How Much Solar Do You Need for Your Electricity Bill?
Last updated at : Aug 13, 2026
The single most common question we hear is also the most practical: "How big a solar system do I actually need?" The answer is not your roof size, it is your electricity bill. Once you know roughly how many units you consume, sizing becomes simple arithmetic. This guide shows how to work it out and what a ₹5,000, ₹10,000, or ₹20,000 bill typically calls for in 2026.
Start with units, not rupees
Your bill in rupees hides the number that actually matters: units (kWh) consumed per month. Find it on your latest bill. Then use a simple Indian benchmark:
- 1 kW of solar generates around 4 to 4.5 units a day, or roughly 120 to 150 units a month.
So if you consume 600 units a month, you need roughly 4 to 5 kW to cover it. That is the whole method in one line. Everything below is just applying it to common bill sizes.
Sizing by your monthly bill
The table below maps typical bills to system sizes, indicative costs, and expected savings. Exact figures shift with your local tariff and how much of your usage happens during daylight.
| Monthly bill | Recommended system | Approx. install cost (before subsidy) | Estimated monthly saving |
|---|---|---|---|
| ₹5,000 | 3 – 5 kW | ₹2 – 3.5 lakh | ₹4,000 – ₹5,000 |
| ₹10,000 | 5 – 8 kW | ₹3 – 5 lakh | ₹8,000 – ₹9,000 |
| ₹20,000 | 10 – 15 kW | ₹6 – 10 lakh | ₹15,000 – ₹18,000 |
A well-sized system commonly removes 70 to 90 percent of the bill, because it wipes out the expensive top-slab units first.
Walking through each case
For a ₹5,000 bill
This usually means 500 to 700 units a month, typical of a mid-sized home with a couple of air-conditioners. A 3 to 5 kW system fits comfortably and needs around 250 to 400 sq ft of shade-free roof. Most homes in this bracket recover their investment in 3 to 5 years after subsidy.
For a ₹10,000 bill
Consumption here is roughly 1,000 to 1,300 units a month. A 5 to 8 kW system handles it. This is the sweet spot for many independent houses, where the savings are large enough that financing the system through monthly savings makes obvious sense.
For a ₹20,000 bill
This points to heavy usage, often 2,000+ units a month, or a large home or small commercial space. A 10 to 15 kW system is appropriate, and the absolute savings are substantial, frequently ₹15,000 to ₹18,000 a month. At this scale the payback is fast and the 25-year return is significant.
The subsidy makes the smaller systems cheaper still
Under the PM Surya Ghar scheme, residential rooftop systems qualify for a central subsidy of up to about ₹78,000, weighted toward the first few kilowatts. That meaningfully lowers the effective cost of a 3 to 5 kW home system and shortens payback to the 3 to 5 year range. If the upfront amount is a hurdle, solar loans let your savings effectively cover the EMI from day one.
Don't oversize "just in case"
In a net-metered home, generating far more than you consume rarely pays, because most DISCOMs do not pay full retail rates for large annual surpluses. The goal is to match your consumption, not exceed it. A few practical notes:
- Leave a little headroom if you plan to add an EV or air-conditioner soon.
- Account for shade from tanks and parapets, which reduces usable roof.
- Reserve roughly 80 to 100 sq ft per kW of clear, well-oriented roof.
For panel-type comparisons and payback details, see our solar blog.
How Solnce helps
At Solnce Energy we size every residential solar system from your actual unit consumption, not a generic chart, so you buy exactly the capacity that pays. We handle the subsidy application, net-metering approval, and installation end to end. Get a free quote and we will tell you the precise system size your bill calls for.
