Solar calculator for a new house
Building or buying a home and don’t have an electricity bill yet? Choose your appliances and how you use them, and we estimate your units and a solar size range to match. You don’t need to give a phone number.
- 1Home
- 2Cooling
- 3Kitchen
- 4Lights
- 5Water, EV
- 6Plans
- 7Result
How the estimate is worked out
- For each appliance, we work out the units it uses on a day it runs. Lights and fans use their wattage and hours. Fridges, routers and CCTV run all day. Washing machines, irons and ovens are counted per load or use, and geysers per hot-water use, because a geyser heats its tank and then switches off.
- ACs are counted at an average draw for their size and type. The compressor cycles on and off, so that average sits well below the rating on the box.
- In Punjab, use changes a lot with the season. ACs run only in the months you choose, fans for about 8 months, coolers for about 4 and geysers mainly in winter. That gives a yearly total and a separate peak-summer month.
- The yearly units are divided by what a kW of panels makes in Punjab: about 1,224 units a year after losses, give or take 10% for roof direction, shade and weather, which is why the answer is a range.
- An EV and anything you plan to add are shown separately, so you can size for now or for later.
The same generation figures drive the bill calculator, so the two agree once you have a real PSPCL bill to check against.
What an AC uses in a Punjab summer
Average units an hour while the AC is switched on, the figures the calculator uses. A hotter room, a lower thermostat setting or an older AC uses more.
| AC size | Inverter | Non-inverter | Inverter, 8 hours a day for 5 months |
|---|---|---|---|
| 0.75 ton | 0.45 | 0.65 | 540 units |
| 1 ton | 0.6 | 0.85 | 720 units |
| 1.5 ton | 0.9 | 1.25 | 1,080 units |
| 2 ton | 1.2 | 1.65 | 1,440 units |
| 2.5 ton | 1.5 | 2.05 | 1,800 units |
| 3 ton | 1.8 | 2.45 | 2,160 units |
Geysers are counted per use: about 1 unit to heat a 25 litre tank from cold in winter. For more on ACs and solar, see solar for a 1.5 ton AC.
Planning solar while you build
Each of these is cheap to do while the house is going up and expensive to change once it is finished.
Ask PSPCL for enough sanctioned load
An on-grid rooftop system can be at most 100% of your sanctioned load. If you plan a 5 kW system, apply for at least 5 kW on the new connection. Raising it later means a separate load-enhancement application before the solar one.
Keep the roof clear and shade-free
Allow about 100 sq ft of open roof per kW. Put the stair cabin and water tanks on the north side where they won’t shade the panels, and keep the south-facing area clear.
Leave a path for the cables
A conduit from the roof to where the inverter will sit, near the main distribution board, saves chasing walls later. The inverter needs a shaded, ventilated spot.
Decide early about backup
If you want lights and fans to run during power cuts, wire them to a separate backup board now. A hybrid system can then run just that board from its battery. See hybrid solar systems and on-grid, off-grid or hybrid.
Subsidy timing
The PM Surya Ghar subsidy needs the house’s own PSPCL connection in the owner’s name, and approval before installation. Plan the solar for after the connection is live. The subsidy guide has the steps.
A typical case: two 1.5 ton inverter ACs, two 25 litre geysers, five fans, twelve LED bulbs, a fridge, a TV and the usual kitchen and laundry.
Worked example: a three-bedroom home in Mohali
Recommended solar capacity
4 to 4.5 kW
For about 430 units a month on average. It’s a range because roof direction, shade and weather change what the panels make.
Estimated electricity use
| A day, on average | 14 units |
|---|---|
| A month, on average | 430 units |
| A month in peak summerACs, coolers and fans all running | 680 units |
| A year | 5,200 units |
| Connected loadEverything switched on at once, in kW | 12.9 kW |
One unit is one kWh. Connected load decides the sanctioned load to ask PSPCL for on the new connection, and an on-grid system can’t be larger than the sanctioned load. The solar size itself comes from the units.
Over Punjab’s 300 free units
Above 300 units a month, general-category homes pay for every unit, so solar has a real bill to cut. Because of the free units, the system that takes a bill to zero can be smaller than one that covers all your use. Once you have a few PSPCL bills, the bill calculator works that out exactly.
Three ways to size it
Which one suits you depends on your budget and your plans. They run from covering the basics to leaving room for what you add later.
-
Essential coverage
2.5 to 3.5 kW
Covers about 70% of your current yearly use. The rest, mostly summer AC use, comes from the grid.
