The bottom line — For a 4-person Algarve home with average consumption (5,000-6,000 kWh/year), expect 10 to 14 solar panels at 420 Wp, i.e. a 4 to 6 kWp installation. But the real answer depends on 5 factors: your annual consumption, usable roof area, budget, daily habits (home or away during the day), and whether you have AC. This guide gives the step-by-step method to get it right.
The golden rule: not too much, not too little
Oversizing = you produce surplus you sell at €0.05/kWh (poor value since 23% VAT). Undersizing = you keep buying grid power at €0.22/kWh.
➡️ The sweet spot is 80-110% of your annual consumption, adjusted to your usage profile.
5-step sizing method
📊 Step 1 — Get your annual consumption
The starting point. Three reliable sources:
- Your latest E-Redes / EDP / Galp bill: look for “Consumo total anual”
- Your supplier customer area (12-36 month history)
- Otherwise: multiply your average monthly consumption × 12
Quick estimate without bills:
| Home type | Typical annual consumption |
|---|---|
| Studio / 1-bed (1-2 people) | 1,500-2,500 kWh |
| 2-bed (2 people) | 2,500-3,500 kWh |
| 3-bed (3-4 people) | 3,500-5,500 kWh |
| 4-5 bed (4-6 people) | 5,500-8,000 kWh |
| Villa with pool | 7,000-12,000 kWh |
| Villa + AC + pool | 10,000-15,000 kWh |
➡️ Our example: 6,000 kWh/year (3-bed Algarve family with moderate AC).
🔭 Step 2 — Calculate solar production per m²
In the Algarve, your roof produces 1,700 kWh/year per 1 kWp installed (South orientation, 25-30° tilt).
Convert consumption to solar capacity: – 6,000 kWh/year ÷ 1,700 kWh/kWp = ~3.5 kWp needed to produce 100% of consumption – But with self-consumption rate of 50-60%, bump to ~5 kWp to target equivalent annual coverage
➡️ Our example: 5 kWp target.
🔢 Step 3 — Convert into number of panels
Modern Tier-1 panels are 400-460 Wp each (2026 models like Jinko Tiger Neo, LONGi Hi-MO 6, Trina Vertex S+).
With standard 420 Wp panels: – 5 kWp ÷ 420 W = 12 panels
More precisely:
| Target capacity | With 400 Wp panels | With 460 Wp panels | | 3 kWp | 8 panels | 7 panels | | 4 kWp | 10 panels | 9 panels |. | 5 kWp | 13 panels | 11 panels | | 6 kWp | 15 panels | 13 panels | | 8 kWp | 20 panels | 18 panels | | 10 kWp | 25 panels | 22 panels |
📐 Step 4 — Check required roof area
A modern 420 Wp panel is roughly 1.75 m × 1.13 m = ~2 m².
| Capacity | Number of panels | Required roof area |
|---|---|---|
| 3 kWp | 8 | 16 m² |
| 5 kWp | 13 | 26 m² |
| 6 kWp | 15 | 30 m² |
| 8 kWp | 20 | 40 m² |
| 10 kWp | 25 | 50 m² |
➡️ Our example: 26 m² of usable roof (typically available without issue on a 3-bed home).
