You are about to learn how a house runs on sunlight
Eleven lessons, one practice quiz, one real exam. Work through it at your own pace on your phone or a laptop. Pass the exam and you print a certificate with your name on it.
- Volts — the pressure pushing it along
- Amps — how fast it is flowing
- Watts — the work it can do (pressure × flow)
- Ohms — how hard the pipe fights back
By the last lesson you will know every part, every wire colour, every number on the screens, the sizing math, the safety rules, and how to read a system drawing.
This course teaches you how solar works. It does not make you a licensed installer. Real installations need a licensed electrician, a permit, and inspection. Never work on live wires without training and proper tools. Electricity kills people every year.
Volts, amps, watts and Ohm's Law
Volts — the pressure
A 12-volt battery is a garden hose. A 48-volt battery is a fire hose. More pressure means you need less flow to deliver the same power, and less flow means thinner, cooler, cheaper cable.
Amps — the flow
Amps measure how much electricity is moving through the wire right now. High amps mean heat, so high amps need thick wire. This one fact decides half of every system design.
Watts — the work
Watts are power: pressure times flow. A 100-watt bulb pulls 100 watts the whole time it is on.
Ohm's Law — the rule under everything
Push resistance up and, at the same voltage, current falls. That is why installers use short, thick, clean-terminated wire: less resistance, less power burned off as heat in the cable instead of arriving at your fridge.
Watt-hours — the size of the tank
Watts tell you how fast you are spending. Watt-hours tell you how much you spent.
A 100-watt TV running 5 hours uses 500 watt-hours, which is half a kilowatt-hour — half of one unit on your BPL bill.
Batteries are sold in amp-hours, so convert before you compare anything:
A 100 Ah battery at 12 V holds 1,200 Wh. The same 100 Ah at 48 V holds 4,800 Wh. Same label on the box, four times the energy. Always compare batteries in watt-hours, never in amp-hours.
P = V × I · I = P ÷ V · V = I × R · Wh = Ah × V
Every device, every port, and what it does
The solar panel
A panel turns light into DC electricity. Behind it sits a junction box with two cables ending in MC4 connectors — one positive, usually red-marked, one negative, usually black. They only click together one way, which is the point of them.
Charge controller — the traffic officer
It sits between the panels and the batteries. It decides how much current reaches the battery, stops it overcharging, and blocks current draining backwards out of the battery into the panels after dark.
Battery bank — where the day is kept
Deep-cycle batteries are built to be drained and refilled every day, which is exactly what a car starting battery is not built for. Positive terminals are red, negative black. Bus bars are the shared bolt-down strips that let several batteries join cleanly instead of stacking six ring lugs on one post. A battery monitor reports state of charge, voltage and current.
Inverter — DC becomes AC
The inverter takes the battery's DC and manufactures the alternating current your appliances expect: 120 V at 60 Hz here, the same as the utility supply.
The tools of the trade, and what each one is for
A solar technician is judged by two things on a job site: whether the work is safe, and whether the terminations are clean. Both come down to owning the right tool and knowing when to reach for it.
Hand tools
| Tool | What it does | When you reach for it |
|---|---|---|
| Insulated screwdrivers, 1000 V rated | Drives terminal screws without putting your hand on a conductor | Every terminal, every time. Not the set from the kitchen drawer |
| Lineman's pliers | Grips, twists, and cuts conductors up to about 8 AWG | General wire work and pulling |
| Wire strippers, gauged | Removes insulation to a set depth without nicking copper | Every conductor you terminate. A nicked strand is a hot spot |
| Cable cutters | Shears large battery cable cleanly instead of mashing it | 2 AWG and up. Hacksaws leave frayed ends |
| Lug crimper (or hydraulic crimper) | Cold-welds a lug onto a large conductor | Battery and inverter cables. Hammer crimps are not crimps |
| MC4 crimp tool and spanner pair | Terminates and locks solar connectors properly | Any panel lead you make up yourself |
| Torque screwdriver and torque wrench | Tightens to the manufacturer's number | Every lug on the bank, controller, and inverter |
| Ratchet, sockets, hex keys | Rail hardware and clamp bolts | Mounting the array |
| Fish tape and conduit tools | Pulls conductors through conduit | Any run in pipe |
Layout and mounting tools
- Tape measure, chalk line, speed square — rail spacing and panel layout are set out before anything is drilled.
