lownslow Reader
6/22/24 12:04 a.m.

We moved to a new place, built a home which we are moving into. The local small power distribution company has had a succession of outages lasting 1 to 4 hours.

I have a 1,000 gallon propane tank and want to get a generator.  We have propane hit water and a gas range so the big draws will be the A/C, 2 split systems, and refrigerator and freezers. We would turn one system off.

200 amp service. Would a 14kw be enough? 

81cpcamaro SuperDork
6/22/24 1:10 a.m.

For a 200 amp service, to cover all circuits, the recommended size is 48kw.  Figure out what you would actually need to run to see if 14kw is enough to cover them.

Karacticus SuperDork
6/22/24 6:48 a.m.

Would you need to cover a well pump too?

We've got one at the vet clinic, though it can't recall the exact power.  My recollection is it's around 24 kWh-- the biggest you could get in an air cooled unit. There's a big cost jump going to liquid cooled. 

As a business expense, it's worth having a maintenance agreement with the installer/dealer, which is not the same thing as the manufacturer branded extended warranty offers that seem a bit scammy. 

Installation costs can vary depending on what the installer's bid includes in the way of a transfer panel and automatic cut outs. We've got two automatic cut outs, one for heat pump backup resistance heat, and I think the other is for hot water.

DeadSkunk  (Warren)
DeadSkunk (Warren) MegaDork
6/22/24 7:17 a.m.

I've got a natural gas whole house generator and it's 22KW. It's not connected to the AC, but will run the entire house otherwise. That's an electric stove, washer, dryer, and a well included. My heat and hot water are gas. 2700 square foot house with a full basement.

stuart in mn
stuart in mn MegaDork
6/22/24 8:55 a.m.

For a 4 to 8 hour outage you don't really need all that much backup capacity, I sure wouldn't worry about being able to run the whole house - just the essentials.  Heat or a/c depending on the time of year, the well pump if you have one, a few select outlets and a few select lights.  The fridge and freezer will probably be okay without power for that time period as long as you don't open the doors.  Many manufacturers have sizing information available on their websites, you plug in the various devices you want to run at the same time and it tells you what size you need.

lownslow Reader
6/22/24 9:01 a.m.

No well pump. I would like to use an air cooled unit.

It's just the 2 of us as well. 

11GTCS SuperDork
6/22/24 9:52 a.m.

In reply to lownslow :

In simplistic terms the capacity of a 14KW generator at 230 V is about 60A.   How big is the split system you plan to run? What size breaker does it have in the panel?  It's the compressor in the outdoor condensing unit that's the biggest draw on start, the inrush current on start is significantly higher than running load.   One last thought, some generators are dual fuel, make sure you're looking at the propane rating as that's lower than the gasoline rating.

alphahotel Reader
6/22/24 9:52 a.m.

Depends on what you want and how much money you want to spend.  You don't need anywhere close to 48kW because you are not running 200A continuously, ever.

I am not an electrician and don't know much about codes, but I have a couple data points:

A friend pushed the easy button and called a generator company.  They installed a 22kW Generac with an automatic transfer switch.  It is a largish house, two electric water heaters, IIRC two A/C units.  There are load-shedding devices on the water heaters and A/C units (that automatically disconnect them if the generator becomes overloaded).

I am doing it more GRM-style.  I bought a 7.2kW dual-fuel (gas and propane) generator (6.8 kW on propane).  It is connected to a breaker in the panel with an NEC-approved lockout device so that the main breaker has to be off before the generator breaker can be turned on.  When the power goes out, I have to manually start the generator, then go turn off the main and connect the generator.   The electric water heater gets turned off, but the generator can run everything else in the house (including the 3-ton central A/C).   It can barely start the A/C but can run it no problem.  Going to get an "easy-start" box for the A/C.  If we run out of hot water, I turn the A/C and well pump off, then run the 4.5kW water heater until it is hot again, then reverse the process.  Total cost about $1k.

