Off-Grid Solar: We Keep Teaching the Basics and Skipping the Decisions.

I picked up The Backwoodsman’s off-grid issue expecting a useful discussion of how to keep the lights on when no utility comes to the rescue.

The contents cover everything from building shelters and growing food to wells, wood heat, and composting toilets. That is a lot of territory for one publication. I understand the space constraints.

The electrical backbone of the off-grid homestead got four pages of solar basics and another two on portable solar. If you’re curious about how sunlight becomes electricity, that’s a start. If you’re trying to figure out whether a system will run your refrigerator, start your well pump, and survive three miserable days in January, you’re still on your own.

The beer brewing and outhouse made the cut. The energy budget did not.

If you’re new here, I’m Greg Smith—the Snarky Solar Guy. I’ve worked in solar and battery storage since 2008, training people to install, operate, and troubleshoot these systems, and I wrote The Battery-Powered Home. The snark comes from years of seeing the gap between what people are told this equipment will do and what happens after they buy it. Service calls have a way of making you less patient with explanations that leave out the important parts.

Useful Basics, Missing Math

“The Basics of Solar Energy,” by Charles R. Hampton, introduces solar modules, batteries, charge controllers, and an inverter. It explains volts, amps, and watts, and correctly distinguishes deep-cycle batteries from automotive starting batteries. It also tells readers to research their location, needs, and budget before spending money.

Those are useful starting points. I’m not expecting a magazine article to replace an installation manual or a complete system design. Knowing what the equipment is called doesn’t tell you how to run it on electricity.

A simple line diagram showing sunlight flowing through some boxes to a refrigerator explains the general idea. It doesn’t tell you whether the refrigerator will still be cold on Thursday.

I read articles like this all the time. Here’s a solar module. Here’s a battery. Here’s an inverter. Connect the boxes, enjoy your independence, and remember to do your research. Someone inevitably says, “Well, people have to start with the basics.” Of course they do. I teach the basics for a living. My complaint is that these articles keep starting there and rarely go any further. Instead of telling the reader to do more research, they should be their own citation.

Where’s the explanation of whether the inverter can start the well pump? How long will the battery actually last? Can the solar array run the house while recharging it after three cloudy days? Those are basic questions for anyone planning to depend on this equipment.

I’ve taken enough service calls to know what happens when those questions go unanswered. People buy equipment, build expectations, and then the limitations become apparent after they've spent the money. Then somebody has to explain what the introduction left out.

The fundamentals matter, but they need to lead to practical decisions. Naming the components is the beginning of the lesson. Too often, these articles stop there.

Start with what you need to run

The first useful question is: What needs electricity, and how much does it use?

Write down the loads: refrigeration, lights, communications, water pumping, fans, and whatever else you intend to operate. Then identify their daily energy use and the power they require while running. Motor-driven equipment may also need substantially more power to start. This is called a load spreadsheet and arguably the most important (but least sexy) part of the entire off-grid planning process.

That brings us to two units people routinely mix up:

·       Kilowatts (kW) describe power: how much equipment demands at a given moment.

·       Kilowatt-hours (kWh) describe energy: how much it consumes over time.

A 1,000-watt load running for two hours uses 2 kWh. Simple enough. But a battery with enough stored energy for those two hours may still be paired with an inverter that cannot start the load.

You need enough energy to keep equipment running and enough power to operate it. Buying a big battery addresses only part of that problem.

The solar basics article never turns its explanation of watts into a practical daily energy budget. That’s the bridge an aspiring off-grid homeowner needs.

Your system has to work when the weather sucks

Solar production changes with location, season, shading, orientation, and weather. The article acknowledges some of that, but acknowledging clouds is different from planning for them. An off-grid system needs a plan for the period when available solar energy is low relative to your loads. Summer production won’t pay back the electricity you need in December.

Here’s an illustrative example, not a system recommendation. Suppose your selected loads consume 5 kWh per day. Three days with poopy solar production would require about 15 kWh delivered to those loads. Your battery’s nameplate capacity must account for the permitted discharge range, conversion losses, and any operating reserve. System standby consumption also belongs in the budget.

Then comes the question people miss: What happens when the sun returns?

The solar array must supply today’s loads and recharge the depleted battery. If it only produces enough for normal daily consumption, you have no meaningful surplus for reovery. You survived the cloudy stretch. Congratulations!

Your battery is still empty.

A useful introduction should at least explain how daily consumption, battery autonomy, and recharge capability connect. Otherwise, readers get a shopping list when they need a plan.

A camping system is useful. Understand its limits.

“Solar: The Portable Version,” by Dave Storm, describes an 18-watt folding module and a jump-starter power pack with a 17-amp-hour gel battery. The author presents it as a small system for lighting and communications. That’s a reasonable application. Let’s put those numbers in context.

At a nominal 12 volts, 17 amp-hours represents approximately 204 watt-hours of nominal stored energy. Not all of that is necessarily available to your appliances. Usable output depends on the battery, discharge limits, load, and losses.

