Energy
Electricity Cost Calculator
Estimate daily, monthly, and annual energy use and cost from power, time, and your local electricity rate.
Practical home planning tools
Plan home projects with clearer numbers.
Estimate energy costs and renovation materials using your own local values, transparent formulas, and plain-language assumptions.
Planning estimates—not quotes. Your usage, measurements, and local prices determine the result.
- Use local values
- See each formula
- No account needed
Featured calculators
Choose the estimate you need
Start with a focused estimate for energy use or renovation materials. Every tool will show the formula, assumptions, and values behind its result.
Energy
Appliance Running Cost Calculator
See what one appliance could cost to run across active days using its wattage and your electricity price.
Renovation
Paint Quantity Calculator
Turn room dimensions, openings, coats, coverage, and waste into an estimated paint quantity.
Renovation
Flooring and Tile Calculator
Estimate adjusted floor area and the packs or tiles needed after your chosen waste allowance.
How it works
From your values to a clearer estimate
A useful estimate should be easy to create and easy to inspect. Each calculator follows the same clear path.
Enter your local values
Add the measurements, usage, and price that match your home or project.
Review the estimate
See the result with its units, formula, and useful breakdown shown together.
Check the assumptions
Read what the estimate includes, then use it as a planning guide—not a professional quote.
Built for clarity
Know what is behind each estimate
Useful planning numbers need clear limits and enough context to check them. These rules guide every Watt & Wall calculator.
Formulas you can inspect
Every result shows its units, formula, assumptions, and rounding so you can understand how the estimate was produced.
Sources with context
Defaults identify their source, geography, and last-reviewed date. You can replace regional averages with your own local values.
Private by default
No account is required. Calculator inputs are processed in your browser and are not uploaded or stored.
Planning aid, not a quote
Results support early planning; they are not professional advice, contractor quotes, or guaranteed savings.
Common questions
Before you use an estimate
Quick answers about scope, local values, privacy, and what each result can—and cannot—tell you.
The formulas calculate consistently from the values you enter, but the usefulness of a result depends on accurate inputs and the stated assumptions. Treat every result as a planning estimate, not an exact prediction.
Start your estimate
Ready to make a clearer estimate?
Choose a calculator, enter the values you know, and review the formula and assumptions behind the result.
No account required. Your values stay in your browser.