A daytime solar unit is worth the grid charge it actually avoids at that hour, subject to the meter and settlement rules. A business with time-of-day (ToD) billing should therefore model solar against its hourly consumption, not multiply annual generation by one flat unit rate. Gujarat, Maharashtra and Madhya Pradesh use different windows and category rules in their cited 2026 orders.
Direct answer. ToD tariffs change energy charges by time of day. Solar produces in daylight; many businesses still import after sunset. In the cited 2026 schedules, eligible DGVCL categories face morning and evening ToU charges and a midday discount. MSEDCL has solar-hour rebates and an evening surcharge. MPERC specifies solar, night and peak treatment for listed HV categories. Match the tariff code, meter and export settlement before valuing solar or storage.
How does a time-of-day tariff change the value of solar?
A flat-tariff calculation values every avoided grid unit at the same energy rate. A ToD tariff attaches a different charge or rebate to imports in defined slots. Rooftop solar is most useful when it directly serves a load during a slot with a high avoided cost. If the daytime slot is discounted, self-consumed solar may avoid less per unit than a flat-rate proposal assumes. That does not make the project uneconomic; it changes the hourly calculation and may make load timing more important.
The ToD tariff glossary defines the bill labels. The Ministry of Power’s 23 June 2023 explanation of the Electricity (Rights of Consumers) Amendment Rules sets the national framework: state commissions specify the actual solar and peak hours, and category implementation depends on metering. The national rule is not a replacement for the applicable state order. A business must use the slot and rate on its current licensee schedule.
The Hourly Avoided-Cost Map has four columns for each hour: site load, solar generation, grid import avoided and the applicable ToD energy charge. Add export units in a separate column because the settlement mechanism may value them differently. Then add demand, PF or kVAh and fixed charges outside the hourly energy calculation. This prevents a solar proposal from using a peak import rate for every midday generated unit.
Suppose a hypothetical factory uses 100 units from 11 a.m. to noon and a rooftop plant supplies 60 units in that hour. The 60 units are self-consumed if the connection and meter arrangement permit it, so the avoided energy charge follows that hour’s import tariff. If the plant instead exports 20 units after serving its load, those 20 follow the applicable export and settlement rule. The figures are illustrative, not a bill forecast. They show why the same solar plant can have different value for two businesses with different operating hours.
A ToD rebate on solar-hour imports can create a counterintuitive result: shifting a flexible load into midday may be valuable even though midday grid energy is cheaper, because the load can absorb solar that might otherwise be exported at a lower settlement value. The answer depends on the export rule and the business’s load. This is a case for interval data, not a universal instruction to run every machine at noon.
What are the cited 2026 ToD windows in the three states?
The table below is a dated comparison of selected business categories, not a universal tariff card for every consumer in each state. Every window and rate comes from the named order in its row. A bill for Torrent Power, a different Maharashtra licensee or an MP category outside the row needs its own schedule. “Normal” means no listed ToD adjustment to the energy-charge component in that slot; it does not mean the whole bill is zero or unchanged.
| State, order number and date | Selected category and windows | Listed energy adjustment |
|---|---|---|
| Gujarat, GERC DGVCL order 2581/2025, 25 March 2026, HTP-1 clauses 11.3 and 11.10 | Peak periods 07:00 to 11:00 and 18:00 to 22:00; midday 11:00 to 17:00 | Peak ToU charge 45 paise/unit for billing demand up to 500 kVA or 85 paise/unit above 500 kVA; midday discount 60 paise/unit. Eligibility and meter conditions in the order apply. |
| Maharashtra, MERC MSEDCL Case 75 of 2025 review order, 25 March 2026, Table 8 | Normal 00:00 to 09:00; solar 09:00 to 17:00; peak 17:00 to 24:00 for eligible categories | FY 2026-27 business-category solar-hour rebate 15% of energy charge in April to September and 25% in October to March; peak surcharge 20%; night rebate removed in this review order. Check category footnotes. |
| Madhya Pradesh, MPERC Petition 140/2025 order, 26 March 2026, section 1.14 for listed HV-2 to HV-5 categories | Peak 06:00 to 09:00 and 17:00 to 22:00; solar 09:00 to 17:00; night 22:00 to 06:00 | Peak surcharge 20% of normal energy charge; solar-hour rebate 20%; night rebate 10% June to September and 7.5% April to May and October to March. Other categories have separate treatment. |
These rows cannot be compared by looking at percentages alone. DGVCL’s listed peak amount is paise per imported unit, while the cited MERC and MPERC examples express adjustments as a percentage of an energy-charge base. The underlying normal tariff, fuel adjustment, taxes and fixed or demand charges differ. A comparison requires the actual bill and category. Even within Gujarat, the HTP-1 row does not describe all LT consumers or Torrent Power schedules.