I didn't size the generator expecting to be able to run the central A/C, that was a bonus.  I plan to buy a load-shedder for the water heater (so if it tries to heat while too much other stuff is running, it will be locked out) so there is one less manual step.

Streetwiseguy MegaDork
6/22/24 10:34 a.m.

My brother installed a 17kw, I think, unit when building his new semi rural house.  It came with a sub panel and all the stuff needed, and was around $7kcdn. (10 or so years ago.) Seemed really inexpensive to me.

Insignificant in the overall cost of a new home, and we had a lovely Boxing Day while everyone else was in the dark for 12 or 14 hours.

Building new, I wouldn't question it.  Pony up the dough.

lownslow Reader
6/22/24 7:47 p.m.

A/C breaker is 50 amp. I guess I should look at a bigger unit. 



11GTCS SuperDork
6/22/24 9:46 p.m.

In reply to lownslow :

Yeah, that's likely a 5 ton / 60,000 BTUH system.  That's quite a bit for a standby generator to start if anything else is running.

OHSCrifle UberDork
6/22/24 10:19 p.m.

I've had this in my Amazon wish list for about three years. Pick a few circuits and have a manual switch option. 


lotusseven7 (Forum Supporter)
lotusseven7 (Forum Supporter) Dork
6/23/24 1:16 p.m.

We have a 20k Generac and it fired up last night due to an outage from storm related damage. The area has been in a 6 day heat wave(consecutive 90*+ days) and our power went out last night at around 8:15pm. We had the a/c running, took showers(Rannai tankless hot water heater) with no issues. We run off of a 1000 and 500 gallon tanks linked together. When we built the house, we looked at all of the individual breakers/circuits and decided which ones to put on the generator panel. Stove, microwave, living room lighting, mbr lighting, m-bath lighting, hot water heater, a/c and furnace, garage doors, alarm and exterior panic lighting. There might be a few others, but had to decide on the important stuff(heat, cooling, cooking and washing). Really, you won't be using everything at once, so with just 2 people in the house and using common sense when the power does go out, you'd be fine with a 17k or better.

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) MegaDork
6/23/24 2:25 p.m.

I have a 3500w to install.  If you want to power everything, it's gonna be a big one.

I prioritized certain circuits and the genny will only supply a few of them: freezer, fridge, gas furnace, and the outlets in the living room which supplies a floor lamp, wifi, and computer.  3500 isn't enough to run the central air (it's likely closer to 5000w) but I could get a smaller window A/C if it's that hot.

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) MegaDork
6/23/24 2:33 p.m.

I might suggest some research on your house first.  There are devices you can install to show actual panel draws on an app for your smart phone.  200A service doesn't necessarily mean you need 200A worth of generator.

I might be tempted to find your peak use (A/C running, stove and oven on, all the TVs, etc) and size it that way.  Your generator subpanel could be a 100A or a 60A, then the genny could be sized at 24k or 15k.

You might have to be a little cautious with what you're using during genny times, but as long as the subpanel breaker is properly sized to match the genny, you can save a truckload of money if you just cook dinner first and run the dryer later.

Shadeux SuperDork
6/23/24 2:48 p.m.

We have a NG Generac system with an auto transfer panel. It's either a 21k or 22k. Runs everything, but we have light loads in a smaller house.

Oh, P.S.: We spent years doing an 7.5k rolling generator with a transfer switch. It became such a pain getting gas, storing the generator all year, etc. We finally said we're getting older, let's splurge and be comfortable. It's worked for about 4 years - the power has not gone out once.

Floating Doc (Forum Supporter)
Floating Doc (Forum Supporter) UltimaDork
6/23/24 3:07 p.m.

In reply to Shadeux :

I bought a 4k Yamaha after the year Florida had four hurricanes make landfall in a few weeks. I think it was 2004, put gas in it for it's first use in 2015. It was the sixth place we lived after buying it.

OHSCrifle UberDork
6/23/24 3:24 p.m.
Floating Doc (Forum Supporter) said:

In reply to Shadeux :

I bought a 4k Yamaha after the year Florida had four hurricanes make landfall in a few weeks. I think it was 2004, put gas in it for it's first use in 2015. It was the sixth place we lived after buying it.