- Torpedo level and a digital angle finder — for setting and checking tilt.
- Stud or rafter finder — mounts go into structure. Into sheathing alone is a hurricane waiting for a date.
- Cordless drill, impact driver, hole saw, step bit — the day-to-day drivers.
- Hammer drill with masonry bits — essential here, where so much is poured concrete and block.
- Caulk gun and flashing — every roof penetration gets flashed and sealed, no exceptions.
Test equipment
| Instrument | Measures | Why a solar tech owns one |
|---|---|---|
| Digital multimeter | Volts, amps, ohms, continuity | The instrument you will use on literally every job. Lesson 4 is entirely about it |
| Clamp meter with DC capability | Current without breaking the circuit | Reads array and battery current safely. An AC-only clamp reads nothing on DC |
| Insulation resistance tester (megger) | Insulation quality at high test voltage | Finds damaged cable and ground faults before they find you |
| Irradiance meter | Sunlight intensity in W/m² | Tells you whether low output is a fault or just cloud |
| Infrared thermometer or thermal camera | Surface temperature | Hot lugs, hot cells, failing connections show up as heat first |
| Non-contact voltage tester | Presence of AC voltage | A first check, never a final one. It cannot confirm a circuit is dead |
Personal protective equipment
Eye protection, insulated gloves rated for the voltage with leather protectors over them, hard hat, and proper footwear. On any roof, a full-body harness with a lanyard tied to a rated anchor. A fibreglass ladder, never aluminium. Arc-rated clothing when working live equipment, and a lockout-tagout kit so nobody re-energises what you are standing in.
Salt air destroys tools faster than the work does. Wipe down, dry, and oil steel at the end of every day, and keep silica packs in the meter case. A corroded crimper jaw makes bad crimps you cannot see.
Multimeters: every type, every symbol, every procedure
This is the longest lesson in the course, and it should be. The meter is how you find out what is actually happening instead of guessing. A technician who can read a meter properly is worth three who cannot.
4.1 The four kinds of meter you will meet
Analog meters
A moving needle over a printed scale. They are slower to read and easier to misread, but they show a trend beautifully. A needle drifting or flickering tells you about a loose connection in a way a jumping digital number does not. Many older shops and boat yards still run them.
Three things trip people up on an analog meter, and lesson section 4.7 walks through reading one properly: the scale you read depends on the range you selected, the ohms scale runs backwards and is not evenly spaced, and you must kill parallax by lining the needle up with its own reflection in the mirror strip.
Digital multimeters
- Auto-ranging picks the range for you. Easier, slightly slower to settle.
- Manual-ranging makes you choose. Faster and more precise once you know roughly what to expect. Start high and work down if you do not.
- Counts describe resolution. A 6000-count meter can show 599.9 before it has to jump to 6.000 with less detail.
- True RMS matters on the AC side. An average-responding meter reads the distorted waveform from a cheap modified-sine inverter incorrectly, sometimes by twenty percent or more. On pure DC it makes no difference.
Clamp meters
A cheap clamp meter uses a current transformer, which only works on AC. Clamp it around a DC array conductor and it reads zero forever while you chase a fault that is not there. For solar you need a Hall effect clamp, sold as "DC/AC" or "DC amps". It has a ZERO or REL button, because it drifts and must be zeroed with the jaws closed and empty before every reading.
Insulation resistance testers
A megger pushes 250, 500, or 1000 volts into the insulation and measures resistance in megohms. Ordinary meter ohms ranges use a couple of volts and will happily call damaged cable "fine". This is the instrument that finds a chafed conductor rubbing a rail, and it is required on commissioning tests. Never megger a circuit with electronics connected — controllers and inverters must be isolated first or the test voltage destroys them.
