- A time-of-day (ToD/ToU) tariff charges different rates by hour of the day.
- Solar generates at midday; demand peaks in the evening — the timing rarely lines up.
- Under net metering, an exported unit's value depends on the slab it lands in.
- This can change C&I payback a lot, so model with real slabs, not a flat rate.
- ToD thresholds and peak/off-peak multipliers are set per SERC and change yearly — verify current slabs; do not state multipliers as universal.
For a home, net metering is simple: a unit out is worth a unit in. For a commercial or industrial client on a time-of-day (ToD) tariff, it is not that simple. The price changes by the hour, and solar generates at the wrong time of day to catch the peak. EPCs who quote a flat rate get the payback wrong.
What ToD/ToU tariffs are
A time-of-day (ToD) tariff, also called time-of-use (ToU), charges different rates for electricity depending on when you use it. Power costs the most in the peak hours, usually the evening, and the least in the off-peak hours, usually at night. A normal or base rate covers the rest of the day.
The idea is to push demand away from the peak, when the grid is strained, towards cheaper times. ToD is spreading to more consumers under the Rights of Consumers Rules, but the slabs, the hours and the rate multipliers are set in each SERC tariff order and change yearly. So verify the current slabs for your client's state, and do not treat any multiplier as universal.
How ToD changes export value
ToD changes solar export value because, under net metering, the worth of an exported unit depends on the slab it is credited in. With a flat tariff, a unit exported is a unit imported, and the value is plain. With a ToD tariff, the value shifts by the hour.
Net metering nets your export against your import in units, but when the tariff varies by time, the rule that converts those units into rupees matters. Some SERC orders credit export at a time-weighted value; others net units within the same slab. The mechanism is set in the tariff order, so read it for your state before you promise a number.
The solar timing problem
The core issue is timing. Solar generates most around midday, and a business often uses that power on site, which is good. But surplus solar is exported at midday too — a time some tariff orders price as a cheaper slab. Meanwhile the business buys power back in the evening peak, after the sun has set, at the highest rate.
Self-consumption beats export
Because export can be credited at a lower value than the evening import rate, the best outcome is to use solar on site rather than export it. A factory that runs through the day captures most of its solar directly and exports little. An office that empties at 6 pm exports a lot at midday and buys back in the peak — a worse fit for ToD.
Match the system to the load shape
Size the system to the daytime load, not just the roof. Oversizing a low-daytime-load site under a ToD tariff can push lots of cheap midday export while the costly evening peak stays on the grid. Read the client's load profile first.
A ToD tariff-band example
The table below shows an illustrative ToD band structure to explain the idea. The hours, the band names and the rate levels are examples only — your client's actual slabs and multipliers are set in the SERC tariff order and change yearly, so verify the current order.
Source: illustrative structure based on common SERC ToD tariff designs and MoP ToD provisions. Bands, hours and rate levels are examples only — verify the current slabs and multipliers in your state's SERC tariff order.
The lesson from the example: solar lands in the day and midday bands, while the customer's most expensive band is the evening peak, when solar is gone. That gap is what makes ToD modelling different from flat-rate modelling.
ToD and banking of credits
Under net metering, surplus export is often banked as a credit and carried forward. With a ToD tariff, the question is whether a unit banked in a cheap midday slab can be drawn down against a costly evening unit, or only against the same slab.
Some SERC orders apply a time-band rule to banking, so a midday credit does not fully offset an evening peak unit. Others net within the settlement period more simply. How credits carry and settle is set per state, so check the surplus settlement rules for your client's DISCOM and verify the current order.
What it means for C&I clients
For a commercial or industrial (C&I) client, ToD can swing the payback either way. A daytime- heavy load — a factory, a cold store, a data-light office that runs 9 to 6 — captures most of its solar on site and gains a lot. An evening-heavy or low-daytime load exports cheap and buys expensive, so the gain is smaller.
Does ToD even apply to this client?
ToD usually applies to C&I consumers and larger loads first, with the threshold widening over time. The applicability threshold is set in the SERC tariff order and changes, so confirm whether ToD applies to this specific client before you model anything. For larger loads, also weigh the net metering vs open access choice, which can change the economics again.
