some watts!
 
Brawny said:
That's a good point about bigger not necessarily being better.
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They went big at the department I worked at, 100KW diesel vs my recommendation for 60KW natural gas. It was only $20K more for the diesel. It ran for two days and they cried when the got the diesel fuel bill plus the trip charge to fill it up. It runs at 40% capacity 😀
 
Button Pusher said:
They went big at the department I worked at, 100KW diesel vs my recommendation for 60KW natural gas. It was only $20K more for the diesel. It ran for two days and they cried when the got the diesel fuel bill plus the trip charge to fill it up. It runs at 40% capacity 😀
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2 - 1750kw Gens at work run a shared load at ~70% each
0n a 6hr. run its $1200..... Each.

When all 16 Gens ( of various sizes) on campus run for an hour power outage... its about $8000 to re-fuel

OP, bigger is not always better. you should size your gen to run at 80% load most of the time.
 
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I’d look at alternate heat sources personally, save the generator for the fridge, freezer, lights etc. I’ve got a 7,500 dual fuel (which I recommend) and it was enough to run our well pump at the old house which was a priority for me. It’ll also run the water heater and stove but probably not at the same time. I recently picked up a 2,500 champion inverter generator, usually that’s all I need.
 
Bigger is always better until you start thinking fuel consumption. My FIL has a 13kw whole house propane model which while awesome during Hurricane Florence he was almost out of fuel from a hundred gallon tank within four or five days. He milked it and made it the entire 6 days along with a backup 100 lb cylinder but he was getting nervous. He’s added a larger tank since but it’s something to keep in mind. I had enough gas for my 5000 kw portable but just barely after 7.5 days.
 
I'm in a 2400 sq ft house and use a portable 8kw (running watts) generator.

In my case, I can run everything in the house, just not all at once.

Well pump, water heater, HVAC (heat pump), stove/oven...I have to pick which 2 I want running at once, while leaving the rest of the house running as usual. The one caveat is the "emergency heat". The gen can't handle that.

If I ever get a whole home backup generator, I'd probably go for something in the 14kw range.
 
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Button Pusher said:
They went big at the department I worked at, 100KW diesel vs my recommendation for 60KW natural gas. It was only $20K more for the diesel. It ran for two days and they cried when the got the diesel fuel bill plus the trip charge to fill it up. It runs at 40% capacity 😀
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Yeah, a lot of people forget about the "emergency" part of "emergency use".

A generator for the house isn't supposed to be able to carry nominal full loading. Under emergency conditions (hurricane, tornado, etc.) power isn't the only thing in short supply...goods and services are, too...like gas for the generator.

You want something that will comfortably power the essentials and not much more. For food, that's the fridge and freezer. For medical conditions, that might be some other devices, typically low power. Most everything else ought to be looked at as "seriously rationed". No lights during the day, minimal number at night. Cook food on the gas grill (or the neighbor's gas grill). Use radio for news, not TV. Keep your phones charged. Bathe out of a sink to conserve water and electricity. That kind of thing.

If heat is exceptionally oppressive, move everybody into a small room with one of those window units in it instead of running central air. Same for needing heat....don't heat the whole house when all you really need is one room for everybody.
 
You might also consider getting remote thermometers for the freezer/fridge. This way you can ensure you only run them on the generator when you need to, which would come in handy if you need to also assist the neighbors for some reason.

If you're smart, you can do a lot to stretch your resources.
 
RetiredUSNChief said:
Yeah, a lot of people forget about the "emergency" part of "emergency use".

A generator for the house isn't supposed to be able to carry nominal full loading. Under emergency conditions (hurricane, tornado, etc.) power isn't the only thing in short supply...goods and services are, too...like gas for the generator.

You want something that will comfortably power the essentials and not much more. For food, that's the fridge and freezer. For medical conditions, that might be some other devices, typically low power. Most everything else ought to be looked at as "seriously rationed". No lights during the day, minimal number at night. Cook food on the gas grill (or the neighbor's gas grill). Use radio for news, not TV. Keep your phones charged. Bathe out of a sink to conserve water and electricity. That kind of thing.

If heat is exceptionally oppressive, move everybody into a small room with one of those window units in it instead of running central air. Same for needing heat....don't heat the whole house when all you really need is one room for everybody.
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I've never been in a power outage without heat (we have a gas fireplace), If all you had was electric - are you at risk for potential pipes freezing/bursting? I know after the power goes out, I'm sure there would be several hours in which everything would be OK.... but for how long?

