What Size Generator Do I Need for My Farm, Ranch or Off-Grid Home?

How to Choose the Best Standby Generator for Your Needs

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What Size Generator Do I Need for My Farm, Ranch or Off-Grid Home?

Reading Time: 10 minutes

When most people think of Connecticut they envision a state covered in pavement and cramped little houses stacked on top of one another, but nothing could be farther from the truth. Surprising as it may seem, the majority of New England is rural in nature, dotted with farms and homesteads averaging from five to 100+ acres per parcel. Along with the rural nature of our state comes some inconveniences, chiefly the time it takes to fix our long and complex electrical grid. That’s why I’ve had to consider what size generator do I need before a power outage occurs.

Within the last 10 years, New England has seen some brutal winter weather patterns, which is a notable shift from the otherwise expected hurricane damage we used to see on a regular basis. Losing power during a hurricane is no fun, but when the grid goes down in a major snowstorm it impairs the movement of equipment, machinery and repair personnel, which adds considerable time to outages. Albeit not the norm, Rural Nutmeggers know that spending an entire week without power can and does happen. That’s why all of my neighbors own a generator, especially us, however not all generators are created equal as we have found from experience.

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The Knee-Jerk Buying Frenzy

The best time to buy a generator is on a nice, clear sunny day with not a hint of impending adverse weather in the forecast, but that’s not how most people buy their generators since it’s not usually considered as part of their emergency essentials. During our last big power outage (that week long stretch of darkness many of us remember vividly), residents were madly waving cash at anyone who had anything resembling a generator for sale, and it looked like some manufactured doomsday to me. Creative entrepreneurs were renting U-Haul vans and commercial box trucks, driving as far as Pennsylvania and New Jersey to buy every generator they could find, just to return and sell every last one to panicked homeowners, making big profits in the process. You’d best believe people were getting fleeced on these generators, and the fleecing was only beginning.

Cheap Generator Syndrome

We all know that old saying “you get what you pay for,” but honestly, sometimes you don’t even get that. During our last power outage, these miracle generators cost an awful lot of money when every Tom, Dick and Harry homeowner was willing to drop big dollars on a generator before their pipes burst. These off-brand, off-shore built generators did not feature the usual Honda or Briggs & Stratton engines Americans are used to working on, but instead some no-name engine that you can’t get parts for without waiting three weeks for that slow boat from China to arrive. Things were so bad that local power equipment repair shops were turning away generator repair jobs because of the backlog! Was the engine itself junk? Not really, but these generators were being run way too long and way too hard for what they were. More on that in a minute.

Robbing Peter to Pay Paul

Today’s modern household is a mixture of energy-efficient devices and a few good old-fashioned energy hogs, such as our old chest freezers, clothes dryers, electric ranges and well water pumps (for those of us without city utilities). When considering the purchase of a standby generator, you need to consider your electrical needs. People who were blindly panicked buying any generator they could find, quickly figured out that their new nifty 2500 KW generator couldn’t run their house full of appliances. Folks who had purchased an under-powered generator had to pick and choose what ran and what didn’t, for instance; “Well, I can run the refrigerator and a few lights until 7 p.m., then I have to shut the fridge off so I can power the furnace so we don’t freeze tonight…” was a typical story line.

This 50KW monster is a self-contained unit that includes a diesel engine, generator and fuel tank. This is the fully automatic system my local volunteer fire department just installed. Note the radio tower just behind the unit.

What Size Generator Do I Need?

I recently had a conversation about generators with my father, a retired industrial electrician, and for your typical three-bed, two-bath American household he suggests a generator that makes no less than 10 Kilowatts (KW), or 10,000 watts of power. Seeing as your standard electric stove can take up to 8,000 KW of power to run (that’s all burners and oven operating at the same time), 10 KW would be a good minimum consideration, keeping in mind you would still need to be relatively conservative with your power consumption. If you have an all electric home with electric baseboard heaters (which take about 1500 watts to run a single 6-inch base board), consider 15 KW a minimum.

