Help sizing a generator for home backup?

[BrokenTrack]

there are loss' and no generator OR diesel runs at 100% efficiency, so to run a 20kw generator at full power you would need 40 pto hp...

Efficiency is already factored into the equation: pto horsepower ratings are measured at the pto, so 27 hp is available to do work, that is why on tractors it is measured at that point. It is also measured at pto rpm speed so the tractor is not operating at peak rpm.

They rate tractors this way so it is a real-world application.

You can power a 20 kw generator with a 40 HP tractor of course, but you can power it with a 400 hp tractor too, it is just over-kill in either situation.

Look at commercial gensets: 21 KW units only have 32 HP engines on them.

Isuzu 21 kW Diesel Generator

 

[LittleBill21]

i actually have 2(3) generators. i have my 7k for when i need my well, dryer, stove, electric water heater, etc.... but those uses are low. i then wire in an inverter generator(2 if needed) and primarily run off that. my 7k can use close to 1g per hour at close to full load, the inverters run for several hours on a gallon, and are a crapload quieter.

if you don't need everything all the time, the inverters cut it for me when i don't need 240v or high amperage.

 

[Sawyer Rob]

Efficiency is already factored into the equation: pto horsepower ratings are measured at the pto, so 27 hp is available to do work, that is why on tractors it is measured at that point. It is also measured at pto rpm speed so the tractor is not operating at peak rpm.

They rate tractors this way so it is a real-world application.

You can power a 20 kw generator with a 40 HP tractor of course, but you can power it with a 400 hp tractor too, it is just over-kill in either situation.

Look at commercial gensets: 21 KW units only have 32 HP engines on them.

Isuzu 21 kW Diesel Generator

Like I said, direct drive is more efficient, over pto hp, and no matter, the 80% rule still applies, at least on tractors for tools on the pto...

So, your example, pretty much fits into that equation for direct drive...

SR

 

[newbury]

Hi, folks. Does anyone have any insights regarding sizing a portable generator for home backup?
<snip>
That being said, any recommendations regarding what'd be an adequately sized portable generator to provide backup power for my home? In terms of usage/load, my goal would be to maintain power to the pumps/computer associated with my propane boiler (home heat + hot water), well pump, freezers (one chest, one upright), refrigerator, air exchange system, and then I guess some lights and probably a laptop/phone charger. I don't own air conditioners nor would I plan on running power tools during a power outage. <snip>

I should also mention (perhaps very important) that my power doesn't go out very regularly. Furthermore, if and when it does go out it rarely lasts more than a few hours. And again, this is perhaps twice a year. I just happen to live in a very cold part of the country (Northern Minnesota) and a modestly priced generator seems like reasonable "insurance" against frozen pipes!

Thanks for your time..

Well I have not seen any recent posts by the OP.
Now I've lived in Northern Vermont, and I'm cheap.
I've lived in houses that you could almost fly a kite inside if there was a strong breeze outside.
If his power only goes out twice a year for a few hours and he is worried about frozen pipes he should let them drip. For all else he should be able to just hunker down, heck he has a woodstove for heat. If he's worried about his freezers they won't warm up if it's cold.
Try not to open the fridge too often.
Then like Eddie wrote just get a decent small inverter generator and some extension cords.

 

[BrokenTrack]

That is so true, but a lot of that depends on the family structure.

I used to do that when the power went out, but now that I have four daughters, three of whom are teenagers, life is a little bit different. Lighting a single lightbulb and the refrigerator is no longer going tocut it. For me...for my wife, yeah it is fine, but not teenagers in 2020! (LOL)

I really like PTO generators just because you get so much more clean power for the same amount of money, and most people on here (hence the forum name) have tractors. A few weeks ago the power went out, and my kids did not even know we were operating on back-up power.

I have always loved Tiny Houses, and lived in a few, so we are planning to retire to one when the littlest daughter leaves the nest. If we do that, we will go to cogeneration for heat and power. We got a nice spot, but its a LONGGGGGGG ways from grid-power!

It is not that I am antisocial, but...

 

[MAD777]

We are all being anti-social these days!