Every homeowner considering solar in Singapore asks the same question: how many solar panels do I need? The answer depends on your electricity consumption, your roof, and the panels you choose.
This guide gives you the exact formula, worked examples for every landed property type, and the real-world factors that determine your final panel count.
The Simple Formula: How Many Solar Panels You Need
Here is the core equation that every solar sizing calculation starts with:
Monthly kWh consumption ÷ 125 kWh per panel per month = number of panels needed
That's it. Three numbers. Let's break down where each one comes from, why 125 kWh is the benchmark, and how to adjust the result for your specific situation.
Step 1: Find Your Monthly Electricity Consumption
Your electricity bill from SP Group is the starting point. Every SP bill shows your monthly consumption in kilowatt-hours (kWh). This is the single most important number in your solar sizing calculation.
How to Read Your SP Bill
On your SP bill, look for "Electricity Usage" or "Total kWh". If you're on an OEM plan with a retailer like Geneco or Keppel, your retailer bill shows the same figure.
If you only know your dollar amount, divide your bill by the prevailing tariff rate. As of 2026, the SP regulated tariff is about S$0.2911/kWh. OEM rates range from S$0.25 to S$0.30/kWh. For quick estimates, dividing by S$0.29 works well — a S$400/month bill translates to roughly 1,379 kWh/month.
For a deeper dive into how OEM electricity plans interact with solar, read our guide to OEM electricity plans and solar.
Typical Monthly Consumption by Home Type in Singapore
- Terrace house: 700–1,500 kWh/month (S$200–S$450/month)
- Semi-detached house: 1,200–2,400 kWh/month (S$350–S$700/month)
- Detached / Bungalow: 2,400–4,500 kWh/month (S$700–S$1,300/month)
- Good Class Bungalow (GCB): 4,000–8,500+ kWh/month (S$1,200–S$2,500+/month)
These ranges are wide because consumption depends on occupant count, pool ownership, aircon efficiency, and EV charging. A semi-D with a family of six running four aircon units and an EV charger consumes far more than a retired couple in the same house type.
For a complete overview of solar for every property type, see our complete solar guide for Singapore in 2026.
Step 2: Calculate Solar Panel Output in Singapore
Singapore receives an average of 4.5 peak sun hours per day year-round. This is the equivalent number of hours at full-rated solar irradiance — not total daylight hours, which are closer to 12. The 4.5 figure accounts for cloud cover, haze, humidity, and the angle of the sun throughout the day.
The Panel Output Formula
Daily output per panel = Panel wattage × 4.5 peak sun hours × 0.85 system efficiency
The 0.85 factor (15% system losses) accounts for inverter conversion (2–4%), wiring losses (1–2%), temperature derating in Singapore's heat (3–5%), soiling (1–2%), and module mismatch (1–2%). Some systems achieve 0.87, others fall to 0.82 — 0.85 is a reliable planning figure backed by years of tropical field data.
Why 60 kWh Per Panel Per Month Is the Benchmark
Using a 540W AIKO ABC panel — the premium panel we install at Sunollo — the calculation looks like this:
- 540W × 4 hours =Estimated 2 kWh per day after transfer losses
- 2kWh per day× 30 days = ~60kWh/month per panel
This is a conservative, bankable number. Well-oriented panels with minimal shading often produce 128–135 kWh/month in Singapore. We use 125 kWh to ensure your system meets or exceeds projections.
Learn more about the AIKO ABC panel technology in our AIKO ABC N-type panel deep dive.
Step 3: Account for Your Goals — How Much Do You Want to Offset?
Not every homeowner wants — or needs — to offset 100% of their electricity consumption. Your goal changes the panel count significantly.
100% Offset
Your system generates as much electricity annually as you consume. To achieve true 100% offset, you'll typically need to oversize by 10–15% because the buy-back rate is lower than your purchase rate and some generation is lost to timing mismatches.
70–80% Offset (The Sweet Spot)
Covering 70–80% of consumption delivers the best ROI for most homes. You capture high-value daytime consumption, avoid diminishing returns from oversizing, and keep the investment manageable. Monthly savings typically exceed financing payments from day one.
Budget-Constrained Sizing
If your roof fits 20 panels but your budget stretches to 12, that's fine. A 12-panel system generates roughly S$350–S$440/month in savings and pays for itself in 4–5 years. You can add more panels later if your inverter is sized for expansion.
For a detailed breakdown of costs and ROI, see our solar panel cost guide for Singapore.
Solar Panel Sizing Table by Property Type
Here's how the formula translates across Singapore's landed property types:
HDB Flats
HDB residents cannot install individual rooftop solar systems. Solar on HDB blocks is managed through the national SolarNova programme, where HDB partners with solar developers to install panels on common rooftop areas. Individual flat owners benefit indirectly through reduced common area electricity charges. For a full explanation of what's available for HDB residents, read our HDB solar guide.