The 25 March 2026 MERC review order matters because it removed a night rebate from the reviewed MSEDCL ToD structure. Older articles that still apply the night rebate can misvalue storage. MPERC’s 26 March 2026 order has a separate HV-6 row; a shopping mall, bulk residential complex and industrial unit should not be treated as the same category without checking their tariff code. These are examples of why the order number and date belong in a proposal.
Verdict. The value of one rooftop unit is determined by its hour, self-consumption or export route, and current category order. A state-level peak-window graphic is useful only as a starting point.
Why does a midday rebate change solar sizing in Gujarat?
The cited GERC DGVCL order 2581/2025, 25 March 2026 lists both a peak ToU charge in 07:00 to 11:00 and 18:00 to 22:00 and a 60 paise per unit discount in 11:00 to 17:00 for HTP-1. Meter and category conditions matter. The same order describes a 45 paise peak charge for billing demand up to 500 kVA and 85 paise above that level. These are energy adjustments, separate from demand and PF lines.
A rooftop plant generally produces through the midday discount window. If it serves an HTP-1 factory load at 1 p.m., the avoided import energy rate reflects the normal energy charge less the applicable ToU discount. It is incorrect to value that unit at the evening peak rate merely because the factory also operates at 7 p.m. Conversely, if the plant produces during the 7 a.m. to 11 a.m. charge window, an avoided grid unit may have a different energy value. The actual generation profile and local shading determine how much output falls in each slot.
A hypothetical example makes the method clear without using a Heaven Green price. Suppose a plant generates 100 units on a representative day, with 20 before 11 a.m., 70 from 11 a.m. to 5 p.m. and 10 after 5 p.m. The first and middle blocks have different avoided energy adjustments under the cited DGVCL HTP-1 schedule if all 100 units are self-consumed. The last block may or may not overlap the evening charge window depending on season and actual irradiance. A proposal should use an hourly simulation, not assume all 100 units land in one tariff slot.
Also inspect the meter. The order says ToU charges are levied where a meter with ToD recording facility is provided, and the commission adjusted the schedule to pair charges with discounts. Ask the DISCOM for the applicable register labels and whether the current bill is using the ToU schedule. The solar and tariff hike guide gives broader tariff context, but a plant-specific model needs the current order, meter and interval load profile.
Gujarat meter check
Do not apply the DGVCL HTP-1 ToU row to a Torrent Power or LT bill. Match the licensee, tariff code and ToD meter on the actual invoice.
What changed in Maharashtra’s reviewed ToD tariff?
MERC’s Case 75 of 2025 post-remand review order dated 25 March 2026 revised the MSEDCL ToD table for eligible categories. Table 8 sets normal treatment from midnight to 9 a.m., solar hours from 9 a.m. to 5 p.m. and peak hours from 5 p.m. to midnight. It lists a 15% solar-hour rebate in April to September and 25% in October to March for the relevant business-category column, and a 20% peak surcharge. The review removed the night-hour rebate. These are the cited FY 2026-27 terms; later orders must be checked before using them in a future bill.
This structure changes a rooftop calculation in two ways. First, generation from 9 a.m. to 5 p.m. offsets grid imports that already receive a solar-hour rebate. The avoided cost per self-consumed unit is therefore different from the evening peak import cost. Second, a business with significant evening demand may still buy expensive peak-slot power after rooftop output has faded. Solar alone does not move afternoon generation into the evening. A battery or a production shift might, but each needs an hourly economic model.
The order’s ToD table has a separate column for LT residential and HT group housing, so a commercial buyer should not copy that rupee-per-unit column. Likewise, MSEDCL’s ToD slots should not be attributed to every Maharashtra licensee. The tariff code on the bill decides which column applies. Ask the EPC to name the source table and season in the proposal. A single annual average percentage hides the April-to-September and October-to-March distinction.
Maharashtra’s 2019 rooftop regulations also make ToD relevant to net-metered energy. They define banked energy after same-slot set-off and say consumption in a time block is first compensated with injection in that block. Excess injection is accounted for under the regulation’s off-peak treatment. That rooftop rule should be read separately from the MERC review order’s discussion of distribution open-access banking. They serve different transaction types.
The practical result is a sizing question. A roof sized to midday consumption may have strong self-consumption. A larger roof with midday export needs an accurate export and banking model before its extra units are valued. The banking electricity glossary explains the concept, but the specific mechanism must come from the business’s approved rooftop or open-access route.
- ✓ Import and export are valued in their actual windows.
- ✗ Every solar unit is valued at the same tariff.
How should an MP factory read its solar and peak slots?