Yep summer/fall 2004. I remember because we moved to Tampa that year. 

Shadeux SuperDork
6/23/24 4:31 p.m.

In reply to Floating Doc (Forum Supporter) :

Lol, Monday morning before the first out of four hurricanes I bought the last generator coming in on the truck. Picked it up Tuesday, built a box for it to live in, locked it to a tree, and wired in the 8 circuit transfer switch. We had everything but A/C working. It felt so weird during the four days without power because the whole house was lit up and we're eating ice cream under ceiling fans watching a DVD movie and there would be people standing in the street looking at the last remnants of civilization. We were the only lights in sight.

We ran an extension cord next door so the neighbor could run their refrigerator and a lamp so he could get dressed to go to work. Hey, we weren't heartless.

z31maniac MegaDork
6/24/24 11:01 a.m.

1-4 hours? This is the concern? 

The reason I want to get a generator is for when big storms roll through and knock out power for DAYS. 

Everything in the fridge will be fine for a few hours.

golfduke Dork
6/24/24 11:31 a.m.

We put in a 26Kw air cooled Generac with auto transfer/autostart when we moved into our house in 2020.  We are also on a 1000 propane tank.  When I say we run everything on it, we run EVERYTHING-  Well pump, 5 zone mini split, pellet stove, hot tub, electric dryer, dishwasher AND electric range... everything.  The only thing it doesn't run is the propane on-demand WH.  It's never once overloaded on us in 4 years, and our outages are typically 48-72 hours due to our remoteness (2mi private road off of a dirt road sort of scenario). 


FWIW we are on a 200a panel as well, and our mini split breaker is 50A too.   On average usage, we burn abour 4-6% of our proane tank per 24hr period, on a 1000gal tank.  We were quoted a 16Kw to run everything except the hot tub and dryer on our original quote, but opted for the 'Murican way and just sent it with the bigger unit since it really wasn't that much more expensive to install. 

Edited to add-  This does our 2000sf modest house and garage circuits, which does include a second fridge too. 


Toyman! MegaDork
6/24/24 12:34 p.m.
z31maniac said:

1-4 hours? This is the concern? 

The reason I want to get a generator is for when big storms roll through and knock out power for DAYS. 

Everything in the fridge will be fine for a few hours.

This is where I ended up. I built a 10kw diesel generator after Hurricane Huge left us without power for a week. That was 1992. I haven't needed it since. Our current house has lost power twice in 15 years. Both times were due to a car running over a transformer and power was restored within an hour. That's not enough to justify the expense of a house generator, nor is it worth the time to get the diesel started and hooked up.  

Our mountain house is in the sticks about 25 miles out of town. It loses power fairly often. It has a 7KW propane-fired Generac on an automatic transfer switch to keep minimal heat on during winter storms to keep the pipes from freezing when no one is there. It is only running a 9k BTU mini-split, the internet and camera system, and the refrigerator. It is on a maintenance contract for annual service and it automatically starts every Thursday at 8 am and runs for 20 minutes to keep the system working and battery charged.

MiniDave HalfDork
6/24/24 12:47 p.m.

I bought a 12,500 watt genset because I had bought a piece of land out in the country and needed power to run saws and such while building my new house......except that health issues with my wife intervened and I never built the house......so I  have it at my suburban house instead. 

It came in handy one winter when the power was out for over a week due to an ice storm, and I have run it a few times since......usually about the time I decide the power's going to be out long enough to make it worthwhile to get it pulled out of the shed, hooked up and running, the power comes back on.

It will not start the main house A/C, but we have a couple of window units and it will carry those easily, one in the bedroom so we can sleep and one in the main room where we usually are. 

We also ran an extension cord next door one winter outage so the family with small children could have heat and lights.

If I were building a new home I would def spend the money to have a whole house unit installed with the build, only ours would run on nat gas. 


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