How Many Solar Panels Do You Need for a 3BHK Home? A 2026 Sizing Guide

Introduction

Ask three installers how many panels a 3BHK home needs and you will get three different answers — usually because they are guessing from the size of the house rather than from the electricity it uses. Two identical 3BHK floors in the same Gurgaon sector can consume 250 units and 900 units a month depending on how many air conditioners run and for how long.

This guide gives you the actual method: how to size a system from your own bill, how many panels that translates to in 2026, how much roof it needs, and specifically how much an air conditioner adds. Five minutes with an old electricity bill will give you a better answer than any installer’s rule of thumb.

The Only Calculation That Matters

Start with your electricity bill, not your floor plan. In Delhi NCR, every 1kW of installed solar generates roughly 120 units a month averaged across the year.

System size in kW = your average monthly consumption in units ÷ 120. Use the average of twelve months, not one summer bill — otherwise you will oversize badly.

A word on why the annual average matters: a Delhi household might use 900 units in June and 250 in November. Sizing on the June figure gives you a system that spends the winter exporting surplus you cannot fully recover, since year-end settlement rates are far below the retail tariff.

System Size by Consumption

Average Monthly Consumption	System Size	Panels Needed (550 Wp)	Roof Space
150 – 250 units	2 kW	4 panels	200 – 250 sq ft
250 – 400 units	3 kW	6 panels	300 – 350 sq ft
400 – 550 units	4 kW	7 – 8 panels	380 – 450 sq ft
550 – 750 units	5 kW	9 – 10 panels	450 – 500 sq ft
750 – 1,000 units	7 kW	13 panels	650 – 720 sq ft
1,000 – 1,300 units	10 kW	17 – 19 panels	900 – 1,000 sq ft

Panel counts assume 540–590 Wp modules, which is the current mainstream size in India. Older 330–400 Wp panels would need roughly 40% more units and correspondingly more roof.

So What Does a Typical 3BHK Need?

Across Delhi NCR, most 3BHK households fall into one of three patterns.

Household Pattern	Monthly Units	Recommended System	Panels
3BHK, one AC used seasonally, small family	250 – 400	3 kW	6
3BHK, two ACs, moderate summer use	450 – 650	4 – 5 kW	8 – 10
3BHK, three or more ACs, heavy summer use	700 – 1,000	6 – 8 kW	11 – 15

If you want a single number: a 5kW system with nine to ten panels covers the majority of 3BHK homes in Delhi NCR. But confirm it against your own twelve-month average before ordering.

How Many Panels Does an Air Conditioner Add?

This is the question behind the question, and it deserves a direct answer. A 1.5-ton five-star inverter AC consumes roughly 1.1–1.3 units per hour of actual compressor running time.

AC Usage	Units per Month	Additional System Size	Additional Panels
1 AC, 6 hrs/day, 4 months a year	~75 units (annual average)	0.6 kW	1 – 2
1 AC, 8 hrs/day, 6 months a year	~150 units (annual average)	1.25 kW	2 – 3
2 ACs, 8 hrs/day, 6 months a year	~300 units (annual average)	2.5 kW	5
3 ACs, 8 hrs/day, 6 months a year	~450 units (annual average)	3.75 kW	7

Two things to understand about these numbers. First, they are averaged across the year — the summer months will run far above and the winter far below, and net metering is what smooths that out. Second, an on-grid solar system does not “run” your air conditioner at night; it offsets the units your AC consumes over the billing cycle. The distinction matters when someone tries to sell you a battery to “run the AC”.

Roof Space: The Practical Constraint

Allow roughly 100 sq ft of completely shadow-free roof per kW installed. But usable roof is always less than measured roof.

• Water tanks, stair-head rooms and parapet walls cast shadows that move through the day and across seasons. Winter shadows are far longer than summer ones.
• A neighbouring building or a tree to the south can rule out a section of roof entirely — even partial shading on one panel can drag down the output of its whole string.
• Access paths between panel rows are needed for cleaning and maintenance; a fully carpeted roof is impossible to service.
• Elevated mounting structures can recover space above water tanks, stairwells and parking areas, typically adding ₹8,000–₹15,000 per kW.

A proper site survey uses shadow analysis across the year, not a glance on a sunny afternoon. Any installer who quotes a system size without visiting the roof is guessing.

