Letter Re: Advice on Generators?

A few comments in regard to fuel choices, in response to what is posted on your web site. There is mention of the legal difficulty of getting a 1,000 gallon tank of diesel installed at a homesite. I guess I have to ask, what is the difficulty? I’ve lived in several rural areas in the northeast, and it’s never been a problem here. Where I live now in central New York state, anybody
can have up to 1,000 gallons per tax-map parcel without any interference, permits, etc. Many homes in my area have dual 275 or 500 tanks inside the house, down the basement, out of sight. I have five tanks – but since my farm is composed of eight separate deeded parcels – all contiguous but still with distinct tax-map numbers – I can easily install more tanks with zero permits or legal issues.
I also have two diesel pickup trucks with 100 gallon capacity each – which gives me more storage.

There is nothing wrong with liking or preferring liquid propane (LP) gas – however – in many ways it is inferior to other fuels. Getting a large quantity of LP gas in my area is more difficult than for diesel. I own two 1,000 gallon LP tanks. I bought them myself since no local gas company would install one of their own – since I do not use enough gas to satisfy them. And, even after buying the tanks, nobody was willing to fill them without an inspected gas line and regulator system, along with a county permit. All that is not exactly what I call “easy.”
When it comes to using LP for electric generators – the big advantage is when it is used for gensets that spend most of their lives sitting around in “stand-by” mode. This is very common since many consumers buy such generators for emergency situations that rarely occur. On the other hand, if someone intends to use their generator – LP can be a waste of energy and money. Heating oil/diesel fuel has about 130,000 BTUs per gallon. Gasoline about 114,000 per gallon. LP has only 84,000 BTUs per gallon. Now – take prices. I just bought 1,000 gallons of dyed farm diesel/heating oil for $2.30 per gallon. I bought LP last month for $1.99 per gallon. So at present prices, for dyed diesel, that is 5,652,174 BTUs of energy. Meanwhile, the same number of dollars spent on propane yields just 4,236,181 BTUs.
Besides the better bargain in BTUs per dollar, a diesel engine will run more efficiently than an engine run on propane. Take one example with a typical modern 12,000 watt generator. A typical propane powered unit will run 36 hours at full load on 100 gallons of LP – costing approximately $199 ($1.99 per gallon). A same size diesel genset will run 36 hours at full load on 40 gallons of fuel costing approximately $92 ($2.30 per gallon). I’m no math wiz, but that seems to be twice as efficient, overall. The same [multi-fuel] unit – when run on gasoline at full load with run 59 hours on 100 gallons of gas costing approximately $290 ($2.90 per gallon).

Obviously, all the fuels have their advantages and disadvantages. But, if planning for a crisis and trying to maximize on short supplies – I can’t figure where LP makes any sense on a long term basis – except for this: Many small gensets sold for LP use are tri-fuel – i.e., they will run on natural gas, LP vapor, or gasoline. It is possible to further convert such a unit to run on wood smoke – if needed – which you cannot do with a diesel. On the other hand, you can run a diesel on many types of plant matter extracts, vegetable oils [both virgin and waste], waste motor oils, et cetera. – John from central New York

JWR Adds: There is one other important factor to be considered: The service life of low-RPM diesels versus other genset engines, which generally run at higher RPM. If a diesel engines lasts three times as long, with all other factors being equal, its derived lifetime cost per hour of lighting is substantially less than with higher-RPM gensets that use other fuels. Aside from installations in Arctic climates (where diesel fuel gelling can be a problem), diesel gets my vote!