4.2 Anatomy of a digital multimeter
4.3 The symbols, decoded
| Symbol | Name | What it is for |
|---|---|---|
| V— or V with a solid line over dashes | DC voltage | Batteries, panels, controller terminals. Your most-used setting |
| V≈ or V~ | AC voltage | Inverter output, house circuits, the utility supply |
| A— | DC current | Array and battery current, meter wired in line |
| mA / µA | Small current | Signal and leakage measurements, not array current |
| Ω | Resistance in ohms | Checking a conductor, a shunt, a heating element. Dead circuits only |
| •))) | Continuity | Beeps if there is a path. Fuses, breakers, broken wires, bonding |
| ┃▶┃ | Diode test | Bypass diodes and blocking diodes |
| F or ―‖― | Capacitance | Inverter and motor capacitors |
| Hz | Frequency | Confirming inverter output sits at 60 Hz |
| °C / °F | Temperature | With a thermocouple probe. Battery and terminal temps |
| ⌕ | Earth / ground | Marks the grounding reference |
| CAT III 600V | Category rating | How much fault energy the meter can survive. See below |
4.4 CAT ratings and meter safety
The CAT rating describes how much energy is behind the circuit you are probing, not just its voltage. Higher category means the meter is built to survive a bigger transient without exploding in your hand.
| Category | Where it applies |
|---|---|
| CAT I | Protected electronics. Not adequate for any part of a solar install |
| CAT II | Appliances and receptacle-level circuits |
| CAT III | Distribution wiring, panels, inverters, battery banks. The minimum for this work |
| CAT IV | Service entrance, meter base, overhead supply |
- Use a meter rated CAT III 600 V minimum, and CAT III 1000 V for high-voltage strings.
- Inspect leads every time. Cracked insulation, exposed metal, or a loose banana plug means new leads, not tape.
- Use fused leads and keep the meter's own fuses correct. That fuse is the only thing between a wrong dial position and an arc blast.
- Keep fingers behind the probe guards. Work one-handed where you can, other hand in your pocket, so current has no path across your chest.
- Never leave the leads in the 10 A jack. The next person to check voltage with them there creates a dead short.
- Prove the meter on a known live source before and after any test that concludes "it is dead".
Meter procedures, one at a time
Each procedure below is written the way you would actually do it on a job. Read the whole procedure before you start it.
A Measuring DC voltage (battery, panel, controller terminal)
- Black lead into COM. Red lead into VΩmA. Confirm the red lead is not in the 10 A jack.
- Turn the dial to V— (DC volts). On a manual-range meter choose a range above what you expect: 200 V for a 48 V bank.
- Prove the meter on a known source, such as a good battery.
- Touch black to negative, red to positive. Keep fingers behind the guards.
- Read the number. A minus sign only means your leads are reversed, which is itself a useful polarity check.
A 12 V lead-acid bank at rest: about 12.7 V full, 12.0 V roughly half, below 11.8 V is deeply discharged. A 48 V bank: multiply by four, so about 50.8 V full and 54 to 57 V while charging. A 12 V bank reading 13.6 V is charging, not overfull.
B Measuring a panel's open-circuit voltage (Voc)
- Disconnect the panel or string from the controller. Voc is measured with nothing connected.
- Set the dial to V— and a range above the expected string voltage.
- Probe into the MC4 pair: red into the positive connector, black into the negative. Use proper MC4 test leads rather than jamming probes into the connector body.
- Compare against the panel's nameplate Voc. Cold and bright pushes it above the sticker; hot pushes it down a little.
- A string reading far low means one panel is dead or a connector is not seated. A string reading zero means an open circuit somewhere.
C Measuring DC current with the meter in line
- De-energise the circuit first. Open the breaker or disconnect.
- Move the red lead to the 10A jack. Black stays in COM.
- Set the dial to A—.
- Break the circuit at one point and connect the meter across that break, so current must pass through it.
- Re-energise, take the reading quickly, then de-energise and put the lead back in VΩmA before you forget.
In-line current measurement means opening a live DC circuit, and array current can be well beyond the meter's 10 A jack. On a real solar system a Hall effect clamp is the correct tool for almost every current reading. Learn the in-line method so you understand what is happening, then reach for the clamp.
D Measuring DC current with a clamp meter
- Confirm the meter actually does DC amps. Look for A— or "DC A" on the dial.
- Set the dial to DC current and close the empty jaws.
- Press ZERO or REL so the display sits at 0.0. Hall effect sensors drift; skip this and every reading is wrong.
- Open the jaws and close them around one conductor, centred, with the jaws fully shut.
- Read. If the sign is negative you have the arrow pointing the other way, which is fine and tells you the direction of flow.
