This campus is an illustrative example. It is not a completed Ray2Volt installation. The loads and financial figures show how a college might evaluate solar; the images represent the setting only. Your institution's bills, roofs and tariff will determine its result.
For figures based on your campus, request a site-specific estimate.
Main points from the example
- Schools and colleges use much of their power in daylight. This campus uses more than 80% of its solar output directly during term.
- The modelled 120 kWp Tier-1 DCR plant produces about 1,74,000 units a year and reduces the annual bill from about ₹22 Lakhs to below ₹8 Lakhs.
- During the two-month summer break, permitted exports can create APSPDCL credits for later bills, subject to current settlement rules.
- The worked CAPEX calculation gives roughly 3.7 years of simple payback and more than 26 years of output within its 30-year design life. Businesses typically plan for 3 to 5 years, subject to a site audit.
A college electricity bill now covers much more than lights and fans. Computer labs need cooling; CAD/CAM and robotics workshops run machines; libraries, smart classrooms and auditoriums add screens, sound and lighting. Reverse osmosis (RO) drinking water equipment and campus pumps add steady demand. Trustees have to fit those costs within an academic budget.
Private trusts and societies may be billed by APSPDCL under an applicable institutional or commercial LT or HT category. Using the APERC order dated 25 March 2026, the example assumes an effective ₹8.60 to ₹9.80 per unit after energy charges, demand charges and duty. A 2,500-student campus in this scenario faces an annual bill of ₹20 Lakhs to ₹28 Lakhs. Check the current tariff order and your bills; a higher power cost can leave less of a fixed academic budget for teaching facilities.
Classroom blocks and libraries may offer broad concrete terraces, while teaching hours overlap solar production. We use a representative 120 kWp engineering college in Chittoor district to examine sizing, summer exports, roof safety and long-term costs. See our solar options for education and commercial solar services for the wider context.
When the campus uses electricity
Teaching hours shape the campus load. Unlike a factory working 24-hour shifts, this example's demand rises through the morning, stays high around midday and eases after classes. Compare that pattern with hourly solar production before choosing a system size:
- 8:00 AM to 9:30 AM: Staff arrive, pumps fill overhead tanks and classroom lights switch on as solar output begins to rise.
- 10:00 AM to 2:30 PM: Hundreds of lab computers, split ACs, workshop machines and cafeteria warmers raise demand during the strongest solar hours.
- 3:30 PM to 5:00 PM: Classes and labs finish, students leave and demand falls as generation declines.
During the academic term, that overlap lets the model campus use more than 80% of its solar generation as it is produced. The rooftop string inverters feed building distribution boards, reducing grid purchases without a battery in this design. The remaining output needs an approved export arrangement.
Students can also use the plant as teaching equipment. Engineering, physics and environmental science classes can examine live SCADA generation records, inverter PF curves and irradiance readings, with access controlled by campus staff.
The representative Chittoor college
Here are the inputs for the illustrative technical college near Tirupati. They establish the load and roof area used throughout the worked calculation:
- Buildings: A 15-acre campus with a 4-storey administration block, two 3-storey classroom blocks, mechanical and electrical workshop sheds, and a 600-seat auditorium.
- People on campus: 2,500 students plus 180 teaching and administrative staff.
- Sanctioned demand: 150 kVA on the applicable APSPDCL HT institutional or commercial category.
- Use before solar: About 2,45,000 kWh a year, with a ₹21,80,500 annual bill. The average monthly bill is ₹1,81,700 at an assumed effective ₹8.90 per unit.
- Roof space: 14,000 sq ft of shade-free, flat reinforced concrete (RCC) terrace on the library and electronics buildings.
Account for the summer break
May and June need separate treatment in the energy model. The college runs with fewer people during this two-month break, but the panels continue generating. Trustees should ask how those surplus units will be settled before approving the plant size.
In the example, campus consumption falls by roughly 75% during the break. May and June also bring strong solar irradiance in Rayalaseema, so the 120 kWp array is expected to produce about 15,000 to 16,500 units each month. Lower occupancy therefore increases the share available for export.
Where APSPDCL approves net metering, a bidirectional four-quadrant meter records power sent to the grid on quiet campus days. Credits may then offset later imports under the applicable settlement rules. When students return in July, cooling and lab use rise with occupancy and monsoon humidity. The model applies the summer credit to those later bills, while fixed charges remain payable. Confirm the banking period and treatment of unused credit with the DISCOM.
The worked example carries permitted May and June exports forward against July to October academic demand. The credit depends on APSPDCL approval and the current net-metering rules.
How a trust can own or buy solar power
Many institutions are non-profit societies or charitable trusts registered under Section 12AB. A tax-exempt trust may have no taxable income against which to use the 40% accelerated depreciation on written down value under section 33 of the Income-tax Act, 2025. Its chartered accountant should confirm the trust's own position. The two ownership routes in this example are:
1. Buy and own the plant
Under CAPEX, the trust pays from its reserves or finances the purchase. The illustrative loan assumption is 8.5% to 9.5% from a public-sector bank such as SBI or Canara Bank; obtain a current lender quote. The trust owns the plant and receives 100% of the value of its used output and eligible export credits from day one. This model shows roughly 3.7 years of cash payback and considers a 30-year design life, but a site audit and financing terms will determine the actual return.
