The 3-Step Method
You can estimate your panel count in five minutes with three numbers:
- Your daily consumption (units/kWh). Take your monthly bill’s unit count and divide by 30. A 3,000-taka bill is very roughly 250–300 units/month → 8–10 units/day (tariff-dependent).
- Daily generation per kW in Bangladesh. Use 3.5–4.5 units per day per kW of panels (yearly average; monsoon lower, dry season higher).
- Panel wattage. Standard panels today are 550W–585W — see current panel sizes and prices.
Formula: Required kW = daily units to offset ÷ 4. Panel count = (kW × 1000) ÷ panel wattage.
Worked Examples
| Home Type | Daily Use | System Size | Panels (585W) | Roof Needed |
|---|---|---|---|---|
| Small flat (fans, lights, TV, fridge) | 5–7 units | 1.5–2kW | 3–4 | ~100–140 sq ft |
| Medium home (+ 1 AC used evenings) | 10–14 units | 3–3.5kW | 5–6 | ~180–210 sq ft |
| Large home (2 AC + water pump) | 18–25 units | 5–6kW | 9–10 | ~320–360 sq ft |
| Very large / duplex | 30–40 units | 8–10kW | 14–18 | ~500–650 sq ft |
These are estimation starting points. The full sizing method accounts for the factors below.
Why the Simple Formula Isn’t the Final Answer
- When you use electricity matters. Panels generate at noon; if your consumption peaks at 8 PM, you need either a battery or a grid arrangement, and the design changes completely.
- Backup goals change everything. If your priority is running fans and lights through load shedding, the battery — not the panel count — is the design driver.
- Shading is brutal. A water tank’s shadow crossing one panel for two hours can cut a whole string’s output. This is why we insist on a physical site visit before quoting.
- Roof reality. Usable roof area is always less than total roof area — walkways, tank bases, railings, future rooms. A 585W panel needs its 2.28 × 1.13 m footprint plus service access.
- Inverter matching. Panel count must form valid strings within the inverter’s voltage/current window — sometimes 9 panels beats 10.
Common Mistakes
- Sizing to the highest bill of the year. Sizing for April’s AC peak leaves the system oversized (and money wasted) for eight months. Size to the pattern, not the peak.
- Forgetting degradation. Panels lose ~0.4–0.55%/year. A system sized with zero margin underperforms expectations by year 5.
- Counting nameplate watts as real watts. Heat, dust, cable losses and inverter efficiency take 15–25% off nameplate in real conditions. Honest designers size with these losses declared — see our ROI and payback guide for realistic numbers.
- Buying panels before the design. Panel count is an output of design, not an input. Design comes first.
Frequently Asked Questions
How many solar panels do I need for a 3-bedroom house in Bangladesh?
Typically 5–10 panels (3–6kW) depending on AC usage and whether you want backup. The bill-based method above narrows it to your case in minutes.
How many panels for 1kW?
Two modern panels (2 × 550W or 2 × 585W). Full costs in 1kW solar panel price in Bangladesh.
Can I add more panels later?
Yes, if the inverter capacity and roof structure were planned for it. Say so before your first purchase.
How much will the panels cost me?
Multiply your panel count by current per-watt rates in the solar panel price guide — then remember panels are only 30–40% of the installed system cost.
Want the exact number for your roof, calculated from your actual bill? Send us your electricity bill via the quotation form — Frostec engineers size the system from your real data, free.
