Time of Day Tariff Calculator
Peak, normal and off-peak consumption costed separately, with the demand charge alongside — and the figure that actually matters, which is what moving load out of the peak band is worth over a year.
Consumption
Tariff
What could move
Shifting units between bands does not reduce consumption, so it does nothing for the demand charge unless the peak demand itself moves. If the demand charge is the larger line on your bill, cutting the peak matters more than moving units.
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Time of Day Tariff Calculator · ToD / TOU tariff structure · EnergyCalcHQ · energycalchq.com
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The gap is the point, not the peak rate
A Time of Day tariff charges different rates at different hours — typically a surcharge of 15–25 % during morning and evening peaks, the base rate through the day, and a rebate of a similar size overnight.
Most reactions to a ToD tariff focus on the peak surcharge, which is the wrong number. What matters is the difference between the peak and off-peak rates, because that difference is what a shifted unit earns. Everything else is just the bill.
If a unit costs 20 % more at peak and 20 % less overnight, moving it saves 40 % of the base rate — not 20 %. That is the entire economics of load shifting in one line.
Who is being paid, and for what
A ToD tariff is not a penalty. It is the utility passing on its own cost structure: evening peaks are met by the most expensive generation on the system, and overnight there is surplus capacity nobody is using. You are being offered a discount for rescheduling.
Two consequences follow. A plant that genuinely cannot move anything is simply paying more, and should say so when the tariff is negotiated. A plant with any flexible load is being handed a saving that costs nothing but a change to a timer.
What can actually shift
| Load | Shiftable? |
|---|---|
| Water pumping to an overhead tank | Almost always — the tank is the storage |
| Cold storage pull-down | Yes — thermal mass carries through peak |
| Battery and EV charging | Yes, and it is the easiest of all |
| Batch processes, mixing, grinding | Often, with scheduling |
| Compressed air into receivers | Partly |
| Electroplating, heat treatment | Sometimes — long cycles suit night running |
| Production line | Only if you move the shift |
| Lighting, HVAC, offices | No — they follow occupancy |
The honest input to this calculator is not “what fraction of our load is in the peak band” but “what fraction could we move without anybody noticing”. On most plants that is 10–30 % of the peak, and it is worth measuring rather than guessing — the method is in turning meter data into savings.
Shifting does not touch the demand charge
This is the trap. A ToD saving is an energy saving: you consume the same units, later. The demand charge is billed on the highest recorded kVA in the month, and moving units between bands does nothing to it unless the peak demand itself falls.
Worse, careless shifting can make demand worse. Move three batch processes to the same off-peak hour and you have built a new peak overnight — one that sets your demand charge for the month while saving a few hundred rupees on energy.
Stagger what you shift. And if the demand charge is the larger line on your bill, the priority is cutting the peak, not moving units — which usually means power factor correction first, because that reduces kVA without touching production at all. Work out what it is worth with the power factor calculator.
Where storage changes the arithmetic
A battery turns a ToD tariff into an arbitrage: charge at the off-peak rate, discharge during the peak. The margin per unit is the rate gap, less round-trip losses of 10–20 %.
Run the numbers before believing it. A gap of ₹2 per unit on a 100 kWh bank cycled daily is a few thousand rupees a month against a capital cost in lakhs — payback measured in years, and the bank wearing out on daily cycling. Storage for ToD arbitrage alone rarely pays; storage that also provides backup, or that soaks up surplus solar, often does. Size it with the battery bank calculator, which applies the depth-of-discharge and rate effects that make nameplate Ah misleading.
Before you act on the number
- Get the actual band timings from your tariff order. They differ by state and by season, and some tariffs have two peak windows a day.
- Get the band split from interval data, not from an estimate. Your meter records it; the DISCOM portal usually exposes it.
- Check whether the demand charge is also time-differentiated. Some tariffs bill peak-hour demand separately, which changes the priority entirely.
- Confirm the meter supports ToD registers before designing around it — see choosing an energy meter.