For our purposes which include an electric washer and dryer, electric stove, microwave, oil-burning furnace and a strong well pump as well as leaving us the option to run our tools or even run the welder if need be, we chose a 25 KW generator for our homestead. Having a 25 KW generator means we don’t have to pick and choose. It’s OK to do laundry, cook dinner and weld all at the same time, just as if we had grid power.

The Difference Between Two-Pole and Four-Pole Generators

Generators come in two styles; two-pole and four-pole. Generator heads typically have an outer winding of copper wire, and within that winding spins a rotor with either two magnetic poles or four magnetic poles. Two-pole generators are smaller and cheaper to produce, but they have to spin twice as fast to put out 60 cycle electricity (the standard frequency in North America) unlike the more expensive four-pole versions. What does this mean to us? It means deciding between a generator that has to scream continuously at 3600 RPM to create usable power, or a generator that only requires an engine to spin at 1800 RPM.

Let’s go back to that whole cheap generator syndrome thing for a moment. These small “inexpensive” generators have small gas engines that need to scream at a constant 3600 RPM (revolutions per minute) to give you power you can use. All the bearings in the generator are spinning at 3600 RPM too. Cheap components don’t live all that long when you run them constantly at high RPMs, but these generators are engineered to survive running for up to eight hours a day at a job site and typically do well in that capacity. What they were not designed for is constantly running for days on end, which is why they were giving up after three days of nonstop operation. It wasn’t really their fault, the homeowners were really asking too much of their cheap little generator.

Which Design Is Best For You?

When you consider what size generator do I need, if you only expect to run your generator for a few hours a day, then a less expensive two-pole generator might just fit the bill, but be sure to buy a quality one with a common, name brand engine you can get parts for easily and quickly in your area. One caveat worth mentioning; some generators use a gear box to change a lower input RPM into 3600 RPM which is fine, but remember there is a mechanical energy loss associated with the gear box that will detract from the fuel efficiency of the engine, and the high RPM will still wear harder on internal components like contact brushes and bearings.

If you fully intend to run your generator all day and all night until the power comes back on, or if you’re powering your off-grid home without solar panels and off-grid battery bank, you definitely need a four-pole generator. A four-pole generator will run quieter, eat less fuel, run cooler and generally be much less likely to break down. Any engine will run better and for much longer at 1800 RPM than at the breakneck pace of 3600 RPM. In addition, changing over to a four-pole generator opens up the option of diesel engines since 3600 RPM is close to or in some cases over “red line” or maximum safe operating RPM for most commercial diesel engines.

Engine Options

Generators come with all sorts of engine options and it’s important to consider what size generator do I need before making a purchase. In a two-pole generator, you’re usually stuck with a small gas engine similar to your lawn mower or ride-on garden tractor, but when you take the leap into four-pole generators, you have a few options. Gasoline, propane, natural gas and diesel are all common fuel choices for generators, but which to choose has a lot to do with your location, fuel availability and cost.

If you have a natural gas line or propane line running to your house already, then a generator that utilizes that fuel source makes sense, but propane and natural gas contain significantly lower BTUs (British Thermal Units, a measure of energy density when speaking of fuel) per gallon or pound, so unless you have a gas line feed, it’s not a very viable option. A local gun club in the next town over installed a new propane fed generator and found that their generator ate through a rather large stationary tank of propane in about three days, and due to the power outages and road closures the gas company couldn’t make a delivery to refuel them. Not good.

Gasoline is a good option for people who are isolated, or far from the nearest town and especially in very cold climates since gasoline tolerates the cold far better than diesel fuel. One bonus to gasoline is it’s easier to find fuel at a gas station since not all gas stations carry diesel, but are sure to carry gasoline unless they’ve sold out. If pressed, someone could siphon gasoline from a vehicle to feed the generator if gas stations are out of fuel or have no power themselves.

