Generator buying advice

The average internal-combustion engine loses 10% efficiency when run on propane instead of gasoline (as reported by SAE testing). And, on top of that - a gallon of propane has less BTU energy than a gallon of gasoline or diesel.

Propane has an average of 87K BTUs per gallon.

Gasoline has an average of 125K BTUs per gallon.

Diesel has an average of 139K BTUs per gallon.

Today the average national fuel prices are:

Propane - $2.75 per gallon
Gasoline - $3.10 per gallon
Diesel - $3.32 per gallon
Off-road diesel - $2.90 per gallon

That means that - Propane - one dollar buys 31,600 BTUs
Gasoline - one dollar buys 40,300 BTUs
Pump diesel - one dollar buys 41,900 BTUs
Off-road diesel - one dollar buys 47,900 BTUs

This also means that actual use of propane making power due to the 10% drop in engine efficiency as reported by several SAE test shows:

Propane - one dollar buys 28,500 useable BTUs
Gasoline - one dollar buys 40,300 of useable BTUs

In regard to propane units being easier starting - that's a mostly YES and a sometimes NO. Propane does not gum, but certainly can freeze - usually due to water vapor in fuel freezing at the regulator. Vapor systems can be prone to this unless the propane tanks are maintained properly.
I've had to thaw out many. Propane is certainly convenient for auto-start units and also works well with households that already happen to have a large propane storage tank.

Propane - $2.75 per gallon
Gasoline - $3.10 per gallon
Diesel - $3.32 per gallon
Off-road diesel - $2.90 per gallon

Is that propane the road price? I just filled the bulk tank with propane for $1.75. I seriously doubt my vender is selling below the average.

The other thing to consider is the fact he's running this a couple hours per year - its not like he's running an irrigation system. His biggest issue is going to be gummed up carbs - not the actual cost of running the generator.

In regard to "The other thing to consider" that you mentioned - I already made reference to those things in what I already posted. Read what I already wrote.

Please tell me what exactly I wrote that you have shown to be in error.

It seems you are the one making a few blunders.

You wrote - "The other thing to consider is the fact he's running this a couple hours per year."

I assume you are referring to the opening subject of this thread? The poster (tractormarkb) started this thread with -

"I live off grid, I will use it about twice a week for about 3 hrs/week. "

Where I come from, three hours a week is much different than your "couple hours per year."
Seems it is closer to 156 hours per year.

Second you claim an advantage of gas/diesel over propane is that water vapor freezes at the regulator, but fail to mention/realize that water doesn't do much good for a gas or diesel engine either. After 40 years of dealing with fuel systems both gas and diesel I have yet to encounter a frozen propane regulator (batch dryers, tractors, home furnaces) but have cursed and serviced several gas and diesel systems/engines infected with water (could it be the underground tanks?). Heads up - water is bad in all fuel systems - especially at freezing temps.

You go on and on about the lower BTUs with propane but fail to realize its still cheaper to use 20% more propane than it is to use gas or diesel at current prices.

On top of that a diesel engine will cost much more up front than a gas or propane powered unit that gains you little even if you use your 150 hours a year total. In 20 years you'll only have 3000 hours - well within the wear cycle of a propane engine. After 20 years - who really cares? You'll be lucky to buy parts for either.

If you don't want details don't ask for them.

You wrote "First off you were quoting average road fuel prices (with tax) for propane."

No, I was not. Where on earth do you get this stuff? Today - the homeowner's price for propane in bulk for household heat is $2.59 per gallon here in New York. NO highway tax. At my place in Northern Michigan it is $2.50 for "new customers" and $2.70 for existing customers. Not highway - just for heat. I called my son last night in Colorado, and he is paying $2.43 for propane to heat his house.

Your second point - i.e.

"you claim an advantage of gas/diesel over propane is that water vapor freezes at the regulator, but fail to mention/realize that water doesn't do much good for a gas or diesel engine either."

Yes, I did not mention the problems or contaminants in gas or diesel since it was already mentioned by someone previous to me. I was responding to the claim that propane was free of those issues that gas has. It is not. Propane bulk storage tanks can get moisture in them just as gas and diesel tanks do. I have had to thaw many LP systems and add ethanol to prevent future freeze-ups. Why do you suppose major propane suppliers sell and carry ethanol injectors?