The MPERC order in Petition 140/2025, dated 26 March 2026, section 1.14, lists ToD treatment for specified HV categories. For the listed HV-2 to HV-5 group, 6 a.m. to 9 a.m. and 5 p.m. to 10 p.m. are peak periods with a 20% surcharge on normal energy charges. The 9 a.m. to 5 p.m. solar period has a 20% rebate. The 10 p.m. to 6 a.m. rebate is 10% in June to September and 7.5% in April to May and October to March. The same order has other category treatment, so confirm the exact code.
For a daytime factory, rooftop generation mainly offsets units in the solar period, where the cited HV group already receives a lower import rate. It may offset some morning peak consumption, depending on season and system orientation, but a standard annual yield estimate cannot tell you how much. Evening production after 5 p.m. is usually outside strong rooftop generation. That gap can make load shifting or storage relevant, yet it must be compared with the cost and operational constraints of those options.
An illustrative hourly ledger can show the effect. Suppose an MP factory imports 40 units from 8 to 9 a.m., 100 units from noon to 1 p.m. and 80 units from 6 to 7 p.m. A rooftop plant supplies 50 units at noon and little in the other slots. The 50 avoided units belong to the 9 a.m. to 5 p.m. solar slot under the cited order, not the 5 p.m. to 10 p.m. peak slot. If the factory moves a flexible process from 6 p.m. to noon, the value comes from the changed grid purchases and solar self-consumption together. These load and generation figures are hypothetical, not a case study.
MPERC notes that ToD adjustments in section 1.14 apply to energy charges rather than fixed charges. A savings model should therefore leave demand and fixed lines intact unless another intervention changes them under their own rule. MPERC also notes that the slot definitions are relevant for specified open-access banking treatment. That does not automatically make rooftop export equal to evening retail import. Ask the EPC to show the approved mechanism and a slot-by-slot settlement calculation.
Mid-article action
Bring a ToD bill and interval load data to the commercial solar proposal page. Ask for a state-specific hourly model with export shown separately.
| Model input | Check on the official order | Proposal output |
|---|---|---|
| Solar-hour slot | Current DISCOM ToD window | Avoided import by slot |
| Peak slot | Current surcharge and hours | Residual grid energy cost |
| Export or banked unit | Applicable rooftop or open-access rule | Settlement value, separately |
The same generation profile can have a different value when the tariff windows change.
How do net metering and banking interact with ToD?
Three different questions often get combined: what a self-consumed solar unit avoids, how an exported unit is credited, and whether banked energy can be drawn in another ToD slot. The answer changes with rooftop net metering, net billing and open access. A proposal should identify the approved route before claiming that a noon export can cancel an evening peak import at the same value. The banking electricity glossary and net-metering glossary define the terms.
For Maharashtra rooftop systems, the MERC Grid Interactive Rooftop Regulations, 2019 say same-slot consumption is set off first when ToD applies; excess injection has the regulation’s off-peak treatment. The 25 March 2026 MERC review order separately discusses distribution open-access Regulation 20.3, under which monthly banked energy follows slot restrictions. Do not use the open-access rule as if it were the rooftop net-metering rule.
Gujarat’s DGVCL HTP-1 tariff order 2581/2025, 25 March 2026 sets import ToU adjustments. The rooftop export and settlement mechanism comes from the separate GERC rooftop regulation and the approved application, not from the tariff’s peak-charge paragraph alone. MPERC’s 26 March 2026 order ties the listed ToD periods to specified open-access banking rules, but a rooftop consumer must still check the rooftop order and category.
A useful accounting table has a row for each ToD slot and four separate quantities: site consumption, solar self-consumption, export and grid import. Add the applicable import energy rate, the export valuation and any banked-energy adjustment. The resulting bill model can reveal whether an oversized roof creates many lower-value exports. It can also show why shifting a process into solar hours may be more valuable than exporting those units.
The MERC review order makes a further point about slot hierarchy in open access: banked energy from a lower-priced slot cannot simply be used in a higher-priced peak slot under the stated rule. This is a regulatory design choice, not an engineering loss. Any claimed evening offset from daytime exports needs a citation to the correct mechanism and a written calculation.
When could a battery pay under a ToD tariff?
A battery can store midday solar energy or lower-priced grid energy and discharge during a higher-priced period. The gross tariff spread is only the start of the calculation. Charging and discharging lose energy, the battery has operating and replacement costs, and its power rating may limit the load it can serve. There may also be demand-charge value or a backup requirement, but those benefits should be modelled separately to avoid counting the same discharge twice.
The BESS glossary distinguishes power in kW from capacity in kWh. A plant with a 100 kW peak for one hour needs a different design from a 20 kW evening load lasting five hours, even though each is 100 kWh before losses. State ToD windows help identify when discharge might have value. In the cited MERC Case 75 of 2025 order, 25 March 2026, eligible business categories have a 17:00 to 24:00 peak surcharge. In the cited MPERC Petition 140/2025 order, 26 March 2026, the listed HV group has a 17:00 to 22:00 peak period. DGVCL’s 25 March 2026 order 2581/2025 lists an evening ToU charge from 18:00 to 22:00 for HTP-1.