- Example system
- 3 kW
- Panels
- about 6 × 550 W
- Roof area
- about 300 sq ft
- Solar generation
- 3,300 to 4,050 units a year
- Covers
- about 70% of current use
-
Recommended coverage
4 to 4.5 kW
Sized for all of your current yearly use.
- Example system
- 4 kW
- Panels
- about 8 × 550 W
- Roof area
- about 400 sq ft
- Solar generation
- 4,400 to 5,400 units a year
- Covers
- about 94% of current use
-
Higher coverage
4.5 to 5.5 kW
Leaves about 20% room for appliances you add later.
- Example system
- 5 kW
- Panels
- about 10 × 550 W
- Roof area
- about 500 sq ft
- Solar generation
- 5,500 to 6,750 units a year
- Covers
- about 117% of current use
Where the units go
| Group | Units a month | Share |
|---|---|---|
| Cooling | 180 | 41% |
| Lights and fans | 110 | 24% |
| Kitchen | 47 | 11% |
| Water heating | 46 | 11% |
| Electronics | 28 | 7% |
| Water pumps | 15 | 3% |
| Laundry | 13 | 3% |
Every appliance
| Appliance | Units a year |
|---|---|
| 2 × 1.5 ton inverter AC | 2,150 |
| Ceiling fans, regular × 5 | 900 |
| 25 litre geyser × 2 | 550 |
| Refrigerator, standard | 370 |
| LED bulbs (12 × 9 W) | 240 |
| Domestic water pump (1 × 1 HP) | 180 |
| TV, up to 43 inch | 130 |
| Microwave | 110 |
| Washing machine | 100 |
| Laptop | 91 |
| Wi-Fi router | 88 |
| LED tube lights (2 × 20 W) | 73 |
| Exhaust fans × 2 | 58 |
| Mixer grinder | 55 |
| Iron | 52 |
| Phone and small chargers × 3 | 33 |
| RO water purifier | 29 |
Turn this into a quote
Send us the estimate and your plans or site address. We check the roof, shade and your sanctioned load and come back with a system and a price.
Treat this as a starting point for a conversation with us. Real use depends on your family’s habits and the season, and AC use swings the most. Solar output depends on shade, roof direction and tilt, the panels and inverter chosen, and the weather. It assumes 1,224 units per kW a year, give or take 10%. We fix the size after a site survey, and we don’t promise a particular bill, saving or payback.
Next steps
- Solar calculator from your electricity billOnce the house has a few months of PSPCL bills.
- 3 kW, 5 kW and 8 kW system pricesWhat each size costs in Punjab, after the subsidy.
- Rooftop solar in Mohali and across PunjabWhere our own team installs, and where our dealers do.
- Contact RSK Solar EnergyPhase 8B, Mohali. Call, WhatsApp or visit.
Questions we are asked
How do I work out solar for a new house with no electricity bill?
Estimate the units your appliances will use, then divide by what one kW of panels makes in a year. The calculator on this page does both: you choose your ACs, geysers, fridge, lights, fans and other appliances, and it gives your daily, monthly and yearly units and a solar size range to match. After a few months of bills, the bill calculator can check the estimate.
How much solar does a 3 BHK house in Punjab need?
It depends mostly on the ACs. A three-bedroom home with two 1.5 ton inverter ACs, used eight hours a day through summer, comes to roughly 430 units a month on average, which needs about 4 to 4.5 kW. Without ACs, the same home often stays under Punjab’s 300 free units and solar has little to save.
How many units does a 1.5 ton AC use?
We assume about 0.9 units an hour for a 1.5 ton inverter AC and 1.25 for a non-inverter one, averaged over a Punjab summer day with the compressor cycling. The rated figure on the box is higher, but an AC rarely runs flat out for a whole hour. Eight hours a day for five months comes to about 1,080 units a year for the inverter model.
Should I size solar for an EV I haven’t bought yet?
You can, and the calculator shows the EV separately so you can decide. Sizing for it now means one installation and one net-metering application. Adding panels later is also possible if the roof has room and your sanctioned load allows it, so leave space on the roof either way.
What is the difference between connected load and units?
Connected load is the power drawn if everything were switched on at once, in kW. Units (kWh) are the energy actually used over time. Solar is sized from units. Connected load matters for the sanctioned load you ask PSPCL for, and an on-grid system cannot be larger than your sanctioned load.
Can I get the PM Surya Ghar subsidy on a new house?
Yes, once the house has its own PSPCL connection in the owner’s name. You apply on the national portal with that connection’s consumer number and install after PSPCL approves feasibility. The subsidy guide covers the steps and the reasons applications get rejected.