So, You Wanna Live Off-Grid?
Categories: On The Farm
When Does Off-Grid Make Sense?
Your motivations and goals are key in coming up with your own answer. It doesn’t need to make sense to anyone else if you want to be off-grid. But it is important to be realistic about what can be done and what it will cost—both in dollars, and in your time and attention. Additionally, there are some situations that make off-grid living either the only possible option or the most appropriate.
If you have property miles from the grid, or in a location that has no grid, your only affordable option may be to set up an independent system. If extending the utility grid to your property is possible, find out how much it will cost, and what the ongoing cost will be. Then you can make a sensible comparison to base your decision on. While $20,000 in line-extension costs may seem high, if you are looking to power a large home that has many loads, spending that money may be the best option. Be realistic about the burden (financial and otherwise) of living off-grid! On the other end of the scale, if it’s going to cost you a quarter of a million dollars to extend the grid, an off-grid system may be very economical and sensible. (See “Methods” in this issue for more on the economics.)
There are situations where utility policies make connection costly or difficult. While many utilities encourage RE systems, others seem to throw up roadblocks to easy interconnection. Some utilities have high monthly base charges. Others require expensive equipment that is not necessary to safe interconnection. And others have burdensome paperwork and/or insurance requirements. Talking with your local utility, installers, and other RE users will help you understand the full cost and difficulty. Then you can make a sensible decision.
Off-Grid System Design
The first major task in off-grid system design is load analysis. Without accurate measurements or estimates of energy use, it’s impossible to design a system that will satisfy the need in the most economical way. Electricity consumption is measured in kilowatt-hours (kWh), and an accurate daily or monthly number is needed to start your system design.
If you currently live on-grid, you can start with your utility bill, which tells you how many kWh were used during the last billing period, and often summarizes the last year or more. Even better would be to have a year’s worth of bills—which should be available from your utility. This will give you a baseline for your current energy lifestyle. Then you need to estimate how much energy your off-grid lifestyle will use. To be most cost-effective, you need to identify energy-efficiency and conservation measures you can implement, and you’ll likely need to shift some loads from electricity to other energy sources.
It’s fairly easy to reduce the energy load in a typical North American home by 15% to 20% using common energy-efficiency measures. More radical efficiency work can reduce the load up to 50% or more. On-grid, reducing your energy demand not only saves you money, but also reduces demand for energy created by nonrenewable sources. Off-grid, this strategy is especially profitable, since every kWh comes at a cost in generating capacity, battery bank size, and the need for a backup generator.
Most off-grid systems will need to find non-electric ways to provide for:
- Space heating
- Water heating
- Other significant heating loads, often including clothes dryer and range
Options include passive solar design; solar hot water; solar cooking; wood heat and cooking; and propane. Larger RE systems on homes that include ultra-efficient appliances (such as minisplit heat pumps) may be able to handle some of these loads. But these will come at a high cost in RE generating capacity, depending on the need and the resource.
The second step in off-grid system design is resource assessment. How much sun, wind, and/or falling water do you have?
Most off-grid properties rely on solar electricity, since sunshine is the most common resource. How much you have—measured in peak sun-hours—and when you get it is crucial to successful system design. Using measured data to find out your regional resource, and then a shade-analysis tool, such as the Solar Pathfinder, will give you a good idea of what a solar-electric system will do for you.
Wind resource assessment is more complicated, as are wind-electric systems in general. Your goal is to measure or predict the average wind speed at your proposed wind turbine location and height. With this hard-to-get information, you can make an accurate prediction of how many kWh your chosen wind turbine could produce in a month or year.
Hydro resource assessment is fairly straightforward, and very specific to your stream. Measuring the “head” (vertical drop) and flow allows you to calculate the power and energy potential. If you have a decent hydro resource, it may be all you need.
System design also includes battery bank and backup generator sizing. Both are influenced by your loads—in the amount of energy they use and when they’re needed. RE capacity, battery bank, and generator sizing need to take into account your weak season. Solar-only systems have a season of fewer sun-hours (usually, during the winter), and this needs to be planned for. Hybrid (two or more sources) systems may find a balance that reduces the need for a larger battery bank and backup generator.
On-grid RE system owners have a great deal. When their resource—sun, wind, or water—is available, they use it. When they make too much energy, the grid takes the surplus and gives credit. And when it’s dark, calm, or the creek is dry, the utility is there to provide the needed energy. Off-grid system owners have to take all the responsibility of generating all of their energy, all of the time.