Terrace Houses
- Typical consumption: 700–1,500 kWh/month (S$200–S$450/month)
- Panel count: 8–18 panels
- System size: 4–9 kWp
- Usable roof area: 25–55 m² (after obstructions)
Terrace houses have the most constrained roof area. The typical roof fits 10–14 panels, with corner terraces accommodating up to 18 on a wrap-around roof. A north-facing main slope produces 10–15% less than south-facing. Our terrace house solar guide covers layout strategies for narrow roofs.
Semi-Detached Houses
- Typical consumption: 1,200–2,400 kWh/month (S$350–S$700/month)
- Panel count: 15–25 panels
- System size: 7–12 kWp
- Usable roof area: 45–80 m²
Semi-Ds offer more roof area than terraces, often with multiple planes for panels on both the main roof and rear extensions. The shared wall limits one side, but remaining orientations provide excellent coverage. For detailed strategies, see our semi-detached solar guide.
Detached Houses and Good Class Bungalows
- Typical consumption: 2,400–8,500+ kWh/month (S$700–S$2,500+/month)
- Panel count: 25–60+ panels
- System size: 12–30 kWp
- Usable roof area: 80–200+ m²
Detached homes and GCBs have both the highest consumption and the most roof area. Systems of 30–60 panels are common. Pool pumps, large-capacity aircon, and multi-zone climate control drive consumption where solar delivers S$1,000–S$2,000+/month in savings. Read our GCB solar guide for large-estate strategies.
Real Examples: Sizing Calculations for Three Singapore Homes
Let's walk through three real-world scenarios using the formula.
Example 1: Corner Terrace — S$300/Month Electricity Bill
- Monthly consumption: S$300 ÷ S$0.291 = 1,030 kWh/month
- Panels needed (100% offset): 1,030 ÷ 125 = 8.2 panels
- Recommended system: 10 panels (4.8 kWp)
We round up to 10 panels for two reasons. First, a buffer accounts for heavier cloud cover days. Second, consumption tends to rise over time — new appliances, a home office, or more aircon use. Ten panels at 125 kWh each generate 1,250 kWh/month, a comfortable 21% buffer.
Estimated monthly savings: S$300–S$365/month, depending on your self-consumption ratio and OEM plan rate.
Example 2: Semi-Detached — S$500/Month Electricity Bill
- Monthly consumption: S$500 ÷ S$0.291 = 1,717 kWh/month
- Panels needed (100% offset): 1,717 ÷ 125 = 13.7 panels → 14 panels
- Recommended system: 18–20 panels (8.6–9.6 kWp)
Why 18–20 instead of 14? This homeowner plans to buy an EV within two years. Home EV charging adds 250–350 kWh/month. By sizing for 18–20 panels now, the system is future-proofed without costly retrofitting. Twenty panels generate 2,500 kWh/month — enough for current consumption plus one EV.
Estimated monthly savings: S$500–S$580/month today, rising to S$570–S$680/month once the EV replaces fuel costs.
Example 3: Detached Bungalow — S$1,200/Month Electricity Bill
- Monthly consumption: S$1,200 ÷ S$0.291 = 4,124 kWh/month
- Panels needed (100% offset): 4,124 ÷ 125 = 33 panels
- Recommended system: 35–40 panels (16.8–19.2 kWp) with a 15 kWh home battery
We recommend 35–40 panels paired with a 15 kWh battery. The battery captures excess midday generation and discharges it during the evening peak, pushing self-consumption from a typical 35–45% to 70–85%. The additional panels beyond the base calculation ensure the battery charges fully on most days.
Estimated monthly savings: S$1,050–S$1,350/month, including the battery's contribution to shifting consumption away from grid purchases.
Why Panel Efficiency Changes the Equation
Not all solar panels are created equal, and the efficiency rating of your panels directly affects how many you need.
The AIKO ABC panel at 24.2% efficiency generates approximately 125 kWh per panel per month in Singapore conditions. A standard tier-1 panel at 20.5% efficiency — using the same physical footprint — generates approximately 106 kWh per panel per month.
That 19 kWh/panel/month difference compounds across a system:
- 10-panel system: AIKO produces 1,250 kWh/month vs standard at 1,060 kWh/month — a 190 kWh/month difference
- 190 kWh × S$0.29/kWh = S$55/month in additional savings with the higher-efficiency panel
- Over 25 years, that's S$16,500+ in extra generation from the same number of panels and the same roof area
Alternatively, higher efficiency means fewer panels to reach the same output. A homeowner needing 1,250 kWh/month requires 10 AIKO panels or 12 standard panels. For roof-constrained properties like terrace houses, this difference often determines whether solar is financially viable at all.
Our guide to the best solar panels in Singapore compares efficiency, warranties, and long-term value across leading panel brands.
