About KilowattCost
KilowattCost answers one question as accurately as we can: what does this actually cost to run?
Electricity pricing is needlessly confusing. Utility tariffs hide behind PDFs, manufacturers quote best-case figures, and most "cost calculators" online are lead-capture forms with a number attached. We built the opposite — tools that give you a straight answer, show the arithmetic, and don't ask for your email.
How these calculators are built
Every formula lives in a single shared library that is covered by automated tests. Those tests check the output against figures worked out by hand and against published reference values — so if a formula ever drifts, the build fails before anything reaches this site.
We publish the reasoning too. The methodology page lists every default assumption, where it came from, and when it was last checked. If you disagree with one of our defaults, every input on every calculator can be overridden with your own figures.
What makes these different
- Charging and conversion losses are counted. Roughly 10% of the electricity an EV draws never reaches the battery. Calculators that ignore this understate your real cost by about a tenth.
- We show you when the answer is unfavourable. An EV charged only at fast chargers can genuinely cost more per mile than an efficient hybrid. A heat pump is not always cheaper than gas. Where that is true, we say so plainly.
- No sign-up walls. Every tool works immediately, for free.
How this site is funded
KilowattCost is free to use and is supported by advertising. We may also earn a commission if you request a quote through a partner link. This never changes the numbers a calculator produces — the formulas are fixed, published, and tested, and they do not know or care whether a partner link exists on the page. Our disclaimer covers this in full.
Corrections
If you spot a formula error, a stale utility rate, or a result that looks wrong, please tell us — get in touch. Corrections are made promptly and the page's update date is revised. We would much rather be corrected than be confidently wrong.