Generator install - where to start

[WinterDeere]

Geez... 2am. I guess I'd better get a few hours sleep, the alarm goes off at 5:50am.

But I did have a moment to tally our loads tonight:

Looks like I need a system capable of delivering at least 132 kWh per day or 5.5 kW average power, with some healthy margin.

My peak usage is likely somewhere near 32 kW with undocumented lighting, depending on how accurate my guess on the pool equipment might be. But in reality, the pool heater usually only runs mornings, when all other loading is minimized. I also guessed at the electric WH draw, I just didn't feel like walking up to the attic to check that tag.

I'll leave sizing up to the pro's, but I'm guessing we have options from < 10 kW genny with big batteries, right up to > 30 kW genny with no storage.

 

[Duds13]

Not sure if this matters to you, or you may already have one, but when I had mine installed I had the company put a whole house surge protector on the panel. It was cheap, provides a lot of coverage and has lifetime replacement should your house ever get struck twice. Kinda off topic so hopefully it doesn't derail the thread.

 

[MAX-24-Dean]

Possible way to lighten your generator load.

Amazon.com

transfer priority load to non priorty load

You can use this if your hot water heater and dryer are in close proximity to lower the load on a generator.
I know it say Dryer to EV transfer, but it can be used for any load you want to run as a secondary load when the primary load is not using power. Works fine.

 

[ponytug]

Possible way to lighten your generator load.
...
transfer priority load to non priorty load

You can use this if your hot water heater and dryer are in close proximity to lower the load on a generator.
I know it say Dryer to EV transfer, but it can be used for any load you want to run as a secondary load when the primary load is not using power. Works fine.

FWIW: I've seen a number of items like this over the years, I have yet to see one that is UL listed, which gives me pause as these are high current loads.

This particular one just splits the load between the two outlets, which may not be enough for some uses. Other models have a priority load and a secondary load that gets power when the primary is "off/done".

@WinterDeere because of the large starting draws from motors, you probably want to have the well pump and air compressor at 3-5X running power.

I'm not a buried propane tank expert, but I do know that they last longer if you attach a sacrificial or powered anode to them. (Cathodic protection) Not burying them in acidic or salt soils helps, too...

All the best,

Peter

 

[MAX-24-Dean]

FWIW: I've seen a number of items like this over the years, I have yet to see one that is UL listed, which gives me pause as these are high current loads.

This particular one just splits the load between the two outlets, which may not be enough for some uses. Other models have a priority load and a secondary load that gets power when the primary is "off/done".

All the best,

Peter

Agreed, At home we used to use a breaker interlock so that only one load (either hot water heater or dryer) could be on at a time, so the inverter doesn't trip out on overload. Now its controlled by PLC logic so that no combination of loads exceeds inverter output. But PLC's are not for everyone.

 

[ning]

One, if you plan on using propane for backup, keep the tank full (80%). Attempting to run the generator at low tank levels will cool fuel in the tank, and if it is wintertime, the evaporation rate becomes rate limiting, and the generator runs out of fuel well before the tank is empty. The exact details are depending on the generator consumption (base size and actual load) and the temperature. Burying the tank helps. I would look around for a keep full service that has a WiFi monitor on the tank, and a commitment to keep it more than 50% full.

I'd imagine that the tank will "recover" as its temperature comes back up to ambient? (Assuming we're not talking northern Alberta) Still, sounds like a pain, and possibly not the best for the equipment.

 

[WinterDeere]

Not sure if this matters to you, or you may already have one, but when I had mine installed I had the company put a whole house surge protector on the panel. It was cheap, provides a lot of coverage and has lifetime replacement should your house ever get struck twice. Kinda off topic so hopefully it doesn't derail the thread.

Good idea. I'd been wanting to install one, but since my mains panel is totally jammed full and the easiest connection is to use a double-slot in the mains panel, I haven't gotten around to it yet. They'll be putting a transfer switch upstream of the mains, and so giving another possible connection point for the surge suppressor, if they plan for it.

@WinterDeere because of the large starting draws from motors, you probably want to have the well pump and air compressor at 3-5X running power.

Yep. Depends a lot on what I do with battery and/or load management. Having several of those big loads try to start at the same time, like when transfer switch first actuates, could indeed be hard on the genny.

I'm not a buried propane tank expert, but I do know that they last longer if you attach a sacrificial or powered anode to them. (Cathodic protection) Not burying them in acidic or salt soils helps, too...

I'm pretty sure my propane supplier installed a new sacrificial anode in my tank in 2023, but should double check that. Tank itself is probably 20 - 30 years old.