E Continuity: testing a fuse, a breaker, or a suspect wire
Continuity and resistance both push the meter's own small voltage through the circuit. Any outside voltage present gives a false reading and can damage the meter. Isolate first, and prove it dead on volts before you switch to continuity.
- Isolate the component and remove at least one end of it from the circuit, otherwise you may be reading a path around it.
- Dial to •))). Touch the probes together: it should read near zero and beep. That proves the meter and the leads.
- Probe across the fuse or conductor end to end.
- Beeps, near 0 Ω means a good path. Silence, or OL / 1 on the display means open: the fuse is blown or the conductor is broken.
- Same method for grounding: probe from an array frame to the grounding busbar. Anything other than a near-zero reading means your bonding path is not there.
F Resistance, diode, and the rest of the dial
- Resistance (Ω) — dead circuits only. Useful on shunts, heating elements, and comparing one panel's readings against an identical panel.
- Diode test (┃▶┃) — a healthy silicon diode reads roughly 0.4 to 0.7 one way and OL when reversed. A bypass diode reading near zero both ways is shorted, which is a common cause of one panel dragging down a whole string.
- Frequency (Hz) — on the inverter output, confirm 60 Hz. Drift means an inverter fault.
- Temperature — with a thermocouple, check battery and terminal temperatures. A lug measurably hotter than its neighbours is loose or corroded.
G Voltage drop under load, the test that finds bad cable
- With the system running under a real load, set the meter to DC volts.
- Measure at the battery terminals. Note it.
- Measure at the far end of the same run, at the inverter lugs. Note it.
- The difference is your voltage drop. On a 48 V system, more than about a volt on the run says the cable is undersized, too long, or your terminations are poor.
- Narrow it down by measuring straight across a single connection while loaded. Any measurable voltage across one lug means that lug is a resistance, and a resistance carrying current is a heater.
H Insulation resistance test, in outline
- Isolate completely. Disconnect the controller, inverter, and anything else with electronics inside it.
- Connect the tester between the conductor and the grounded array frame.
- Select the test voltage the manufacturer or the code calls for, commonly 500 V for a system in this class.
- Press and hold TEST and let the reading settle.
- Megohms, high and steady, is healthy. A reading down in the low megohms or worse means moisture or damaged insulation, and you go looking for it.
- Discharge the circuit afterwards. The tester stores energy in the cable.
4.7 Reading an analog meter
- Select a range above what you expect. If you have no idea, start at the highest and come down.
- Find the scale matching your range. A 0–300 scale on the 300 V range is read directly; on the 30 V range you read the same scale and divide by ten.
- Line up the needle with its mirror reflection before reading.
- For ohms, short the probes together first and use the zero-adjust knob to bring the needle to 0 Ω. Redo this every time you change the ohms range.
- Remember the ohms scale is reversed and compressed at the high end, so a reading up near infinity is a rough figure, not a precise one.
4.8 The five mistakes that cost people meters and fingers
- Leads left in the 10 A jack, then used to check voltage. That puts a near short across the source.
- Measuring resistance or continuity on a live circuit. Wrong reading, dead meter.
- Opening a live DC circuit to insert the meter. DC arcs do not self-extinguish. Isolate first, or use the clamp.
- Assuming an AC clamp reads DC. It reads zero, and zero looks exactly like "no fault" while the array is live.
- Trusting a non-contact tester to prove a circuit is dead. It confirms voltage is present. It never confirms it is absent.
Installing a system, start to finish
First, the decisions
- Choose the shape of the system: on-grid, off-grid, or hybrid.
- Add up the watt-hours the house actually uses in a day. Lesson 7 walks the math.
- Pick a system voltage — 12 V for a shed or a boat, 24 V for something in between, 48 V for a house.
- Buy the four things that matter: panels, an MPPT controller, a pure sine inverter, and deep-cycle or LiFePO4 batteries.
Then, the physical work
- Fix the mounting rails into structure, not just into sheathing. Every penetration gets flashed and sealed.
- Face the array true south and tilt it roughly to your latitude — about 24° here in the islands.
- String the panels in series, parallel, or both, so the array voltage lands inside the controller's window.
- Run UV-rated solar cable from the roof down to the controller, secured every few feet so nothing flaps in wind.
- Connect the controller to the battery first. Then, and only then, connect the panels.
