How Whatt works, how to pull a usable rate off a bill, how leaks show up as volume, and the questions people ask first. Appliance-specific notes still live on each item’s estimate screen and on the guide pages.
How Whatt figures a cost
Whatt multiplies typical use by a rate, then shows a simple 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 × your dollars-per-kWh, shown in ¢. Water ≈ volume (or flow × time) × your water rate. Gas dryer, gas furnace, and gas stove add typical fuel while that setting is on, using the same ¢/kWh as a stand-in so the total is not only the electric motor or igniter.
Duty cycle matters on cycling gear. A fridge compressor is not at nameplate watts every second of the day. AC and heat cards can use a percent of full power for the hours the system is “on.” If you set 0%, that means off — the estimate should go to zero, not a hidden minimum.
How to find your rate
Electricity: On the bill, find kWh used and the energy charges tied to that usage. Divide dollars by kWh. Example: 90 dollars ÷ 500 kWh ≈ 0.18 dollars per kWh, which is 18¢ in Whatt. Or open Find your rate and enter the totals the form asks for. ZIP and state averages are a start when you do not have a bill yet.
Water: Bills often list usage in gallons or CCF (1 CCF = 748 gallons). Bill total ÷ (gallons ÷ 1000) is a simple per-1,000-gal rate. If the bill splits water and sewer, put each on its line, or paste an all-in number on water and leave sewer at 0.
Location: Use my location is optional. The browser may share coordinates; Whatt only wants a ZIP or state for a typical area rate. You can type those instead and never share location.
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 — 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. My Home is only what you added. Typical bills also include fridge, hot water, and lights if you have not saved those cards yet.
Guide: How to read a power bill
Usage (kWh). How much energy the home used in the period. Look for “kWh” or “energy used,” not only “amount due.”
Energy charges. The dollar amount tied to that usage. Customer charges, taxes, and late fees often sit on other lines.
A simple rate. Divide energy charges by kWh. If the bill already prints 0.14 per kWh, that is dollars — type 14 in the ¢ box.
Other lines. A fan left on an extra hour does not change a fixed meter charge. Whatt focuses on usage cost so small habits stay comparable.
Guide: Habits that quietly add up
Hours beat myths. Leaving a fan on all day is hours × watts. For modern LEDs, how long the light stays on matters more than flipping the switch. Heat and cool dominate: heating, AC, and electric water heat often dwarf a phone charger. Always-on loads such as routers and consoles in standby draw a little all day. Water habits — longer showers, extra rinses, a running toilet — add volume you can estimate. A gas stove’s heat is fuel, not a tiny electric igniter; use the gas stove card so cooking is not missing from the total.
Guide: Finding a water leak
Use Leak / drip on Water to price what a continuous leak costs. Pick the closest type (faucet, toilet, outdoor, irrigation). The estimate runs 24/7. What-if can show a week or a month of leaving it.
Meter test. Turn off all water. If the meter still moves, something is leaking.
Toilet dye test. Color in the tank; wait without flushing. Color in the bowl is a silent flapper leak — very common and expensive.
Look and listen. Under sinks, water heater base, outdoor spigots, hissing valves, wet spots in the yard when irrigation is off. Main house shutoff is usually near the meter. This is volume cost, not a plumber’s quote.
FAQ
Is Whatt my real bill? No. It estimates usage cost for the habits you set.
Why doesn’t the number match my statement? Fees, rate structure, weather, or habits not in the estimate yet.
Are the default watts and flow rates exact? Typical starting points. Labels and Fine-tune in the app are better when you have them.
Does Whatt need an account? No. My Home and rates stay on this device. Download backup saves a file on that device; Restore reads that file. Nothing is uploaded to a Whatt server.
Who is behind Whatt? See About. Questions: support@whatt.net.
Missing an appliance? Email support with the name. Gas stove, work lights, and well-house bulbs are examples of items that started as missing and then got their own cards.
Saving a household
My Home is a list on this device. Download backup writes a file you can restore later. Restore only keeps known appliances and catalog names — a backup cannot inject HTML into the list.
Related
Usage estimate only — not a utility bill, load calc, or advice.