If you just want the headline answer: a 5 kW array typically uses 10–17 panels, depending mainly on panel wattage (and secondarily on layout and losses). Below I’ll show you the exact math, roof-space needs, realistic energy output by location, and what changes when you add batteries for off-grid.
Panels Needed for a 5 kW System (by 330 W / 400 W / 550 W)
Formula (transparent and repeatable):
Panel count = 5,000 W ÷ panel STC power (W).
| Panel STC rating | Panels for ≈5 kW | Typical panel size (m²)* | Roof area needed (approx.) |
|---|---|---|---|
| 330 W | 15–16 | 1.95–2.10 | 29–34 m² |
| 370 W | 14 | 1.95–2.10 | 27–30 m² |
| 400 W | 12–13 | 1.95–2.20 | 24–29 m² |
| 450 W | 11–12 | 1.95–2.20 | 22–26 m² |
| 500 W | 10 | 2.10–2.35 | 21–24 m² |
| 550 W | 9–10 | 2.10–2.35 | 19–24 m² |
*Most modern 54–72 cell (or 108–144 half-cut) modules fall in this footprint range. Your exact panel datasheet prevails.
Why the range? Racking gaps, orientation (portrait/landscape), obstructions (vents, skylights), and module availability can nudge counts up or down by one panel.
5 kW Solar Output
Real-world energy depends on peak sun hours (HSP) and system losses, captured by Performance Ratio (PR). A reasonable PR for residential string/MLPE systems is 0.75–0.85 (we’ll use 0.80 mid-case).
Formula:
Daily kWh ≈ HSP × 5 kW × PR.
| City (example) | Typical HSP | Daily energy (kWh) | Monthly (~30 d) |
|---|---|---|---|
| Seattle, WA | 3.0 | ≈ 12 kWh | ≈ 360 kWh |
| Atlanta, GA | 4.5 | ≈ 18 kWh | ≈ 540 kWh |
| Phoenix, AZ | 5.5 | ≈ 22 kWh | ≈ 660 kWh |
Tip: Look up your local HSP (NREL, PVGIS, etc.). Multiply by 5 kW and your chosen PR to sanity-check expectations year-round.
Roof Space for a 5 kW Solar Array
Most 5 kW arrays need ~19–34 m² (200–365 ft²) of unshaded, structurally sound roof once racking clearances and access paths are considered. If you’re roof-constrained, favor higher-wattage modules (e.g., 500–550 W) to reduce panel count.
Quick estimator:
Area ≈ panel area × panel count × 1.05–1.10 (allow small spacing/racking overhead).
5 kW Solar System with Battery Storage (Off-Grid Sizing Basics)
If you want resilience or true off-grid, add batteries and size at 48 V to keep currents manageable.
- Decide your daily energy target (kWh).
Example: you want 15 kWh/day. - Choose autonomy days (how long to ride through poor sun): say 1.5 days.
- Pick chemistry & depth-of-discharge (DoD).
LiFePO₄: usable 80–90%; we’ll use 85% usable. - Battery capacity (kWh):
Required kWh = daily kWh × autonomy ÷ usable DoD
→ 15 × 1.5 ÷ 0.85 ≈ 26.5 kWh. - At 48 V, Amp-hours (Ah):
Ah ≈ (26,500 Wh ÷ 48 V) ≈ 552 Ah (round to a common size like 560–600 Ah at 48 V). - Charge equipment:
- MPPT charge controller(s) sized for array Isc and Voc (add cold-weather Voc multiplier).
- Off-grid inverter/charger sized for peak AC loads (see next section).
Off-grid adds complexity (generators, load management, charge profiles). If you’re mainly seeking bill savings, grid-tie + small backup battery is often the best value.
Can a 5 kW Solar System Run Air Conditioners?
A 5 kW inverter can deliver up to ~5 kW AC at a time, but energy is about kWh per day:
- A single 1–1.5 ton (12–18 k BTU) mini-split often draws 600–1,200 W while running (higher at startup). Two minisplits plus lights and a fridge may already consume most of a 5 kW system’s daytime output.
- For whole-home cooling or resistive loads (electric oven, water heater), you’ll likely need load scheduling, larger PV, or battery+generator support.
Rule of thumb: size your inverter for peak simultaneous watts, and your array/battery for daily kWh.
Wiring & Code: 120% Rule and 33% Oversizing
- 120% rule (NEC): In many jurisdictions, the busbar rating and main breaker size limit how much PV backfeed you can land on a service panel. Your installer may downsize the main breaker or use a supply-side tap / load-side combiner to comply.
- 33% PV oversizing: It’s common to oversize the DC array by up to ~1.33× the inverter AC rating to improve production at low/shoulder irradiance. Check your inverter’s DC:AC ratio spec.
Always follow local code, module/inverter datasheets, wire-ampacity tables, and voltage-drop best practices (<3% branch, <5% total typical targets).
Cost & Payback Snapshot
Prices vary by region, roof type, and components. As a rough orientation:
- Grid-tie 5 kW turnkey: often $2–3/W before incentives → $10–15k gross.
- With battery (10–20 kWh): typically adds $7–15k depending on chemistry/inverter.
Local incentives, net metering rules, and usage profile dominate payback. Use your utility bill (12-month kWh) to model ROI credibly.
Worked Examples You Can Copy
Example A (compact roof):
- Choose 500 W modules → 10 panels ≈ 5.0 kW DC, ~22 m².
- In HSP 4.5 region, PR 0.8 → ~18 kWh/day.
- Goal is bill savings with occasional outage cover → add a 10 kWh battery for essentials.
Example B (off-grid cabin):
- 400 W modules × 13 → 5.2 kW DC (slight oversize), ~26–28 m².
- Daily need 12 kWh, autonomy 2 days, LiFePO₄ usable 85% → ~28 kWh storage at 48 V (~580 Ah).
- Inverter/charger 6–8 kW to tolerate motor starts; keep a generator for storms.
FAQ
Is 5 kW enough to run a typical house?
For efficient homes using 12–20 kWh/day, yes—especially with net metering. Heavy electric heating/cooking may need more PV or load shifting.
How many kWh per day does 5 kW produce?
About 12–22 kWh/day for most US locations (see HSP table).
How many panels do I need for a 5 kW system?
Roughly 10–17 panels depending on panel wattage (550 W → 9–10; 400 W → 12–13; 330 W → 15–16).
How much roof space is required?
Plan on ~19–34 m² (200–365 ft²), depending on module size and layout.
What’s the 120% rule?
A panelboard backfeed limit used in many NEC jurisdictions; it governs how PV ties into your service panel. Installers adjust breaker sizes or use alternate interconnection methods to comply.
Do I need batteries for 5 kW?
Not for grid-tie savings. For backup or off-grid, size batteries by daily kWh × autonomy ÷ usable DoD (see example).
Quick Reference Table
| Target | Use this |
|---|---|
| Panel count | 5000 ÷ panel_W (round up) |
| Daily kWh | HSP × 5 × PR (PR 0.75–0.85) |
| Battery kWh (off-grid) | daily_kWh × autonomy ÷ usable_DoD |
| 48 V battery Ah | (battery_kWh × 1000) ÷ 48 |
What to do next
- Pick a panel wattage you can actually buy, compute the panel count, and check roof area.
- Use your 12-month utility kWh (or daily off-grid target) to decide whether 5 kW fits your goals—or if you should step up to 6–8 kW.
- If you need help matching 48 V batteries, MPPTs, and inverter size, tell me your city, panel model (if any), and your top 5 appliances—I’ll size it precisely.