Agreed, At home we used to use a breaker interlock so that only one load (either hot water heater or dryer) could be on at a time, so the inverter doesn't trip out on overload. Now its controlled by PLC logic so that no combination of loads exceeds inverter output. But PLC's are not for everyone.

The first company to come out and evaluation the property was talking about a 28 kW generator, the largest air-cooled option from Generac, and then using smart load management modules to just delay start-up of a few of the largest loads.

Personally, I had liked the idea of a 15 kW generator with a big battery bank, as my average draw is only 2.5 to 5.5 kW. But this installer had a few issues with that idea:

1. They don't do batteries, he'd have to look into contracting that part out.
2. He argued the single-cylinder Generacs (15 kW and under) are less reliable than the V-twins, he really likes to stay with their larger models, from experience.
3. He suspected the cost of battery + maintenance is going to be higher than just installing a 32 kW unit with load management.

I'd imagine that the tank will "recover" as its temperature comes back up to ambient? (Assuming we're not talking northern Alberta) Still, sounds like a pain, and possibly not the best for the equipment.

My tank is buried pretty deep, the riser must be more than 3 feet to the surface. I'd suspect its temperature does not drop too easily, even with a draw on it.

 

[ning]

3. He suspected the cost of battery + maintenance is going to be higher than just installing a 32 kW unit with load management.

Batteries are expensive, yes - one time, though you need to counter that with lower generator cost + lower fuel costs (and better power recovery during an outage) + your fuel lasting longer.
No maintenance to speak of; he may be back in the lead acid battery days.

 

[WinterDeere]

Even modern batteries have a finite lifespan. I suspect this may be what he meant, when using the word “maintenance “.

All I can do is see where the various quotes shake out

 

[Carl_NH]

My guess at a ROM is $25K installed with a 30KW+- genset, new/larger LP tank, and distributed power, then $45K with a smaller 14-16K genset and 45KW backup battery storage and distributed power.

 

[WinterDeere]

Maybe. I have no idea what to expect, which is why I'll get a few quotes. At $45k, I'd just keep using my portable genny with suicide cord.

This installer said don't touch the tank, 500 gal is plenty for 4 - 5 days at 50% or better fill. Since my LP company has gauranteed me 3 days or less from time of call, I think we're probably in good shape there, as long as I never let tank get too low.

We'll see what other installers say.

 

[Carl_NH]

Nothing surprises me anymore - we asked for a bid to install a propane line from our LP tank to the generator last fall.

When I called them, they said, oh, we factored in digging the trench!!

Hi Nicole

Ryan came by today promptly at 8:30 am then called back about 1 pm with the estimate $10,055 - yes $10 thousand dollars to run and connect 10’ of gas pipe and fittings for a 10 kw generator in a trench we will dig/provide and on a pad and post we provide.

Ryan was very professional and pleasant and we were pleased with his assessment and overall presentation as a professional.

However we will not be engaging with your company.

 

[EddieWalker]

A thousand dollars would have been ridiculous. I don't even know the words to describe how bad ten thousand dollars is!!!!

 

[WinterDeere]

I had really expected to find companies offering hybrid energy solutions, essentially a generator upstream of some large managed battery system. This would allow generator to be sized just a little larger than average daily load, e.g. 10 kW generator for my 5.5 kW daily average in July, and have battery capacity fill in the occasional 30 kW peaks.

But I'm really not finding any local vendors for such a solution, and the little bit of digging I've done on equiopment suppliers is not generating a lot of confidence in ever finding one.

Any suggestions? I think we'd be looking for ~60 kWh of storage with a peak delivery capability greater than 35 kW. System must be able to charge while discharging. I'd pair this with whatever lowest-cost reliable 10 - 15 kWh generator a local installer promotes, for my July peak of 5.5 kW average daily load.

I'd probably also want to install battery outside, knowing full well capacity will be reduced in cold weather. I don't really care, as our cold-weather usage is only half of our hot weather usage, just 2.5 kW average and 60 kWh/day.

I don't really need or want an enormous 30 kW class generator, just to have that capacity available on those few minutes or hours each day when multiple appliances all call for energy at once.

 

[Duds13]

Something like this? Looks like you can pair it with a generator

EcoFlow DELTA Pro Ultra X Whole-Home Power | EcoFlow US

Keep your home powered with EcoFlow DELTA Pro Ultra X, featuring 12–36kW output, 12–180kWh expandable storage, and intelligent app control for seamless backup.

www.ecoflow.com

 

[WinterDeere]

Something like this? Looks like you can pair it with a generator

EcoFlow DELTA Pro Ultra X Whole-Home Power | EcoFlow US

Keep your home powered with EcoFlow DELTA Pro Ultra X, featuring 12–36kW output, 12–180kWh expandable storage, and intelligent app control for seamless backup.

www.ecoflow.com

Thanks! I saw that page last week, but pretty much blew past it, since it appeared to have been more about a smart panel than just a battery + transfer switch. But your post made me look a second time, and fill out their support request form, so maybe they'll be able to steer me right.