2. Buy the output from a RESCO
Under a renewable energy service company (RESCO) arrangement, an investor installs, owns and maintains the roof plant. The college buys its output through a 20 to 25-year power purchase agreement (PPA). This example assumes ₹4.50 to ₹5.50 per unit and a 35% discount against its grid tariff, with no upfront plant purchase. Contract terms, tariff and savings need a current proposal. Our CAPEX and OPEX comparison explains both routes.
Keep students away from electrical equipment
On a teaching campus, roof access and cable routes need to be planned around students and maintenance staff. The example includes these safeguards:
- Controlled roof access: Set modules back at least 1.5 metres from exterior edges. Galvanised handrails and lockable steel doors restrict entry to authorised staff.
- Safe maintenance routes: Hot-dip galvanised perforated walkways provide grip between rows. Rigid raised galvanised iron (GI) conduit keeps DC cables away from foot traffic and standing rainwater.
- Protected inverter area: Place the two 60 kW three-phase string inverters, with Sungrow or Polycab as model examples, in lockable ventilated IP66 aluminium enclosures at an isolated stairwell landing. Add warning signs and external emergency shutdown buttons.
The 120 kWp campus cost model
The illustrative design uses 207 Tier-1 DCR-compliant 580 Wp TOPCon monocrystalline bifacial modules for 120 kWp DC. After the June 2026 ALMM List-II shift, we prepare new commercial quotes with DCR panels unless a verified exemption applies. The assumed DCR premium is ₹9 to ₹12 per Wp. Including modules, string inverters, raised galvanised structures, net-metering synchronisation and safety walkways, the modelled turnkey cost is ₹52,80,000 (₹44,000 per kWp). This is an example figure, not a quote for your campus.
| Measure | Grid-only case | 120 kWp campus case | Effect in the model |
|---|---|---|---|
| Grid electricity bought each year | 2,45,000 kWh | 71,000 kWh | 71.0% fewer utility units |
| Solar electricity produced each year | 0 kWh | 1,74,000 kWh | 1,450 kWh/kWp yearly yield |
| Solar used directly on campus | N/A | 82% (~1,42,680 kWh) | Used by labs, ACs and workshops |
| Vacation and Sunday export credits | 0 kWh | 18% (~31,320 kWh) | Credited by APSPDCL under the assumed terms |
| Average monthly bill | ₹1,81,700 | ₹63,000 | ₹1,18,700 lower each month |
| Annual electricity bill | ₹21,80,500 | ₹7,56,000 | ₹14,24,500 less on the annual bill |
| Yearly O&M and cleaning allowance | ₹0 | ₹60,000 | Covers quarterly preventive checks |
| Net saving each year | Not applicable | Not applicable | ₹13,64,500 per year |
| Calculated simple payback | Not applicable | Not applicable | 3.87 Years |
| Modelled net saving over 25 years | Not applicable | Not applicable | ₹3.82 Crores after all costs |
The table puts the annual net saving at about ₹13.6 Lakhs and the 25-year cumulative figure above ₹3.8 Crores after its stated costs. The broader equipment life is modelled at 25 to 30 years. A trust could apply retained funds to scholarships, laboratory equipment or faculty research, but should budget for future maintenance and equipment replacement. For your own inputs, see how to size a solar system and the rooftop solar return guide.
APERC tariffs, export settlement periods, net-metering limits and schemes can change. These figures are indicative. Review the current rules and your institution's eligibility with a technical adviser before signing. Confirm any tax treatment with your chartered accountant; Ray2Volt does not give tax or investment advice.
Frequently asked questions
Where does the solar output go during the summer break?
With an approved bidirectional net meter, surplus May and June output goes to APSPDCL. The example carries its export credit forward to help offset electricity used when students return in July. Ask the DISCOM how your connection's credits are valued and when they expire.
Can a tax-exempt trust use accelerated depreciation?
A Section 12AB trust with no taxable income may have no way to use the 40% written down value deduction under section 33 of the Income-tax Act, 2025. It can still own the plant under CAPEX, use an operating lease or buy power through a RESCO PPA. Its chartered accountant should confirm eligibility and the current tax rate.
What keeps students away from a school roof solar plant?
Restrict terrace access with keyed or biometric locks and provide perimeter handrails. Route DC cables through grounded galvanised steel conduit, away from walkways. Place the inverters in lockable, ventilated weatherproof enclosures with clear emergency shutdown controls.
How much clear roof does the 120 kWp design need?
The model's 580 Wp Tier-1 TOPCon modules need about 10,000 to 11,500 sq ft of shade-free area. That space can span classroom, library and auditorium roofs. Check structural strength, shade, access routes and the actual module layout before reserving it.
What payback should the college put in its budget?
Businesses typically use a 3 to 5-year planning range, subject to a site audit. This 120 kWp example calculates 3.87 years using an illustrative ₹8.50 to ₹9.50 tariff range. Its table models ₹3.82 Crores of net savings over 25 years within a 30-year design horizon. Actual bills, export credits and costs can change the result. These figures are indicative; Ray2Volt does not give investment advice.
Ray2Volt Solar Private Limited
We design, install, and service rooftop solar for homes and businesses across Tirupati district and Andhra Pradesh, from PM Surya Ghar residential systems to commercial and industrial plants. Every enquiry starts with a free power audit.
Review solar for your campus
Send us recent electricity bills and roof plans. We can assess the teaching-term load, summer use and available terrace area, then prepare a campus design and budget estimate.