Factors That Reduce the Number of Panels You Can Install
The formula tells you how many panels you need. Your roof determines how many you can fit. Several real-world factors reduce usable roof area:
Roof Shading
Nearby trees, neighbouring buildings, and architectural features cast shadows that reduce output. Even partial shading on one panel can drag down an entire string's performance. Modern microinverter and power optimiser systems mitigate this by allowing each panel to operate independently, but shaded panels still produce less.
Roof Orientation
Singapore sits at 1.3°N latitude, nearly on the equator. This means the sun passes almost directly overhead, and east-west orientations perform well. However, north-facing roof slopes lose approximately 10–15% compared to optimal south-facing or flat orientations. For most homes, this means the north-facing slope is still worth using — just factor the lower yield into your panel count calculation.
Roof Obstructions
Vents, water tanks, satellite dishes, antennas, skylights, and roof access hatches all consume space that panels cannot occupy. Setback requirements — the mandatory clearance from roof edges — further reduce usable area. On a terrace house, obstructions can eliminate 20–30% of the theoretical panel capacity. On a large bungalow roof, the impact is proportionally smaller.
Structural Limitations
Older homes may lack the roof structure to support a full array. Each panel weighs 22–25 kg plus 3–5 kg of mounting hardware. A 20-panel system adds roughly 500–600 kg distributed across the roof. Most modern homes handle this easily, but pre-1990 properties may require structural assessment. Our installation process guide explains how we assess structural readiness.
To understand how real-world conditions affect the numbers you see in proposals, read our analysis of solar production reality versus simulation.
When to Add a Battery — and How It Changes Sizing
A home battery fundamentally changes the solar sizing equation. Without a battery, the goal is to match daytime generation to daytime consumption. With a battery, you can deliberately oversize your panel array to generate surplus energy during the day, store it, and use it at night.
How a Battery Changes Your Panel Count
Without a battery, a typical home self-consumes only 35–45% of its solar generation. The rest is exported at a lower buy-back rate. With a battery, self-consumption jumps to 70–85%.
To take full advantage of a battery, add 3–5 extra panels beyond the basic formula. These ensure the battery charges fully on most days, including those with intermittent cloud cover. A half-empty battery is an underperforming asset.
When Does a Battery Make Sense?
- High evening consumption: Homes where occupants are away during the day but run heavy loads (aircon, cooking, entertainment) in the evening benefit most from stored solar energy
- Large systems (>10 kWp): The economics improve at scale because excess generation that would be exported at low buy-back rates is instead stored for high-value evening use
- Backup power needs: If power continuity matters — home offices, medical equipment, security systems — a battery provides hours of backup during grid outages
- Future-proofing: As Singapore moves toward time-of-use tariffs, stored solar energy used during peak-rate periods will become increasingly valuable
For a comprehensive guide to home battery storage, explore our Singapore home battery guide featuring the Abundance Pro.
When to Plan for EV Charging
If you own or plan to purchase an electric vehicle, factor that consumption into your solar sizing before installation — not after.
How Much Energy Does an EV Add?
The average Singaporean drives 12,000–15,000 km per year. At 15–18 kWh per 100 km, that translates to:
- 150–225 kWh/month per EV for average driving
- 250–350 kWh/month per EV including buffer for longer drives and aircon load
For sizing purposes, add 250–350 kWh/month per EV to your household consumption figure before applying the formula. For two EVs, add 500–700 kWh/month.
Example: Semi-D With One EV Planned
Base consumption: 1,717 kWh/month. With one EV: 1,717 + 300 = 2,017 kWh/month. Panels needed: 2,017 ÷ 125 = 16.1 panels → 18 panels recommended.
Without future-proofing, you'd install 14 panels and find yourself short within a year. Adding panels later costs more per panel due to mobilisation and potential inverter upgrades.
Our solar EV charging guide covers charger selection, load management, and integration with your solar system.
Single-Phase vs Three-Phase: The 5 kWp Threshold
Your home's electrical phase configuration imposes a hard constraint on solar system size that many homeowners don't discover until late in the process.
Single-Phase Homes
Most terrace houses and some older semi-Ds in Singapore are wired for single-phase power. Under EMA (Energy Market Authority) regulations, single-phase homes are limited to a maximum solar system size of 5 kWp. That's approximately 10 panels using 480W AIKO ABC panels.
For many terrace homeowners, 5 kWp is sufficient to offset 60–80% of consumption. But if your consumption exceeds 1,500 kWh/month, you'll hit the ceiling before reaching full offset. In these cases, upgrading to three-phase power is worth considering — though it involves rewiring and SP Group coordination, typically costing S$3,000–S$8,000 depending on the property.
Single-phase homes with solar also face a higher risk of system tripping during high-generation, low-consumption periods. Our guide on why single-phase solar systems trip frequently explains the technical reasons and solutions.
