Off-grid solar power
An off-grid solar system is four parts doing four jobs: the panels generate, the charge controller regulates, the batteries store, and the inverter converts. This section takes each part in turn, then the wiring and safety that hold them together.
If you are new to this, start with Off-Grid Solar Basics and read in order. If you already know what you are building, the calculators and buying guides are further down.
Start here
How an off-grid solar system works end to end, the vocabulary you need to read the rest of the guide, and the order in which the decisions have to be made.
Solar Generator vs DIY Solar: What the Box Trades Away
A solar generator puts the battery, inverter and charge controller in one case. What that buys you, what it costs you in solar input, expansion and voltage, and which loads each shape of system suits.
The four parts
How to read a solar panel datasheet, what monocrystalline and polycrystalline actually change, why panels never make their rated power, and how wiring them in series or parallel affects the rest of the system.
Types of Solar Charge Controllers: PWM, MPPT and Sizing
What a charge controller does, how MPPT and PWM differ, how to size one correctly, and why panel voltage decides which type is worth buying.
How off-grid batteries actually work: chemistry differences, usable versus rated capacity, cycle life, and how to compare real cost per kilowatt-hour.
How to Size an Off-Grid Battery Bank
A step-by-step method for sizing an off-grid battery bank, including days of autonomy, depth of discharge, inverter losses, and the cold-weather derate people forget.
Lithium vs AGM: Where Each One Still Wins
A direct comparison of lithium, AGM and flooded lead-acid for off-grid use, on usable capacity, cycle life, real cost per kilowatt-hour and cold weather behavior, including the two cases where lead-acid is still the right answer.
What an off-grid inverter does, why pure sine wave matters, how to size continuous and surge capacity, and how off-grid, hybrid, and grid-tie inverters differ.
Wiring and safety
Conductor sizing, voltage drop, overcurrent protection, grounding, and disconnects for off-grid DC systems, following the NEC.
DC Voltage Ratings: Why a 48V Switch Is Not for a 48V Bank
A 48 volt battery bank is never at 48 volts. Published maximum voltage ratings for common battery switches and fuses, why a part labeled 48V is the wrong part, and how to check a rating against the number that matters.
Fuse Interrupt Rating: 12V Is Not 48V
Interrupt capacity is the fuse specification most off-grid builds get wrong. Published AIC figures for Class T, ANL, AMG and MRBF terminal fuses, and why one of them changes verdict entirely between 12 and 48 volts.
Working safely with solar panels: why an array is live whenever there is light, DC arc hazards, roof and ground-mount risks, and safe wiring practice.
The real hazards of an off-grid battery bank: short-circuit energy, hydrogen venting, thermal runaway, and the overcurrent protection that prevents all three.
When the sun is not enough
Generators for Off-Grid Systems
Choosing and sizing a generator for an off-grid system: why it charges the bank rather than running the house, why an inverter/charger can refuse dirty power, and why propane usually beats gasoline off-grid.
Off-Grid Solar in Cold and Difficult Climates
How cold, snow, short winter days, and extreme heat affect an off-grid system, and how to size and site one so it works in the month that matters.
Buying guides
Choosing Solar Panels: The Specs That Decide
A buying guide for off-grid solar panels that compares published specifications rather than prices: open circuit voltage and what it does to your charge controller, module versus cell efficiency, and temperature coefficient.
Best Off-Grid and RV Battery: The Four Specs That Decide
How to choose a deep cycle battery for an off-grid cabin, a van or an RV by comparing published specifications rather than prices: charge temperature range, BMS current limit, cycle life at depth of discharge, and series and parallel limits.
Choosing an Off-Grid Inverter: The Specs That Decide
How to choose an off-grid inverter on the specifications that decide it: low-frequency against high-frequency, whether you need an inverter/charger, and the surge duration that decides whether motors start.
Portable Power Stations: The Specs That Decide
How to choose a portable power station or solar generator by the specifications that decide it: cell chemistry and cycle life, usable against rated watt-hours, continuous against surge watts, and the solar input voltage window that most makers leave out of the table.
What We Don't Recommend, and Why
Products and brands researched for this site and then rejected, with the published specification or the reason behind each decision, including one recommendation that was published wrong and corrected.
Calculators
Wire Gauge and Voltage Drop Calculator
Sizes a conductor for both ampacity and voltage drop, and tells you which one decided the answer.
Battery Bank Runtime Calculator
How long a bank runs a load, accounting for depth of discharge, inverter losses, and the Peukert derate on lead-acid.
Appliance Power Budget Calculator
Turns a list of appliances into daily watt-hours and the inverter size they need, with duty cycle handled properly.
Off-Grid System Sizing Calculator
Daily energy use into array wattage, battery bank capacity, and charge controller current.
Worked projects
Solar Power for a Shed or Workshop
A worked off-grid solar system for a detached shed or workshop: lighting, tool charging, and occasional power tools, with the numbers computed rather than guessed.
A worked off-grid solar system for a full-time tiny house, with every figure computed from the load list rather than estimated.
Solar Power for an Off-Grid Cabin
A worked solar system for a weekend and seasonal off-grid cabin, sized from the load list, with the intermittent-use problem that makes cabins different from houses.
Solar Power for a Full-Time Off-Grid Homestead
A worked solar system for a full-time off-grid homestead with a well, workshop, and outbuildings, and why this is the scale at which 48 volts and a generator stop being optional.