Ex. - If everyone is camping out in the living room with a space heater running off a generator, would a bathroom far away from the space heater be at risk of freezing pipes?
 
BowWow said:
I've never been in a power outage without heat (we have a gas fireplace), If all you had was electric - are you at risk for potential pipes freezing/bursting? I know after the power goes out, I'm sure there would be several hours in which everything would be OK.... but for how long?

Ex. - If everyone is camping out in the living room with a space heater running off a generator, would a bathroom far away from the space heater be at risk of freezing pipes?
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That's my fear, depending on temps. 30* I don't worry so much about. 20* I would.
 
BowWow said:
I've never been in a power outage without heat (we have a gas fireplace), If all you had was electric - are you at risk for potential pipes freezing/bursting? I know after the power goes out, I'm sure there would be several hours in which everything would be OK.... but for how long?

Ex. - If everyone is camping out in the living room with a space heater running off a generator, would a bathroom far away from the space heater be at risk of freezing pipes?
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Multiple days well below freezing is the only time I’ve experienced problems. If there’s water in the pipes under the cabin and it gets cold enough for long enough they will freeze (multiple days where the temp stays below freezing with nights in the 20s) This is in a cabin built over the alligator river. When I say built over the river it’s on pilings built on the water. You can get there by boat or by swimming if you’re brave enough. When you take a dump and flush the toilet the waste falls right into the alligator river. That’s the only place I’ve personally experienced plumbing problems from frozen lines. I think a lot of it has to do with sitting right in the water like it does. Here’s a pic just to show this isn’t a “normal” house by any means. I think I’m most people leave a faucet dripping but that is not an option for us here there is a well but the only power we have is generators we haul back and forth. 25887D63-BB91-4142-88D6-0476BDC989C5.jpeg
 
Based on my personal experiences growing up down east where week-long power outages were the norm after every hurricane, a 4500w generator will run a fridge, fans, lights, tv, or a microwave without issue.

If you plan to run a central HVAC unit off of it, you're going to need big power. Those have multi phase motors, and while they may run all day on 2000w, they might need 6000+ for a few seconds at startup.

I'm planning on buying one for my place sometime in the near future, and I'm thinking I'll just get a 3500w. I just need to run the fridge, a few lights, and the internet router. Fans in the summer, or a 1500w electric radiator to provide some heat in the winter. A 3500 will handle that just fine.
 
BowWow said:
I've never been in a power outage without heat (we have a gas fireplace), If all you had was electric - are you at risk for potential pipes freezing/bursting? I know after the power goes out, I'm sure there would be several hours in which everything would be OK.... but for how long?

Ex. - If everyone is camping out in the living room with a space heater running off a generator, would a bathroom far away from the space heater be at risk of freezing pipes?
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In my 2 story house, 1790 square feet, a radiator space heater will keep the entire downstairs at 60-65 degrees. Combined with a slow drip of a faucet and I wouldn't worry too much. My biggest issue is the water line coming into our house is on a garage wall that doesn't get heat. Had a freeze once when the temperature was below freezing for about a week. Fed heat back down the pipe with a hairdryer blowing on the pipe at the shut off valve and water started flowing again in about 10 minutes.
 
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I'm thinking a 3500w for emergency use is what we need. I do have a fireplace that I haven't even tried to use yet. We've only been here for a year and a half and haven't seriously even considered the fireplace, but we've got plenty of wood around the place to keep us from freezing to death!
 
Something else to consider and have on hand is properly sized extention cords. Not the thin cheap kind, the heavy gauge stuff that costs a fortune. Don't buy more length than you need to get power where it needs to go.
 
RedneckFur said:
If you plan to run a central HVAC unit off of it, you're going to need big power. Those have multi phase motors, and while they may run all day on 2000w, they might need 6000+ for a few seconds at startup.
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I wonder if a soft starter would help with that. They put one on my parents heat pump because even with a fairly good sized generator, there have been known issues with the compressor starting.
 
noway2 said:
I wonder if a soft starter would help with that. They put one on my parents heat pump because even with a fairly good sized generator, there have been known issues with the compressor starting.
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Any techs on here who can install a soft starter on my AC in Raleigh? I have a service contract with a local outfit and I've asked them twice if they would put one on - they say they will get back to me but they never do. Obviously I'm not in a big rush :p.
 
