Generator Size Based On Average Kilowatts

[trader4]

I'd also consider a propane powered portable generator with a panel mounted lockout switch and inlet. That can be had for a fraction of the cost of the installation of one of the whole house standby units. And if it fails, you just buy another generator and it's replaced with no muss, no fuss. Has the advantage of being portable, for possible other uses too. There are kits available to convert many of the gasoline ones to nat gas, propane or even tri-fuel, so it can take any of the three.

Oh, an if you're considering Generac, I'd go to Amazon and similar and look at all the horrific customer experiences with their whole house units.

For sizing, I'd say it has little to do with the average monthly bill and a lot to do with adding up the loads that you want to run at the same time. A 10KW load that has to be run for 10 mins is a lot different than a 1KW load that runs for 100mins.

[Stormin Mormon]

I think there are different type of people. Me, living in a trailer park of day to day people. I do what I can to prepare for when things go wrong. Others around me live for the moment, from what I can tell. My guess is that the Mc Mansion people also live for the moment.

. Christ>

own generators. They put in a McMansion development up on the ridge a few years back but I think a few rounds of .308 would convince them to go back home and freeze in the dark.

[NotMe]

I have a little gas-powered generator rated at 6,500 watts that I use to power the pump, boiler, refrigerators, etc., but it would be nice not to have to run out in the rain to start and fuel it during an outage.

I've read that an 11,000 watt unit should be enough to power a house, and we wouldn't be using the electric oven or dryer during outages. That would be almost 5 times the average usage, which should give coverage for start-up peaks.

Does anyone have any official formulas for this sort of thing?

Paul

{{{{

The determination is a bit of a black art but for a good ball park idea check some of the off grid news groups and blogs. (you can trust but best to verify independently what you're told)

First identify the mission critical requirements. Then the start and run requirements. With that you can guesstimate the require size of the gen set. Rotory gen sets have ~ 30% surge capacity, inverter gen set system less or not at all.

Also if you're careful and a bit anal retentive you can balance the start/run loads and do more with a smaller gen set. As example a well pump can be run and shut off when the reserve tank is full or left off if you don't need running water except for select times of the day (cooking washing as example).

This can be done with a pencil, paper and a clock or with an automated system (as a function of how much you want to spend).

Depending on the local circumstances you might benifit from salavging the waste heat for your wife's green house.

My kids have a 10KW (mil surpluses) with a 3K battery (salvaged from communications towers) backed dc to ac inverter. Duel fuel NG with a 250 G LP back up.

They can run, depending on load, the innverter for 3+ hours before a recharge. This to reduce the need for running the gen set or starving the neighbors. Works great for the microwave, TV/internet and the fridge.

We have provided the neighbors within safe range of a HD extension cord power (enough to run, in cycles, the fridge, window unit (this is N. Texas) TV/internet and a few lights) Key benefit, aside from being neighborly, this has cut the complaints about the gen set noise to zero.

The neighborhood posse sets up BBQ grills in the street in front of the house (we provide trouble lights) with tables/benches pulled from the back yards so we have a community cook out in the evenings. But not a power outage single event as this happen at various times of the year just for fun

[(PeteCresswell)]

Per Stormin Mormon:

Somebody on this list observed the distinction between "lifeboat" and "cruise ship".

I opted for the lifeboat approach based partially on fuel consumption.

If I had the sense to get a nat gas install, that would not be a consideration - but I bought a little Honda EU2000 that runs on gas and gets about five hours run time per gallon. My neighbor's el-cheapo

6,500 watt gennie gets more like five gallons per hour... OK, that's an exaggeration.... but it does drink gas.

[Stormin Mormon]

When the power is out, often the gas stations are unable to pump fuel. Best to have a system that runs as long as possible on fuel.

Years ago, I worked the numbers. IIRC, a gallon of gasoline puts out 2,000 watts for 1 hour.

. Christ>

[Stormin Mormon]

What did that Honda cost? My ETQ brand 1200 watt unit was $140, shipped (this about five years ago). Says it runs some hours on a gallon, can't remember. Nine hours or something.

OK, make that five and a half hours. On half load. Mine didn't start except on ether. I bought some 91 octane pure gas, and it runs and starts much better.

. Christ>

[(PeteCresswell)]

Per Stormin Mormon:

Honda's are not cheap.

I can't recall exactly, but it was somewhere in the 800's - and on the high end.

[Stormin Mormon]

I'd dare to guess that you get good clean power. And I'd guess that when the neighbor is out of gas for his big generator, you'll be purring along on your second gallon of gas, with 8 more gal left in your gas cans.