I'm not looking to start replacing breaker panels, in fact my primary interest in battery capacity is so that I don't need to mess with the panel or any other indoor hardware. I'm really just looking for a big dumb battery I can sit in the front garden, with whatever minimal inverter and charge circuitry is required to feed and pull from the battery.

Anker seems to have some systems like this, their SOLIX products. But they're sized for tiny houses, just 6 - 12 kW max output. I need 35 kW or more, and I don't even have electric heat! I wouldn't think 6 kW could satisfy peak demand in a mobile home.

I'm really surprised this isn't just the standard way of doing home backup, size generator to a little greater than average daily load during most-demanding months of the year, and then install whatever battery is needed to make up for peak to average ratio. This is basically how grid storage works, whether of the water tower or reservoir variety, or chemical battery storage.

 

[ponytug]

I had really expected to find companies offering hybrid energy solutions, essentially a generator upstream of some large managed battery system. This would allow generator to be sized just a little larger than average daily load, e.g. 10 kW generator for my 5.5 kW daily average in July, and have battery capacity fill in the occasional 30 kW peaks.

But I'm really not finding any local vendors for such a solution, and the little bit of digging I've done on equiopment suppliers is not generating a lot of confidence in ever finding one.

Any suggestions? I think we'd be looking for ~60 kWh of storage with a peak delivery capability greater than 35 kW. System must be able to charge while discharging. I'd pair this with whatever lowest-cost reliable 10 - 15 kWh generator a local installer promotes, for my July peak of 5.5 kW average daily load.

I'd probably also want to install battery outside, knowing full well capacity will be reduced in cold weather. I don't really care, as our cold-weather usage is only half of our hot weather usage, just 2.5 kW average and 60 kWh/day.

I don't really need or want an enormous 30 kW class generator, just to have that capacity available on those few minutes or hours each day when multiple appliances all call for energy at once.

I would have a look at Briggs & Stratton, Enphase, Franklin (aPower 2), and Generac. Generac does offer their Pwrcell battery backup systems. I like, but do not have the Enphase battery system, because of its ability to have partial failures and continuing to operate.

Historically, the battery cost has made the cost/benefit for most customers come out on the "add a mongo generator" page. That is changing, but your goal is not common, yet. The first system that I did like that was '99, and I have been a fan ever since.

All the best,

Peter

 

[WinterDeere]

Yeah, Enphase does seem to have something very similar to my needs. But none of their installers are very local, and the half dozen I looked at were all solar equipment installers, not generators. In any case, I left a message with their closest installer, we'll see what I learn.

The last thing I want to deal with is installers who make a hard sale on solar. Between the disadvantageous roof lines, tree shade, cost, and impact on appearance, solar is not an option here.

Will check the other brands, as well...

 

[WinterDeere]

Interesting that the prices Google throws up for Generac Power Cell are only $500/kWh on the small units, but $1000/kWh for larger units. Usually economy of scale pushes things the opposite direction, more of something usually costs less per unit.

In any case, based on that alone, I'm re-evaluating my numbers. Clearly, 60 kWh of storage is not a realistic plan.

I think I have some old hourly usage data stored from July 2024. I could integrate that over time and see how much battery I'd really need to keep up with a typical ~15 kW generator. It might be a pretty small number, if we can dig up all of the details on charging rate / efficiency, etc.

 

[ponytug]

Interesting that the prices Google throws up for Generac Power Cell are only $500/kWh on the small units, but $1000/kWh for larger units. Usually economy of scale pushes things the opposite direction, more of something usually costs less per unit.

In any case, based on that alone, I'm re-evaluating my numbers. Clearly, 60 kWh of storage is not a realistic plan.

I think I have some old hourly usage data stored from July 2024. I could integrate that over time and see how much battery I'd really need to keep up with a typical ~15 kW generator. It might be a pretty small number, if we can dig up all of the details on charging rate / efficiency, etc.

Pretty much any Enphase solar installer should be up to speed on batteries. I can't speak to others, but I was 7nder the impression that at the corporate level Generac and Briggs & Stratton were both pushing batteries fairly hard.

That $1k/kWh is exactly the stumbling point for most people. I would comment that seems high to me, but often installers are like that when they have more business than they can support. You know that is.

I would not overlook the power of "soft starts" or VFDs to ramp up the large motor loads in a reasonable manner. A few dollars spent there might reduce the maximum surge current that your system needs to support.

All the best,

Peter