Looking for free energy calculators? This page collects 5 free tools in the Energy Calculators category on Ultimate Free Tools — each one checked by a human for genuinely free access, so you can open it and start working straight away.
Energy Calculators tools solve a specific, repeatable job. Rather than signing up for a subscription you'll use twice, you can open one of the options below in your browser, finish the task, and close the tab. No account, no trial, no credit card.
Frequently used energy calculators tools here include Home Battery Savings Calculator UK (SolarGridCheck), Hisab Ul Omar – Age Calculator, Calc and CalculatorQueen Milliwatt Calculator. Every listing explains what the tool actually does, whether the free tier has limits worth knowing about, and which similar tools to compare it against.
How to choose: start with the job, not the brand. Check whether the tool processes files in your browser (better for privacy), whether it puts a watermark or size cap on the free tier, and whether it exports in the format you need. Save the ones that work to your favourites so they sync across every device you sign in on.
5 free tools — each one vetted for genuinely free access, no sign-up or credit card.
Free UK calculator that estimates a home battery's annual savings, payback period and recommended size, with or without solar panels, on any electricity tariff. From SolarGridCheck.
Open toolFree age calculator to calculate exact age in years, months and days using Gregorian or Hijri dates.
Open toolPractical calculators with transparent formulas
Open tool
Convert milliwatts to watts or watts to milliwatts with exact SI formulas, direct equality, a power-scale chart, a conversion table, and CSV export.
Open toolFree no-signup heat pump calculators and guides for US homeowners, covering sizing, installed cost, savings, rebates, brands, balance point and mini-split planning.
Open toolYes. Every tool listed under Energy Calculators has a genuinely free way to complete the job — no credit card, no trial countdown. Where a tool also sells a paid plan, we label it clearly so you know what the free tier covers.
No. You can open and use everything listed on this page without creating an account on Ultimate Free Tools. A free Ultimate Free Tools account is only useful if you want your favourites and history to sync across your devices.
A human opens each tool, completes a real task with it, and confirms the free path works end to end. Nothing is scraped, and anything that quietly moves behind a paywall gets relabelled or removed.
We review listings continuously and add new tools every week. Pricing changes, broken links and replacements are corrected as soon as we spot them or a reader reports them.
Absolutely. Submit it through the "Submit a tool" page and our editors will review it. If it is genuinely free and useful, it gets added to Energy Calculators.