Choosing the right solar system size (kW) is the step that decides your savings. If you install too small, you’ll still pay a high bill. If you install too big, you may overspend and take longer to recover your investment. The simplest way to size solar in Bhopal is to start from your monthly electricity units (kWh) and match it with realistic solar generation for Madhya Pradesh.
A practical rule of thumb in India is: 1 kW rooftop solar generates ~3.5 to 4.5 units/day on average, with good sunny days higher and cloudy/rainy days lower. (Fuji Electric India)
For Madhya Pradesh, a common estimate is around ~4.5 units/day per kW on average. (IREC Consulting)
Step 1: Find your monthly units (kWh) from the bill
Look at your electricity bill and note:
- Monthly consumption in Units (kWh)
- Your sanctioned load (if mentioned)
- Whether your usage is stable or seasonal (summer AC spikes)
If your bill shows money only, it still usually shows “units consumed” somewhere—use that.
Step 2: Convert monthly units to daily units
Simple math:
- Daily units = Monthly units ÷ 30
Example:
- If your home uses 450 units/month, daily use ≈ 450 ÷ 30 = 15 units/day
Step 3: Estimate the kW you need (quick formula)
Use a realistic daily generation number.
For Bhopal/MP, you can estimate with 4.5 units/day per kW as a working average. (IREC Consulting)
Formula:
- Required kW ≈ Daily units ÷ 4.5
Example:
- Daily use ≈ 15 units/day
- Required size ≈ 15 ÷ 4.5 = 3.33 kW
So a 3 kW to 4 kW system is usually the right range (final depends on roof space, shading, and your goal).
Quick sizing guide (based on monthly units)
(Approximate, for easy understanding—actual may vary with shade/tilt/roof direction.) (Fuji Electric India)
Points:
- 150–250 units/month → ~1.5–2.5 kW
- 250–350 units/month → ~2.5–3.5 kW
- 350–500 units/month → ~3.5–5 kW
- 500–650 units/month → ~5–6.5 kW
- 650–900 units/month → ~6.5–9 kW
Tip: If your goal is “maximum bill reduction,” you size closer to your higher usage months (summer). If your goal is “best ROI,” you size closer to your average yearly use.
Step 4: Decide your offset goal (don’t always aim for 100%)
Many homeowners think: “I want to cover 100% of my bill.” Sometimes it’s not necessary.
Points:
- 70–90% offset is often a sweet spot for cost vs savings
- If your roof is limited or shaded, a slightly smaller system can still give great returns
- If you plan to add appliances later, you may size slightly higher now
Step 5: Consider future usage (important in Bhopal summers)
Solar sizing should include what you’re likely to add in the next 1–3 years.
Points:
- Adding 1–2 ACs can significantly increase summer units
- Water heater/geyser, induction cooking, and pumping add load
- If you plan an EV in future, tell your installer early (it changes sizing and wiring planning)
Practical rule:
- If you expect your usage to increase soon, add +10% to +25% buffer to your calculated kW (only if your roof allows).
Step 6: Check roof space (this can limit the final kW)
Even if your bill suggests 5 kW, your roof might only support 3 kW shadow-free.
A widely used benchmark is:
- 1 kW rooftop solar needs ~12 sq. meters (about 130 sq. ft.) of flat, shadow-free roof area (preferably south-facing). (SECI)
So roughly:
- 3 kW → ~390 sq ft
- 5 kW → ~650 sq ft
(These are indicative—panel efficiency, layout, and walkway/spacing can change it.)
Step 7: Understand why “4–5 units/day per kW” can change
This avoids wrong expectations.
Main factors that change output:
- Shade (tanks, parapet walls, nearby buildings)
- Roof direction + tilt
- Dust and cleaning frequency
- Inverter efficiency and wiring quality
- Season and cloud cover (monsoon months drop generation) (Fuji Electric India)
So always treat generation as a range, not a fixed number.
A smarter way: Use the official rooftop solar calculator (optional but useful)
If you want an indicative recommended capacity using your state and monthly bill/roof area, the MNRE National Portal for Rooftop Solar provides a calculator you can use. (Solar Rooftop API)
(Your installer can also do this professionally with a site survey.)
Important description
Selecting the correct kW based on your electricity consumption ensures you don’t overspend on a system that’s too large—or underinstall and still face high bills. Use your monthly units, a realistic MP generation estimate (~4.5 units/day per kW), and your available shade-free roof area to choose the right range. (IREC Consulting)
Want to know how many kW you need in Bhopal? Get a free roof survey + system sizing estimate today—based on your bill units, roof layout, and future appliance plan.