Sanctioned Load — The Constraint People Forget

Even with plenty of roof, your system size is capped by your sanctioned load. Across Delhi, Haryana and Uttar Pradesh, net-metered capacity is generally limited to 100% of the load sanctioned on your connection.

1. Check your electricity bill for the sanctioned load, usually printed in kW near the tariff category.
2. If your desired system exceeds it, apply to your DISCOM for a load enhancement before submitting the solar feasibility application.
3. Remember that enhanced load usually means higher fixed charges every month, so weigh that against the extra generation.
4. Systems above roughly 5kW will generally require a three-phase connection.

A Worked Example: 3BHK in Delhi

Take a 3BHK independent floor in South Delhi with two air conditioners, a refrigerator, a water pump and standard lighting.

Step	Value
Twelve-month average consumption	580 units per month
System size (580 ÷ 120)	4.8 kW → round to 5 kW
Panels required (550 Wp)	9 – 10
Shadow-free roof needed	450 – 500 sq ft
Gross system cost	₹3,10,000 – ₹3,60,000
Central subsidy	₹78,000
Delhi state subsidy	₹30,000
Net cost	≈ ₹2,27,000
Annual generation	7,000 – 7,600 units
Annual saving at ₹9 per unit	₹63,000 – ₹68,000
Simple payback	3.5 – 4 years

The same household in Gurgaon would install the identical system but pay around ₹2.57 lakh net, since Haryana offers no general state subsidy, and would save less each year because DHBVN domestic tariffs are lower — pushing payback to roughly five years.

Common Sizing Mistakes

• Sizing on a single summer bill rather than a twelve-month average — the most common cause of oversizing.
• Sizing to fill the roof rather than to match consumption. Surplus units settled at year end are worth a fraction of the retail tariff.
• Forgetting the sanctioned load cap, and discovering it only when feasibility is refused.
• Ignoring winter shadows during the site survey, then losing output for four months of the year.
• Assuming a larger system means a larger subsidy. Both the central and Delhi state subsidies are capped at 3kW.

Conclusion

Most 3BHK homes in Delhi NCR need a 3kW to 5kW system — six to ten panels of 540–590 Wp, occupying 300 to 500 sq ft of shadow-free roof. Each 1.5-ton air conditioner in regular seasonal use adds roughly two to three panels.

The method matters more than the rule of thumb: divide your twelve-month average monthly consumption by 120 to get your kW, then confirm that both your roof and your sanctioned load can accommodate it. That single calculation prevents the two most expensive sizing errors — buying too much system, and discovering too late that your connection will not support it.

Get a Free Quote from Solar Squad

Solar Squad carries out a proper shadow analysis and load assessment before recommending a system size, across Delhi and Gurgaon. Send us twelve months of electricity bills and we will tell you exactly what size you need — including when a smaller system is the better investment. Contact us for a free site survey.

Official Sources and Further Reading

Subsidy amounts, tariffs and net metering rules are revised from time to time. These are the primary sources this guide is based on — always confirm current figures on the official portal before you sign a contract.

• PM Surya Ghar Muft Bijli Yojana — official national portal
• Delhi Solar Portal — state subsidy and Generation Based Incentive rates
• Delhi Electricity Regulatory Commission (DERC)

FAQs

How many solar panels are needed for a 3BHK home?

Typically six to ten panels of 540–590 Wp, corresponding to a 3kW to 5kW system, depending on how many air conditioners you run. Confirm against your twelve-month average consumption rather than the size of the house.

How many solar panels do I need to run a 1.5 ton AC?

A 1.5-ton inverter AC used eight hours a day for six months of the year adds roughly 150 units to your annual monthly average, which is about 1.25 kW — two to three additional panels.

How do I calculate what size solar system I need?

Divide your average monthly consumption in units by 120, which is roughly what 1kW generates per month in Delhi NCR. Use a twelve-month average, not a single summer bill.

How much roof space do solar panels need?

Around 100 sq ft of shadow-free roof per kW. A 5kW system therefore needs 450–500 sq ft, allowing for access paths between rows for cleaning.

Can I install a bigger system than my sanctioned load?

Not for net metering. Capacity is generally capped at 100% of sanctioned load across Delhi, Haryana and UP, so a load enhancement must be approved first — which usually raises your monthly fixed charges.