Privacy notice

Last updated 4 September 2026

SunWatt is a free calculator. You can use every part of it without giving us anything. This page sets out the two cases where data does reach us, and what happens to it.

The calculator itself

Everything you enter into the calculator — country, appliances, hours, panel and inverter sizes, battery figures — is processed in your browser and never sent to us. It is not saved to any database. If you share a result, the values travel inside the link you copy; we do not receive or store that link.

If you ask us to email your results

Entering an email address and pressing send transmits your address and the figures shown on screen to our server, which passes them to Mailtrap, our email delivery provider, so the message can be sent.

• What we receive: your email address, the country selected, and the calculated system size, panel count, inverter size, daily consumption, battery figures, savings and payback.
• Why: to send the single email you requested. Under UK and EU GDPR the lawful basis is your consent, given by submitting the form.
• How long: delivery logs are retained by our email provider for a short operational period and we do not build a marketing list from these addresses. You will not be added to a newsletter.
• Who else sees it: Mailtrap, acting as our processor, and Vercel, which hosts the function that handles the request.

Analytics

We use Google Analytics 4 and Vercel Analytics to count visits and see which parts of the calculator get used. These record standard technical information such as approximate location derived from IP address, device and browser type, referring site and pages viewed. Google Analytics sets cookies. We do not use this data to identify you, and we do not run advertising or sell data to anyone.

You can opt out of Google Analytics with the browser add-on Google provides, or by blocking analytics in your browser or an extension. Blocking it does not affect the calculator.

Cookies

We set no cookies of our own. The only cookies present come from Google Analytics as described above.

Your rights

If you are in the UK, the EU, or another jurisdiction with comparable law, you can ask for a copy of any personal data we hold about you, ask us to correct or erase it, object to our processing it, or withdraw consent. In practice the only personal data we are likely to hold is an email address you submitted. Write to hello@sunwattcalc.com and we will action it. You also have the right to complain to your national data protection authority.

Children

SunWatt is not directed at children and we do not knowingly collect data from anyone under 16.

Changes

If this notice changes we will update the date at the top. Material changes will be summarised here.

Who we are

SunWatt is an independent tool. For any privacy question, or anything else, write to hello@sunwattcalc.com.

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