ToD, batteries and load shifting
A battery can turn the ToD timing problem into an advantage. Store cheap midday solar, then use it during the costly evening peak instead of exporting it for a lower credit. This load shift can be worth more than export when the peak-to-midday price gap is wide.
Whether it pays off depends on the slab gap, the battery cost and the net-metering rules in the state. The net metering vs battery storage guide walks through the trade-off. Verify the current SERC slabs before you model the benefit, because a small gap rarely justifies the battery.
Quoting ToD clients honestly
An honest ToD quote starts with the client's load profile — when they actually use power — and the current SERC slabs, not a flat average rate. Model the self-consumption, the export value by slab, and the peak buy-back, then show a payback range, not a single rosy number.
Build the savings in the ROI and payback worksheet with the real slabs, and mark every slab figure "verify with SERC". A C&I client who later finds the export was credited at a lower rate will not trust the next quote.
How SuryaHub helps you quote ToD clients
Flat-rate quotes break on ToD clients. SuryaHub lets EPCs build a C&I quote using the client's load profile and the state ToD slabs, so the export value and payback reflect real timing. It keeps each state's net-metering rules and tariff notes in one place, so the slabs you quote are current. SuryaHub is pre-revenue; real pilots are Suryantra Energy and RGESPL, and every ToD slab here is illustrative and must be verified with the SERC.
Quote ToD clients with real slabs
See how SuryaHub models export value against time-of-day tariffs.
Related guides
Frequently asked questions
What is a time-of-day (ToD) tariff?+
A time-of-day tariff charges different rates for electricity depending on the time you use it. Peak hours, usually in the evening, cost the most, and off-peak hours, usually at night, cost the least. ToD slabs and rates are set in each SERC tariff order and change yearly, so verify the current slabs.
How do ToD tariffs change solar export value?+
ToD tariffs change solar export value because solar generates in the day, often during cheaper slabs, while demand peaks in the evening when solar has stopped. Under net metering, the value of an exported unit depends on the slab it is credited in. The peak/off-peak multipliers are set per SERC, so verify the current slabs.
Why does solar export earn less under a ToD tariff?+
Solar export can earn less under a ToD tariff because solar peaks at midday, which some tariff orders treat as a lower-priced slab, while the customer buys back power in the costly evening peak. The exact effect depends on how the SERC slabs and multipliers are set, so verify the current order before quoting.
Do batteries help with ToD tariffs and net metering?+
Batteries can help with ToD tariffs by storing cheap midday solar and using it during the costly evening peak, instead of exporting it for a lower credit. Whether this pays off depends on the slab gap, the battery cost and the net-metering rules. Verify the current SERC slabs before modelling the benefit.
Do ToD tariffs apply to all net-metering customers?+
ToD tariffs do not apply to all customers. They usually apply to commercial and industrial consumers and to larger loads first, with the threshold widening over time. The applicability threshold is set in each SERC tariff order and changes, so verify whether ToD applies to your client before quoting.
How does SuryaHub help quote ToD net-metering clients?+
SuryaHub lets EPCs model a C&I quote with the client load profile and the state ToD slabs, so the export value and payback reflect real timing, not a flat rate. SuryaHub is pre-revenue; real pilots are Suryantra Energy and RGESPL, and all ToD slabs must be verified with the SERC.
Sources & references
ToD provisions come from the Ministry of Power, and the actual slabs and multipliers come from each state's SERC tariff order. Always confirm the current slabs before you quote a client.
- Ministry of Power ↗
Electricity (Rights of Consumers) Rules, including ToD tariff provisions.
- State Electricity Regulatory Commissions (e.g. MERC) ↗
Tariff orders that set ToD slabs and peak/off-peak multipliers.
- Ministry of New & Renewable Energy (MNRE) ↗
Rooftop solar policy context for C&I consumers.
Written by the SuryaHub team · reviewed against MoP & SERC sources · updated 19 June 2026.
Method: ToD provisions are taken from the Rights of Consumers Rules and the band example from common SERC tariff designs, re-checked every 30 days. All slabs and multipliers are illustrative and change yearly — verify the current SERC tariff order. SuryaHub is pre-revenue; only Suryantra Energy and RGESPL are real pilots.
Change log: 19 Jun 2026 — first published.