Brawny said:
Every year this time and during hurricane season I realize we need a generator.
We have a 2500 sq ft house, central air, with all the normal appliances.
What size generator do we need to at least keep the heat, fridge, water heater and stove on? Not necessary at the same time.
I know there are calculators for this but just would like real world experience.
I know, as in a lot of things, bigger is better.
Thanks,
Stephen
Click to expand...
I have quite a few generators, ranging from 2KW all the way up to 225KW. In order to best answer your question, some additional information is needed.

1 - well or city water?
2 - Gas furnace or electric?
3 - gas stove or electric?
4. how many air conditioners?
5. Any electric vehicles that will need charging?
6. How many refrigerators'?
7. Do you have natural gas or propane?
8. Are any of your vehicles diesel?


Any critical health machines such as CPAP, etc? Also, how much are you willing to "rough it" during an outage?

Electric stoves and electric dryers are two of the biggest power consumers in a modern house, along with electric HVAC. They are closely followed by electric water heater, then well pump. If you have to charge an electric car, the fast charger may require even more power than your stove.

For most homes, if you want to minimize the compromises that you need to make, you'll need 17KW or more of generator. I can power my house quite comfortably on 12KW (including running the well pump, air conditioner, two refrigerators and a freezer, BUT I have a gas furnace, stove and water heater. If I did not need to pull the air conditioning, I could get by on 5KW by being frugal.

During one of the ice storms back around 2003, I ran a 5500 1800 rpm 2 cylinder propane generator to back up the fridge, well pump, bathrooms, TV, etc (no air conditioning), on around 1.1 gallons of LPG per hour. It ran for 3.5 days and consumed around 100 gallons of lpg.

Generators are one thing where you don't want to go too big; just large enough to be able to carry the typical load and still be able to start your largest load. My older 2.5 ton see 13 air conditioner required a hard start kit to run off of my 12KW generator, but the current 3 ton Seer 16 unit starts up just fine. Again with gas heat.

Typically lower rpm generators last longer and are higher quality, but they cost more. Inverter generators are nice, especially the ones with the load based rpm governors.

If you're plumbed for natural gas (and the service is large enough), it's one of the best options for a generator. The fuel does not go bad, you don't have to worry about refueling it during an outage, you don't have to keep spare fuel on hand, and it is almost unheard of to lose natural gas at the same time as and electric outage.

Propane is similar but your limited on fuel on hand.

Gasoline is the most problematic in terms of fuel storage, but easiest to obtain fuel for. Diesel is more efficient and the fuel lasts longer and w/o carb problems associated with gas, but again you need to have an adequate supply on hand during the outage.
 
noway2 said:
I wonder if a soft starter would help with that. They put one on my parents heat pump because even with a fairly good sized generator, there have been known issues with the compressor starting.
Click to expand...

Do you mean a hard start kit? Typically that is an oversized capacitor. Soft starters are usually used for industrial 3 phase motors.
 
Scsmith42 said:
Do you mean a hard start kit? Typically that is an oversized capacitor. Soft starters are usually used for industrial 3 phase motors.
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Thx Scott. What I mean is "whatever equipment is necessary to ease the instantaneous load of starting up the AC"
 
Scsmith42 said:
This will work for most air conditioners. Very easy to install.

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Awesome, thank you. I'll study it. I have a genset that comfortably runs the whole house (which is mostly gas), and it will start and run the AC too, but the AC is slow to start on the genny. I'd like to give the AC a boost, to make life easier on the motor.

And I'd like to second your recommendation on natgas. I have mine plumbed with QD connectors and properly sized line (you need a big one for natgas) and regulators. I can (and have) run it on gasoline, propane or natgas. Natgas is the fuel of choice for anything but a short session!
 
Scsmith42 said:
Do you mean a hard start kit? Typically that is an oversized capacitor. Soft starters are usually used for industrial 3 phase motors.
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To be honest, I can't say with 100% certainty as I haven't looked at it directly, but I was told soft starter (and it sure cost enough - several hundred dollars). While common in 3 phase applications, it wouldn't be difficult to make a 240V single phase one with four SCRs. Just monitor the voltage between the two phases and gate them on as desired to reduce the inrush and they'll naturally commutate off.
 
BowWow said:
I've never been in a power outage without heat (we have a gas fireplace), If all you had was electric - are you at risk for potential pipes freezing/bursting? I know after the power goes out, I'm sure there would be several hours in which everything would be OK.... but for how long?

