Limits: sanctioned load, net-metering caps, roof area and budget

The bill tells you what size the customer needs. Four limits decide what size they can have. A good designer checks all four before quoting, and explains the binding one in plain words.

The four limits

1. Consumption

Size to cover the year's units (lesson 2), allowing for planned new loads. Going far beyond consumption rarely pays: surplus units at settlement earn only the export rate, for example about ₹2.25 in Gujarat, ₹2.79 for new prosumers in Kerala and ₹2.82 in Maharashtra (indicative, October 2026; check the current order). Some states also cap capacity relative to consumption or connected load.

2. Sanctioned load and the net-metering rules

This is the limit installers most often forget.

• Under the Electricity (Rights of Consumers) Rules, 2020, as amended, net metering is available for systems up to 500 kW or the sanctioned load, whichever is lower. Many states follow the same rule: Uttar Pradesh allows domestic systems up to 100% of sanctioned load, and Madhya Pradesh up to sanctioned load (maximum 500 kW).
• The 2024 amendment made life easier for small systems: systems up to 10 kW are exempt from the DISCOM's technical feasibility study, the DISCOM bears any network strengthening needed for systems up to 5 kW, and the timeline to commission was cut to 15 days (check the current notification and your state's adoption).
• If the system exceeds the sanctioned load, the customer must apply for load enhancement. That means a fee, sometimes a security deposit, and a slightly higher fixed charge in states that bill fixed charges per kW.

Phase and connection limits (part of limit 2)

• DISCOMs usually allow single-phase inverters up to about 5–6 kW (lower on three-phase connections, to limit imbalance).
• Above 10 kW, connection must be three-phase (CEA connectivity regulations).
• Watch state-specific thresholds: in Maharashtra a grid support charge applies on gross generation for systems above 10 kW; in Kerala the KSERC Renewable Energy Regulations, 2025 (in force from 6 November 2025, but challenged in court) set a domestic limit of about 20 kW and a grid support charge on night-time drawal for systems above 10 kW; summaries of the net-metering, net-billing and storage terms conflict, so check the current notification before sizing a Kerala system.

3. Roof area

Count modules on a real layout (module m02). Planning figures: about 7.5–10 m² per kWp for tilted rows on RCC, 5–6 m² per kWp flush on a shed.

4. Budget and subsidy

Most homes decide on price after subsidy. PM Surya Ghar central financial assistance (CFA) for residential rooftop solar (2024 guidelines; the scheme runs to FY 2026-27, so check for changes):

For sizes in between: ₹30,000 per kW for the first 2 kW plus ₹18,000 per kW for the part between 2 and 3 kW. So 2.75 kWp earns 60,000 + 0.75 × 18,000 = ₹73,500. Special-category states (north-eastern and hill states and union territories) get higher rates: ₹33,000 and ₹19,800, up to ₹85,800. DCR modules are mandatory for CFA.

Some states add a top-up. Uttar Pradesh adds ₹15,000 per kW, capped at ₹30,000 (check the current status; it has an installation cap).

Worked example: a large Lucknow home

A family in Lucknow uses 900 units a month, mostly from three ACs. Single-phase connection, sanctioned load 5 kW. Terrace fits 12 modules. Budget about ₹3,50,000 out of pocket.

1. Consumption: 900 × 12 = 10,800 units ÷ 1,390 = 7.8 kWp
2. Sanctioned load: 5 kW, and UP allows up to 100% of it: 5 kW
3. Roof: 12 × 550 Wp = 6.6 kWp
4. Budget: at about ₹56,000 per kW installed (a 7 kW-class assumption between the Sunlectric 5 kW and 10 kW benchmarks), ₹3,50,000 + ₹78,000 CFA = ₹4,28,000 buys about 7.6 kWp

The binding limit is the sanctioned load. Options to put to the customer:

• Option A: 9 × 550 Wp = 4.95 kWp now, within the sanctioned load. Generation ≈ 4.95 × 1,390 = 6,881 units, covering 64% of use. Net cost ≈ 4.95 × ₹57,000 − ₹78,000 − UP top-up ₹30,000 (if available) ≈ ₹1,74,000.
• Option B: apply for load enhancement to 7 kW (three-phase may be needed), then install the roof maximum of 6.6 kWp. Generation ≈ 9,174 units, 85% of use. Extra steps: enhancement fee, possible phase change, a three-phase inverter, and the inverter phase limit above about 5–6 kW.

Let the customer choose with numbers in front of them. Many choose A now and B later; if so, pick an inverter and layout that make expansion easy.

A quick decision order

1. Size for consumption, including planned loads.
2. Check sanctioned load and phase; plan enhancement if needed.
3. Check state-specific thresholds (10 kW, storage rules, grid support charges).
4. Fit to the roof.
5. Price it, deduct the correct CFA and any state top-up, and compare with the budget.
6. Quote the smallest of these limits, and explain which one bound it.

Key points

• Four limits decide the final size: consumption, sanctioned load (with net-metering and phase rules), roof area and budget.
• Net metering is generally allowed up to the sanctioned load (maximum 500 kW); exceeding it needs load enhancement.
• Systems up to 10 kW skip the technical feasibility study under the 2024 amendment; check state adoption.
• PM Surya Ghar CFA is ₹30,000 per kW for 2 kW, plus ₹18,000 for the third kW, capped at ₹78,000.
• Quote the smallest limit and explain it; offer the customer options with numbers.

Check yourself

1. Calculate the CFA for a 2.2 kWp residential system in Rajasthan.
2. A home needs 6 kWp by consumption but has a 4 kW sanctioned load. What are the customer's choices?
3. Does the PM Surya Ghar CFA increase for a 6 kW system compared with a 3 kW one?