Choosing the right solar and inverter setup for your new home is not just a green choice, it is a smart lifetime saving. With Chennai’s long summers and clear skies around Padappai and the Oragadam belt, your rooftop can quietly power your day while cutting electricity bills and grid anxiety. This guide walks you through a simple, localised method to size panels, inverter, and batteries with practical examples you can copy for house construction in Chennai.
What exactly are you sizing
• Solar panels measured in kWp decide how much power you can generate in peak sun
• Inverter in VA or kW converts DC from panels or batteries into AC for your home
• Battery bank in Ah and V stores energy for night time and outages
• Balance of system includes mounting, DC combiner, charge controller or hybrid inverter, wiring, earthing, surge protection
Quick thumb rules for Chennai and Padappai
• Average usable sun hours per day for sizing is typically 4 to 4.5 in the Chennai region
• A 1 kW rooftop system can generate about 4 to 4.5 units per day in good conditions
• For net metering and grid tie approvals, follow TANGEDCO processes and current norms
• South facing roofs with minimal shade perform best, but east west split mounts can help early and late sun
Step 1: List your essential loads
Start with devices that must run during power cuts or that you prefer to run on solar every day.
• Lighting LED 10 to 15 points
• Fans 3 to 6
• Refrigerator 200 to 300 L
• TV 32 to 50 inch
• Washing machine
• Router and laptop charging
• Water pump and mixer grinder are short duration but high draw
• Optional air conditioner choose energy efficient models if planning solar backup
Write down the wattage W and typical daily use in hours for each item. If a device shows only amps A and volts V, W equals A times V.
Step 2: Calculate your daily energy need kWh
Example for a 2BHK in Padappai
• 8 LED lights at 12 W for 5 hours equals 0.48 kWh
• 4 fans at 60 W for 8 hours equals 1.92 kWh
• Refrigerator 180 W average for 10 hours cycling equals 1.8 kWh
• TV 120 W for 3 hours equals 0.36 kWh
• Router and laptop 40 W for 6 hours equals 0.24 kWh
• Washing machine 500 W for 1 hour equals 0.5 kWh
• Miscellaneous buffer 10 percent equals about 0.53 kWh
Total daily energy is roughly 5.83 kWh or about 6 units per day. If you can shift some high draw tasks to sunny hours, the solar contribution rises without oversizing batteries.
Step 3: Decide your backup hours
For grid tied homes in Chennai with occasional outages, many owners choose 2 to 4 hours of essential backup. If your locality near Padappai has longer cuts, size for 6 to 8 hours for critical circuits only. Mark one or two rooms, the fridge, and WiFi as essential. Heavy loads like geysers and AC rarely go on backup unless you plan a large system.
Step 4: Size your inverter
Inverter power must cover the highest simultaneous wattage, not the total daily units.
• Sum of essentials that may run together in a short window
• Add starting surge for motors like refrigerator and pump about 2 to 3 times running watts
• Add a safety margin of 20 to 25 percent
From the example
• Fans 4 at once 240 W
• Lights 8 at once 96 W
• Refrigerator surge up to 400 to 500 W
• TV 120 W
• Router 20 W
Peak simultaneous is around 976 to 1,000 W. With margin, choose a 1.5 kW hybrid inverter or about 2 kVA VA rating. If you want to include a half HP water pump during daylight, consider 3 kVA.
Step 5: Size your battery bank if you want backup
Battery energy needed equals essential load in kWh times desired hours divided by depth of discharge DoD.
• Choose lithium for compact, higher cycle life and fast charging
• Lead acid tubular is budget friendly but heavier and needs maintenance
Example
• Essential continuous load at night is around 300 to 400 W fans lights router
• For 4 hours, energy is 1.6 kWh
• For lithium with 90 percent DoD, required capacity equals 1.6 divided by 0.9 which is about 1.8 kWh
• At 48 V nominal, needed Ah equals 1,800 Wh divided by 48 which is about 37.5 Ah
A standard 48 V 50 Ah lithium pack around 2.4 kWh gives good headroom. If using 24 V systems, adjust Ah accordingly. For lead acid at 50 percent DoD, you would need about double the Ah.
Step 6: Size your solar array
Panel size depends on daily units you want to offset and charging needs.
Method A daily energy
• You want 6 kWh per day
• With 4.5 sun hours and 80 percent system efficiency, array kWp equals 6 divided by 4.5 divided by 0.8 which is about 1.67 kWp
Round up to 2 kWp to cover cloudy days and seasonal dips
Method B battery charging
• Battery is 2.4 kWh
• To recharge fully in 4 sun hours with margin, panel Wh per day should be at least 3 kWh
• 3 divided by 4.5 divided by 0.8 equals about 0.83 kWp
Since you also want to run day loads, 2 kWp remains a good fit
For homes planning an AC or induction cooking on solar during the day, consider 3 to 5 kWp with net metering. Discuss your roof area and shadow pattern with an installer.
