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Example data table
| Scenario | Loads/week | Old kWh/load | New kWh/load | Rate | Upfront | Year 1 savings |
|---|---|---|---|---|---|---|
| Light use | 4 | 3.1 | 1.9 | 0.14 | $650.00 | $49.94 |
| Average use | 6 | 3.2 | 1.8 | 0.16 | $650.00 | $84.89 |
| Heavy use | 10 | 3.6 | 1.6 | 0.18 | $750.00 | $202.20 |
Formula used
- Loads per year = Loads per week × 52
- Annual kWh = kWh per load × Loads per year
- Annual energy cost = Annual kWh × Electricity rate
- Year 1 savings = (Old energy − New energy) + (Old maintenance − New maintenance)
- Net upfront cost = Purchase − Rebates − Old resale
- Simple payback = Net upfront ÷ Year 1 savings
- Discounted savings (year t) = Savings(t) ÷ (1 + Discount rate)t
- NPV = −Net upfront + Σ Discounted savings(t)
How to use this calculator
- Estimate your average loads per week over a normal month.
- Enter kWh per load for your current and new dryer.
- Add your electricity rate from a recent bill.
- Include the purchase cost and any rebates or trade-in value.
- Adjust life, escalation, and discount rate if needed.
- Click Calculate savings and download the CSV or PDF.
Operating cost baseline
The calculator standardizes operating cost by converting loads per week into annual loads, then multiplying by kWh per load and your electricity rate. This produces an annual energy cost for the existing dryer and the replacement unit.
Usage driven savings
Savings are driven by both behavior and efficiency. Moving from 3.2 to 1.8 kWh per load at six loads weekly reduces use by about 437 kWh per year. At 0.16 per kWh, that is roughly $70 in annual energy savings, before any maintenance change.
Upfront and payback
Upfront economics depend on incentives. Net upfront cost equals purchase price minus rebates and any resale value of the old dryer. With a $950 purchase and $150 incentive, net upfront is $800. Simple payback divides net upfront by year‑one total savings to estimate break‑even.
Discounted lifetime value
Because savings occur over time, the model applies escalation and discounting. Electricity escalation grows energy savings each year, and maintenance escalation can adjust service savings. A common planning choice is a 5–8% discount rate, reflecting alternative uses of cash. With 6% discounting, $100 saved in year five is worth about $75 today. Escalation assumptions matter too; a 3% electricity increase raises later-year savings, improving NPV and shortening discounted payback for many households.
Emissions and interpretation
If you enter a CO2 factor in kg per kWh, avoided emissions are calculated from annual kWh saved and reported as yearly and lifetime totals. Use the Plotly charts to validate realism: the bar comparison shows annual operating costs, and the cumulative discounted line shows when value turns positive. If results look extreme, revisit kWh assumptions, loads, and rebates. NPV is computed as the sum of discounted annual savings minus net upfront cost. A positive value suggests the upgrade meets your financial hurdle. Sensitivity is highest for kWh per load and electricity rate, so use label data when possible. For high-usage homes or higher tariffs, payback shortens materially and lifetime savings usually increase by a meaningful margin overall.
FAQs
What if my dryer is gas?
Use the electricity portion of cost for comparison, or convert gas cost to an equivalent per‑load cost. Enter kWh estimates that represent total drying energy you pay for.
How do I estimate kWh per load?
Start with the energy guide label, manual, or smart‑plug measurements. If unknown, test a few typical loads, record kWh used, and average the results.
Why can discounted payback differ from simple payback?
Simple payback ignores timing. Discounted payback reduces future savings using your discount rate, so it usually takes longer to recover the upfront cost.
Do rebates change the savings calculation?
Rebates reduce net upfront cost, which can shorten payback and increase NPV. They do not directly change annual energy savings unless the upgrade changes usage patterns.
How should I choose escalation rates?
Use your best estimate from recent utility bills or local trends. If uncertain, try a conservative range such as 0–3% and see how NPV and payback respond.
Is the CO2 estimate accurate for my location?
It is an approximation. The kg per kWh factor varies by grid mix and time of day. Use a factor from your utility or national grid data for a better estimate.