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1 edit | reply to pandora
Re: Anyone have a suggestion for standby whole home generator? said by pandora:His suggestion is a 20K air cooled Generac. These run around $4,000. That seems grossly exaggerated. I have a 2350sqft house, all-electric and the highest momentary load (for more than 1sec) that I've seen in months of monitoring was below 15kW. That with both heat pumps, the range and the drier running.
This is 3 days worth of power usage in Feb 2011 when I registered the highest momentary use.
If you have propane then it makes sense to use it for heating in an emergency - so your highest load would be greatly reduced. To me it makes no sense to use propane to produce electricity at 25% efficiency and then turn it back into heat at 100-300% efficiency.
said by pandora:Does anyone have a link comparing the electrical quality of power produced by various generator brands? For example how well shaped the sine waves are, and how much noise is created? Then reliability and of course price. That will highly depend on the load that you connect. In theory the waves are sine with no load connected. Once you connect a load all bets are off. Connect a heater? Will likely stay sine. Connect a massive load with a switching power supply? No more sine. However many current electronics couldn't care less about the shape of the wave - just think that a typical UPS feeds a somewhat square wave. |
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AndrewG2
join:2006-01-20
Niagara Falls, ON | reply to 49528867
Ah right, but if you were to rig a heat exchanger to pipe the genny heat back inside, you probably would not need to run it for heat per se, apart from a couple of weeks of the coldest winter. |
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 herdfanPremium
join:2003-01-25
Hurricane, WV | reply to pandora
This past summer as a result of the derecho that came through my area, knowing power was going to be off a week, it seemed like a good time to buy a big generator. We lose power several days a year here, so we had previously considered one. The small 5500 would get us through in the winter (gas heat) but it was a pain and this past summer most gas stations did not have gas so it was almost useless.
So I went down to HD and bought the only Generac they had, a 17/16 kW. It is rated for 17kW on propane and 16kW on NG. But since my HG is fairly high BTU, I figure I am closer to 17 than 16.
Mine came with the EZ-Switch transfer switch which let me chose 16 circuits. It come pre-wired with 3 240V, but needing only one, I changed out the 50 and 40 am breakers for 4 20's. Initially I just rigged it to get us through the week without power, but then we sat down and figured which circuits we needed. After the needs: refrigerator, garage (extra freezer) A/C & heat, we started going through what others we needed. Added a bathroom for showers etc, my daughter's bedroom, the media room, the kitchen lights and island receptacle circuit and a couple of others.
We figured we could run a couple of extension cords to the 2 hot water heaters (they are gas, but one has a power vent and the other a circuit board) so they could operate, and from the office (got to have internet  ) to run some lamps in the living room.
With that setup, we figured we would be able to get by fairly comfortably. Upgrading to a 20kW would have just cost another grand and not really gotten us much more.
But If I ever build another house, it will have a full panel on a big 45-60kW generator. |
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pandoraPremium
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Outland
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| reply to IowaCowboy
said by IowaCowboy:Powering 400 amps off of an LP generator is a large load and will burn through a tank of propane pretty quickly. Maybe you could decide which circuits you absolutely have to power (such as fridge, lights, heat/AC, etc) so you can go with a smaller generator and your propane supply will last longer.
I think it's 83 amps on LP for a 20 KW Generac, about 10 gallons of propane an hour. 500 gallons would last 2 days at full load. The DLM permits running a whole home by cycling on and off heavy load appliances. The DLM stuff is new to me, but seems to permit a smaller generator to run a home during power failures.
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pandoraPremium
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said by nunya:OP, if your house is still in the construction phase you should probably do some quick research on propane appliances if you are going to have a tank installed anyway.
Quite often, even propane beats operating costs of electric heating appliances. Electric resistance heat is very inefficient.
We already have a number of propane appliances, but the draw at full load for a 20kw generac is much larger than our 45 gallong tank could supply. Even if the tank could keep up, it'd be dead in about 4-7 hours depending on load.
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pandoraPremium
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said by nunya:OP, if your house is still in the construction phase you should probably do some quick research on propane appliances if you are going to have a tank installed anyway.
Quite often, even propane beats operating costs of electric heating appliances. Electric resistance heat is very inefficient.
We already have a number of propane appliances, but the draw at full load for a 20kw generac is much larger than our 45 gallon tank could supply. Even if the tank could keep up, it'd be dead in about 4-7 hours depending on load.
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"People demand freedom of speech as a compensation for the freedom of thought which they seldom use." |
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pandoraPremium
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1 edit | reply to Bob
said by Bob:said by nunya:Electric resistance heat is very inefficient.
Nitpick: Don't you mean to say electric resistance heat is very expensive? I thought it was 100% efficient in that all of the energy consumed goes into heating the house (at least for electric baseboard heating). We will be installing 2 four ton 18 SEER heat pumps with electric resistance axillary heat. Already installed is a Geospring heat pump assisted water heater.
Oil has been removed from my home, after 7 years with a heat pump, it was fine. Last winter we had 1 day when auxiliary heat was required. The newer units are more efficient and have better cold weather performance.
