Firstgreen Energy Transition Insights | White paper | Rajasthan case study | 11 November 2026
For commercial buildings, lower electricity costs and dependable backup are connected decisions—but they require different design choices. Our new white paper, Lower-cost power, right-sized backup, examines how solar open access, wind procurement and onsite battery storage can serve a typical 1 MW commercial building.
The report brings procurement and backup within one electrical boundary. Remote renewable supply can reduce the electricity bill; an onsite battery and existing diesel generator serve critical loads when the local grid connection fails.
1.0 Why buildings should plan offsite renewables and onsite BESS together
A building’s electricity strategy must address both the cost of energy over the year and the continuity of essential services during an outage. Offsite solar and wind procurement can reduce exposure to retail energy costs where the delivered tariff and generation timing are favourable. An onsite battery serves a different purpose: it can supply the critical-load bus when the local grid connection fails. Procuring renewable electricity remotely does not, by itself, provide power through that failed connection.
This is the case for evaluating an integrated hybrid approach: match offsite solar and wind to the building’s demand, then size onsite BESS for the backup and flexibility services actually required. Each component should earn its place in the least-cost portfolio.
2.0 What each component contributes
| Component | Role in the hybrid approach | Condition for cost optimisation |
|---|---|---|
| Offsite solar | Supply daytime electricity through open access, particularly where roof space is insufficient for the required generation. | Match generation to actual daytime consumption; count losses, network charges, surcharges and unused energy. |
| Offsite wind | Complement solar when the selected wind resource produces during the building’s residual demand periods. | Use the project’s hourly and seasonal profile and delivered PPA cost; wind does not guarantee evening or night supply. |
| Onsite BESS | Serve defined critical loads during outages; provide additional load shifting where the operating rules and economics permit. | Size usable kWh and kW for the required service, preserve backup reserve, and include charging losses, ageing and replacement costs. |
| Grid and existing DG | Meet residual demand and provide backup beyond the battery’s designed duration. | Compare equal reliability requirements; retain the cost of residual imports and DG rather than assuming either disappears. |
3.0 What the report’s facts show
- Renewable procurement drives the base-case saving. For the modelled 1 MW Rajasthan office, solar open access saves ₹28.66 lakh/year against grid supply with existing DG. The lowest lifecycle-cost tested portfolio is 1.4 MWp solar, with no wind or battery.
- Backup must be sized around a defined service. A 375 kW / 771.6 kWh nominal battery meets the modelled first-hour requirement for a 300 kW critical load. DG supplies residual critical demand during longer outages.
- A useful backup battery is not automatically a profitable investment. Its incremental 15-year, pre-tax NPV is −₹41.52 lakh under the report’s base assumptions. Reliability and diesel reduction therefore need to be assessed alongside capital cost.
- Generation timing determines whether wind adds value. The preferred solar–wind mix changes with the wind price, resource profile and building load. Annual renewable units alone do not establish the best combination.
4.0 Optimise the combination against the building’s load
Start with actual 15-minute demand and critical-load data. Compare solar-only, solar–wind and solar–wind–BESS portfolios at the same reliability requirement. Calculate the complete landed open-access cost, account for applicable banking and ownership rules, and test battery reserve, grid headroom, ageing and replacement. Choose the combination with the lowest lifecycle cost that meets the building’s energy and backup objectives—not a fixed solar–wind ratio or a standard battery size.
For building owners and facility managers: the decision is to optimise procurement and backup together. The final design may favour all three technologies, or a smaller subset, depending on the evidence. Read the two-page preview below, then register free or sign in to open the complete five-page white paper.
What the two-page preview covers
- Procurement savings: the Rajasthan screening case estimates ₹28.66 lakh in annual savings from solar open access against grid supply with existing diesel backup.
- Defined backup service: a 375 kW / 771.6 kWh nominal battery meets the modelled first-hour backup requirement for a 300 kW critical load.
- Quarter-hour operation: demand, renewable allocations, battery charging and discharge, reserve requirements, and IEX price context.
These are modelled screening results, not guaranteed project savings. The analysis uses synthetic demand, renewable resource and outage profiles, with provisional cost and tariff assumptions. The battery’s incremental financial return is negative in the reported base case. Actual investment decisions require building interval data, firm supplier offers and confirmation of applicable charges.
Read the first two pages
Preview pages 1–2 of Firstgreen’s five-page white paper, published 11 November 2026.
Register free to read the complete report
Unlock all five pages, including the cost comparison, solar–wind–battery optimisation and state policy decision gates.
Planning renewable supply and backup for your building?
Firstgreen Consulting supports load assessment, open-access procurement analysis, solar–wind–battery sizing and project engineering. Contact our team to assess your building’s electricity costs and critical-load backup requirement.
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