The most challenging part of off-grid living is dealing with the variable resource. Raising a bunch of kids off-grid taught me a lot of lessons. One is that folks usually assume that electricity will be constant and abundant. This is part of our culture, and off-grid folks are not immune, since they interact with the on-grid culture on a regular basis. While there are many times when RE is very abundant—most every sunny day and whenever there’s a windstorm, for example—there are other times when it’s scarce. Surfing this wave of abundance and scarcity can be satisfying to some of us, but it’s challenging to others.
Systems can easily be designed to overcome the variation, and to allow use of any load at any time. But this will come at the increased expense of needing more RE generation capacity, a larger energy storage system, and a larger backup generator. This also means a less efficient and less environmentally friendly system.
Your solar-electric array will give you 30 to 50 years of trouble-free service. Meanwhile, your battery bank—even if well cared-for—will need to be replaced multiple times. And if you don’t treat it well, you may learn a hard lesson of having to replace this expensive component in just a few years. Some RE professionals suggest that new off-grid systems use a less costly battery bank initially—since there’s a learning curve with battery care and it’s best not to risk ruining an expensive bank while you learn.
Typical battery maintenance includes adding water, cleaning, and checking connections. More difficult but even more important is setting up a charging regimen to work well. Batteries last longest if they are regularly recharged fully. The worst thing you can do for your battery bank is to discharge it and leave it in that state for days. Ideally, your battery bank should be fully recharged every few days—one way (RE) or another (fuel-fired generator).
A few off-grid systems are blessed with year-round hydro, or with a balance of resources (sun/wind and sun/hydro are common) that eliminate or radically reduce the need for a backup generator. And there are also users willing to reduce their usage when resources are not available, limiting the need for backup. But for most off-grid systems, a fuel-fired generator is a crucial part of the system. It’s also one of the weaker parts—a loud, dirty, inefficient, and costly way to make electricity. Best system design includes a modest backup generator that is used as little as possible.
Getting it Done
If you’re determined to live off-grid, you need to figure out how to make it happen. A crucial decision is whether you will leave the system design and installation to the pros or do it yourself.
If DIY sounds like fun, you’ll need to get an education. Home Power articles, and classes, workshops, and more advanced training may be part of your learning process. And in the end, you’ll need to buy your equipment from someone. I recommend not buying from the cheapest online source, but finding a source (preferably local) that can also give you advice and support as you design and install your system. This will be worth the somewhat higher cost, since one or two bad buying or design choices can negate a “bargain” purchase.
Most modern RE systems are installed by experienced contractors. But bear in mind that nearly all solar contractors spend their time selling and installing batteryless on-grid systems. And many of them have zero experience with battery-based systems—avoid these companies, even if they are professional and want to help. Find an RE contractor with a history of designing and installing off-grid systems, or at least one who has experience with battery-based systems.
Take a hard look at your situation before you jump into the off-grid lifestyle. You may find that a grid-tied system will serve your motivations and goals best—at a lower cost and lower environmental impact. If you choose to be off-grid, get realistic, get educated, and get good help. And then enjoy your independence with renewable electricity!
For more details about the differences between on- and off-grid systems, see homepower.com/PV-Basics.
“Before You Go Off Grid” by Allan Sindelar • homepower.com/137.100
“PV Systems Simplified” by Justine Sanchez & Ian Woofenden • homepower.com/144.70
For more on load analysis, see “Analyzing Your Electrical Loads” by Ian Woofenden • homepower.com/156.104
“Off-Grid Appliances” by Ian Woofenden • homepower.com/140.106
For more on system design, see “Designing a Stand-Alone PV System” by Khanti Munro • homepower.com/136.78
“Getting Started with Renewable Energy” by Ian Woofenden with Chris LaForge • homepower.com/120.44
“Choosing the Best Batteries” by Chris LaForge • homepower.com/127.80
For more on generator selection and sizing, see “Engine Generator Basics” by Allan Sindelar • homepower.com/131.96
“Sizing a Generator for Your RE System” by Jim Goodnight • homepower.com/138.88
“DIY or Pro?” by Joe Schwartz, Ian Woofenden & Justine Sanchez • homepower.com/145.48
Check out our many off-grid system profiles at homepower.com/solar-electricity/project-profiles.