ENERGY COMPARE BETA
Compare appliance
electricity costs.
Electricity use in kWh equals watts divided by 1,000, multiplied by hours per day and days. Multiply that result by your own price per kWh to estimate variable cost; fixed charges are excluded.
01 / YOUR INPUTS
What are we comparing?
Starting values are examples only, not current electricity rates.
02 / YOUR COMPARISON
See the difference.
Your result goes here.
Enter your values and compare. See energy use, cost and the difference between both options together.
W ÷ 1000 × hours × days = kWhVariable electricity cost difference, based on your inputs.
Results are rounded to at most 6 decimal places. This is not an accounting or billing tool.
BEHIND THE NUMBERS
Clear maths.
Visible assumptions.
Power × time gives energy use. We multiply that by the number of days and the price you enter per kWh. Both scenarios use the same period and currency.
Power and daily use are assumed constant throughout the period. Thermostats, standby use, efficiency differences and tiered rates are not calculated automatically. Standing charges and taxes you have not included in the unit price are excluded. This is not a total bill estimate or a savings guarantee.
Your data & sharing
Calculations run in your browser. No accounts, cookies, persistent browser storage or ads. Optional usage counts are sent only if you allow them; they never include your calculation inputs. Your input values are not sent to a server for calculation.
The share button puts your values in the # part of the link. This is not sent to a server in a standard HTTP request, but recipients, browser history, extensions and your messaging app can see the values. Normal web requests to open this site may appear in server or hosting-provider logs.
About this tool
Atheronix Energy Compare is a beta web tool for comparing two usage scenarios with visible assumptions. Use your own bill rate, or explicitly choose the dated GB reference shown above. The reference is an average, not a personalised tariff.
Limits: 0–100,000 W, 0–24 hours per day, 1–366 whole days, and 0–10,000 currency units per kWh. Device names have a 40-character limit. The example is not a rate or product recommendation.
Use the price on your bill
If your bill shows 25p/kWh, select pence and enter 25. This equals £0.25/kWh. These are illustrative numbers, not a current tariff.
Example: 1,000 W for 2 hours/day over 30 days at 25p/kWh costs £15. A 600 W device under the same assumptions costs £9: a £6 variable-cost difference. Different heat output or comfort is not compared.
Read the calculation guide and limitationsHelp improve this tool
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Method, examples and sources
Electricity use in kWh equals watts divided by 1,000, multiplied by hours per day and days. Multiply that result by your own price per kWh to estimate variable cost; fixed charges are excluded.
Example only: 1,000 W × 2 hours × 30 days = 60 kWh. At an invented £0.25/kWh, the cost is £15.
Use the unit rate on your bill. The prefilled prices are illustrative, not current tariffs; they may be out of date. The source explains energy billing; it does not supply these invented example prices.
Ofgem: unit rates and standing charges · Source checked: 2026-10-16.
Aggregate requests
We count page requests by day, page, language and broad source category. IP addresses, browser identifiers, queries, cookies and calculator inputs are not recorded. Intermediate records remain in temporary memory and are deleted after daily aggregation. Aggregates are kept for 90 days; they are not counts of people. Optional calculation measurement can be disabled separately.