We are building a home and will be off the grid and I need to pick the generator. It will be propane powered and that's all I'm sure about. My solar installer thinks I should get the Generac Ecogen 6kW. I know it's designed for off grid use and I see it says it can go 500 hours between maintenance but besides that, is there any other reason I should pick this one. It is $2000 more than a Generac Guardian that is 8kW, which says 200 hours between maintenance. Any advice or recommendations would be greatly appreciated.

What's the RPM? The noise level (dBA @ xx distance)? At least look at Onan - for example, RV QG 6500 LP.

I never considered noise level:
Onan RV QG 6500 - 2880 RPM
Generac Ecogen - 2600 RPM
Generac Guardian 8kW - I can't find that info, gather that must mean it's bad

Jonr - do you have experience with Onan - do you think they might be better or at least just as good? I haven't come across prices or a close retailer yet, I'm in southeastern Ontario, but I'll keep looking. Thanks for giving me another thing to look out for.

I know people who have had Onan. Their experience was good, although I think that initial price and parts prices were higher than others.

There is a big difference between residential standby generators that are expected to run < 100 hours/year and ones that are expected to run 500+ hours/year. For the latter, I would look at water cooled, 1800 rpm and probably diesel.

Onan has made gas gensets since the dark ages. Well, okay, maybe almost a hundred years. They could make a good one if they want to. In fact, "Onan" used to be the generic name for a genset. They are owned by Cummins now.


I just got a 22kW liquid-cooled propane-fueled Generac. The head sparkie says they are good right now. This is just for a little emergency power. If you want a generator for off-grid, get the kind of generator jonr described. Diesel, water cooled, 1800 rpm.

I've never been able to find any good data regarding propane/nat gas vs diesel longevity. Ie, once you have a equally well built engine, same oil capacity, the same RPM and liquid cooling, does a diesel really last longer than a clean burning propane one? If so, why?

Just curious, are there any co-gen units available out there? 25 years ago I got a TOTUM co-gen that used a 1L Fiat engine and provided 15kw of power and 45kw of heat. I haven't seen any smaller ones like that on the market since then.

I've never been able to find any good data regarding propane/nat gas vs diesel longevity

It would be hard to say that a comparison consists of "data" because it is an apples/oranges sort of thing. Yes, they both look like "engines", but the similarities don't go much farther. When you get into the nuts and bolts of maintaining either one, the advantages of the diesel combustion system become apparent. Briefly, the spark plug ignition system and the carburetion system are both maintenance issues with gas. Another major difference is that diesels by nature, must be built more heavily which has benefits in vibration, wear and heat transfer. It is just too easy to build a cheap gasoline fueled generator. My rule of thumb is that a quality diesel engine should run over 30,000 hours. Gas, and you're happy with more like 5,000 hours, which includes a lot of hassles along the way. Homeowners tend towards the gas units, particularly once they see the upfront cost, but if you want a long-run generator, it's gonna be diesel. Some of the cheap gas units are run out at 1,000 hours or even less. I chuckle when I see the "survivalist" types who have outfitted themselves with a gas generator.

Co-gen units are a great idea. This 22kW unit is sized big, to run some heat pumps, but most folks overlook the fact that it is wasting 100,000 btu per hour just out the cooling system.

There are 1800 RPM propane alternatives.

An advantage of propane is that the fuel never "goes bad"...Diesel degrades when stored too long.

While I agree Diesels are often long-lived, I don't automatically equate gas engines with short lives. I remember being shown a natural gas engine in a plant in Philly that had been in service since the 1930s.

Much will depend on the forecast operating regimen of the generator - if it only needs to run a couple hours every now and then to make up for a stretch of cloudy or windless weather, then it should be able to be cheaper than one needing to run continuously.

Diesel degrades when stored too long

I store it for years with no issues. It's one of the best fuels to store. Get a leak in your propane system and it all goes away. Moreover, the delivery system for propane is very fragile and depends on trucks, roads and drivers coming to work. I can squeeze diesel fuel out of the field next door.

I remember being shown a natural gas engine in a plant in Philly that had been in service since the 1930s.

Homeowners don't have that kind of support capability.

A vacation home can get by with propane as can a residence where the generator is needed for periods when the grid is down, but if you are going to rely on the generator for use routinely, diesel is where it's at.

I disagree.

Propane has the additional advantage of being able to meet other point and bulk heating needs in an electricity-premium off-grid situation - water heating, cooking, clothes drying, steak grilling.

Its delivered cost is on par with Diesel, but it is so much more versatile.

Its delivered cost is on par with Diesel

Ha ha. If there is a real emergency, propane will be the first thing that is NOT delivered. Diesel generators will continue to run on all kinds of oil.

Sherri,
I am in the same position so your question intrigues me. I was steered to the Generac Ecogen too. My use is the same - off grid solar house needing generator back up and - especially during the summer vacation rentals when tenants want "normal" power available. There are several issues I'm aware of. One is warrantee - most standby gensets have warrantees that do not cover alternative energy back up use. They are meant to operate occaisionally to excercise and then during blackouts. This to look for in a genset that I know off - compatibility with the inverter and battery charging system, two wire starting, low rpm (quiet). I am in a location where propane is very expensive ($5.60/gal) so I am considering a diesel but have not found one yet.

One other thing I've been told by multiple folks with no product to sell - it is best to have a manual start provision as well as auto start based on battery charge. This allows you to take more control and avoid operating the genset as often. My family would operate this way however I would not expect vacationing tents to do so. For example, the auto start may kick in at 8:00 am on a day with a clear forecast and top off the batteries while you might not start the genset and simply wait till the afternoon to do a load of wash or vacuum.

What size solar array are you contemplating and where are you located?

I would appreciate hearing the results of your research and I will share mine here.

Kohler makes a unit designated for alternative energy backup (Model 6VSG) This is propane unit that produces DC power to charge batteries directly.

Curiously the warrantee is 18 months/1000 for off grid applications and 5 years/2000 hours for on grid applications. I wonder why they have less faith in their machines when tied to the grid? Generac's is a "limited" 2000 hour/ 3 year warrantee

Note this unit has a 62 dB sound rating. The price I found was about $5,800 compared to the Generac EcoGen is about $3,700.

By the way - I am not connected in any way with any manufacturer (I'm an architect) so I have not bias and am making no recommendations - just reporting on research.