Wait till he sends his kid over to borrow a cup of gas. "No, boy, but you can come in and get warm for a few.... you look cold. How is school going?"

. Christ>

[woodchucker]

2kw is 2000 watts

so I think his little 6500 trumps your little generator by a factor of 3.

are you sure you didn't mean 20kw?

[(PeteCresswell)]

Per Stormin Mormon:

That was another major consideration. I wanted an inverter-type gennie because of all the computer-type stuff I have.

I don't know enough to make a decision, but it seems at least possible that, with all the computer stuff on UPS', the clean waveform might be moot... but, like I said, I don't know enough so I went with the conservative approach.

If outages were frequent and/or medical considerations mandated continuous power and/or I found I had too much money laying around, I'd have to think about having a nat gas hookup to something like the Honda EM5000iS inverter generator of an EU6500....

Except for A/C, I'm at a loss as to why I'd ever need more than 4KW continuous - probably more like 3KW. This is based on observation of the readouts on my APC UTS-6H smart transfer switch while it is running our house on a 2,000 watt generator.

Dunno what our central A/C takes, but it's got to be way out of proportion to the rest of the load.

If A/C were a "must" I think I would have a couple of small window boxes or freestanding units in storage for use under generator power: one for the kitchen and one for the bedroom - and they would determine whether to get a 5 or 6.5 KW generator.

[(PeteCresswell)]

Per woodchucker:

No. During outages I run the house on a Honda EU2000, which is rated at 1,800 watts continuous.

Needless-to-say, we don't even think about having air conditioning or electric cooking.

For cooking I've got a half-dozen little propane bottles and a couple of screw-on stove burners for them - which I run on a picnic table on the patio just outside of the kitchen. I've also got an el-cheapo low-wattage microwave stored in the garden shed.

But the rest of the house manages to get buy.

If somebody forgets and tries to make toast or turns on a hair dryer or some other electrical/heat appliance (most of which pull 1,500 watts), the APC panel will shut off other circuits for a predetermined time and then attempt to bring them back online - hopefully after the offender realizes why most of the lights went out.

I've tried this in test a few times and it works. In practice, it has yet to happen except for the kitchen refrigerator - which is an old unit that pulls some ungodly amount of watts when it starts up before throttling back to about 130 watts. For that, the smart switch turns off the rec room (where my computer stuff is - all hooked up to battery-powered UPS units) for a few minutes and then brings it back on line after the refrigerator has gotten it's startup surge.

"Lifeboat".... not "Cruise Ship".

If I wanted more capacity and were going to stay with gasoline, I'd buy another EU2000 because those things can be run in parallel so the house sees just one generator. It would also let me be a Good Guy in an extended outage where other people's freezers/refrigerators needed a fix.

[1+1=3]

I live in a Republican neighborhood so I don't need to worry about the petty theft of a generator.

However, Republicans *will* rob your pension and 401K account.

[Stormin Mormon]

Would that be on the way home from throwing granny off a cliff, and starving some children? Enquiring minds want to know.

. Christ>> The modern view is that

[krw]

Aren't they all "inverter type", now?

Computer gear uses switching power supplies. The waveform doesn't matter. Certainly the voltage doesn't (within the 90-250V range). They'll probably even work on DC.

[krw]

Nonsense. It's not the Rs who are talking about seizing your 401K.

[krw]

All that racist stuff.

[Stormin Mormon]

Mine spins a coil. So, not all.

. Christ> >

[Stormin Mormon]

That only leaves the party of "the rich didn't pay their fair share (as defined by us)".

. Christ>>

[trader4]

No, only the most expensive generators are inverter type. Not the typical 6KW that you buy for $800 to $1200. The inverter ones I've seen have been 3 to 4X the price of the equivalent conventional types.

I wouldn't expect computer gear to be the most sensitive to the generator type either. But on the other hand, when I'm running on any generator, I generally only use the essentials. And if I had a 21" TV or a 55" one, I'd use the 21 during the power outage. A neighbor had a small ~2KW generator and his coffee maker died while it was on it. But who knows why....

[Stormin Mormon]

I may have it figured out. The Dems, by focusing endless energy on identifying peoples race and by endless discussion of race, and studying the matter from a racial point of view, and who focus lots of attention on the racial background of everyone, have determined that the Reps are racist?

One evening I accidentally tuned in NPR on the radio, during one of the Republican conventions. The NPR voices talked endlessly about the racial makeup of the convention, and how many minorities, and which races. The Reps talked about reducing government, and living within our means.

. Christ> >