Your third comment:

"You go on and on about the lower BTUs with propane but fail to realize its still cheaper to use 20% more propane than it is to use gas or diesel at current prices. "

I did not fail to realize anything. You keep failing to read carefully.

At today's prices - here in New York, also in Michigan - this is the actual cost to make the same power with equal sized gensets with the various fuels. Why don't you tell me more about my errors. Use facts please. And, let me repeat for those that can't read well - this all can vary depending on what YOU pay for fuel in your area.

Here in New York - today:

Household Propane makes 10,500 watts at a cost of $6.73 per hour.

Gasoline makes 10,800 watts at a cost of $5.66 per hour.

Off-road diesel makes 11,200 watts at a cost of $3.70 per hour.

Highway taxed diesel makes 11,20 watts at a cost of $4.53 per hour.

More details:
12,000 watt propane can make 10,500 watts for 38.5 hours on a 100 gallon tank. (Coleman)
At $2.59 per gallon that costs $259 to run 38.5 hours, thus $6.73 per hour.

12,000 watt gasoline can make 10,800 watts for 58.8 hours on a 100 gallon tank. (Winco)
At $3.33 per gallon that cost $333 to run 58.8 hours, thus $5.66 per hour.

12,000 watt diesel can make 11,200 watts for 83 hours on a 100 gallon tank. (Kubota diesel)
Farm fuel at $3.07 per gallon that costs $307 to run 83 hours, thus $3.70 per hour.
Highway diesel at $3.76 per gallon costs $376 to run 83 hours, thus $4.53 per hour.

Your next comment:

"On top of that a diesel engine will cost much more up front than a gas or propane powered unit that gains you little even if you use your 150 hours a year total. "

Well, your have a faulty premise to start with - i.e. your comment "gains you little."
Also about cost. Cost is not just what you pay up front, it how long the unit lasts and how much fuel it uses doing so. There are many good deals to be found with extremely HD diesel gensets at a low price when bought used or reconditioned.
Now, this IS an antique tractor site - correct? So, I'll assume that at least some people here have some mechanical aptitude. Perhaps you are lacking in this department.

I have a Delco diesel 12 KW genset I bought for $1400. I've had it five years now and used it a lot. It has a Detroit Diesel and runs at 1300 RPM. All parts are available cheap (engine and gen) and it's easy to work on. Same units are available "factory reconditioned" right now for $3000. You can easily go to Home Depot and pay close to $3000 for a gas-powered Guardian standby unit at 10,000 watts for $2600.

I can buy, right now, a brand new, Chinese Diesel water-cooler, 1800 RPM 12KW genset for $3800. These units are installed and used all over the world.

A Coleman 10KW gas genset with a Honda engine costs $3100 and has a limited 5 year/1500 hour warranty.

A Kohler LP and NG 12KW genset costs $3300 with a 3 year limited warranty. Engine is GC CH740 that runs at 3600 RPM.

A Norpro diesel 12.5 KW genset costs $7400 with a Yanmar engine. Has a 5 year, 5000 hour warranty.

The Chinese Diesel 12 KW genset costs $3800. Has a water-cooled 1800 RPM engine. Some places sell it with a 1 year unlimited hour warranty, and some with a 6 month unlimited hour warranty. Many of these units have been documented to run 50,000 hours without a teardown.

Now - in regard to your last comment towards me:

"If you don't want details don't ask for them."

Yes, I do want accurate details and I am open-minded. I'm also a more careful reader than you, and apparently better informed.