For illustration, an 18-watt module receiving the equivalent of five full-output sun hours would produce 90 watt-hours before losses. Replacing 204 watt-hours would therefore take more than two such days even in that simplified calculation, with no loads running. Real charging conditions and battery behavior add complications.

That’s useful for understanding scale. The little system can have a perfectly worthwhile job without pretending it’s a miniature power plant for your homestead.

The article also suggests setting up a system you’ll never outgrow. That’s a generous promise for any fixed amount of equipment. Add more equipment to run, and you may need more solar, more battery capacity, or a larger inverter.

One of the axioms in my book is this: Homeowners will use every kilowatt-hour you give them. Once electricity is available, people find more uses for it. A system intended for lights and phone charging soon faces requests for a refrigerator, a coffee maker, or another appliance. Those additions require energy, and some demand more power than the inverter can supply.

Another issue is that this article blurs three different systems together. The portable article shifts between battery power stations, small off-grid kits, and kits with microinverters that feed electricity into house wiring through an outlet. Those applications need clear separation.

Plugging a refrigerator into a portable power station is straightforward, provided the station can supply its running and startup power. Plugging a power source into a household wall outlet to supply the house is a different application. The article moves between these uses without clearly explaining the difference. Readers need to know whether the kit powers appliances directly, supplies electricity alongside the utility, or provides backup during an outage. Those capabilities are not interchangeable.

The article’s wall-outlet claim does not allow you to connect an ordinary portable power station’s AC output to a household receptacle. Feeding house wiring requires equipment and a connection designed for the purpose. CPSC specifically warns against powering house wiring by plugging a portable generator into a wall outlet because dangerous backfeeding can result.[1]

Purpose-built grid-interactive equipment does not make every box with an AC outlet interchangeable.

“Plug-and-play” describes a product, not an electrical design.

A charge controller doesn’t manufacture sunshine

The basics article also describes MPPT controllers as boosting solar-array voltage to allow charging during reduced sunlight. That is not a sound general explanation of MPPT.

Maximum power point tracking adjusts operation to extract available power from the solar array. Whether a controller can step voltage up depends on its actual converter design. Common MPPT solar chargers step higher array voltage down to battery charging voltage; MPPT alone does not mean voltage-boost capability.

For a concrete example, Victron’s SmartSolar manual specifies that the array voltage must exceed battery voltage by 5 volts to start charging and remain at least 1 volt above it to continue.[2]

An MPPT controller can improve energy harvest under suitable conditions. It cannot invent the energy your array isn’t producing.

"Paid off" does not mean free forever

The basics article says that after the system is paid off, the electricity is free, then briefly acknowledges maintenance. Sure, sunlight has no fuel invoice, but the equipment still has a working life. Batteries age. Electronics can fail. Connections and mounting need attention. If a generator is part of your bad-weather plan, fuel and maintenance belong in the costs. Replacement expenses don’t disappear because the original purchase has paid for itself.

Off-grid solar can make excellent economic sense, especially where extending utility service is expensive. But the comparison should include the cost of providing the reliability you actually need. Your battery has never heard of your ROI/LCOE payback calculation.

Six Questions Before You Cut the Cord

A short article can’t teach everything. It can, however, leave readers with the right questions:

1.     What will I run, and how much energy will it consume each day?

2.     Can the inverter and battery supply the running and startup power?

3.     How long must the system operate with little solar production?

4.     How will it recharge while continuing to serve the loads?

5.     What will I turn off, or use as another power source, when production falls short?

6.     What installation, protection, maintenance, and replacement requirements come with the equipment?

Those questions turn an interesting solar project into a dependable electricity source.

Before You Buy Anything

Before shopping for equipment, make a daily energy budget. List each appliance, its running watts, and its expected hours of use. Multiply watts by hours to calculate watt-hours. A 50-watt fan running for eight hours consumes 400 watt-hours. Ten watts of lighting for five hours adds another 50.

For cycling appliances such as refrigerators, use measured daily consumption rather than assuming they draw their rated power continuously. Record motor startup requirements separately; a daily energy total won’t tell you whether an inverter can start your well pump.

That list is the beginning of a system design. It gives you something concrete to size around—and something more useful than a shopping cart full of equipment.

Final Thoughts

Despite all this bitching, I’m irritated enough to do something about it. I’m putting together a more practical treatment of off-grid power—the load calculations, equipment limits, bad-weather planning, and daily decisions these introductions keep skipping. It may become a new section in a second edition of my book or a standalone guide. Either way, I intend to carry the discussion past identifying the boxes and into whether they’ll actually run your home.

Because your refrigerator doesn’t care how independent you feel.

Sources

Primary article: The Backwoodsman off-grid issue, “The Basics of Solar Energy,” Charles R. Hampton, pp. 22–25; “Solar: The Portable Version,” Dave Storm, pp. 26–27. Reviewed from the supplied scan. Publication date was not established from these pages.

[1] CPSC and USFA generator safety guidance. The cited warning concerns portable generators; it is not a determination about a particular purpose-built plug-in solar product.

[2] Victron SmartSolar MPPT manual, section 8.3.1: PV voltage too low. Example of documented voltage requirements, not a claim that every MPPT controller uses the same design.