Three-Phase Homes
Three-phase homes — most semi-Ds and all detached properties — can install solar systems well beyond 5 kWp, typically up to 30+ kWp for residential properties. The three-phase connection distributes load across three circuits, preventing the voltage rise issues that constrain single-phase systems.
If you're in a single-phase home and your solar sizing calculation calls for more than 10 panels, discuss the three-phase upgrade option with your installer early. The upgrade cost is often recovered within 1–2 years through the additional solar savings it enables.
The Sunollo Approach: Precision Sizing for Your Specific Roof
The formula gives you an excellent starting estimate. But it can't see your roof — the shadow from your neighbour's extension at 2pm, the water tank blocking four panel positions, or the perfectly-angled south-facing plane. At Sunollo, we go beyond generic calculations:
- Drone-based roof survey: We capture high-resolution imagery and 3D models of your roof to identify every usable square metre
- Hour-by-hour shading analysis: We model shadow patterns across every hour of every month, identifying zones that receive consistent irradiance versus areas affected by seasonal shading
- Panel-level layout optimisation: We design the exact placement of each panel to maximise total system generation, not just fit the most panels possible — sometimes fewer panels in better positions outperform more panels in compromised positions
- Consumption pattern matching: We analyse your 12-month consumption history to size the system for your actual usage pattern, not just a monthly average, including seasonal peaks and troughs
- Future-proofed design: We factor in your plans for EVs, batteries, home expansions, and lifestyle changes so the system you install today remains optimally sized for the next decade
The result is a system proposal that tells you exactly how many panels, which positions, what expected generation, and what financial return — specific to your home, not a generic calculator output.
Frequently Asked Questions
Can I start with fewer panels and add more later?
Yes, but your inverter must be sized to accommodate future additions. Adding panels later costs 15–25% more per panel due to separate mobilisation, scaffolding, and EMA re-application. If you'll likely want more panels within 2–3 years, it's almost always cheaper to install them upfront.
What if my roof can't fit enough panels to offset 100%?
This is common with terrace houses. If your roof fits 12 panels but you need 18 for full offset, install the 12 — they'll still offset 65–70% of your bill and deliver excellent ROI. Partial offset systems often have better returns than full-offset systems because every kWh they produce is consumed directly by the home (high self-consumption ratio), rather than exported to the grid at lower buy-back rates.
Do I need to account for panel degradation over time?
Premium N-type panels like the AIKO ABC degrade at 0.4–0.5% per year; older technology at 0.5–0.7%. Over 25 years, a quality panel retains 87–90% of original output. This degradation is factored into our 125 kWh/panel/month figure. By year 25, expect about 110–113 kWh/month — still highly productive.
How does the net metering buy-back work in Singapore?
Under Singapore's simplified credit treatment (SCT), excess solar energy exported to the grid is credited against your bill at the prevailing tariff (about S$0.2911/kWh). If you export more than you import, the credit rolls over — but you won't receive cash. This is why maximising self-consumption (using solar directly or storing in a battery) is always more valuable than exporting.
How many panels can I fit on a flat roof vs a pitched roof?
Flat roofs require tilt frames angled at 5–10°, creating inter-row spacing that reduces panel density. A flat roof accommodates roughly 60–70% of the panel count a similarly-sized pitched roof holds. However, flat roofs face no orientation penalty since panels can be aimed in the optimal direction.
What happens during a power outage — do my solar panels still work?
Without a battery, your panels will not power your home during an outage — the inverter shuts down for safety (anti-islanding). With a battery that includes backup capability, your home can run on stored solar energy for 4–12 hours depending on capacity and load.
Is there a maximum number of panels I can install on my home?
The practical limit is your roof area and structural capacity. Single-phase homes are capped at 5 kWp (~10 panels); three-phase homes can go much higher. Systems above 30 kWp may require additional EMA approvals, but most landed homes fall within standard limits.
How accurate is this formula compared to a professional assessment?
The formula gives you a panel count typically within 10–15% of a professional assessment. The professional assessment adds precision through your specific roof geometry, shading profile, and electrical configuration. Think of the formula as your budgeting starting point — the assessment confirms exact numbers.
Your Next Step: From Formula to Proposal
You now know the formula, the variables, and the adjustments for your specific situation. You can estimate your panel count with confidence. But the gap between a formula estimate and an installation-ready design is where expertise matters.
At Sunollo, we provide a detailed, no-obligation solar assessment with a precise panel count, layout, generation projection, and financial analysis for your property. We use AIKO ABC panels — the highest-efficiency residential panels in Singapore — paired with the Abundance Pro battery system when appropriate.
Whether your calculation says 10 panels or 40, we'll confirm the exact number and demonstrate your expected savings over the next 25 years.
Ready to move from estimate to exact? Start with our complete solar guide or explore the full cost breakdown to continue your research.
