How Whatt works, two short guides for reading bills and everyday habits, and common questions. Appliance-specific tips still live on each item’s estimate screen.
How Whatt figures a cost
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.
Technical detail
Power ≈ (watts ÷ 1000) × hours × $/kWh
Water ≈ volume (or flow × time) × your water rate
How to find your 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.
What these numbers include
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.
Guide: How to read a power bill (plain English)
Most electric bills mix a few different ideas. You only need a few numbers to get a useful rate for Whatt.
Usage (kWh). This is how much energy the home used in the billing period. Look for “kWh,” “kilowatt-hours,” or “energy used.”
Energy charges. The dollar amount tied to that usage—not the whole bill if it also lists separate fees. Some bills split “generation,” “delivery,” or “supply”; adding the energy-related lines is fine for a simple average.
A simple rate. Divide energy charges by kWh. Example: $90 of energy charges ÷ 500 kWh ≈ $0.18 per kWh. Enter that in Whatt (or use Find your rate and type the bill totals).
Other lines. Customer charges, taxes, and one-time fees often do not change when you run a fan an extra hour. Whatt focuses on usage cost, so those fixed lines are usually left out of the rate you type in.
Bills vary by utility. If a line is unclear, use the totals Whatt asks for and treat the result as a practical average—not a lawyer’s reading of the tariff.
Guide: Habits that quietly add up
Big appliances get the attention, but small patterns stack over a month.
Hours beat myths. Leaving a box fan on all day is mostly about hours × watts. Flipping a light switch on and off like a strobe is a classic warning from relatives; for modern LED bulbs the energy story is usually about how long the light stays on, not dramatic “surges” from toggling. Whatt is built for those calm, hour-based questions.
Heat and cool dominate. Space heating, air conditioning, and electric water heat often dwarf a phone charger. A small change in thermostat hours or setpoint can outweigh unplugging a few gadgets.
Always-on loads. Routers, DVR boxes, and game consoles in standby draw a little all day. Each one may look tiny; together they can show up as a steady slice of the bill.
Water habits. Longer showers, extra rinse cycles, and a toilet that runs between flushes use volume you can estimate. A slow leak is easy to ignore and expensive over weeks.
Compare, don’t guess. Open two similar ideas in Whatt—fan all day vs a short AC window, or one long shower vs a shorter one—and use What if on the estimate screen when you want a side-by-side feel.
FAQ
Is Whatt my real bill?
No. It estimates usage cost for the habits you set. Your bill can include fixed fees, taxes, tiers, and other lines Whatt does not model.
Why doesn’t the number match my statement?
Different rate structure, fees, weather-driven HVAC, or habits that aren’t in the estimate yet. Start with your bill-derived rate, then add the main loads you actually use.
Are the default watts and flow rates exact?
They are typical starting points. Labels, manuals, and your own Fine-tune values are better when you have them.
Does Whatt need an account?
No. My Home and rates stay on this device. See Privacy for ads and cookies.
Power and water in one place?
Yes. Use the Power and Water modes for the matching items. Some machines (like washers) have both sides when it matters.
Can I share or save my list?
My Home can store items on this device. Backup/restore and share tools are in the app where available—nothing is uploaded to a Whatt account, because there isn’t one.
Who is behind Whatt?
A personal project. Story and disclaimer are on About. Questions: support@whatt.net.