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pandoraPremium
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said by Mr Matt:I ran a calculation on the relative efficiency of diesel vs propane powered generators see the chart above.
The Onan generator in the chart varies from 18% to 26% depending on load. There are three different diesel generators listed, all efficiency ratings are based on full load fuel consumption for those generators.
Regarding the relative cost of propane vs electric appliances, I included a description on how to calculate the relative cost in another thread here:
»Heater / Central Air recommendations.
For my situation I calculated the cost of propane vs electric fuel by dividing the kilowatt hours used into the total bill which comes out to about $0.13 per kilowatt hour. The cost for heating water with propane using a storage type water heater with a 70% efficiency and $4.00 per gallon cost for propane works out to an equivalent cost of $0.2132 per kilowatt hour. In order for the cost of propane to be equal to the cost of electric fuel the cost per gallon of propane would have to be less than $2.44.
Matt most diesel generators are liquid cooled, and require extra maintenance. Additionally, I'd be concerned with several hundred gallons of diesel oil sitting for perhaps years as the generac would be the only load.
We currently use about 40 gallons a month of propane and have a 45 gallon tank. With 2 new fireplaces, and a cooktop, the use should increase slightly.
500 gallons would cycle in about a year, for diesel, at 12 minutes a week on a generac or other brand, it could take a decade or longer for 300-500 gallons of diesel to cycle. Does diesel remain stable for a decade?
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pandoraPremium
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said by cowboyro:said by pandora:His suggestion is a 20K air cooled Generac. These run around $4,000. That seems grossly exaggerated. I have a 2350sqft house, all-electric and the highest momentary load (for more than 1sec) that I've seen in months of monitoring was below 15kW. That with both heat pumps, the range and the drier running. After remodel the house will be approximately 5,000 sq ft. We will have 2 4 ton heat pumps running 4 A/C zones.
The electrician has suggested a 20K unit, guess I could ask him for more information about why he made this suggestion.
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pandoraPremium
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said by herdfan:But If I ever build another house, it will have a full panel on a big 45-60kW generator.
DLM allows the generator to shed and add load as needed. I'm still not entirely clear on the technology, in places it indicates an ability to rotate heavy loads. My electrician indicates this permits a smaller generator to feed a home than would otherwise be needed.
Heat pumps, hot water, well, oven, and other high power loads can be cycled on and off as needed to keep the generator from overloading.
Our last electric bill for the older (smaller home, 3,200 sq ft) was about 2600 KWH over 28 days. 93 KWH per day, 3.8 KW per hour if all use was average.
The house is going from $3,200 sq ft, to about 5,000 sq ft, and we are moving from a 14 SEER 3.5 ton heat pump to 2 4 ton heat pumps. Our old boiler was removed, and in the past 2 weeks (for which we do not have a bill) the hot water heater was changed to a GE Geospring heat pump assisted unit.
I anticipate the larger home, and electric hot water heater (even with heat pump assist) will consume a bit more electricity than our older home. The new heat pumps are variable speed, as are the air handlers. A lot of this is new to me, and I'm unable to predict exactly what my new usage should be.
Aside from the basic home infrastructure, about 4,000' of Cat 6, and 2,500' of RG 6 is being installed, as is an alarm system, and a 16 channel surveillance DVR (of which we anticipate setting up 8-10 initially).
It is a lot of change for us.
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 mix
join:2002-03-19
Utica, MI | reply to pandora
How big of a battery bank could you build to power your computer equipment for the price you are paying for a generator, propane tank and accessories? |
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 nunyaWho is John Galt?Premium,MVM
join:2000-12-23
O Fallon, MO
kudos:8 | reply to pandora
Don't let the DLM feature baffle you. It's nothing fancy. It's just contactors.
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Mr Matt
join:2008-01-29
Eustis, FL
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I spoke to an acquaintance that has a 20 KW Generac Generator, they claim that they use 30 to 35 Gallons of propane a day running the generator continuously. Generac rates the full load propane consumption of a 20 KW air cooled generator at 2.9 Gallons per hour. Onan rates the fuel consumption of their 20 KW generator at a 5 KW load, at 1 Gallon per hour, 3 Gallons per hour at full load. You will need at least a 250 Gallon tank to meet the draw down requirements of a 20 KW Generator.
I visited a relative in New Hampshire and learned that most propane consumers there, bury their propane tank below the frost line to stabilize the temperature and eliminate draw down issues when temperatures are below freezing. I would recommend a 500 Gallon tank which should give you about 10 Days of operation without a refill. Purchase your propane tank rather than renting it and you can purchase propane from any local bulk propane dealer. Lease a tank and you can only purchase propane from the company you leased the tank from.
When I was considering installing a generator, I was advised by a local homeowner to purchase a propane tank that can hold at least a 10 day supply of fuel. I live in Central Florida where we are subject to long term outages caused by hurricanes. Some homeowners were without electricity for over 30 days and wound up with inoperative generators because they ran out of fuel and could not get a refill for a week.