For a hypothetical 100-unit midday charge and 80-unit evening discharge, the first question is whether the 80 units can avoid a higher evening import charge after round-trip losses. The next is whether those 100 midday units would otherwise have been self-consumed, exported or curtailed. If they would have displaced midday grid imports, charging the battery has an opportunity cost. A spreadsheet that calls charging energy “free” will overstate the result.
The Ministry of Power’s 2023 energy-storage framework discusses ToD and storage policy, but it does not quote a project-specific payback. Ask for interval load data, dispatch simulation, usable capacity, cycle limits, efficiency, safety design and the approved grid interface. A business should see the same model with and without the battery. If the difference relies on a tariff that may change, include a sensitivity case instead of a fixed return promise.
- Evening import overlaps peak ToD
- Charging source and opportunity cost shown
- Losses and usable capacity modelled
- Meter-side dispatch simulated
- All midday solar called free charging
- No repeated peak data
- Export rule omitted
- One tariff spread used for every day
How Heaven Green Energy helps model ToD Value
A proper ToD proposal begins with the actual tariff code, licensee, meter type and current order. It includes hourly or 15-minute load data across representative production and low-load periods. The generation model should show monthly and hourly output, not just one annual total. The bill model should apply the state order to each import slot, then calculate export under the correct rooftop or open-access mechanism.
The Hourly Avoided-Cost Map is a simple way to audit the result. For each slot, show baseline grid imports, solar self-consumption, post-solar imports, exports and the tariff adjustment. Keep demand, PF or kVAh and fixed charges in separate rows. If a battery is proposed, add its charging source, losses, discharge schedule and state of charge. If load shifting is proposed, show which equipment moves and whether the new time affects production.
- Ask for the order number, date, tariff code and meter capability.
- Request an interval load export and a monthly solar generation profile.
- Separate direct self-consumption from export and banking.
- Test the proposal under summer, monsoon and low-production conditions.
- Add a battery only after a dispatch simulation shows the marginal value.
The commercial solar route is for a business proposal, while the industrial solar route is for a larger factory. Provide twelve bills, interval meter data and shift hours. Ask the EPC to show the value of each ToD slot and the order that supports it. This makes it possible to compare two bids without treating every generated unit as an evening peak unit.
Record the tariff order and billing period on the proposal. Recheck the windows, rebates and export treatment before the investment decision. Recheck the order when the application is approved and again before the investment decision. The written model is useful because its assumptions can be updated without rebuilding the entire commercial case from a single per-unit slogan.
The service routes for a site-specific review are:
- Commercial solar for a business bill and rooftop proposal.
- Industrial solar for a larger factory connection and protection review.
Frequently asked questions
Is every midday solar unit worth the evening peak tariff?
No. A self-consumed solar unit normally avoids the import charge in the hour it serves the load. A daytime export follows the applicable settlement or banking rule. It cannot be valued automatically at an evening peak import rate. Use the current order, meter data and approved rooftop or open-access route to calculate the relevant value.
What is the DGVCL HTP-1 ToU window in the cited 2026 order?
GERC DGVCL order 2581/2025 dated 25 March 2026 lists peak charge periods of 07:00 to 11:00 and 18:00 to 22:00, plus a discount period of 11:00 to 17:00 for HTP-1. The charge and discount depend on the order’s billing-demand and meter conditions. Other Gujarat categories and licensees need their own schedule checked.
Did MERC keep the night ToD rebate for MSEDCL businesses?
The MERC post-remand review order in Case 75 of 2025 dated 25 March 2026 removed the night-hour rebate in its revised table for eligible categories. It retained a solar-hour rebate and evening peak surcharge in the cited table. A business should check the applicable tariff category, billing month and any later order before using an older night-rebate chart.
Can rooftop exports be banked into a peak slot?
Do not assume that. Maharashtra’s rooftop regulation first sets off same-slot consumption and treats excess injection under its own rule. The MERC review order also discusses separate distribution open-access banking restrictions. These routes are not interchangeable. Gujarat and MP require their own approved settlement rules. Ask the EPC for a slot-by-slot calculation linked to the correct regulation.
When does a battery improve a ToD solar project?
It may help when a repeatable evening import overlaps a higher-priced slot and the value after charging losses and battery costs is sufficient. It may also provide demand or backup value, but those should be separate model lines. Ask for an interval dispatch simulation and a case without the battery. A tariff spread alone does not establish a project return.
What documents should a business send for a ToD proposal?
Send twelve months of bills, the tariff code, the meter’s ToD register or interval export, production shift hours, planned load changes and the approved solar connection route if already known. Ask the EPC to show hourly self-consumption, export, demand and a separate battery case. The order number and date should appear beside every modelled window and adjustment.