- Connect the inverter to the battery bank with short thick cable and a correctly rated fuse at the battery positive.
- Land the inverter output on its own breaker, or on a critical-loads sub panel for an off-grid build.
Salt air eats hardware. Use stainless or anodised fasteners, coat lugs, and inspect terminals twice a year. Hurricane country means the mounting engineering matters more than the panel brand — an array is a very large wing.
The touches that separate a pro from a weekend
- Torque every terminal to spec. Loose lugs start fires; over-tight lugs crack cases.
- Fit DC and AC disconnects somewhere a person can actually reach in a hurry.
- Fit rapid shutdown on roof arrays. Modern code requires it.
- Label every wire, every breaker, every disconnect. Do it now, not later.
- Use a proper BMS on any lithium bank.
- Set up monitoring so faults show on a phone instead of showing as a dead freezer.
Wiring methods, and how to read any wire you find
Series and parallel
- Series — positive of one panel into the negative of the next. Voltage adds, current stays the same.
- Parallel — all positives together, all negatives together. Current adds, voltage stays the same.
- Series-parallel — strings of series panels joined in parallel. This is what most real roofs use.
Reading the wires
| Colour or marking | Normally means | Where it lives |
|---|---|---|
| Red | Positive (+) | Battery and DC side |
| Black | Negative on DC, hot on AC | Both sides — check before assuming |
| White | AC neutral | AC side |
| Green or bare copper | Ground / earth | Everywhere, always |
| Red with a stripe, or taped and labelled | PV positive string | Roof down to the controller |
| Thick black UV cable | PV cable, sunlight rated | Outdoors |
Somebody before you may have used what was on the truck. Put a meter on it every single time before you cut, touch or terminate.
Breakers, fuses, disconnects
- DC breaker or fuse — protects the battery and controller from a dead short. It must be DC rated. An AC breaker on a DC circuit can fail to stop the arc.
- AC breaker — protects house wiring from the inverter output.
- DC disconnect — kills the array so you can work.
- AC disconnect — lets the utility or a firefighter shut you down without asking.
12 V, 24 V, 48 V — and grid, off-grid, hybrid
| Voltage | Suits | Good | Bad |
|---|---|---|---|
| 12 V | Boats, RVs, a small cabin | Cheap, simple, parts everywhere | Huge current, fat cable, wasteful over distance |
| 24 V | Medium homes, big rigs | Reasonable middle ground | Runs out of room on a full house |
| 48 V | Almost every modern home | Lowest current, best efficiency, what the industry builds | Batteries cost more up front |
Grid, off-grid, or hybrid
- On-grid — no big battery. Surplus goes out to the utility. Cheapest to build, but when the grid dies your solar dies with it, because anti-islanding forces the inverter off to protect the linemen working the fault.
- Off-grid — fully independent, big battery bank, usually a generator for the week it rains. Right answer for a remote cay.
- Hybrid — battery plus grid. Runs through blackouts, charges from either source. For a house that already has a meter, this is nearly always the answer.
Grid connection, metering and any credit arrangement are decided by the utility and the regulator, not by the installer. Confirm the current rules and the interconnection paperwork before you quote.
Reading the screens
Battery monitor
Amp-hours remaining, percentage full, estimated time left, and the charge and discharge history. When the monitor and the controller disagree, trust the shunt-based monitor.
Inverter display
- DC input volts from the bank — if this sags hard under load, your cable or bank is undersized
- AC output volts and frequency — should sit near 120 V, 60 Hz
- Watts being drawn right now
- Fault codes such as E01 — look them up in that model's manual, they are not standardised
Sizing a system with a pencil
Step 1 — list what the house actually runs
| Appliance | Watts | Hours a day | Watt-hours |
|---|---|---|---|
| LED lights × 10 | 100 | 5 | 500 |
| Fridge (cycling) | 150 | 8 | 1,200 |
| TV and router | 120 | 4 | 480 |
| Laptop | 60 | 3 | 180 |
| Phone charging | 20 | 3 | 60 |
| Daily total | 2,420 Wh |
Step 2 — add the margin
Multiply by 1.3 to 1.5 for cloudy weeks, dirty glass, cable losses and inverter overhead. 2,420 × 1.4 ≈ 3,400 Wh a day.
