Example data
Use these sample values to test different scenarios and confirm your setup.
| Scenario | Baseline kWh/mo | New kWh/mo | Rate | Cost | Rebate |
|---|---|---|---|---|---|
| Lighting upgrade | 320 | 190 | $0.18 | $450 | $75 |
| HVAC tune-up | 900 | 810 | $0.20 | $220 | $0 |
| Process optimization | 2,500 | 2,125 | $0.16 | $1,600 | $200 |
| Behavior program | 1,150 | 1,035 | $0.14 | $80 | $0 |
| Equipment retrofit | 3,800 | 3,230 | $0.22 | $7,900 | $1,000 |
Formula used
- kWh saved (month) = max(0, baseline kWh/mo − new kWh/mo)
- Bill saved (month) = kWh saved (month) × rate per kWh
- Appliance kWh/mo = (watts × hours/day × days/month × quantity) ÷ 1000
- Net upfront cost = max(0, implementation cost − rebate)
- Annual savings (year y) = annual savings (year 1) × (1 + escalation)^(y−1)
- Discount factor (year y) = 1 ÷ (1 + discount rate)^y
- NPV = −net upfront cost + Σ(net annual savings × discount factor)
How to use this calculator
- Select a mode: direct, percent reduction, or appliance upgrade.
- Enter your electricity rate and how many months per year the measure applies.
- Provide baseline and new usage, or the reduction percent, or appliance details.
- Add cost, rebate, escalation, and discount rate for a realistic payback view.
- Submit to see results above, then download CSV or PDF if needed.
Usage baseline quality
Start with a baseline. Typical homes run 600–1,200 kWh monthly; small offices often 2,000–5,000. Use three recent bills and align for seasonal months. Enter baseline kWh/month and either new kWh/month, a reduction percent, or appliance wattage and run‑time. A solid baseline avoids inflated savings and clarifies whether the measure targets summer cooling or steady loads.
Savings translation to cash
kWh savings turn into money through the rate. At $0.18/kWh, saving 180 kWh per month equals about $32.40 monthly and $388.80 per year. The calculator multiplies saved kWh by the months-per-year setting for measures that operate part‑time, such as cooling upgrades. If you have tiers or time‑of‑use, test a low and high blended rate to bracket outcomes.
Upfront costs and incentives
Financial results hinge on net upfront cost. Enter implementation cost and subtract rebates or incentives to reflect cash outlay. Add annual maintenance for inspections, filters, or monitoring subscriptions. Example: an $850 upgrade with a $100 rebate costs $750 net. If savings uncertainty is high, run scenarios by adjusting both kWh reduction and rate, then compare payback and NPV across options.
NPV and payback view
For longer horizons, include escalation and discounting. Annual savings can grow with energy prices (for example 3% yearly) and future savings are discounted using your required return (for example 8%). Net present value equals discounted net savings minus net upfront cost. Simple payback estimates the break‑even year, while ROI compares discounted savings to cost, helping you rank projects competing for capital.
Operational tracking tips
Use results for planning, then verify with tracking. After implementation, record monthly kWh and compare a rolling average against baseline. If you provide an emissions factor in kg/kWh, the model estimates annual CO2 avoided for reporting. Re‑run the calculator when occupancy shifts, equipment degrades, or rates reset. Ongoing measurement turns a one‑time estimate into a reliable budget control.
FAQs
What rate should I enter?
Use your average delivered electricity price per kWh from recent bills. If you have tiers or time‑of‑use, test a low and high blended rate to see a realistic savings range.
How does appliance mode calculate kWh?
It converts wattage to kWh using: watts × hours/day × days/month × quantity ÷ 1000. You can still override baseline and new kWh values if you already track usage.
Why are my savings zero?
Savings are capped at zero if new usage is higher than baseline, or if baseline is missing in direct and percent modes. Recheck units, months-per-year, and the selected mode.
What does NPV mean here?
NPV is the value today of future net savings, discounted by your chosen rate, minus net upfront cost. Positive NPV suggests the upgrade beats your required return under the assumptions.
How is simple payback estimated?
The calculator accumulates annual net savings until the upfront cost is recovered. It interpolates within the break‑even year to estimate a fractional payback time.
Can I estimate emissions savings?
Yes. Enter an emissions factor in kg per kWh. The tool multiplies annual kWh saved by that factor to estimate CO2 avoided each year for reporting.