Why renewable power procurement needs a new system

A C&I consumer, a manufacturer, a data-centre operator, a developer assembling a captive portfolio, issues an RFP for renewable power, and over the following weeks the responses arrive. On paper it looks like a comparison problem: line the offers up, take the lowest tariff, sign. In practice they do not line up at all. One bid is a group-captive structure in which the captive users collectively hold at least 26% ownership in the SPV and consume at least 51% of its annual generation, with consumption proportionate to their ownership shares within the permitted variation. Another is a third-party open-access PPA at a flat $48/MWh. A third is a time-of-day-shaped tariff, cheaper at midday and dearer through the evening peak. A fourth is a rooftop captive quote; a fifth prices merchant exposure against the exchange. Tenors run 15 to 25 years, escalation from flat to a few percent a year, and the curtailment, deviation, and change-in-law terms are all worded differently. The one field every offer shares is the headline number, and that is the one field that does not mean the same thing twice.

A flat $48/MWh tariff, a ToD-shaped tariff, and a group-captive equity structure are not three prices for one product; they are three different products, a scalar, a vector, and a balance-sheet position. And a contract’s worth is set less by its price than by how its generation shape lines up against your consumption and the shaped market curve behind both. A flat solar PPA delivers most of its energy into the midday belly of the duck curve, where exchange prices have collapsed toward zero, and nothing into the evening ramp, where the market pins the ₹10/kWh (≈ $120/MWh) ceiling. For an evening-heavy buyer, a two-shift factory, an EV charging depot, a distribution licensee serving residential demand, the “cheap” flat solar PPA hedges the hours it least needs and leaves it exposed in the hours that hurt. The cheapest-looking offer can be the worst fit, and the tariff says nothing about it.

The quoted tariff is also not the price you pay. Between the two sit cross-subsidy surcharge (CSS), additional surcharge, transmission and wheeling charges, banking rules, and scheduling and deviation charges, each varying by structure and by state. CSS alone runs roughly $6–$30/MWh; a group-captive structure that meets the 26%/51% test is exempt from CSS and additional surcharge, so in high-surcharge states its delivered cost lands roughly $10–$18/MWh below third-party open access at the identical generator tariff, a gap wider than the spread between the headline numbers. And the risk terms are prices in disguise: generous curtailment rights with no compensation, a 3%-a-year escalation over a 25-year tenor, or a change-in-law clause that passes future surcharge revisions through to the buyer can each move the effective cost by double digits. None of it appears on the cover page.

Making offers comparable means resolving every one onto a common basis before anything is ranked. At a minimum, a procurement system has to normalise:

• Contract structure: group captive, third-party open access, rooftop captive, and merchant, each mapped to the charges it actually triggers and the exemptions it actually earns
• Tariff shape: flat and time-of-day tariffs resolved to a block-level price vector, not collapsed to an annual scalar
• Delivered cost: generator tariff plus CSS, additional surcharge, transmission, wheeling, banking, and scheduling charges for the specific state and voltage level
• Tenor and escalation: each offer’s escalation applied during its term and its costs discounted over a common evaluation horizon, including explicit replacement-power assumptions after a shorter contract ends, so a flat 15-year and an escalating 25-year contract cover the same period of demand
• Risk terms: curtailment, deviation, and change-in-law provisions expressed as an expected cost rather than left as prose
• Load alignment: each offer’s generation shape scored against the buyer’s actual sub-hourly consumption and the shaped market curve

The step a spreadsheet cannot perform is the one that matters most: pricing each offer against the buyer’s own consumption at the resolution the market settles, the 15-minute block, 96 of them a day. Averages flatter shape-mismatched assets and understate shape-matched ones, so an annual-average comparison overvalues a flat solar PPA for an evening-heavy buyer and undervalues a storage-firmed or ToD offer that genuinely covers the peak. The only way to see the real economics is to run each offer’s generation against the buyer’s real load, block by block, net it against the shaped market curve, and read the delivered and effective cost that falls out. That is a modelling problem, not a sorting problem, and no arrangement of columns solves it.

Once every offer is normalised and priced against real load, the decision stops being a single-number ranking and becomes a multi-metric one, delivered cost, risk-adjusted cost, and impact on project IRR or landed cost of power, not the headline tariff alone. Structures that looked incomparable, captive against open access against merchant, now sit on a common basis. And the decision becomes auditable: when a CFO, a lender, or a board asks why the second-lowest headline tariff was the right choice, the answer is not a judgement call defended in a meeting but a model with every charge, term, and block accounted for.

This is what ES Source is built to do: it ingests offers in their native shapes (group captive, open access, rooftop, merchant) and normalises each through a single model, resolving the tariff structure, applying the state- and structure-specific surcharges and exemptions, and pricing it against the buyer’s actual sub-hourly load and the shaped market curve. The comparison discounts costs over a common evaluation horizon, applying each offer’s escalation during its term and explicit replacement-power assumptions after a shorter contract ends. It surfaces a like-for-like delivered and effective cost alongside risk-adjusted cost and IRR impact, so captive, open-access, and merchant offers can finally be ranked on one axis. The traditional RFP treats procurement as a sorting exercise with the tariff as the sort key; renewable-plus-storage procurement is a modelling exercise in which the tariff is one variable. The buyers who get this right will be the ones who priced every offer against their own load and chose the contract that is cheapest to fulfil.

• Electricity Rules, 2005: Rule 3: collective ownership, annual captive consumption and proportionality requirements
• Ministry of Power: Electricity Rules & Green Energy Open Access Rules 2022 https://powermin.gov.in
• CERC: open access & cross-subsidy surcharge framework https://cercind.gov.in
• Indian Energy Exchange: short-term market prices https://www.iexindia.com