Everyday Calculators
Electricity Usage Comparison Calculator
Compare monthly energy and fixed charges for two plans, keep the one-time switch cost assigned only to Plan B, and show monthly savings, horizon totals, and the monthly saving required to recover that cost within the selected horizon.
Total monthly electricity use (kWh)-
Plan A monthly energy charge-
Plan A estimated monthly bill-
Plan B monthly energy charge-
Plan B estimated monthly bill-
Plan B monthly saving versus Plan A-
Plan A cost through horizon-
Plan B cost including switching-
Plan B saving through horizon-
Monthly saving needed for horizon recovery-
Decision view
Flat-rate versus time-of-use tariff map
Flat-rate versus time-of-use tariff mapOff-peak and peak consumption are placed on a 24-hour tariff band before monthly and horizon costs are compared.
Exact scenario comparisonPeak electricity use per month (kWh) changes while all other entered assumptions remain constant.
| Peak electricity use per month (kWh) | Total monthly electricity use (kWh) | Plan A monthly energy charge | Plan A estimated monthly bill | Plan B monthly energy charge | Plan B estimated monthly bill | Plan B monthly saving versus Plan A | Plan A cost through horizon | Plan B cost including switching | Plan B saving through horizon | Monthly saving needed for horizon recovery |
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How to use Electricity Usage Comparison Calculator
- Export a representative interval-usage period and allocate every kWh to the tariff's actual off-peak and peak clock windows.
- Enter Plan A and Plan B energy rates, recurring fees, switching cost, and comparison horizon from current tariff documents.
- Calculate both monthly bills from the same 600 kWh profile before applying the one-time switching cost.
- Compare actual monthly savings with the monthly saving required to recover switching cost within the entered horizon.
- Repeat the comparison for heating, cooling, shoulder-season, occupancy, and load-shifting cases before choosing a plan.
Calculator guide
Understanding Electricity Usage Comparison Calculator
A flat tariff and a time-of-use tariff must price the same off-peak and peak consumption before switching cost is considered.
Detailed calculation process
Price one load profile under flat and time-of-use tariffs
The default uses 420 off-peak kWh, 180 peak kWh, a $0.21/kWh flat rate with a $15 fee, Plan B rates of $0.14 and $0.28/kWh with a $24 fee, a $65 switching cost, and 24 months.
General formula: E = E_o+E_p; A = E r_A+F_A; B = E_o r_o+E_p r_p+F_B; S = A-B; H_A = Am; H_B = Bm+C; S_H = H_A-H_B; S_req = C/m Both plans price the same entered energy profile. The one-time cost is excluded from monthly Plan B cost and added once to its horizon total; dividing that cost by months gives the monthly saving required for recovery within the horizon.
What each symbol means
Worked substitution with the default inputs
Under the default constant profile, Plan B saves $7.80 monthly and $122.20 over 24 months after the $65 switching cost; the required monthly recovery threshold is about $2.71.
Tariff contract
Translate the utility schedule before comparing prices
The model is only as accurate as the clock windows and bill components entered for each plan.
Tariff references: U.S. Department of Energy, Evaluating Your Utility Rate Options (https://www.energy.gov/cmei/femp/evaluating-your-utility-rate-options) and Demand Response and Time-Variable Pricing Programs (https://www.energy.gov/cmei/femp/demand-response-and-time-variable-pricing-programs). The controlling source remains the customer's current utility tariff.
Load profile
Test whether cheap-period use is durable
A favorable average depends on when electricity is consumed, not only on the monthly kWh total.
Decision map
Read monthly economics and horizon economics separately
A lower monthly bill does not automatically create positive horizon value after switching cost.
Worked situations
Practical examples
- The default 420 off-peak kWh plus 180 peak kWh gives the same 600 kWh monthly total under both plans.
- Plan A costs $126 in energy plus a $15 fixed fee, or $141 per month; Plan B costs $109.20 in energy plus $24 fixed, or $133.20.
- Plan B saves $7.80 per month before switching cost. Over 24 months, Plan A costs $3,384 and Plan B costs $3,261.80 including the $65 switch, leaving $122.20 of horizon savings.
- Recovering a $65 switch within 24 months requires at least $2.71 monthly savings. That output is a required monthly threshold, not a recovery-time result.
Better inputs
Useful tips
- Use utility interval data rather than estimating peak share from a whole-month bill.
- Model shoulder periods separately outside this two-period calculator when the tariff includes them.
- Run several seasonal profiles because heating, cooling, water heating, and occupancy can move peak share.
- Confirm enrollment fees, credits, minimum terms, opt-out rules, rate revisions, and switching dates directly with the utility.
Before relying on the result
Limitations and common mistakes
- Taxes, demand charges, tiers, credits, minimums, export compensation, and automatic load shifting are excluded.
- Rates, fixed fees, and the entered monthly usage profile remain constant through the horizon.
- The horizon comparison is nominal and does not discount future savings or model rate escalation.
- A two-period model cannot reproduce tariffs with shoulder periods, critical-peak events, real-time prices, seasonal windows, or demand ratchets.
Reference
Key terms
- Flat plan
- One entered variable energy rate applied to all monthly kWh.
- Time-of-use plan
- A tariff that prices entered kWh differently in defined off-peak and peak periods.
- Off-peak share
- Off-peak kWh divided by total kWh for the measured usage profile.
- Peak share
- Peak kWh divided by total kWh for the measured usage profile.
- Monthly saving B
- Plan A estimated monthly bill minus Plan B estimated monthly bill before switching cost.
- Horizon cost
- Monthly plan cost multiplied by entered months, with switching cost added once to Plan B.
- Horizon saving B
- Plan A horizon cost minus Plan B horizon cost including switching cost.
- Required monthly switch recovery
- Switching cost divided by comparison months; the minimum monthly savings needed to recover that cost by the horizon.
Important note
Confirm current tariff windows and all bill components with the utility. The result assumes the same entered monthly load profile and rates persist for the full horizon and does not guarantee realized savings.
Frequently asked questions
Why can Plan B cost more despite a lower off-peak rate?
Peak pricing and fixed fees can outweigh the off-peak discount, especially when the household cannot move its largest loads.
What if monthly saving is negative?
Plan B cannot recover its switching cost under those inputs and its horizon result will be worse than the flat plan.
What does the switch-recovery result mean?
It is the monthly saving required to offset the one-time switching cost by the entered horizon. It is not the number of months to break even.
Are taxes and demand charges included?
No, unless already embedded in entered rates or fees. Demand-based and multi-period tariffs need a more detailed model.
Does the model shift load automatically?
No. It prices the entered off-peak and peak quantities, so every load-shifting scenario must be entered explicitly.