Building
You’ve got a design, you’ve got the equipment, and everything tested good out of the box. Time to build.
This isn’t a step-by-step wiring manual — your inverter manufacturer’s documentation covers your specific equipment. What this covers is the practical stuff: what order to do things, what to watch out for, and mistakes you can avoid.
Before you start
Post your line diagram. Print it, tape it to the wall, pull it up on a tablet. Every connection you make should match the diagram. If it doesn’t, stop and figure out why.
Stage all your tools and materials. Lay everything out before you begin — wire, connectors, fuses, brackets, conduit, sealant, multimeter, wire strippers, torque wrench, drill. If you’re heading to a roof, pre-assemble anything you can on the ground: brackets on panels, connectors crimped, hardware sorted and bagged. Climbing down a ladder for a forgotten bolt gets old fast.
Check the weather. Don’t start a roof project the day before rain. Give yourself a clear window — ideally a weekend with good weather and no time pressure.
Line up your buddy. Panels are bulky, batteries are heavy, and pulling wire alone is annoying. You need another person for the roof work at minimum.
Installation order
There’s a sequence that keeps you safe and working efficiently:
- Mount the panels. Most physical work — do it while you’re fresh. In summer, late afternoon is better for roof work; the surface cools and the sun angle drops.
- Run wire from panels to equipment location. Pull PV wire through conduit. Leave service loops at both ends — extra slack so you can make connections without pulling wire tight.
- Install the inverter and battery rack. Mount the inverter on the wall, set up the battery rack, position everything where it’s going to live permanently. Check ventilation and maintenance access.
- Wire the DC side. Panels to combiner, combiner to DC disconnect, disconnect to inverter MPPT input. Leave the DC disconnect off.
- Wire the battery side. Batteries to the inverter’s battery input through the battery fuse or breaker. Don’t energize yet.
- Install the transfer switch and wire the AC side. Mount near your main panel, wire AC output from inverter to transfer switch, run your selected house circuits through it.
- Connect to house circuits. Final link — selected breakers in the main panel route through the transfer switch. Double-check every connection before proceeding.
Solo vs. two-person tasks
Fine to do alone: mounting the inverter, running conduit, wiring connections, racking batteries, configuring inverter software.
You want help for: carrying panels up a ladder, positioning them on the roof, pulling long wire runs through conduit, and having a second set of eyes on your work.
Safety note: Even for solo work, tell someone what you’re doing. Let them know you’re working on electrical and when to expect to hear from you. Same common sense as checking in on a solo hike.
Common gotchas
MC4 connectors. A click doesn’t always mean fully seated. Tug-test every one after connecting. A loose MC4 creates resistance, which creates heat, which creates a potential fire point. Use matched connectors from the same brand — this isn’t the place to save money mixing manufacturers.
Torque specs. Battery terminals, wire lugs, grounding connections — all have specified torque values. Too loose creates heat over time. Too tight cracks terminals. Use a torque wrench or torque screwdriver, tighten to spec, and move on.
Panel polarity. Double-check positive and negative before connecting anything to your inverter. Reversing DC polarity can damage equipment instantly. Measure with your multimeter. Verify. Then connect.
Panels are always live. Once sunlight hits a panel, it’s generating voltage — there’s no off switch. Treat the panel-side wires as energized during any daylight hours. Cover panels with an opaque tarp or cardboard while wiring if you can; it drops the voltage and makes the work safer.
Wire management. Leave service loops at every connection point — enough slack that you could remove a component and set it on the floor without cutting wire. Size conduit for what you’re running now plus room for growth.
Testing and commissioning
You built it. Don’t just flip everything on.
Before energizing: Visual inspection of every connection. Check torque on all terminals. Verify DC polarity at every connection with your multimeter. Look for pinched wire, unseated connectors, missing fuses. Take your time — this is your safety review.
Energize DC first. Turn on the DC disconnect. Check string voltage at the inverter’s MPPT input — it should match your expected string voltage given current temperature and sun conditions. If it’s significantly off, stop and find out why.
Connect the battery. Close the battery breaker. Verify the inverter sees the battery — state of charge should display, communication status should show connected. Battery and inverter not communicating? Resolve it before proceeding.
Energize AC. Turn on the AC output. Measure voltage at the transfer switch — you should see 120V or 120/240V depending on your system.
Switch circuits one at a time. Move one circuit from grid to solar. Verify it works. Then the next. One at a time lets you catch circuit-specific issues before everything is running.
Monitor for a full day. Watch battery state of charge throughout the day and overnight. Is it charging as expected? Draining at the predicted rate? Any inverter errors? A day of observation tells you whether the system is performing as designed.
Your first real test
Once everything looks normal, run a fire drill.
Intentionally disconnect the grid. Flip your main breaker off. Watch what happens: does the transfer switch respond? Do essential circuits stay powered? How fast is the battery draining?
Do this on a Saturday afternoon — relaxed, home, no time pressure. Run on battery for a few hours and compare reality to your math. If your numbers said 10 hours of overnight coverage and the battery drops faster than expected, figure out why now. Not during the next ice storm.
Flip the main breaker back on. Everything returns to normal. You now know exactly what your system does when it matters.
From here, head to Living with Solar for what day-to-day operation looks like.
DATA SOURCED FROM: Standalone Solar Design Guide, Section 5 (primary source for build sequence, installation gotchas, and commissioning methodology). Safety practices aligned with NEC residential electrical guidelines.