What I've been talking about is the cost of making electricity, period. It IS an issue to some people. My neighbor has a solar off-grid electric system. This year, he had to use his generator 2 hours a day, almost every day - for two months since it's been so dark here this year.
He uses a propane genset in the winter and a diesel in the summer. The propane is more expensive to make the same KWhs - but - propane is expensive here and off-road diesel is a much better BTU bargain. That could change, and I'm sure those price-disaparities differ in other parts of the country. I will also add that he's gone through two, and is now on his third genset in 7 years. And, the warranty was not honored on last one because the "small print" voids the warranty if the genset is installed for an off-grid household. Seems they only want to honor the warranty if you promise NOT to use it much.
His problems are not fuel related, they are electronic. All three are 10,000 watt Guardian series and cost $2700 each. He also has a problem with the newest one since it's won't support the autostart feature in his inverter/charger system that monitors battery-bank voltage. His diesel genset is a Kubota water-cooled unit. He bought it used almost 10 years ago, uses it every summer and fall, and it's never had a single problem. He doesn't use it in the winter since it's just too complicated with weather that drops to -30F at times.

Prices vary all over the country with various fuels. If you live near deep-water ports, often gas and diesel is cheaper than inland. Propane? Also varies wildly, regardless of average prices Nationwide.

Here in the Northeast, propane has not been a good buy in years - and maybe it's never been.
I installed many electric hot water heaters 30 years ago - and yanked out the propane units. Then electric went up, propane stayed more stabil, and I was yanking out electric heaters and installing propane. Now - around here it's all-most a break-even deal. No real savings by switching to either at present. Natural Gas is still the best buy, but only city dwellers can get it around here.

But, back to the general principals of propane versus gas or diesel - propane has the least energy per gallon, and propane engines are also the least efficient. That can be offset only if the propane is a very good buy as compared to the other fuels.

Take these tables and figure by whatever your fuel cost you.

12,000 watt propane can make 10,500 watts for 38.5 hours on a 100 gallon tank. (Coleman)

12,000 watt gasoline can make 10,800 watts for 58.8 hours on a 100 gallon tank. (Winco)

12,000 watt diesel can make 11,200 watts for 83 hours on a 100 gallon tank. (Kubota diesel)

12,000 watt diesel can make 11,200 watts for 91 hours on a 100 gallon tank. (Isuzu diesel)

Well from what you have, it appears you need too seperate your engine from your generator. You might want to research China Listner diesels that burn 1/2gal/hr, low RPM. Easy to rebuild and the cost wasn't that bad, about $800 delivered a couple years ago. And yes I looked for my bookmark and couldn't find it. Someplace in Washington State tho. This way you only need to replace the parts that's needed, not the whole genset.

You can also make your own fuel from waste oils (WVO) or such. They'll burn just about any type of oil that's clean. The heavier oils may have to be heated or mixed to thinn. TP or paper towels make excellant filters for used oils.

PV's are great but costly but there also a add on system that you can add to each year as money becomes available. The 160w PV's seam to be a good buy this past year, about $650eh for 10a/hr. Charge controllers are under a $100. I'd stick with a brand name tho. I use Uni-Solar on my RV as there unbreakable. Kyrocero is another good brand. I'm sure JD can make a few suggestions too.

I've also had better service from Flotec pumps. I've used sur-flo for many years but lately I can't get them to last very long. Flotec pumps also pump more gpm and cost about $30 more.

You can add a contactor to the refer to shut it off when washing, etc;. A refer can stay off for a couple hours without gaining too much heat. A contactor has a pilot(control) voltage, 24vac to 240vac or more available, then operates a set of line voltage contacts for controling loads.

Another good demand circiut can be made from lawn sprinkler timers, cheap cost $30, as the pilot operator to control a contactor(about$40 for low amperage ones) or relays (about $25 to $40). Contactors will last longer as there heavy duty made but are larger in size. Relays are usually for controlling light demand loads.

The object of load controls is too control peak demand loads so all the appliances can't start at one time thus you can use smaller generating equipment that may cost less to run. In any event, you still have to produce the amount of total watts your using over time.

Another project I'm going to add is a methane generator. A farmer in England runs his entire farm from a 10ft dia x 18" deep MG. Concrete with a top at the surface for solar heating, a gas discharge pipe, a loading door. He uses any type of composting materials, 1part nitrogen, 3parts browns and water. He only recharges once per year and runs his entire farm off methane gas, including tractors and pick-up.

T_Bone

All 4pole generators turn at 1800rpm and all 2pole generators turn at 3600rpm.

