US homes · 120 V · open sources
What size energy system does your house need?
Pick the appliances you would keep running during an outage. You get the four numbers that decide every purchase, and the arithmetic is shown.
Quick answer
A fridge, four LED bulbs, a router and a TV come to about 2,160 Wh a day, 305 W running and 755 W at motor start. A 2 kWh station covers it. Add one window air conditioner and it becomes 10,160 Wh, so the answer turns into a battery-and-panel system.
Power and energy are two different questions
Daily energy decides the battery. Running watts decide the inverter. Surge decides whether the fridge actually starts. The three numbers are not interchangeable, and the table shows where a purchase usually goes wrong.
| Number | What it answers | Where people go wrong |
|---|---|---|
| 2,160 Wh | How much battery | Buying capacity and never checking surge |
| 305 W | What runs at the same time | Adding up watts and calling it energy |
| 755 W | Whether a motor starts | Assuming surge is always double the rating |
What a 120 V station cannot run, at any price
An electric dryer, a central AC compressor or a 240 V well pump. No portable station in this class will start them, whatever the listing says. Those loads need a transfer switch and an electrician, which is a different kind of project.
All 29 pages, in four groups
Filed by the question you arrive with. Ten pages size the system, three pick hardware, seven cover installation, four hold the numbers.
24 content pages above; this homepage, about, disclosure, privacy, terms and 404 sit in the footer.
Where the numbers come from
Appliance draw is a category typical value from public sources, scaled where needed, collected into our own table of 150 appliances. Sun hours are typical US averages from NASA POWER for 51 locations, not a forecast for your roof.
Appliance values are checked against ENERGY STAR product data and the US Department of Energy appliance guidance before they are published. Each row keeps its source and the date it was read, so a number on this site can always be traced back.
What this site does not do
It does not print prices, because a retailer's live price is the only accurate one. It does not publish star ratings it has not earned or tests it has not run. It does not give electrical advice: a panel, a transfer switch or a 240 V circuit needs a licensed electrician and, in most places, a permit.
Questions
Is this site free?
Yes. The calculators and the data table are free to use. Some outbound links are affiliate links, which is how the site pays for itself; that never changes the price you pay, and it never changes a number on the page.
Can I use these numbers for a real installation?
Use them to understand the scale, then have an electrician verify the circuit and the transfer equipment. Our figures describe typical appliances, not your specific wiring.
Why do some pages ask for sun hours?
Because generation and storage solve different problems. A battery buys time; panels refill it. The sun hours page explains the monthly spread.
Do I need to know my kWh bill to use this?
No. A bill tells you a monthly total, which hides the peak that decides hardware. Entering appliances gives you both the energy and the surge, and the surge is the number that stops a system from starting.
Can I run a 240 V appliance such as a dryer?
Not from a 120 V station. Dryers, ranges and central air need a 240 V circuit, which means a fixed installation with a transfer switch, not a plug-in box. The load calculator flags those appliances so you do not size for something you cannot connect.
Not professional electrical advice. Permanent wiring, transfer switches and 240 V circuits need a licensed electrician and a permit.