Calculator Inputs
Example Data Table
Sample scenario for a typical residential pool. Replace with your exact power draw and schedule.
| Item | Current Pump | Variable-Speed | Notes |
|---|---|---|---|
| Power (kW) | 1.50 | 0.60 | Lower average draw at reduced speed |
| Hours/day | 8 | 8 | Same hours for comparison |
| Days/month | 30 | 30 | Runs daily |
| Electricity ($/kWh) | 0.18 | Local utility rate | |
| Upfront (net) | $900 | Excludes rebate/installation in this example | |
Formula Used
- Monthly energy (kWh): kW × hours/day × days/month
- Monthly cost: monthly kWh × electricity rate
- Monthly savings: current cost − new cost
- Annual savings: monthly savings × 12 (+ annual maintenance savings)
- Net upfront cost: (pump + installation) − rebate
- Simple payback (years): net upfront ÷ annual savings
- Lifetime savings: sum of annual savings over life (energy portion escalated)
- NPV: Σ(annual savings ÷ (1 + discount rate)^t) − net upfront
- ROI (%): ((lifetime savings − net upfront) ÷ net upfront) × 100
How to Use This Calculator
- Find your current pump’s typical power draw in kW and enter hours and days used.
- Enter the variable-speed pump’s average kW and its operating schedule.
- Add your electricity rate and any costs, rebates, or yearly maintenance changes.
- Set expected life, discount rate, and energy price escalation for longer-term views.
- Press Calculate Savings to view results above, then export to CSV or PDF.
Insights
Energy profile and run time
Variable-speed pool pumps can cut electricity use by aligning flow with real filtration demand. A single-speed motor often runs near full load even when the pool only needs gentle circulation. If a 1.50 kW pump runs 8 hours for 30 days, usage is 360 kWh per month before adding heaters or lights. Lowering average draw is the primary driver of savings.
Monthly savings calculation
To estimate savings, compare monthly energy for both setups: kW × hours per day × days per month. Using the same schedule, a variable-speed average of 0.60 kW would use 144 kWh monthly, saving 216 kWh. At $0.18 per kWh that is about $38.88 per month, or $466.56 per year, which provides a realistic benchmark for many households.
Upfront cost and payback
Upfront economics depend on net cost and any incentives. Net cost equals equipment plus installation minus rebates or utility credits. Simple payback divides net cost by total annual savings, including any maintenance changes you expect. ROI helps compare upgrades: it measures lifetime savings minus net cost, divided by net cost. A lower net cost or higher savings usually improves both metrics. Include seal replacements, basket cleaning time, or service calls as annual adjustments; even small recurring costs can alter payback directly noticeably over years.
Discounted cash flow and NPV
Longer horizons benefit from discounting and price assumptions. The calculator discounts future savings using your chosen rate and can escalate electricity prices annually to reflect tariffs. NPV reports today’s value of the savings stream after subtracting net cost. A positive NPV suggests the upgrade beats the discount rate. If escalation exceeds the discount rate, the later-year savings become more important.
Operational validation and optimization
Operational choices influence outcomes. Running longer at lower speed can maintain turnover while keeping power low, but verify skimmer action, cleaner performance, and filter pressure. After installation, compare utility bills or a plug-in meter against the baseline. Update power and hours with measured values to refine payback. Consider seasonal schedules, because summer runtime changes can shift annual savings materially.
FAQs
How do I estimate average kW for a variable-speed pump?
Use the pump display, a smart plug, or nameplate curves. Record watts at your common speeds, weight by time at each speed, and divide by 1000 to get average kW.
Should I enter longer run time for variable speed?
Yes, if you plan to run more hours at lower speed. Enter your expected hours so the calculator reflects your circulation strategy and avoids overstating savings.
Do rebates and incentives change payback?
Rebates reduce net upfront cost, which shortens payback and raises ROI. Enter the rebate as a dollar amount applied after equipment and installation costs.
What discount rate should I use for NPV?
Use a rate that matches your alternative return or financing cost. Many homeowners choose 4%–10%. Higher discount rates reduce the present value of future savings.
Why include energy price escalation?
Electricity rates can rise over time. Escalation increases future energy savings while keeping maintenance savings flat, helping you model long-term scenarios more realistically.
How accurate is the CO₂ estimate?
It is an approximation based on your chosen kg per kWh factor. Use a local grid factor if available. The calculator multiplies annual kWh savings by that factor.