Track tariff windows and plan smarter daily usage. Model appliances, EV charging, solar, and batteries. Shift load, cut bills, and keep comfort intact always.
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| Scenario | Monthly kWh | Peak/Mid/Off % | Rates (Peak/Mid/Off) | Shift (to Off / to Mid) | Solar kWh | Battery discharge kWh | Est. Monthly Savings |
|---|---|---|---|---|---|---|---|
| Typical household | 900 | 45 / 20 / 35 | $0.32 / $0.22 / $0.14 | 25% / 10% | 120 | 60 | Varies by rates and behavior |
| EV-focused plan | 1200 | 35 / 20 / 45 | $0.35 / $0.25 / $0.12 | 30% / 5% | 0 | 0 | Often strong off-peak gains |
| Solar + storage | 800 | 50 / 20 / 30 | $0.30 / $0.21 / $0.13 | 15% / 10% | 200 | 90 | Higher savings when peak is avoided |
Time‑of‑use pricing raises peak rates when the grid is constrained and lowers off‑peak rates when capacity is available. If a home uses 900 kWh monthly and 45% occurs in peak hours, expensive energy dominates the bill. With sample rates of $0.32 peak, $0.22 mid, and $0.14 off‑peak, the blended energy price is about $0.24 per kWh before fixed charges.
The baseline cost equals period kWh multiplied by period rates, plus fixed and demand charges. An $18 fixed fee adds $216 annually regardless of usage. If demand charges apply at $12 per kW and your peak demand is 5.0 kW, demand adds $60 monthly. In many tariffs, these adders represent 20% to 35% of the total. Seasonal weather can shift peak shares, so revisit inputs every quarter quickly.
Shifting usage means moving flexible loads, such as laundry, dishwashers, pool pumps, or EV charging, out of peak windows. Moving 25% of peak kWh to off‑peak and 10% to mid shifts 157.5 kWh in a 900 kWh month. With an $0.18 spread between peak and off‑peak, that can produce about $28 in energy savings.
Self‑consumed solar reduces purchased kWh in the period where it is generated. If 120 kWh of solar is allocated 50% to peak and 30% to mid, peak purchases drop first. Batteries add another lever: delivering 60 kWh into peak with 90% efficiency requires 66.7 kWh of off‑peak charging, swapping costly peak energy for cheaper off‑peak energy.
Demand charges are driven by the highest interval kW, so reducing peak kW yields steady savings. A 10% reduction from 5.0 kW to 4.5 kW saves $6 monthly at $12 per kW. Combine shifting, solar offsets, and demand reduction to estimate annual savings, then compare with upfront cost. An $800 upgrade saving $40 per month implies a simple payback near 20 months.
The calculator normalizes peak, mid, and off‑peak percentages to total 100%. This keeps your kWh allocation consistent and prevents accidental overcounting when comparing baseline and new scenarios.
Use the demand value on your bill if available. If not, approximate from major loads running together, like air conditioning plus an oven or EV charging. A rough kW number still improves demand‑charge planning.
This model focuses on self‑consumed solar offsetting purchased kWh. If exports are credited differently on your tariff, treat them separately and set “solar self‑consumed” to the energy you actually use on site.
To deliver peak discharge, the battery must charge earlier. Because efficiency is below 100%, charging kWh can exceed discharge kWh. The benefit comes from purchasing those kWh at a lower off‑peak rate.
Negative savings means the new plan costs more. Common causes include small rate spreads, limited shifting, demand charges without reduction, or aggressive battery charging. Verify your rate windows and adjust assumptions.
Payback is a simple estimate: upfront cost divided by monthly savings. It ignores maintenance, financing, incentives, and seasonality. Use it to screen options, then refine with quotes and your utility’s rules.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.