Calculator Inputs
Example Data Table
These sample values show how energy and cost scale with runtime and wattage.
| Tool | Power (W) | Run (min/use) | Uses/week | Efficiency | Standby (W) | Monthly kWh | Monthly cost |
|---|---|---|---|---|---|---|---|
| Cordless mower charger | 150 | 45 | 1 | 0.88 | 3 | 3.31 | 0.66 |
| Leaf blower | 1200 | 15 | 2 | 0.92 | 0 | 2.36 | 0.47 |
| String trimmer | 500 | 25 | 2 | 0.90 | 2 | 4.23 | 0.85 |
Formula Used
- Hours per use = minutes ÷ 60
- Run energy (kWh) = (watts ÷ 1000) × hours per use × uses per week × weeks per month ÷ efficiency
- Standby energy (kWh) = (standby watts ÷ 1000) × standby hours per day × 30.437 days
- Total monthly kWh = run energy + standby energy
- Monthly cost = total monthly kWh × electricity price
- Monthly CO2 = total monthly kWh × CO2 factor
How to Use This Calculator
- Enter your electricity price per kWh from your bill.
- Set weeks per month, or keep the default average.
- Add each garden tool and its typical weekly use.
- Use the nameplate wattage, or manual’s rated watts.
- Set efficiency below 1.00 for extra losses.
- If chargers stay plugged in, add standby watts.
- Press Calculate to view totals above the form.
- Download CSV or PDF to save your monthly report.
Turning wattage and runtime into monthly kWh
Start with the tool’s rated watts and your typical minutes per use. Converting minutes to hours and multiplying by uses per week reveals weekly energy demand. The calculator then scales that weekly demand to a month using your selected weeks-per-month value. This approach models realistic yard routines, so two short sessions can cost less than one long cleanup day.
Setting electricity price for accurate budgeting
Energy cost depends heavily on the price per kilowatt-hour shown on your bill. If your utility has taxes, surcharges, or time-based pricing, use a blended average that reflects what you actually pay. Updating this single input makes the calculator useful for comparison shopping, because you can immediately see how the same tool behaves under different tariffs.
Accounting for efficiency losses in tools and chargers
Not every watt drawn becomes useful cutting or blowing power. Motors, inverters, and chargers lose energy as heat, especially under heavy loads or older hardware. The efficiency factor adjusts kWh upward to represent those losses. Use 1.00 when unsure, or set 0.85–0.95 when you suspect extra loss from worn blades, dull chains, or inefficient charging.
Including standby draw that quietly accumulates
Many garden setups include a charger, dock, or power brick that stays plugged in for convenience. Even a few standby watts running for hours each day can add meaningful monthly kWh. By entering standby hours per day and standby watts per tool, you can decide whether unplugging, using a switch, or consolidating chargers is worth the effort.
Using exports to compare options and track changes
After calculating, export CSV for spreadsheets or PDF for quick records. Compare models by keeping the same runtime and weekly frequency, then swapping wattage and efficiency assumptions. Re-run results after maintenance, like sharpening blades or cleaning filters, to quantify improvements. This turns the calculator into a practical log for reducing operating cost without reducing garden work. Store seasonal versions to revisit before mowing, trimming, and leaf-fall weeks each.
FAQs
1) Where do I find my tool’s wattage?
Check the nameplate, manual, or charger label. If only amps and volts are listed, multiply them to estimate watts. Use a conservative value if the tool has multiple settings.
2) What efficiency value should I enter?
Use 1.00 if you are unsure. For older chargers or heavy loads, 0.85–0.95 is a reasonable range. Lower values increase kWh to reflect losses.
3) Should I include charging time as tool runtime?
No. Enter tool runtime in minutes per use. Charging impact is captured through efficiency and standby watts. If you know charger watts during active charging, add a separate “Charger” row.
4) Why does standby power matter so much?
Standby runs for many hours. Even 2–3 watts over a month becomes noticeable energy. If you unplug chargers between uses, set standby hours per day to zero.
5) Can I estimate seasonal months like summer mowing?
Yes. Increase uses per week and runtime per use to match that month. Keep the electricity price the same, and export results to compare summer versus winter patterns.
6) Why is my bill different from this estimate?
Bills include other appliances, fixed fees, and pricing tiers. This tool isolates garden equipment energy only. Use a blended price per kWh and realistic usage to improve alignment.