Seasoned pro Allan Sindelar shares his approach to designing high-performance off-grid systems: what works, what doesn’t, and how to select a top-notch installer.
Just a few years ago, most solar installers specialized in off-grid systems, for homes beyond the utility lines. Now, most new solar companies only do grid-tied systems because the largest customer growth has been with residences and businesses with access to the electric grid.
But the two system types are very different, and the skills needed to design, install, and support the two are likewise distinct. Off-grid knowledge is gained through lengthy experience, and many newer solar companies (and those serving only urban markets) simply don’t offer off-grid services. If you’re considering an off-grid RE system, here’s what you need to know to successfully hire a pro.
Working with an off-grid installer is akin to entering a long-term relationship, and it does not end with the installation. Depending on your technical skills, you may need your installer to guide you through the system’s long-term care, and you may need to call on your installer when problems arise. You will want to feel confident that your installer will support you and your system for years to come.
A good designer-installer will generally start with an initial conversation, either in person or by telephone. Answers to these questions are important to the design process:
Besides providing a good initial profile of what you are seeking, and at what level of technical detail your designer should address your questions, a seasoned off-grid installer often hears more “between the lines” than is verbalized. They can often sense (and answer) the questions you don’t yet know to ask, and may even nudge you to revisit the idea of grid connection, if they feel you don’t have a realistic picture of the responsibilities involved in maintaining an off-grid system. Don’t be offended—you would save money and effort by discovering this early in the process. (Note: While there are no monthly electric bills, off-grid living is seldom cheaper than utility power, as amortized battery replacement costs often match utility charges.)
Depending on the property’s location, an installer may also assess your reasons for wanting to live off the grid, and how feasible that might be for you. If you have not yet settled on a property, they may advise you of some things to consider when looking for your site, such as a building site with unfettered solar access (see “Shopping for Off-Grid Property,” previous page).
Most installers do not charge for an initial consultation, which usually lasts about an hour. Think of it as a “mutual employment interview”—at its conclusion, you and your installer will have a pretty good sense of your compatibility, and will decide together whether to move on to the next steps in the design process.
A load analysis is the next essential step in the off-grid design process, providing the hard data necessary to build a system that will efficiently meet your energy demands.
You must provide your designer with a comprehensive list of everything you expect to power in your off-grid home—that means every light, appliance, and mechanical component, big and small. The expected power consumption of these loads and hours of use are summed and averaged to estimate daily energy consumption. This becomes the basis for the system size and design. (For more information, see “Getting Started with RE: Professional Load Analysis and Site Survey” in HP120.)
Most PV system installers or dealers use spreadsheets or fill-in-the-blank forms to walk clients through the process. Besides paper calculations, consider purchasing an inexpensive watt meter that measures power use and energy consumption.
For system designers, a load analysis serves four purposes:
For the client, a fifth benefit arises that is the most important of all—a valuable self-education process. Most of us who live with utility power take energy availability for granted. We use it as needed and pay the bill each month, and we have had little reason to assess our energy use. Doing a load analysis can be an eye-opening activity, since some folks are quantifying their energy use for the first time and may need to reevaluate whether their energy habits are compatible with off-grid living. Additionally, even if the client decides to stay on the grid, they are now armed with information on how to reduce monthly energy bills, which with minimal or no investment can save on future energy bills and reduce the home’s environmental footprint.
Load analysis is a rigorous and time-consuming process, but necessary. By establishing clear expectations of your solar electricity demands, you are far more likely to be satisfied with the final product and can better understand your system’s limitations.
Good wind and hydro sites are rare—for most folks, their off-grid resource defaults to the sun. (To simplify the discussion, that’s what we’ll focus on, although some off-grid folks will implement hybrid systems to meet their energy needs.) Off-grid PV systems can cost as little as $3,000 or more than $100,000. Big or small, the design and education processes are generally the same.
Most clients initiate the budget conversation by asking for ballpark figures. They’ll ask what they think is a seemingly straightforward question, like “How much would it cost to power a 2,000-square-foot home?” What they don’t realize is that the size of the home is nearly irrelevant to the question being asked. Two homes of the same size can have electrical needs that differ by a factor of five or more, since a home’s energy use is largely dependent on how the occupants use it.
