Grid-tie solar system
Grid is reliable and you want a smaller bill: the panels feed the house and the surplus goes to the utility under net metering. Nothing works in a brownout.
Open it in the simulator ▸Size it from my electric bill
What is in it
2,700 W of panels, 3,000 W of inverter. 19 parts in all, wired and sized the way the lab's solar studio sizes them.
- One string of six 450 W modules
304 V at a 10 °C dawn against the inverter’s 550 V; Vmp 215 V hot, well inside its 80 V minimum. - PV disconnect and DC SPD
The array side needs a switch and a surge path like any other. - Grid-tie inverter, 3 kW
Anti-islanding: it stops within 0.5 s of losing the grid (PEC 7.05, NEC 705.40). No battery, no backup. - AC disconnect
So the utility or an electrician can isolate the inverter. - Solar backfeed breaker, 20 A on the house busbar
NEC 705.12: solar breaker + main ≤ 120 % of the busbar. 20 + 63 = 83 A on a 100 A busbar (not drawn) passes. - Net kWh meter, main breaker 63 A, AC SPD
The meter runs both ways under net metering; the SPD at the service. - Ground rod
Electrode for the SPDs and the equipment ground.
A clear day on this system
The lab ran this exact system through a clear day: 36 hours from 18:00 the evening before. The panels harvested 7.1 kWh and the loads used 15 kWh; the grid supplied 18 kWh.
Parts and prices
Philippine prices as estimates (about US$1,270 in all at ₱64 per US$). In the simulator, Buy all the parts gives the same list with shop links where we have them.
| Part | Qty | Est. |
|---|---|---|
| Grid-tie inverter String inverter 3000 W · MPPT 80–550 V | 1 | ₱27,000 |
| Solar panel 450 W · 144 half-cell mono | 6 | ₱48,600 |
| AC breaker 2-pole MCB · C20 | 2 | ₱560 |
| AC breaker 2-pole MCB · C63 | 1 | ₱280 |
| DC breaker 2-pole MCB · C16 | 1 | ₱380 |
| Surge protector (SPD) AC SPD, Type 2, 275 V · DIN-rail module, two pluggable varistor cartridges with a status window each | 1 | ₱650 |
| Surge protector (SPD) PV DC SPD, Type 2, 600 V · DIN-rail module, two pluggable varistor cartridges with a status window each | 1 | ₱950 |
| 220 V bulb A60 E27 · LED 54 W | 1 | ₱90 |
| Household appliance Aircon 1 HP inverter · 900 W max, about 495 W once the room is cool | 1 | — |
| Household appliance Refrigerator · 150 W | 1 | — |
| 12 AWG (3.5 mm²) THHN any colour | 3 m | ₱144 |
| 12 AWG (3.5 mm²) THHN red | 4 m | ₱192 |
| 14 AWG (2.0 mm²) THHN any colour | 3 m | ₱105 |
| 14 AWG (2.0 mm²) THHN black | 1 m | ₱35 |
| 14 AWG (2.0 mm²) THHN red | 1 m | ₱35 |
| 8 AWG (8.0 mm²) THHN any colour | 1 m | ₱110 |
| 8 AWG (8.0 mm²) THHN red | 1 m | ₱110 |
| PV cable 4 mm² black | 16 m | ₱960 |
| PV cable 4 mm² red | 18 m | ₱1,080 |
| Estimated total | ₱81,281 |
What the safety check verifies
- ✓ Cold-morning Voc inside the Grid-tie inverter's input
- ✓ Hot-noon Vmp stays above the controller’s minimum
- ✓ PV conductors rated for 1.56 × Isc
- ✓ Array-to-controller voltage drop
- ✓ DC disconnect between array and controller
- ✓ Grid-tie inverter is grid-interactive (anti-islanding)
- ✓ Surge protection on each side
- ✓ Every SPD’s PE reaches the earth
- ✓ Grounding electrode: the service ground
Questions
How big is this grid-tie solar system?
As drawn: 2,700 W of panels, 3,000 W of inverter. Every size can be changed in the simulator, and Solar & wiring → My house sizes one from your electric bill.
Does it work in a brownout?
No. A grid-tie inverter must stop within half a second of losing the grid (anti-islanding), so the panels do nothing in a brownout. That is by design: it protects line workers.
Is the wiring diagram correct?
It is drawn from the working simulation: every line is a real connection on the bench, and the safety check passes 9 checks with no fails. It is a design to learn from and adapt: check it against your local electrical code and the manuals of the parts you buy.
On the bench
Open it in the simulator ▸All solar systems and builds
Other systems
Off-grid solar system · Hybrid solar system · Off-grid inverter + ATS (budget hybrid) · AC-coupled solar with battery · 12 V solar for an RV, boat or small DIY · Three-phase grid-tie solar