Step 3 — size the bank, honestly
Two days of autonomy: 3,400 × 2 = 6,800 Wh. On a 48 V bank that is 6,800 ÷ 48 ≈ 142 Ah.
You cannot use all of a battery. Lead-acid should only give up about half its capacity if you want it to live for years; LiFePO4 will happily give 80 to 90 percent. Divide by that depth of discharge. 142 Ah of usable energy means roughly 285 Ah of lead-acid, or about 170 Ah of lithium.
Step 4 — size the array
Call it 4 peak sun hours a day, which is a fair year-round working figure here. 3,400 ÷ 4 = 850 W of panel as the bare minimum, so buy 20 to 30 percent more than that. Panels are the cheapest part of the system and the one you will regret undersizing.
Staying alive and not burning the house down
A panel makes voltage whenever light lands on it. Dawn counts. Moonlight is not enough, but a cloudy afternoon absolutely is. There is no breaker anywhere that stops a panel from generating.
- Battery to controller first. Panels last. Every time.
- Insulated gloves and eye protection whenever a circuit could be live.
- Meter the voltage and the polarity before you make any connection.
- Fuse or DC breaker as close to the battery positive as you can physically get it.
- Never work high-voltage DC alone.
- Rings, watches, chains off. Metal tools away from terminals — a dropped wrench across a bank is a welding arc.
- Bond and ground every metal frame, rail and enclosure.
- Ventilate flooded lead-acid. It vents hydrogen, and hydrogen finds sparks.
- Rapid shutdown and anti-islanding are not optional extras on a grid-connected roof.
Reading a system drawing
A blueprint is a map. It tells you where every box hangs, how the wire travels, and what protects what. Learn to trace it with a finger and you can walk any job.
What you are looking for on any drawing
- Roof plan — panel layout, string grouping, mounting points
- Wire runs, with DC and AC drawn differently
- Where the controller, bank, inverter and main panel physically sit
- Every disconnect, breaker and fuse, with its rating
- Grounding and bonding paths back to the electrode
- Notes on conductor size in AWG and conduit fill
Practice quiz
Forty-five questions covering the whole course. Both the question order and the answer order are reshuffled every time the page loads, so no two runs are the same paper. Nothing here is recorded and it does not affect the exam. Take it as often as you like.
Final certification exam
Eighty questions, reshuffled in a fresh order every attempt, with the answers shuffled too. You need 80 percent to pass, which is 64 correct. You cannot go back a question, and every answer — right or wrong — shows you why before you move on. Fail it and you can start again immediately.
These print on the certificate. Nothing is uploaded and nothing is emailed — it stays in this browser. Clear your browsing data and it is gone.
Your certificate
The vocabulary of the trade
You have the foundation. These are the terms you will hear on a real crew, and the ones worth chasing down next.
- MPPT against PWM — MPPT controllers track the panel's best operating point and typically harvest 20 to 30 percent more. There is no good reason to buy PWM for a new build.
- String sizing — total the open-circuit voltage of a series string at the coldest temperature the site ever sees. That worst case must stay under the controller's maximum input, or the controller dies on the coldest morning of the year.
- Temperature coefficients — heat costs you power, cold gives you voltage. Both are on the panel's datasheet.
- NEC Article 690 — the US code chapter for photovoltaics: rapid shutdown, labelling, grounding, conductor sizing. Widely used as the reference standard even outside the States.
- Microinverters against string inverters — a microinverter under each panel handles shade and per-panel monitoring beautifully; a string inverter is cheaper and simpler on a clean open roof.
- LiFePO4 — 3,000 to 6,000 cycles, deep usable capacity, stable chemistry, needs a BMS.
- Voltage drop — size conductors so the drop across a run stays under about 2 percent on DC. Length and current, not opinion, decide the gauge.
- Bonding and grounding — the equipment grounding conductor ties metal together; the grounding electrode conductor ties it to earth. Different jobs, both required.
- Anti-islanding — a grid-tied inverter must drop out when the grid does. This is a life safety function, not a feature.
- kWh — 1,000 watt-hours. The unit your bill is written in, and the only unit worth quoting a customer in.
Keep reading, keep metering, and follow the code and the manufacturer's manual over anything anybody tells you on a roof — including this page.