TOD Tariff: Evaluating Its Impact on Solar Energy in India

Time-of-Day (ToD) tariffs change one basic assumption many C&I solar buyers used to make: that every grid unit costs the same through the day. Once your bill has different prices for solar hours, shoulder hours, and peak hours, the “value” of each kWh from your rooftop also changes. For businesses in Maharashtra, where rooftop solar decisions are often driven by payback and predictable savings, this shift makes hourly planning just as important as plant capacity.

What ToD tariffs mean for C&I electricity bills in India

Under ToD, your energy charge is linked to when you consume electricity. The Ministry of Power’s direction (being implemented via state regulations and smart metering rollouts) broadly pushes two clear signals:

• a discounted “solar hours” window in the daytime (often around 8 hours)

• a premium “peak hours” window, typically evening and sometimes morning

A simple illustration used in policy discussions is a 10 to 20% discount on electricity during solar hours and a 10 to 20% premium during peak hours (state rules can vary). Even if your fixed charges and demand charges remain the same, the variable energy part of the bill starts behaving very differently.

This matters because most C&I solar plants generate heavily in late morning and early afternoon, while many businesses consume heavily in the evening, or run mixed shifts where the last few hours are the costliest.

Why solar savings become more “timing-dependent” under ToD

Rooftop solar usually creates savings in two ways, especially when aligned with renewable energy goals:

1. Self-consumption savings: you avoid buying a unit from the grid because your plant produced it.

2. Export credits (net metering or net billing): surplus solar goes to the grid and gets credited based on the applicable mechanism.

ToD mainly changes the first part, and in some states it may also change the second, as tariffs can vary significantly.

If your solar generation happens during a discounted solar-hours tariff, the avoided cost per unit is lower than it would be under a flat tariff. That can feel counter-intuitive: you are producing clean energy, yet the grid price at that time is intentionally cheaper.

At the same time, ToD increases the penalty for consuming in peak blocks. If your facility buys more units in the peak block because your solar is not available then, the overall bill impact can be mixed unless you plan for it.

A quick numeric example (illustrative, not a quote of any one DISCOM)

Assume a base energy rate of ₹6.00/kWh for simplicity:

• solar hours at 20% discount: ₹4.80/kWh

• peak hours at 20% premium: ₹7.20/kWh

• shoulder/off-peak: ₹6.00/kWh

Now compare two facilities, each installing the same rooftop solar capacity:

• Facility A runs most of its load between 10 am and 6 pm.

• Facility B runs a large chunk of load between 6 pm and 10 pm.

Facility A will use more solar directly (high self-consumption), but each avoided unit offsets ₹4.80 rather than ₹6.00. Facility B may use less solar directly, and still buy expensive peak units at ₹7.20, unless it shifts load or adds storage.

Illustrative ToD blocks and what they do to solar value

The message is not “solar becomes unattractive”. The message is “solar-alone savings depend on how your load sits against ToD blocks”.

Net metering vs ToD: where businesses can get surprised

Many C&I decision-makers are used to net metering logic that feels like one-for-one unit banking. With ToD, regulators may choose different ways to apply credits:

• credit exported units based on the time block in which they were exported

• net units at the end of the billing cycle but apply ToD rates separately to import and export

• continue simplified netting for some categories until full smart metering implementation

The practical risk is this: exporting surplus during discounted solar hours may earn a lower credit value than the cost of importing later during peak hours.

So, ToD pushes businesses toward higher on-site usage of solar rather than exporting large surpluses, unless the state mechanism clearly protects one-for-one value across time blocks.

In Maharashtra, where approvals, tariffs, and metering processes can differ across DISCOM areas and consumer categories, it is wise to model savings using your actual interval data and the latest tariff schedule, not a generic payback assumption.

The ROI levers that matter more once ToD starts

A ToD-aware solar plan focuses on three levers instead of only plant size.

After you map your load curve, these changes often have outsized impact:

• Process scheduling

• Plant orientation and generation profile

• Storage and controls to cover peak windows

Done well, the solar plant becomes a bill-optimisation asset, not only an electricity generator, with a focus on renewable energy sources.

Here are common improvement areas that usually show up when C&I teams review their hourly data:

• Shiftable pumping and water treatment loads

• HVAC pre-cooling in commercial buildings

• Compressed air scheduling in factories

• Batch processes that can move by 2 to 4 hours

• EV charging windows for fleets

Load shifting: the lowest-capex response to ToD

If you can move consumption away from peak hours, you save twice:

• you avoid the premium peak rate

• you often increase solar self-consumption during daytime

This can be as simple as changing start times, adding timers, setting production sequencing rules, or updating SOPs for energy-heavy equipment.