An off-grid system’s cost can vary greatly depending on the loads, lifestyle, and budget of the customer, and what renewable resources are available. A typical modern, full-featured, code-compliant off-grid solar-electric system for a customer who has properly reduced loads has at least a 1 to 1.5 kW PV array and a battery with three days of storage capacity. A system that size can cost between $15,000 and $25,000, including all components, design, labor, and support. It usually excludes appliances and a backup generator, carpentry, excavation, and concrete work, as these are usually best done by you or by another tradesperson at lower cost. Generally, wiring only includes connection to the home’s breaker panel—PV installers usually don’t install conventional household wiring.
If the budget exceeds your out-of-pocket expectations, your installer may be able to advise you of financing resources that others have used successfully (see “How to Finance Your Renewable Energy Home” in HP103). Federal tax credits of 30% for residential solar and 30% for efficiency upgrades apply equally to grid-tied and off-grid systems. While some incentives apply only to homes with utility power, many states offer incentives and tax credits, and few distinguish between the two system types (see www.dsireusa.org). A good installer will explain available incentives and guide you through the application process, as well as pull permits and secure inspections.
Once your installer has a general idea of your loads, lifestyle, and budget, a site visit is next. Survey tools are used to determine one or more possible sites for your RE system. The installer will also measure conduit and wire runs, select a location for equipment and batteries, look for potential pitfalls to avoid, locate your water well, plan for a backup generator, and formulate a general plan for the installation.
Next, the installer will design the power system. Most will already have a good idea of what components will be used in your system—the bulk of the design process involves performing sizing calculations, resolving specific issues, and working through the various design subtleties. Your designer will let you know if your budget isn’t adequate to cover the system you’ll need to meet your loads. Once such issues are resolved, your installer will prepare a proposal for you. It will likely include component descriptions, an estimate of expected performance, inclusions and exclusions, estimated price, and terms of payment. Knowing your desired budget range will help your installer keep the proposal in line with what you can afford.
Because of the legwork involved and the custom nature of off-grid system design, most installers won’t provide “free estimates”—after all, you are purchasing their knowledge and experience, as much as the equipment. You may expect the design process to make up 2 to 5% of the overall system cost—that’s $400 to $1,000 on a $20,000 system. Some will credit part or all of this fee if you buy the system.
Many experienced installers will refuse to install equipment purchased elsewhere, such as from an Internet retailer. Why? The installer would lose control over design and equipment specifics, yet still be responsible for the system’s care. Plus, warranty issues might have no clear resolution: Was a component failure the result of a defect, poor system design, or an incorrect installation practice? Also, the profit on hardware will have been given to a third party who has little incentive to support the end user.
A good installer will stay in touch as the installation days approach. Questions will arise, changes may be necessary, and the starting date may move up or back. Your installer may encourage you to be present and available during installation, to deal with questions that you can best answer. You may be asked to help out from time to time, if only for simple tasks. If you lend a hand it becomes “your” system with your time invested, and as you watch it come together it becomes less forbidding and mysterious.
Once installation is complete, the system is methodically powered up. Next come programming the inverter, charge controller, and system monitor, and the myriad details to complete the job. Your installer should include a high-quality shunt-based system monitor, preferably located in a commonly used location in your home, rather than out with the power equipment. If this is your first off-grid experience, your installer may initially teach you just the basic use of your monitor so that you can live within your energy budget. In a month or so, once the system is more familiar, a good installer will return to present additional maintenance guidance. You should expect a full owner’s manual with all component manuals, design records and notes, maintenance procedures, warranties, and copies of any inspection reports or permits, but this may not be ready until after the system is operational.
Expect some support as you become familiar with your system’s capacities and limitations. You will likely have questions and may encounter problems—this is normal, and you’ll need your installer’s assistance. Better installers warrant their work and support manufacturers’ warranties as well.
A system that’s done well will give you the tools to live well, with minimal dependence on fossil fuels. You will have gained an appreciation of how to use electricity wisely, and how to match your living habits with the natural rhythms of weather and season—a wonderful way to live.
Allan Sindelar installed his first off-grid PV system in 1988, founded Positive Energy Inc. of Santa Fe, New Mexico, in 1997, and has lived off-grid since 1999. He is a licensed commercial electrician and a NABCEP-certified PV installer.
“Starting Smart: Calculating Your Energy Appetite,” by Scott Russell, HP102
“Toast, Pancakes, and Waffles: Planning Wisely for Off-Grid Living,” by Allan Sindelar, HP133