Your one number
1
How you'd rather enter it
The 2026 US average runs about $163 a month.
System sizing
Quick 5-minute system size estimator
Just want a ballpark? Enter your monthly bill or usage below and get a fast panel count and system size. No spec sheets, no sun-hour lookups.
How it works
Two steps, five minutes
Step 1
Grab your average monthly bill or usage
Whatever's on your last statement is close enough. No need to average 12 months for a rough gut check.
Step 2
Use the ballpark, then go deeper if it looks promising
If the estimate looks like it's in a reasonable range for your situation, move to the solar panel calculator for your real sun hours and panel choice, or the minimum viable system size calculator if budget is the driving constraint.
Why a rough number first is worth five minutes
The rule of thumb behind this estimate
A 400-watt panel produces about 525 kWh a year at 4.5 peak sun hours with a 0.80 derate (0.4 kW times 4.5 hours times 365 days times 0.80), so this estimator divides your annual usage by 525, which works out to about one panel for every 44 kWh of monthly use. A home using 10,500 kWh a year needs about 20 panels. A shortcut sometimes quoted online, one panel per 1,000 kWh, would call for only 10 or 11, which would cover roughly half of that home's use. For your local sun hours, NLR's PVWatts calculator runs your address against real weather data, and the solar panel calculator lets you set your own.
What this estimate deliberately skips
This tool doesn't ask for your exact sun hours, your specific panel wattage, or your roof's shading situation, all of which shift the real number meaningfully. That's the tradeoff for speed: a fast ballpark that's useful for a first gut check, not a number to take to an installer as a final figure, To turn the ballpark into a real estimate, the annual kWh output estimator runs the same system through your actual sun hours and roof details.
How close this typically lands to a real proposal
Real installer quotes commonly land within 25 to 30% of this estimate, mostly because sun hours differ: for a 10,500 kWh home, about 15 panels at 6 peak sun hours and 26 at 3.5. At the example values here, a $163 monthly bill, the estimate is 21 panels and 8.4 kW. That is close enough to judge whether solar is worth exploring further before spending time on detailed quotes or running a payback period calculator. A higher-wattage panel doesn't change the system size, only how many panels it takes, and the panel count rounding tool shows how wattage and rounding move the exact count.
What the average US household actually uses
The current US average runs around 875 to 900 kWh a month, roughly 10,500 to 10,800 kWh a year, a figure EIA tracks and updates regularly, though real usage varies widely by state and climate, from under 600 kWh a month in some cooler regions to well over 1,200 in hot, humid ones. If you already know your own annual usage, the net-zero home calculator sizes a full offset from it directly.
Questions
Frequently asked
Divide your annual electricity use by about 525 kWh, which is what one 400-watt panel produces in a year at 4.5 peak sun hours with a 0.80 derate. A home using 10,500 kWh a year needs about 20 panels, or 8 kW, and the real number runs from about 15 panels at 6 sun hours to 26 at 3.5.
Close enough for a first gut check, but typically only within about 25 to 30% of a detailed proposal, mostly because sun hours range from about 3.5 to 6 across the US. It also skips your panel wattage, roof shading, and orientation, all of which shift the real number.
Around 875 to 900 kWh a month, or roughly 10,500 to 10,800 kWh a year, based on EIA figures. Actual usage ranges widely by state, from under 600 kWh a month in some cooler climates to over 1,200 in hot, humid ones. If you enter a bill instead, the tool converts it at about 18.4 cents per kWh, in line with EIA's national residential averages of roughly 17 to 19 cents across 2025 and 2026.
Use this first for a rough sense of scale, then move to a detailed tool once you're ready to plan seriously. The solar panel calculator factors in your actual sun hours, panel wattage, and derate for a real working number.