⚙️ Step 5 — Adjust to your profile
| Profile | Adjustment |
|---|---|
| Home during the day (remote work, retirees) | -10% capacity (high self-consumption) |
| Away during the day | +10-15% (need battery or more panels) |
| With AC 5 months/year | +15-20% (heavy summer consumer) |
| Home with heated pool | +25-30% |
| EV to charge | +30-50% depending on use |
| Holiday home (3 months/year) | -30% (don’t oversize) |
Real-world cases: panels by profile
🏠 Case A — Standard 3-bed Algarve family
Profile: 4 people, 5,500 kWh/year, evening presence, no major AC – Calculation: 5,500 ÷ 1,700 = 3.2 kWp → adjusted to 4 kWp – 10 panels × 420 Wp – Roof area: 20 m² –
🏖 Case B — 2-bed holiday home in Lagos
Profile: Couple, 1,500 kWh/year (3 months use), surplus for sale – Calculation: 1,500 ÷ 1,700 = 0.9 kWp → adjusted to 2 kWp – 5 panels – Roof area: 10 m² –
🏘 Case C — 5-bed villa with AC and pool
Profile: 4 people + occasional rentals, 9,500 kWh/year, AC 6 months, summer pool – Calculation: 9,500 ÷ 1,700 = 5.6 kWp → +25% pool = 7 kWp – 17 panels – Roof area: 35 m² –
🏨 Case D — Active Albufeira holiday rental
Profile: Premium AL, 12,000 kWh/year, permanent AC, heated pool – Calculation: 12,000 ÷ 1,700 = 7 kWp → +30% AL summer peak = 9 kWp – 22 panels – Roof area: 45 m² – With 10 kWh battery for late uses –
Constraints to verify before finalising
🏠 Usable roof area
Check: – Orientation: ideal South (can deviate ±30° without major loss) – Tilt: 25-35° optimal in the Algarve – Shade: trees, chimneys, neighbours? Account for morning/midday/afternoon shading – Antennas / outdoor AC unit: plan around them – Access: cable runs to inverter, panel connection
⚡ E-Redes contractual capacity
If you have a 3.45 kVA contract (very common in rentals), you can’t connect a > 3.45 kVA install without upgrading capacity with E-Redes (~€50-100).
🏛 Local planning rules
Some areas (historic centres, classified villages) impose: – Panel colour (often only black panels) – Visual orientation from the street – Distance from boundaries
➡️ Check with your Câmara Municipal.
💰 Budget : https://climedge.pt/en/solar-pre-study/
The classic mistake: sizing on roof area, not consumption
Wrong thinking: “I have 60 m² of roof, I can fit 30 panels!” Right thinking: “I use 5,500 kWh/year, I need 4-5 kWp.”
Why? Surplus buyback at €0.05/kWh isn’t profitable in 2026. Better a right-sized install than a big one with 60% poorly-valued surplus.
➡️ Unless you’re planning an EV, a pool, or additional AC — then anticipate by slightly oversizing.
Frequently asked questions
Can I start small and add panels later?
Yes — it’s a common strategy. But plan an oversized inverter from the start (e.g. 6 kW for a 4 kWp install) to accept future extension.
My roof is flat — should I tilt the panels?
Yes — on a tilted structure of 10-15° minimum (otherwise dust accumulates and performance degrades). Extra cost: ~€50-80/panel for the tilt structure.
What happens if I exceed 30 kWp?
You move to a different regulatory category (B to C). Heavier procedures: prior DGEG registration, paid E-Redes connection study (~€500-1,500), 2-4 month delays.
Should the battery match panel capacity?
Not at all — both are sized independently. Battery sizing depends on consumption hours, panels on total consumption.
How much do panels actually produce in year 1?
In Portugal, average 1,600-1,800 kWh/year/kWp in year 1 (real irradiation). Then 0.5% degradation per year (Tier-1 manufacturer data). At 25 years, you’re still at 88% of initial production.
Can I install more than my consumption?
Yes, but surplus is poorly valued (€0.05/kWh vs €0.22 buy). Except in special cases (EV anticipation, pool, growing AL), stick to 100-120% of consumption.
Is the inverter sized to the panels or vice versa?
You pick the inverter first (in kW), then panels are wired in strings to match the inverter’s input voltage. An experienced installer optimises both together.
Our solar pre-study service
Rather than calculating manually, start a free CLIMEDGE pre-study: – Enter your exact address – PVGIS calculation (official EU tool) with your orientation + tilt – Enter your 12-month consumption – 3 quoted scenarios (no battery, with battery, optimised self-consumption) – Personalised report within 24h
🔆 Start your free solar pre-study — personalised results, no obligation.
Read further
- 📄 Solar panels in the Algarve: worth it in 2026?
- 📄 Should you add a battery to your Algarve solar setup?
- 📄 DGEG and E-Redes procedures for solar PV
- 📄 Central inverter, micro-inverters or optimisers (coming soon)
About the author — Grégory FRANCHI runs CLIMEDGE, a company specialising in residential solar PV and air conditioning across the Algarve.
📧 info@climedge.pt — 🌐 climedge.pt