Here's a guide for selecting the home generator that's right for you. From emergency power (hurricanes or ice storms or intentional systems disruption) to energy production using alternative fuels/methods.
Within the next decade (by 2020), most prosperous stand alone homes and multifamily buildings/complexes will generate their own power and connect to a larger community Micro grid. This combination will provide protection against frequent national grid failure and in many cases be much less expensive. Operators of home generators will also be able to sell their excess power generation to their neighbors and/or back to the national-grid depending on market pricing.
A Home Generator (using off the shelf commercial products)
A generator can provide you power during an emergency, when the grid goes down. It can also be a source of energy, depending on the source of energy you use and the cost of installation/maintenance, as a partial or full replacement for the power you get from the utilities. Here are some simplified categories for generators, based on use.
The type of generator you select for emergency back-up is a balance between the time and money you are willing to invest in it and the amount of wattage you generate. How much power do you need? Here's a simple wattage calculator from Consumer Reports that can provide you some insight. Play with it a few times to find the right mix.
The Basics of Operating a Portable Generator
There are two basic types of home emergency generators:
- Portable Generators: Can run appliances. Charge/recharge phones, run appliances, and lights.
- Stationary Generators: Run the entire home (at a reduced level). In particular: Hot water heaters to central air conditioning.
What you will need
Here are the requirements for a standard commercial system.
- A generator. Either portable or stationary (mounted).
- Fuel. Gasoline (with stabilizer additive) or connections to natural gas/propane.
- Extension cord(s). For a limited number of low power, corded appliances. Typically limited to 3,000 to 5,000 watts.
Power Cord Examples:
- A single line to a power transfer system (that attaches to your home's electrical system). This power transfer system can by manually or automatically switched (this switch prevents power from flowing back out onto the grid). Suitable for corded and hardwired appliances. These systems are typically supply between 6,000 and 17,500 watts of demand.
- Ventilation and CO (carbon monoxide) detection. Portable gasoline generators should be placed as far away from buildings as is practical, and at least 10 feet away from eves and openings that might capture and accumulate exhaust. Never put a gasoline generator under a covered porch attached to a house. A good practice is to shut the generator off while everyone is sleeping, or sleep in shifts. Refrigeration will not get warm in 6 hours if kept closed. 2 large ABC fire extinguishers should be a few steps away from a running generator. Turn off generator and wait until it's cool to the touch before approaching with portable fuel container and before opening fuel tank cover to refuel. 3rd degree fuel burns are horrible. Move gasoline containers well away from a running generator, preferably to a locked metal shed away from sleeping quarters. Portable generators should be chained down to a thick hardened steel loop set in concrete, if not locked into a sturdy shed or bolted into a vehicle like an RV.
Home Power Production (using DIY and commercial products)
Home power production requires a level of thinking and research that goes beyond simple back up systems. As a first step, the system should use the heat generated producing power to heat hot water and warm your home.
First, reduce expectations. The $0.15 KW/Hour that comes through the grid is nearly perfect and seemingly limitless (as long as we pay the bill!), but it is a rented service that we do not own. Local electric generation should be scaled to reliably support essential uses which can not be served some other way. Elimination of loads like electric range/oven, baseboard or space heating, electric hair driers, and electric bulk hot water heating goes a long way to making local power generation affordable and practical. Load reduction by switching to LCD screens from CRT, CF or LED light bulbs from incandescent/halogen, hyper-insulating & increasing efficiency of refrigeration systems, finding always-on "phantom loads" will help reduce peak and average consumption.
The cost of local power generation can be approximated to pre-paying for the next 20 years of electrical service from the grid, up front. If the grid stays up and remains reliable, it will seem unnecessary and expensive in places with good service now. I liken it to an insurance payment, where premiums are "gone", and the result is to mitigate future BAD into inconvenience with refrigeration, running water, comm, and lights.
Before buying solar panels, generators, heat exchangers, batteries, controllers, wire, inverters, etc., the loads must be accurately determined. It's expensive to greatly oversize as well as under-size and have to re-do.