Ex. - If everyone is camping out in the living room with a space heater running off a generator, would a bathroom far away from the space heater be at risk of freezing pipes?
Click to expand...

Generally several days before freezing you'd have something to worry about.

The pipes most susceptible would be those more exposed to the weather. The ones inside the house would be the least susceptible.

Now is a good time to think about preventative measures, like heat stripes with insulation over such pipes.

You can crack a faucet open in the house and maintain a slow water flow to keep the water from freezing if need be.
 
I've got an 8k, but don't run everything off it. When the grid is down we have lights, well pump, TV&such, fridge, microwave and that's about it. Generator runs at 1/2 load at most, except when the coffee maker fires up, you actually hear it change pitch when the kurig warms up. The 8k means we don't have to worry about the pump starting, and can run a welder off it if required (we've done that before at the range fixing steel targets).

Instead of trying to deal with the HVAC we got a wood stove, and use a space heater to warm just the bedroom. Cooking is microwave or BBQ or camp stove. If it was hot, we would just sweat I guess, maybe I should get a window unit for the bedroom.

It's not perfect, but it keeps us alive and is 'good enough' for what we need in an emergency.

I'm using regular gas, swap half my supply out every 6 months so the oldest gas is never more than a year. With stabilizer it seems to run just fine even that old (especially when I cycle it out and dump the old stuff in the truck). I didn't do diesel since I have nothing else that uses it, and no propane.

We do shut it down at night, the fridge and freezer keep just fine for 8-10 hours without power and no one opening them.
 
Emergency power is just enough to get thru a crisis. You don’t have live in every square foot of the house. Heat pumps are the biggest issue when it comes to power consumption.You will need those auxiliary heat strips for defrost cycles. A 3 ton heat pump with 15kW heat strips will eat up 85% of a 20kW generator capacity when in defrost. A better plan is to buy or invest in better heat systems for parts of your home. For example add a mini split to the most used area. Or get propane heaters that run off small tanks. Then decide what size best meets comfortable emergency situations.
 
Jayne, you explained our situation as well.
emergency electrical power is just that.
pick and choose.
endure.
 
This is not the time to be shopping for a Genset.

Back in the fall had my RV at Cummins 512 Teague St, Greensboro, NC 27406 where they were pushing propane generators.

One item to think about with the big generators - service. If you need maintenance work you can't do yourself your looking at either mobile mechanic (big $) or hauling it in.

Big don't always mean thirsty. My 7.5kw Onan in the RV sips half gallon diesel per hour @ 50% load. I've let it chug away for days at a time.
 
People with campers have the best situation. Doesn’t take much to be comfortable in a little 24’ camper. A used camper might be a great hedge on emergencies. Then it comes down to your refrigerator and freezer. All will work on propane.
 
Well I do not recommend Powerstroke generators if customer service is your thing. Morons can't tell me what spark plug I need without a model number even though I told them the engine is the same as another model. It is like dealing with Autozone. No data plate or anything. Oh well. Run it til it dies I guess.

Edit: They had someone knowledgeable call me and get me straight. Kudos to them for that. Makes me happy, especially since it is made in South Carolina.
 
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My 5.5 genny died last year so I went and got a new one last night. 7.5 kw running. I have gas heat and water heater. My old old ran everything, not sure of how much gas this one will use and I hope I don’t have to this weekend. As far as campers, I sold ours last year but they are great for power outages.
 
We just had a 22kw Generac installed. When they did a load evaluation, we would have been fine with a 17kw and Load Management System.

Biggest draws in our house are well and heat pump emergency heat strips..followed by the stove. Have tankless water heater and gas logs for backup heat.

However, 17kw gen sets are backordered 4-9 months. So we went with a 22kw. We were going to keep it on propane but it was actually more cost effective in the long run to pay to tie into NG.

We are likely going to switch from our induction stove to a dual fuel range, which drops our demand even more.

Would rather have a 22kw running at 40% than a 17kw at 80%.
 
BlackGun said:
Heat pumps are the biggest issue when it comes to power consumption.You will need those auxiliary heat strips for defrost cycles. A 3 ton heat pump with 15kW heat strips will eat up 85% of a 20kW generator capacity when in defrost.
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VERY good point about heat pumps. Even if youre able to start them in cooling season, heating season will provide unique challenges. I should have pointed out that my parents is unit geothermal with a 55f condenser water temp all year round, which also means less compressor lift and a high heating COP.
 
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