Diesel fuel can remain stable for over a year if fuel stabilizer is added during the initial fill. After that fuel life depends on the quality of the fuel provided by the supplier. Diesel does have a finite life and is subject to bacterial growth. |
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 Jack_in_VAPremium
join:2007-11-26
Mathews, VA
kudos:1 | said by Mr Matt:I spoke to an acquaintance that has a 20 KW Generac Generator, they claim that they use 30 to 35 Gallons of propane a day running the generator continuously. Generac rates the full load propane consumption of a 20 KW air cooled generator at 2.9 Gallons per hour. Onan rates the fuel consumption of their 20 KW generator at a 5 KW load, at 1 Gallon per hour, 3 Gallons per hour at full load. You will need at least a 250 Gallon tank to meet the draw down requirements of a 20 KW Generator.
I visited a relative in New Hampshire and learned that most propane consumers there, bury their propane tank below the frost line to stabilize the temperature and eliminate draw down issues when temperatures are below freezing. I would recommend a 500 Gallon tank which should give you about 10 Days of operation without a refill. Purchase your propane tank rather than renting it and you can purchase propane from any local bulk propane dealer. Lease a tank and you can only purchase propane from the company you leased the tank from.
When I was considering installing a generator, I was advised by a local homeowner to purchase a propane tank that can hold at least a 10 day supply of fuel. I live in Central Florida where we are subject to long term outages caused by hurricanes. Some homeowners were without electricity for over 30 days and wound up with inoperative generators because they ran out of fuel and could not get a refill for a week.
Diesel fuel can remain stable for over a year if fuel stabilizer is added during the initial fill. After that fuel life depends on the quality of the fuel provided by the supplier. Diesel does have a finite life and is subject to bacterial growth.
Let's calculate this:
3 gal/hr x 24 hours = 72 gal x $4.00/gal = $288/day
$288/day x 30 days = $8640
You know Mr. Matt I'm not sure I could stand much of that financially. |
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BobAccount deleted
join:2012-07-22
New Jersey Reviews:
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| said by Jack_in_VA:3 gal/hr x 24 hours = 72 gal x $4.00/gal = $288/day You can stay in a pretty nice hotel for less than that. |
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 SwedishRiderRider on the StormPremium
join:2006-01-11
Connecticut
kudos:1 | reply to Jack_in_VA
said by Jack_in_VA:Let's calculate this:
3 gal/hr x 24 hours = 72 gal x $4.00/gal = $288/day
$288/day x 30 days = $8640
You know Mr. Matt I'm not sure I could stand much of that financially.
It's not that expensive for propane where pandora lives (CT) if you have a 500 or 1000 gallon tank: »Re: CT Energy Price Patrol- Oil, Propane, Pellets, Alt. Fuels |
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| reply to Jack_in_VA
said by Jack_in_VA:Let's calculate this:
3 gal/hr x 24 hours = 72 gal x $4.00/gal = $288/day
$288/day x 30 days = $8640
You know Mr. Matt I'm not sure I could stand much of that financially.
I just had my 500 gallon tank filled and it was $2.75/gallon.
Most people with a generator probably won't run it 24 hours a day for an extended outage. 4 hours per day is typical. |
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Jack_in_VAPremium
join:2007-11-26
Mathews, VA
kudos:1 | said by fifty nine:said by Jack_in_VA:Let's calculate this:
3 gal/hr x 24 hours = 72 gal x $4.00/gal = $288/day
$288/day x 30 days = $8640
You know Mr. Matt I'm not sure I could stand much of that financially.
I just had my 500 gallon tank filled and it was $2.75/gallon. Most people with a generator probably won't run it 24 hours a day for an extended outage. 4 hours per day is typical. Wayne I agree but from the OP's post It appears they are going to have a substantial demand.
Even if the price is half on the propane it's still going to be expensive.
There's a neighbor who is CEO of a national plumbing company and he has an old plantation home with a "BIG" generator. We had a 3 day outage and the propane truck driver told me he used $800 worth of Propane. I don't know what he paid per gallon for it though.
I thought the 12 gallons my Honda was sucking up in 16 hours was bad. That would be $48/day at todays prices.
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 IowaCowboyWant to go back to IowaPremium
join:2010-10-16
Springfield, MA
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said by pandora:Our last electric bill for the older (smaller home, 3,200 sq ft) was about 2600 KWH over 28 days. 93 KWH per day, 3.8 KW per hour if all use was average. I don't know what part of the country you live in but if you lived in the Northeast (New England states/New York), your electric bills would be through the roof. I live in Massachusetts and I pay twice as much per month for my side of the duplex than my former neighbor pays for a single family home in Iowa. Connecticut has even worse electric rates than we do in Massachusetts, and Maine is more reasonable. Of course I've changed almost every light with CFL/LED light bulbs (the only place I don't use CFL light bulbs is the full bath because the steam from the shower murders CFL bulbs so I use traditional incandescent light bulbs there) and my electric bills are still high.
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Jack_in_VAPremium
join:2007-11-26
Mathews, VA
kudos:1 | My august usage was 830 kWh. Not bad for around 1500 sq/ft at 75 deg F. |
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