Electricity calculator
Appliance Cost Comparison Calculator
Compare old and new appliance electricity cost using watts, daily hours, rate, and billing days.
When to use this calculator
Use this calculator before replacing a heater, fan, refrigerator, pump, dehumidifier, TV, computer, or other appliance. It shows whether lower wattage can realistically repay the purchase price.
Energy savings only matter when the appliance runs enough hours. A high-efficiency upgrade can be a smart buy for heavy-use appliances but less meaningful for devices used briefly.
Formula used
Monthly cost for each appliance = watts ÷ 1,000 × hours × days × rate. Savings = old cost − new cost.
The formula is intentionally simple so it can be used for quick planning. Real bills, quotes, and installation costs can include fixed fees, taxes, tiers, labor, product limits, and site-specific conditions that a calculator cannot see.
Input guide
| Input | How to use it |
|---|---|
| Old appliance watts | Use the current appliance label or measured wattage. |
| New appliance watts | Use product specifications for the replacement. |
| Hours and days | Keep usage the same for a fair comparison. |
| Electricity rate | Use your local kWh rate. |
Examples
Heater comparison
Replacing a 1,500 W unit with a 900 W unit used 3 hours daily can save 54 kWh per month.
Payback check
If the monthly saving is $9 and the upgrade costs $180, simple payback is about 20 months before other benefits.
How to get a more accurate result
- Compare appliances doing the same job under similar conditions.
- Use measured watts for appliances with variable draw.
- Include non-energy benefits separately, such as noise, safety, or comfort.
Common mistakes to avoid
- Assuming wattage savings equals money savings without usage hours.
- Ignoring purchase price and repair cost.
- Comparing appliances with different output or capacity.
Quick checklist before relying on the result
- Get both wattages.
- Use same usage hours.
- Calculate monthly savings.
- Compare savings with purchase price.
FAQ
Does lower wattage always mean better?
Not always. The appliance must still do the job properly and safely.
What is payback period?
Purchase price divided by monthly savings gives a simple payback estimate.
Should I include maintenance?
Yes for a full decision, especially for old appliances that may need repairs.