Then pick an appliance below
Optional. Skip if you’re not sure.
Adjust hours below — the $ updates live.
This removes every saved appliance total from this device.
Used for things like LED strip length (US default: feet).
Outdoor vs thermostat on AC / heat cards (US default: °F).
Privacy
This policy explains what Whatt does with information when someone uses whatt.net. Whatt is a free personal project for estimating household power and water costs.
Settings such as utility rates, My Home items, theme, and recent selections stay on your device (local storage). Whatt does not require an account and does not run a user database that collects those settings from you.
If you write to support@whatt.net, Whatt receives your message and the address you send from so a reply is possible. That information is used only to handle the request.
Whatt uses Google AdSense to show ads. Third-party vendors, including Google, use cookies and similar technologies to serve ads based on prior visits to this site or other sites. Google’s advertising cookies help Google and its partners show ads based on visits across the web.
To opt out of personalized ads, visit Google Ads Settings or aboutads.info/choices. More detail: Google Advertising.
Whatt is hosted with Cloudflare. Cloudflare may process technical data (such as IP addresses and request logs) to deliver and protect the site, under Cloudflare’s own policies.
Device settings are used only to run Whatt on that device. Email is used only to respond. Whatt does not sell personal information.
This policy may change over time. The current version will always be on this page; the version label in the footer may update when related changes ship.
The idea
Whatt started with the kinds of questions that pop into your head at home—and never get a straight answer. What does it actually cost to leave a fan on all day? Do a few extra flushes really show up on the water bill? And what about those warnings grandparents love, like “stop flipping that light switch on and off—you’ll run up the bill,” as if the room were a strobe light?
I wanted calm, simple numbers in one place. That curiosity turned into Whatt.
Whatt is a free personal project that estimates power and water costs at home—by appliance, fixture, and habit. Use your own bill rate when you have it, or start from typical area averages.
Pick something you use, set how you use it, and Whatt shows a simple dollar estimate. Optional “What if” ideas help you compare small changes. It all runs on your device—no account required.
Whatt provides educational estimates only. These figures are not a utility bill, a quote from a provider, or financial advice. Real bills depend on the utility, plan, fixed fees, taxes, rate tiers, and how energy and water are actually used.
Your My Home list and rates stay on this device. See Privacy for advertising and cookies.
Help
Whatt multiplies typical use by a rate, then shows a simple dollar estimate for the habit you set. Defaults use common ranges so you can start quickly. Change size, hours, and habits anytime—your own bill rate is usually closer than an area average.
Power ≈ (watts ÷ 1000) × hours × $/kWh
Water ≈ volume (or flow × time) × your water rate
Electricity: On the bill, divide energy charges by kWh used for a simple average dollars-per-kWh—or open Find your rate and enter the totals Whatt asks for.
Water: Bills often list usage in gallons (or another unit the utility prints). Use that with the dollar amount, or enter what Whatt requests. A bill-based rate is usually more realistic than a regional default.
Estimates reflect the approximate cost of the energy or water for the use you configure.
They typically do not include every line on a full utility bill—such as fixed monthly service fees, taxes, tiered or time-of-use pricing, demand charges, sewer minimums, or other provider-specific charges.
That is why a Whatt estimate can differ from the total on a bill even when the usage idea is reasonable.