Generac home standby generator ?

[eepete]

At my old house, when I bought the generator, the house was all electric. I got a 200 amp transfer switch for free (it was a spare and the company that had lots of generators was changing to a new brand). This was 1997, and 25Kw generator was about $10K, the 45KW was $12.5K. So it was cheaper to buy more generator than to change out appliances. We had 8 tons in three heat pumps. I wanted everything automatic. One can certainly move load around (in the design phase of a house) to before or after the transfer switch and do just great with substantially less power.
There are price bumps as you move up in engine size, and then smaller price bumps as the generator (alternator) gets bigger.

The automatic paid off in 2002 when we had big ice storms and everyone was out of power. I was in Orlando on business, and it was nice to call home and find that everything was OK. Had the other scenario played out (no generator, call from Florida, spouse in the cold) I'd still be hearing about it today.

Since only people who have had a generator appreciate it, I took it to the new house we're in now. Priced a new 45KW when deciding if we should take the generator or leave it, it was about $18K. What a difference a decade makes. At the new house we have 11 tons on three heat pumps, everything is automatic and it all runs just fine. Even have one of the 10KW resistive electric back-ups on the generator instead of the panel before the transfer switch.

I put both systems in myself. In 1997, the money I "saved" by making it a DIY project was only $8K shy of what the B21 TLB cost, so I got that to do the project (ditching, pad prep, plant the propane tank). Turned out to be real handy to have the TLB around.

So yeah Goose, it's a lot of juice. But fully automatic is nice, and when the big one hits I'm sure we'll have some of the neighbors and most of the fire department over if they need a break from it all.
I guess if you subscribe to the "No such thing as too much horsepower" thinking, then it's just about the right size

Pete

 

[firefighter9208]

what do you think your 8500w version cost to run? my 4500w is about a gal an hr so 1.5-2g an hr for your 8500w..... at $3 a gal gas.... 4.50-$6 a hr.

so it cost him roughly half your cost, for twice the output?

It's rated to run 11 hours on 8 gallons of gas. According to Generacs website. That should be at full load. It seldom runs at full load and hasn't run more than 4 hours at one time since it was bought.

Chris

 

[Matt_Jr]

When looking at generators a while back to replace my 8000W, I noticed a larger one could run on less fuel than a smaller one(to a degree) if haveing the same demand for power, 'cause the larger one won't have to work as hard to put out the same amount of power. I still have the same 8000W genny.

 

[Benbovac]

We are also looking at purchasing one of these generators for our new house. I am just looking to run the basics, refer, freezer and heat, a few lights and a little left over. We do have a geothermal heat/ac unit. Any ideas as to the size we may need. Our house is about 7000 sq ft, but again I am only looking to cover the basics.

Thanks,

 

[BobRip]

We are also looking at purchasing one of these generators for our new house. I am just looking to run the basics, refer, freezer and heat, a few lights and a little left over. We do have a geothermal heat/ac unit. Any ideas as to the size we may need. Our house is about 7000 sq ft, but again I am only looking to cover the basics.

Thanks,

Do you have a well? That can be a big load depending on the depth. You must have water. It's the first thing that you will miss, after lighting. A heat pump takes a lot of power to. Can you use a wood stove for heat?

 

[eepete]

Benbovac, you need to look up the ratings on the things you want to run, or better yet use an amp meter and measure what they use.

But as a 1st order guess (which should Not be used to size your generator...):
fridge - 600W Freezer - 500W. Also budget another 500W for the compressors in those guys to kick in. Don't know what "freezer and heat" means, a few lights - 600W (ten bulbs). A little left over might be 250W per TV, 150 for computer and monitor, so budget 500W.
So you're starting with 2700W, call it 3 KW.
You've not mentioned any kitchen appliances like microwave, cooktop, or oven, and no mention of a well pump or hot water heater.
Now budget 1.5KW per ton of heat pump, and budget 1KW/ton on your largest unit for the ability to start up a compressor.
House square footage doesn't really help, one needs to know what units you have and their size. I suspect you have about 10 tons of HVAC for the 7000 sq ft, probably the biggest unit is 5 ton, so using those guesses that would be 20KW for your HVAC. This does not include running the heat pump resistive electric units, which are probably in the 20 to 30 KW range.

So, you're looking at a 25 KW generator to run it all with the assumption that you've moved the power for your resistive electric onto a panel that is before the transfer switch. If you can shed some heat pump tonnage, you can get that down to an 18 KW range if you're looking at a Generac. Perhaps one of the units doesn't need to run.

Finally, you can see where the rules of thumb might be a good starting point, and can help you focus on what you really need to have running and the option of a panel before the transfer switch. But if you go and measure these devices when they run, and use a peak hold meter to see what their starting current is, then you can truly size this more accurately and buy just what you need. Add up all the running currents, and add in the biggest peak starting current.

Hope this start you on your way to working the problem.

Pete

 

[coobie]

I finally had some time to meet with the fellow who is going to install our home generator unit .We talked awhile about size of units and power to run our house,we ended going with the generac 8kw unit.The only thing it won,t run is our 3 ton central air condition unit.I can live without air for a few days duing the summer,plus it was about $1,500 bucks cheaper than the 17kw unit.coobie

 

[brin]

Just be prepared...once you buy a generator like me...the power will never...ever go out again - I promise..It may have gone out once a month for 10 yrs. straight..but once you buy your generator it will never happen again...see if I am right..that has been our experience but I sleep well knowing we have it..but just be prepared...LOL

 

[Benbovac]

Thanks for the replies, yes we do have city water. I am not sure of the tonnage of our Geothermal system, we have 2 of them in our house. The main one heats/cools the first floor and basement, the second one is just for the 2nd floor.

Our kitchen stove is propane, the main things I want to run are the fridge, freezer in basement, about 20 recessed lights, and the first floor geothermal system. I don't need TV, computer or anything else on the generator.

I will have a Generac salesman come out in the next few weeks to get their suggestions also. I am gussing we should get an LP gererator, but we only have a 250 gallon buried tank. The only items we use LP for are cooking and fireplace. We do not have a woodburner.

We also have an RV that we keep at home that we could move into in the event of a power outage, but I worry about our food that needs to be kept cold. We could move some of it to the RV, but is has a rather small fridge/freezer. I wouldn't want to go to the RV in this kind of weather...20 degrees or so.

Thanks,

 

[coobie]

Just be prepared...once you buy a generator like me...the power will never...ever go out again - I promise..It may have gone out once a month for 10 yrs. straight..but once you buy your generator it will never happen again...see if I am right..that has been our experience but I sleep well knowing we have it..but just be prepared...LOL

I could not agree more.Being a electric lineman I am gone most times it storms.My wife always told me to buy a generator because the power was always out while I was at work.Low and behold I had my electrician buddy hook up a 6500 watt kubota gas generator back in 2001 with all of the doo-dads needed to run our house.Since that time we have run the generator a total of 46 hours.By god those were good hours according to the wife,LOL.coobie

 

[podagrower]

how bout a 450KW with a C-15 engine making about 689 horsepower. It'll make you drool when it spools up.