Hi, so I’m shopping for a home standby generator that would have an automatic transfer switch and run off of the homes ng. I know the real answer is to get the actual data information from everything in the house that runs on elect however i just want to know without doing all of that what to believe. Last year when the power went out for 4 days I hardwired a 6000 running watt generator to my 200 amp panel. This ran my 3 ton heat pump in cooling, two refrigerators, a deep freezer, two TVs and what ever lights I wanted. Never bogged down when the HVAC kicked on. When I go to generator sites like Generac and put in even less info into the generator sizing app it’s telling me I need at least a 16kw almost double what actually worked. Am I missing something? Are they trying to sell me more then what I need or are they just protecting themselves from unknowns? Thanks in advance.
Real Generator Size Needed?
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Welcome to the forums kygene
you are running a lot at once no doubt. 16 kw does seem a bit excessive but they are factoring in you running everything at once. So that would be about right. Remember you are using NG and not regular gasoline for fuel. Big difference right there.
Imo, to run a whole house with a NG generator; for example; hvac, washer & dryer, etc, etc, the whole house, everything running at once you would need at least 12-14000 watt generac NG generator. No doubt you could do it with 6000 watt generac generator but you wouldn't be able to run everything at once. During a power outage most people just run the essential items basically have designated circuits that function during a power outage.
Reason being, output is different for the type of fuel used to run the generator, like NG, propane, regular gasoline etc. again, this is just my opinion.
you are running a lot at once no doubt. 16 kw does seem a bit excessive but they are factoring in you running everything at once. So that would be about right. Remember you are using NG and not regular gasoline for fuel. Big difference right there.
Imo, to run a whole house with a NG generator; for example; hvac, washer & dryer, etc, etc, the whole house, everything running at once you would need at least 12-14000 watt generac NG generator. No doubt you could do it with 6000 watt generac generator but you wouldn't be able to run everything at once. During a power outage most people just run the essential items basically have designated circuits that function during a power outage.
Reason being, output is different for the type of fuel used to run the generator, like NG, propane, regular gasoline etc. again, this is just my opinion.
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Generac offers three choices (KW stated is approximate):
1. A small generator (6-9 KW) with a transfer switch that picks up selected circuits. Other circuits are dead.
2. A mid sized generator (10-15 KW) with a transfer switch and with large loads having modules where you set the priority. It works like a whole house generator but with high demand it will shed lower priority loads.
3. A big generator (20-22 KW) and a transfer switch. This is a true whole house option.
Generac has a calculator but perhaps you tried it. It has KW per square foot for general lighting and convenience, then other loads and how to derate.
Whatever generator you chose, the rating is for propane. It will make less power with natural gas, that should be figured in.
1. A small generator (6-9 KW) with a transfer switch that picks up selected circuits. Other circuits are dead.
2. A mid sized generator (10-15 KW) with a transfer switch and with large loads having modules where you set the priority. It works like a whole house generator but with high demand it will shed lower priority loads.
3. A big generator (20-22 KW) and a transfer switch. This is a true whole house option.
Generac has a calculator but perhaps you tried it. It has KW per square foot for general lighting and convenience, then other loads and how to derate.
Whatever generator you chose, the rating is for propane. It will make less power with natural gas, that should be figured in.
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24,756 Posts
With a smaller generator, and a full load capacity, you will find yourself "camping out", and using only the basics at times. You won't be able to run a well pump, water heater, stove, and other larger appliances at the same time.
We installed a 22k Generac a couple of years ago, with automatic transfer switch, and couldn't be happier. 10 seconds after a power failure, the generator kicks on and we are back to normal living without having to shut down certain items in order for it to provide what we need.
Two weeks ago, I was at my shop, working outside, and thought I heard the generator running at the house (1/4 mile away). I walked in the shop, turned on the lights, and sure enough, no power. I went to the house to check on wife, and she was just going about her normal evening things, totally oblivious to not having power. The only thing we "lose" is clocks, of course, the wireless printer, and internet until it reboots.
We installed a 22k Generac a couple of years ago, with automatic transfer switch, and couldn't be happier. 10 seconds after a power failure, the generator kicks on and we are back to normal living without having to shut down certain items in order for it to provide what we need.
Two weeks ago, I was at my shop, working outside, and thought I heard the generator running at the house (1/4 mile away). I walked in the shop, turned on the lights, and sure enough, no power. I went to the house to check on wife, and she was just going about her normal evening things, totally oblivious to not having power. The only thing we "lose" is clocks, of course, the wireless printer, and internet until it reboots.
You have no error margin with current setup. Generators are not designed to run at 100% of capacity but rather 75% to 80%. This leaves a margin of error for start-up surges for large items like HVAC. Try the Generac calculator and also look at Kohler and Cummins. Generac is the most popular seller of whole house generators and commands a large part of the market. Good luck and buy the size you need.
Remember that generators running on NG are slightly de-rated versus running on LP. The 16kw is about 14kw on NG.
Remember that generators running on NG are slightly de-rated versus running on LP. The 16kw is about 14kw on NG.
Another thing to think about is the engine rpm. As far as my research has found, the smaller units are air cooled 3600 rpm engines. The larger ones are 1800 rpm water cooled. The price is substantially more, but they are quieter, and should last much longer.
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It's frustrating to lose the network and DVR during a power blip if you're recording something or transferring files. Because of that we have both of those devices on a UPS which keeps them online until the generator (20 KW) kicks in.
A small uninterruptible power supply for the modem, router, etc. and you wouldn't even lose the internet. We picked up a small one for about $30 that will power our modem, router, and VOIP phone for 15 to 20 minutes. If the power for the printer can be routed through it, its draw on standby would be negligible.
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