About Lightnest Market
A small, well-lit corner of the web for working out what electricity costs you.
What it is
Lightnest Market is a set of free calculators for everyday energy questions: what an appliance costs to run, what swapping to LED bulbs saves, what devices on standby add up to, how kWh, megajoules, Btu and therms compare, and how big a power bank really is. Despite the name, there is nothing for sale.
How it works
Every calculator runs in your browser and makes no requests with what you type. The formulas are written out on each page with links to the official sources they come from, such as the U.S. Department of Energy, ENERGY STAR, NIST, the FAA and IATA.
What it is not
The results are estimates from the figures you enter, not a bill and not financial advice. Real costs depend on your tariff, standing charges and taxes and on how your appliances actually behave. Airline rules for batteries can be stricter than the general limits shown, so always check with your airline.