Solar Energy Glossary

47 essential solar power terms explained in plain language for Filipino DIY builders. Bookmark this page as a quick reference while planning your solar setup.

AC (Alternating Current)

The type of electrical current used by household appliances and the power grid. Your wall outlets supply AC power. Solar panels produce DC, so an inverter is needed to convert it to AC.

Ah (Ampere-hour)

A unit of battery capacity. A 100Ah battery can deliver 100 amps for 1 hour, or 10 amps for 10 hours. Higher Ah means more stored energy.

Array

A group of solar panels wired together as a single unit. A rooftop solar array might consist of 4 to 20 panels depending on energy needs.

Autonomy (Days of)

The number of days your battery bank can power your loads without any solar charging. In the Philippines, 1-2 days is typical for sunny areas, 2-3 for rainy regions.

AWG (American Wire Gauge)

A standard for measuring wire thickness. Lower AWG numbers mean thicker wire. Solar systems commonly use 10 AWG for panel wiring and 4-2 AWG for battery cables.

Balance of System (BOS)

All components in a solar system besides the panels themselves — inverter, charge controller, batteries, wiring, mounting, breakers, and connectors.

Battery Bank

Multiple batteries wired together (in series, parallel, or both) to increase voltage or capacity. Off-grid systems need a battery bank to store solar energy for nighttime use.

Brownout

A partial or complete power outage from the grid. Common in the Philippines, especially during summer months. Solar with battery backup provides power during brownouts.

Bypass Diode

A diode inside a solar panel that prevents shaded cells from blocking current flow from the rest of the panel. Helps maintain output when part of the panel is shaded.

Charge Controller

A device between your solar panels and batteries that regulates charging voltage and current. Prevents overcharging and battery damage. Two types: PWM and MPPT.

Combiner Box

An electrical box where multiple solar panel strings are combined into a single output before going to the charge controller or inverter.

DC (Direct Current)

The type of electrical current produced by solar panels and stored in batteries. Flows in one direction. Must be converted to AC by an inverter for household use.

Depth of Discharge (DoD)

How much of a battery's capacity you actually use. Lead-acid batteries should only be discharged to 50% (50% DoD). LiFePO4 can safely go to 80-90% DoD.

ERC

Energy Regulatory Commission — the Philippine government body that regulates the power industry, including net metering policies and electricity rates.

Grid-Tie (On-Grid)

A solar system connected to the utility grid. Excess solar energy is exported to the grid for bill credits (net metering). Does not work during brownouts unless paired with batteries.

Ground Fault

An unintended electrical path between a current-carrying conductor and ground. Ground fault protection is required in solar systems for safety.

Hybrid Inverter

An inverter that can work with both the grid and a battery bank. Provides solar power, battery backup during brownouts, and can export excess to the grid. The most flexible option for Philippine homes.

Insolation

The amount of solar radiation received by a surface. Measured in kWh/m2/day or peak sun hours. The Philippines averages 4.5 peak sun hours per day.

Inverter

A device that converts DC power from solar panels or batteries into AC power for household appliances. Pure sine wave inverters are recommended for sensitive electronics.

Isolation Fault

An error displayed by inverters when moisture or damage creates an unintended electrical path. Common during rainy season in the Philippines. Usually appears as 'ISO Low' or 'Isolation Fault' on the inverter display.

kW (Kilowatt)

A unit of power equal to 1,000 watts. Used to measure the size of a solar system. A 3kW system has panels that can produce 3,000 watts under ideal conditions.

kWh (Kilowatt-hour)

A unit of energy. If you use 1,000 watts for 1 hour, that's 1 kWh. Your Meralco bill is measured in kWh. The average Filipino household uses 200-300 kWh per month.

Lead-Acid Battery

The traditional, cheaper battery type. Includes flooded (FLA) and sealed (AGM/Gel) variants. Heavier, shorter lifespan (300-500 cycles), and only 50% usable capacity compared to lithium.

LiFePO4 (Lithium Iron Phosphate)

A type of lithium battery popular in solar systems. Lighter, longer lifespan (3,000-6,000 cycles), 80-90% usable capacity, and performs well in tropical heat. More expensive upfront but cheaper long-term.