Diesel engines constitute the overwhelming majority of commercial standby generators, and for good reason. Diesel engines make the most of their mechanical power at low RPMs, which makes them effective and efficient when working at a constant 1800 RPM for generating power. Diesels are known for being robust, sturdy, reliable, efficient and simple, all of which are positive traits to have in a generator engine. Another inherent bonus of diesel engines are their preferred fuel of consumption; diesel. Diesel fuel is an energy dense fuel, which is partly why diesel engines are as efficient as they are. In addition, look into your local fuel tax laws since there may be more cost-effective alternatives to buying road taxed diesel fuel for your generator. Unfortunately, on the flip side of all this positivity, diesel engines are expensive, so be ready to shell out significant cash for a quality diesel backup generator.

Multi-fuel engines are common in military generators, and for those of us who like to buy military surplus equipment, this will likely be an attractive option. Multi-fuel engines are exactly what they sound like, an engine that will eat just about anything you can call fuel such as gasoline, kerosene, alcohol, diesel, biofuel, vodka, jet fuel, perfume, peanut oil, vegetable oil and a bunch of other stuff. Buying military surplus can be cost effective, but beware that these engines are extremely complicated, hard to source parts for and are not exactly efficient. They took the “jack of all trades” route in engineering these engines, and although they will run with different fuels, they won’t always run efficiently.

A PTO driven generator is a cost effective way to buy a generator if you have the tractor to spin it.

PTO-Driven Generators

For those of us who have a farm tractor with a PTO (power take off), there’s good news! Instead of buying a complete generator system, which can be expensive, we can buy just the generator head without the engine and drive it with our farm tractor. PTO-driven generators are becoming common farm equipment these days thanks to their affordable price tag. This option allowed us to buy our 25 KW generator without going broke in the process, but it does tie up the tractor while generating power. You can’t plow snow or otherwise use your tractor without disconnecting your generator, but for us, it works perfectly fine. Once we plowed our driveway, we left out John Deere to hum along at 1800 RPM for a week straight, uninterrupted, with no hiccups or problems.

Bridging The Gap

Now that you now have an answer to what size generator do I need and have a generator picked out, you need it to be connected to your home’s electrical panel unless you intend to have miles of extension cords, which I don’t recommend. This part is something you need a qualified electrician to handle since you can easily cross wires, burn your house down or God forbid, kill yourself or a power company’s employee. I know us country folk like to rely on ourselves and take a DIY approach to most things, but this is one of those times where a professional installation is the best idea.

Any professional electrician that wants to keep their license will give you two options; a manual transfer switch or an automatic transfer switch. A transfer switch does two things at once, disconnects one power source and connects another. This makes grid power and generator power mutually exclusive, meaning that you can’t be connected to both at the same time. This is done specifically to prevent you from feeding electricity back into the grid so that when a power line worker goes to fix a line that is supposedly not powered, they’re not electrocuted by the electricity you accidentally back-fed into the grid.

An automatic transfer switch is nice, but not mandatory.

If you have a generator that is compatible with an auto-start system, then an automatic transfer switch will make it all seamless. When the grid goes down, your generator will start and the transfer switch will change over to generator power without you having to get out of bed, which is a nice convenience when it’s all set up correctly. My local fire department just installed a 200 amp automatic transfer switch, which would be the correct size for a modern home electrical system, and that switch alone set them back $1700, not including installation. It’s a nice convenience, albeit an expensive one.

For the rest of us, especially those of us with PTO-driven generators, a manual transfer switch is the best option, and far more cost effective at around $300. It’s a simple box with a lever and it will safely transfer you from grid power to your generator and back again when you throw the switch either way, keeping everyone safe all the while.

In Short

Buying a standby generator for your home, farm, ranch or off-grid homestead is a great idea, especially since today’s modern homes rely on electricity to heat, cool, light, cook and pump water to make them livable. Just make sure to consider what size generator do I need to make sure everything runs efficiently and effectively in a lights out situation. As one who likes to not be reliant on the grid, but instead self-reliant as much as is practical, having a generator for those rare occasions just makes sense to me. A quality diesel, four-pole generator system or a PTO driven generator in your choice of KW rating will eventually prove its value, so if you have a mind to, invest in one now before the storm.

Have you considered what size generator do I need for my small farm or homestead? What’s your advice for making sure you have power even when the power grid is down? Let us know in the comments below.

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