A useful way to think about it is the tariff spread. In the earlier illustration, moving 1 kWh from ₹7.20 to ₹4.80 saves ₹2.40 for that unit, even before considering demand charges.

The key is to pick loads that are operationally safe to move and easy to control.

Solar plant design choices that become more valuable under ToD

ToD creates a fresh conversation around design, especially considering the ToD tariff impact on solar India. A plant designed only for maximum annual kWh may not be the plant that gives best tariff savings.

A few design moves can help align generation with expensive hours:

• East-west (split) orientation to widen the generation window and reduce sharp noon peaks

• Slight west bias where late-afternoon generation has higher value for your tariff and load curve

• Sizing to self-consumption rather than oversizing into frequent export, where export value is uncertain under ToD application

These are not universal rules. A warehouse with daytime material handling looks different from a three-shift factory or a hospital. The right design comes from matching generation shape to consumption shape.

Batteries under ToD: when do they start making financial sense?

Batteries are often discussed as the direct answer to ToD, because they can store midday solar and supply evening peak. Still, the economics depend on a few site conditions:

A battery makes more sense when the site has a real peak window exposure and a reliable daily surplus to charge it, or when the tariff spread is wide enough to justify cycling.

If you are evaluating storage, a good internal review typically checks:

• Daily peak duration: a 2 to 4 hour expensive window is easier to target than an all-evening premium.

• Solar surplus profile: consistent surplus after meeting daytime loads improves utilisation.

• Demand charges and peak demand: batteries can also reduce kVA peaks, which may add value beyond energy charges.

One caution: storage returns depend on discipline in controls. A battery that discharges too early, or charges from the grid at the wrong time block, can dilute savings.

A practical way to model ToD impact before you finalise solar sizing

A reliable assessment does not need complex software on day one. It needs your data in the right shape.

After you collect at least 15-minute interval data (or hourly), a ToD-first evaluation usually follows this sequence:

• Baseline: apply ToD rates to your current profile and compute the monthly bill split by time block.

• Solar simulation: overlay expected solar generation by time of day for your roof and location.

• Netting logic: apply the relevant state mechanism for export and import crediting.

• Operational scenarios: test 2 or 3 load shifting moves that your team is comfortable implementing.

• Storage scenario (optional): run one battery size with a strict peak targeting schedule.

The goal is not to forecast perfectly. The goal is to avoid a design that looks great on annual units but weak on billed savings.

After a paragraph like this is where a short checklist helps teams stay aligned:

• Quick access to smart meter or sub-meter data

• Clear ToD slots and seasonal definitions from the applicable tariff order

• A list of top 5 energy-consuming equipment and their operating windows

• Roof constraints: shade, structure, setbacks, and usable area

• A decision on export appetite: minimise export vs allow surplus for future loads

What C&I users in Maharashtra should watch closely

ToD is a policy direction, but the billing reality is created by the state tariff order, metering rules, tariffs, and DISCOM processes, significantly influencing the ToD tariff impact on solar in India. For many SMEs, the difference between expected and actual savings comes down to these implementation details:

• Time blocks and seasons: peak periods may shift by season, and some categories may have more than one peak.

• How credits are applied: time-linked credits vs simplified monthly netting can change the export value.

• Demand charges: even if energy is cheaper in solar hours, a short peak in kVA can still hurt the bill.

• Approval timelines and meter configuration: if the meter is not configured for ToD correctly, billing disputes become time-consuming.

This is where a Maharashtra-focused EPC partner helps, because the project is not only about modules and inverters. It is also about approvals, net metering coordination, and long-run performance support.

How Solarising typically approaches ToD-aware rooftop solar planning

Solarising works with businesses across Maharashtra on rooftop solar projects where savings certainty matters more than headline kW. A ToD-aware approach usually starts with feasibility and hourly savings logic, then moves to execution across approvals, installation, and ongoing support.

Many sites do not need complicated interventions, especially when integrating renewable energy solutions like optimizing electricity use. They need a clean answer to a simple question: Which hours will this solar plant actually reduce my purchased units, and at what rate? Once that is clear, the system design, orientation, and optional storage choices become easier to justify internally.

A final list, this time with decision-oriented prompts, can help when you are comparing proposals:

• What is the assumed tariff basis: flat energy rate, or ToD blocks with peak and solar-hour adjustments?

• What export method is assumed: net metering crediting rules as per your category, or net billing with a separate export rate?

• How is self-consumption estimated: based on your interval data, or a generic percentage?

• What happens if peak shifts: does the savings model handle seasonal ToD windows and future tariff changes?

• Who owns performance tracking and O&M: monitoring, response time, cleaning plan, and generation guarantees (if any)

When ToD rolls into your billing, solar still reduces electricity costs, but the biggest wins go to businesses that treat timing as a design input, not an afterthought.