Load

Any device that consumes electricity — lights, fans, TV, refrigerator, etc. Your total load determines how big your solar system needs to be.

MC4 Connector

The standard connector used to wire solar panels together. Waterproof, snap-lock design. Always use proper MC4 crimping tools — loose connections cause fires.

Meralco

Manila Electric Company — the largest electricity distributor in the Philippines, serving Metro Manila and nearby provinces. Current rate is approximately P11-14 per kWh.

MPPT (Maximum Power Point Tracking)

A type of charge controller that optimizes power harvest from solar panels by adjusting voltage and current. More efficient than PWM, especially for systems above 400W or with higher voltage panels.

Net Metering

A billing arrangement where excess solar energy exported to the grid earns bill credits. Available in the Philippines for systems up to 100kW. Requires a Professional Electrical Engineer (PEE) sign-off.

Off-Grid

A solar system completely independent of the utility grid. Requires batteries to store energy for nighttime and cloudy days. No Meralco connection needed.

Parallel Wiring

Connecting components so current (amps) adds up while voltage stays the same. Used to increase battery bank capacity or connect panels for shade tolerance.

Peak Sun Hours (PSH)

The equivalent number of hours per day when solar irradiance averages 1,000 W/m2. The Philippines averages 4.5 PSH. Manila gets about 4.2, Cebu 4.8, Davao 5.0.

PEE (Professional Electrical Engineer)

A licensed engineer required to sign off on grid-connected solar installations in the Philippines. Needed for net metering applications with Meralco.

Photovoltaic (PV)

The technology that converts sunlight directly into electricity using semiconductor materials. Solar panels are photovoltaic devices.

Pure Sine Wave

A type of inverter output that produces clean, smooth AC power identical to grid power. Required for sensitive electronics like computers, refrigerators, and medical equipment.

PV Wire

Solar-rated wire designed for outdoor use with UV resistance and higher temperature ratings than standard household wire (THHN). Required for panel-to-controller connections.

PWM (Pulse Width Modulation)

A simpler, cheaper type of charge controller that works by rapidly switching the connection between panels and battery. Less efficient than MPPT but adequate for small 12V systems under 400W.

Series Wiring

Connecting components so voltage adds up while current stays the same. Used to increase voltage for MPPT controllers or for long cable runs to reduce losses.

STC (Standard Test Conditions)

The laboratory conditions under which solar panels are rated: 1,000 W/m2 irradiance, 25C cell temperature, AM1.5 spectrum. Real-world output in the Philippines is typically 75-85% of STC rating due to heat.

String

A group of solar panels wired in series. Multiple strings can be combined in parallel using a combiner box.

System Voltage

The DC voltage of your solar system — typically 12V, 24V, or 48V. Higher voltage systems are more efficient for larger setups. 12V for small systems, 24V for 1-3kW, 48V for 3kW+.

THHN Wire

A common household electrical wire rated for 90C. Used for AC wiring from inverter to breaker panel and outlets. Not suitable for outdoor solar panel connections (use PV wire instead).

Tilt Angle

The angle at which solar panels are mounted relative to horizontal. In the Philippines (5-20 degrees latitude), optimal tilt is roughly equal to your latitude. Steeper angles help shed rain and capture low winter sun.

Voltage Drop

The loss of voltage over wire length due to resistance. Keep voltage drop under 2% by using properly sized wire. Longer runs need thicker wire.

Watt (W)

The basic unit of electrical power. Watts = Volts x Amps. A 100W solar panel produces 100 watts under ideal conditions. A 60W fan consumes 60 watts while running.

Watt-hour (Wh)

A unit of energy. Watts x Hours = Wh. A 60W fan running for 10 hours uses 600 Wh. Your daily energy consumption in Wh determines your solar system size.

Wp (Watt-peak)

The maximum power output of a solar panel under Standard Test Conditions (STC). A 400Wp panel can produce 400 watts under ideal lab conditions. Real output is typically 300-340W in the Philippines.