Off-grid living has its own vocabulary. Use this glossary to understand the terms used throughout our guides, product reviews, and solar system discussions.
A
- AGM Battery (Absorbent Glass Mat)
- A type of sealed lead-acid battery where the electrolyte is absorbed in fiberglass mat separators. Better than flooded lead-acid but inferior to lithium for off-grid use. Spill-proof and maintenance-free.
- Ampere-Hour (Ah)
- A unit measuring battery capacity. A 100Ah battery can theoretically deliver 100 amps for 1 hour, or 10 amps for 10 hours, etc. For usable capacity, lithium batteries can use 80-100% of rated Ah; lead-acid only 50%.
- Array (Solar Array)
- Multiple solar panels connected together (in series, parallel, or both) to produce more power than a single panel. A typical residential off-grid array is 4-20 panels.
B
- Battery Bank
- Multiple batteries connected together to store more energy. Off-grid homes typically use 10-40 kWh of battery storage. Most common chemistries are LiFePO4 (lithium iron phosphate) and lead-acid.
- BMS (Battery Management System)
- Electronic system that monitors and protects a lithium battery pack. Controls charging and discharging to prevent overcharge, over-discharge, overheating, and short circuits. Built into all quality lithium batteries.
- Black Water
- Wastewater from toilets. Requires proper treatment (septic system, composting toilet, or municipal sewer connection) for safe disposal. Distinct from grey water, which is less contaminated.
C
- Charge Controller
- Device that regulates the voltage and current from solar panels to your battery bank. Prevents overcharging. Two main types: PWM (older, cheaper) and MPPT (more efficient, recommended for most off-grid systems).
- Composting Toilet
- A toilet system that decomposes human waste into compost without water or sewage connection. Legal in many off-grid applications; regulations vary by state. Eliminates the need for a septic system.
- C-Rate
- The rate at which a battery is charged or discharged relative to its capacity. 1C means the battery charges/discharges in 1 hour. 0.2C means 5 hours. Slower discharge rates (lower C-rate) generally yield more usable capacity from batteries.
D–G
- Depth of Discharge (DoD)
- The percentage of a battery’s capacity that has been used. A battery discharged to 20% state of charge has an 80% DoD. LiFePO4 batteries can safely reach 80-100% DoD; lead-acid batteries should not exceed 50% DoD for longevity.
- Generator (Backup)
- A fuel-burning engine (gasoline, propane, diesel) that produces electricity. Used as backup when solar production is low (cloudy periods, winter). Most off-grid homesteads keep a generator for extended low-sun periods.
- Grey Water
- Wastewater from sinks, showers, and laundry (not toilets). Can often be recycled for irrigation with proper filtration. Many states allow grey water reuse systems. Significantly less contaminated than black water.
- Grid-Tied System
- Solar system connected to the utility grid. Excess power is sold back (« net metering »). No batteries required (or optional). Less independent than off-grid but more cost-effective for most homeowners.
I–L
- Inverter
- Device that converts DC power (from batteries/solar panels) to AC power (used by most household appliances). Key specs: wattage (continuous and surge), efficiency, and pure sine wave vs. modified sine wave output. Pure sine wave is required for sensitive electronics.
- kWh (Kilowatt-Hour)
- The standard unit of energy. One kWh = 1,000 watts used for 1 hour. The average US home uses about 30 kWh per day. Your utility bills are priced in kWh (typically $0.10–$0.30 per kWh).
- LiFePO4 (Lithium Iron Phosphate)
- The preferred lithium battery chemistry for off-grid energy storage. Safer, longer-lasting (3,000–6,000+ cycles), and more temperature-tolerant than other lithium types (NMC, LCO). The gold standard for off-grid battery banks.
M–P
- MPPT (Maximum Power Point Tracking)
- Advanced charge controller technology that optimizes power harvest from solar panels by finding the voltage/current combination that produces maximum power. Typically 15-30% more efficient than PWM controllers, especially useful in cold climates or with higher-voltage arrays.
- Net Metering
- Utility policy that credits solar homeowners for excess electricity fed back to the grid. Rates and policies vary by state and utility. Makes grid-tied solar significantly more economical where available.
- Peak Sun Hours
- The number of hours per day when solar irradiance averages 1,000 W/m² (full sun). Used to calculate daily solar energy production. US average: 4-6 hours. Southwest: 6-7. Pacific Northwest/Northeast: 3-4.
R–Z
- Rainwater Harvesting
- Collecting and storing rainwater from rooftops or other surfaces for later use. Legal status varies by state. Used for irrigation, toilet flushing, laundry, and (with proper filtration) drinking water.
- Solar Generator
- A portable battery power station with a built-in inverter, charge controller, and multiple output ports. Charged by solar panels, wall outlet, or car outlet. Popular brands: EcoFlow, Jackery, Bluetti, Goal Zero. Not technically a generator — it stores and converts electricity, not generates it.
- State of Charge (SoC)
- The current energy level of a battery expressed as a percentage of full capacity. 100% SoC = fully charged. 0% SoC = fully depleted. Most battery monitors display SoC in real-time.
- Watt-Peak (Wp)
- The rated power output of a solar panel under standard test conditions (STC): 1,000 W/m² irradiance, 25°C cell temperature. Real-world output is typically 75-85% of Wp due to heat and non-ideal conditions.
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