On the nature of batteries
Batteries are heavy, expensive, full of corrosive toxic flammables. You want them to last a really-long time, and the best ones, used carefully, can last 10 years. Batteries exist to reduce generator run-time (machine wear / fuel consumption) and supply small and medium DC loads. Large loads should be scheduled for times when the generator is running, so as to not damage the batteries by a heavy load or over-discharge. A true sine wave inverter made by a good US manufacturer like Xantrex, Magnum, or Outback will supply AC power quality as good or better than a generator. Several models of inverter incorporate multi-stage battery chargers that can use generator or grid AC power to charge the battery bank while passing external AC power through to the load.
Batteries charge quickly (1/5th of capacity per hour, so 2.5 hours from 50%-90%, assuming a charger that can do it) and efficiently from 50% charged to about 85%-90% charged, and then require a long time at lower current to become "fully charged". Charging from 90-100% on a fuel-driven generator without some other reason to run the generator is an expensive use of machine run-time. Charging from 90-100% in March or October is a PERFECT application for solar PV, especially an array that is initially sized to do just this.
This dance between generator size, battery bank size, ability to charge the battery bank, ability and need to use DC or AC power is one with several solutions, depending on the user behavior and budget available. Books about using solar PV are generally written by "Green True Believers" in silent all-PV electric systems who don't want to mention the cost advantage of making "Peak Power" and charging batteries with a generator. I believe that Diesel or Bio-Diesel or SVO will always be available to buy (or make), but will become much more expensive than the 2011 rate of 2 gallons per hour of minimum-wage unskilled work.
Which generator? What capacity? What fuel(s)?
For long-term use, 3600 rpm gasoline engines must be ruled out. They are noisy, highly stressed, have high maintenance requirements, and use dangerous liquid fuel. The best of them (Honda/Yamaha inverter models) are probably worth having as a small temporary-use portable unit.
1800 rpm gasoline generators are quieter, heavier, larger, and often use pre-WWII design (flathead combustion chamber, valves in-block), which is not a significant disadvantage at 1800 rpm. A 2 cylinder model like Onan BGE or similar uses a very basic carburetor, points ignition(EMP resistant!), and mechanical governor for speed control to drive a 4-10KW alternator. This model was available in big RV's into the early 1990's, and is available with low hours from mobile homes that have leak/rot problems. It's often cheaper (and less convenient) to buy the whole RV than a pulled-tested generator. An advantage of a low-tech internal combustion engine is that it can be modified for a few hundred Dollars to run on bottled propane, low-pressure household natural gas, wood-gas, methane, or even hydrogen. Low-tech fixed-rpm gasoline engines are not particularly thrifty with fuel and will accumulate carbon in the chambers if run without load for a long time, but this has been a reliable engine/genset that can be rebuilt in a garage with basic hand tools by a hobbyist. Onan/Cummins has released all the service and repair documents for the older models, making them maintainable.
Diesel is a safe fuel
It stores well for years in a tank with a circulating/dewatering/filtering system and non-voodoo fuel preservative/additives. Spilled diesel doesn't become a fuel-air weapon searching for ignition in warm weather like gasoline. Diesel is the fuel used by railroads, heavy trucking, US military, heavy construction equipment, and emergency-responders. Diesel will be available, somewhere, somehow, if you have something to trade.
THE Internal combustion engine for thrifty long-term battery charging is a tiny Diesel. A series known for high quality is the KUBOTA Super-Mini, and EL-300 (larger oil pan, 2000 rpm operation) in particular. Fuel consumption at rated load is about 1 US Pint per hour. Yes, 8 hours on 1 gallon, at speed, loaded. Larger engines can achieve better power/fuel efficiency numbers, but I don't know of anything that uses less fuel per hour at 4HP.
A Seattle company, AMPLE POWER  , uses this engine in an integrated charger/controller they call "Genie" to put out 75A/24V for rapid battery charging. The Seattle area (Ballard, in particular) is a hub of high-quality engineering & manufacturing of compact and fuel-thrifty power units for sailboats. Several of their genset/chargers have fluid-circulating exhaust manifolds that allow for capture and re-use of much of the exhaust heat. Owner manuals from this site share much theory of operation that is useful for anyone wanting to use this kind of technology for a micro-utility.
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