Roof area and placement tips for Padappai plots
• A 1 kWp array needs about 70 to 90 sq ft depending on module wattage and tilt
• Keep modules in full sun from 9 am to 3 pm with no tree or tank shadow
• Use hot dip galvanised structures to resist coastal humidity
• Provide a safe maintenance pathway and fall protection
• Plan inverter and battery inside a cool ventilated utility or under the staircase with proper earthing and surge protection
Off grid, grid tie, or hybrid for Chennai homes
• Grid tie with net metering best for maximum savings without batteries, needs stable grid and approval
• Hybrid gives the comfort of backup plus net metering on the same system, popular for villas around Oragadam SIPCOT where power quality can vary
• Pure off grid suits farmhouses and remote layouts but needs larger batteries and smart energy habits
Approximate bill impact
If you install 2 kWp, expect around 6 to 8 units per day season average. That can offset a large part of a small family’s consumption. Higher slab tariffs in Tamil Nadu mean faster payback when you cross free or subsidised blocks. Real world output varies with season, panel orientation, heat, cleaning, and shading. Clean panels every 15 to 20 days in dusty months around Padappai.
Sample configurations for Velammal Garden style homes
• Budget backup
1.5 kVA hybrid inverter, 48 V 50 Ah lithium 2.4 kWh, 1.5 kWp panels. Runs lights fans TV router for 4 to 6 hours.
• Family comfort
3 kVA hybrid, 48 V 100 Ah lithium 4.8 kWh, 3 kWp panels. Adds fridge and short runs of the pump in day time.
• Solar saver with AC in day
5 kW grid tie or hybrid, 5 to 6 kWp panels, optional small battery for outage ride through. Run one high star AC during sunny hours and cut bills significantly.
Compliance and safety
• Follow current TANGEDCO net metering application steps and use MNRE approved components
• Provide DC and AC surge protection, lightning arrestor, and dual earthing
• Insist on proper cable sizing, crimping, MC4 connectors, and isolators
• Keep a single line diagram and warranty documents filed for future service
How this fits your house construction in Chennai
When you design your home at Velammal Garden, leave a dedicated solar zone on the terrace. Place water tanks and dish antennas to the north side. Plan an electrical conduit from terrace to utility room during construction. If you are building a rental unit above, consider metering and a separate solar sub panel so you can allocate benefits. For layout and orientation ideas, speak to our team at velammalgarden.com and explore plot options that maximise sun exposure.
Simple worksheet you can copy
• Step A list appliances and hours
• Step B compute daily kWh
• Step C pick backup hours and essential circuits
• Step D size inverter by peak simultaneous watts plus margin
• Step E size battery by energy and DoD
• Step F size panels by daily units and charging goals
• Step G map roof area and shade, plan tilt and clearance
Keep this sheet handy during your site visit. Our advisors can help you run the numbers for your chosen plot and roof layout. Start a conversation at velammalgarden.com and book a guided tour.
Frequently asked questions
What size solar is ideal for a 2BHK in Chennai
Most 2BHK homes with efficient appliances do well with 2 to 3 kWp. This covers 6 to 10 units per day and pairs well with a 1.5 to 3 kVA hybrid inverter if you want backup. Actual size depends on your usage pattern and roof shade.
Do I need batteries or is grid tie enough for Padappai
If your locality has stable supply, grid tie with net metering offers the best return. For areas around Oragadam with occasional outages, a hybrid inverter with a small lithium pack gives comfort without oversizing.
How do I size the inverter for my home
Add the highest simultaneous watts that may run together, include motor starting surge for fridge or pump, then add a 20 to 25 percent margin. For many families this points to 1.5 to 3 kVA. If you plan to run AC or a pump on backup, choose a higher rating.
What is the payback period in Chennai
With good sun and rising tariffs, many homes see simple payback in a few years for grid tie systems. Hybrid with batteries costs more but adds resilience. Real payback depends on usage, tariff slab, equipment quality, and whether you shift tasks to sunny hours.
Can I add panels later if my consumption grows
Yes. Choose an inverter with some headroom or use microinverters for modular growth. During house construction, leave extra terrace space and pre lay conduits so that adding capacity later is simple and neat.
Final word
Solar is a once and done decision that rewards a little planning. Use the steps above to estimate your right size and talk to certified installers for a site survey. When you plan your dream home in Velammal Garden, aligning your terrace, utility room, and wiring today will make tomorrow’s energy clean, reliable, and affordable.