I'm not going to repeat what JD said in his excellant info in this thread about fuel types with using BTU's/hr for comparring fuels.

Gas engines can work as generator movers but are costly in both maintance and fuel consumtion. Any time you run a engine above maximum torque then fuel consumtion greatly increases to achive maximum HP. Torque is king at moving load weight, HP is king at winning races but at a very dear cost.

A gas engine typicaly has a sharp peak torque curve where as a diesel engine has a farily flat torque curve. It would be more difficult to design a genset with a gas engine as the engine wants to hunt RPM on either side of the peak torque rpm.

Once you get your generator set up to accept any external engine then it's only your choice as what type of engine to use. Generators, usually out live the engines many times over.

T_Bone

Trojan T-105s have been the most popular for years in off-grid setups. Last year they were $55 each and they often last 7 years, and somtimes 10 years. But - like everything else, the prices up and are now over $100 each.

For somebody that only uses the batteries part-time - e.g. every summer - sometimes buying 12 volt "almost deep-cycle" like Walmart sells is a better deal. They tend to last 5 years. I got one place that I use them all summer hooked to solar. Then when winter comes, I take them home and stick them in tractors for winter starting.

In regard to the gensets - it all depends on how much use. If you're cheap and want longevity, but an older, slow-running water-cooled genset. You can buy a Detroit-Diesel powered Delco 12 KW unit used for $2000 and with proper maintenance, it could last you a lifetime. Runs at 1300 RPM which is nice and makes clean power.

Hopefully, you've got a battery bank. If not, you're throwing your money away no matter what generator you use. A generator needs to be run at the peak RPM range to run most efficiently -and it needs to be sized to the job. So, to do this - you need to operate most of the time off a battery bank - and when it gets low - run the genset at peak power until the batteries are charged and then shut it down.

How are you going to charge the battery bank? Most portable generators only put out 140 - 150 volts at the peaks of the cycles. Grid power is 170 volts at the peaks. Due to this - conventional battery chargers do not work properly on most gensets. To correct, you need a generator that does make the proper current - or - use a special 10-15% voltage corrector - or - use an electronic battery charger like an Iota.

In addition - if you have an inverter/charger - many of them do not accept power from most gensets. A Trace/Xantrex mod-wave DR unit doesn't. A Trace/Xantrex full-wave SW type does.
A full-wave Outback systems usually does not.

I know many off-gridders that have wasted tons of money on bad gensets based on bad advice. It's expensive to learn the hard way. Most people in the off-grid business have lists of which generators work well with chargers , and which ones do not. Also keep in mind - that many gensets will void warrantees if hooked to an off-grid cabin or house - read the very small print.

A DC generator works best if all you need it for is battery charging. I have a 4000 watt powered by a Subaru gas and propane unit. I rarely use it though - it's basically for backup. If I had to make power for many hours - I'd use my diesel.
Many off-gridders make their own from DC auto alternators and five horse engines. The 4000 watt gensets with multi-fuel Subaru 8 horse engines can often be bought brand new for $300. The market was flooded with them awhile back due to a Telecom company that went under and had hundreds of them, brand new, in storage.

I've got three places on solar - two off grid, and one grid-tie. My small cabin in the woods (off grid) has a 1000 watt solar array, four deep-cycle batteries to make a 12 volt bank, a Trace DR2400 inverter/charger, and a 5 horse DC generator and the system works great. I've been building up there for two summers. I run power tools, my wife watches TV, etc.

In regard to fuel choices - propane is very inefficient. For your dollar - you get the least engergy from propane, more from gasoline, and more yet from diesel (especially off-road diesel).
Many people like propane anyway because it works well with an auto-start system. Diesel in cold areas can be a real problem. I own property in the Michigan UP and live here in central New York. It gets colder here - sometimes down to 35 F below - so I'm well acquainted with it.

I'm curious to hear exactly what you are using the genset for. I've worked on many off-grid systems and might be able to point you in the right direction.

That said, if it doesn't have a Honda engine on it I won't buy it. I started mine, 5500 watt, yesterday on the first pull after sitting on my truck in 15 below weather. It runs forever on a tank of gas. Same with my mixers and packers.

• Onan