System sizing

System size by electric bill amount

Enter your monthly bill amount and your rate per kWh. Get a system size built from your actual dollar spend, not a generic usage guess.

Your numbers

1 Project details Optional
Shown on your exported report. Leave blank to skip.
2 Your bill
Your total monthly bill amount, before any credits.
Check a recent bill. Leave blank to use the 2026 national average of $0.1844/kWh.
An atypical month gets corrected toward a more representative baseline.
3 Planning ahead
An EV, heat pump, or pool you're planning to add. Leave blank or 0 if none.
This changes whether a small buffer above your usage is worth adding.

How it works

From a dollar amount to a system size

Step 1

Start with your bill total and your real rate

Enter your monthly bill amount, then your actual rate per kWh if you know it. Your rate matters as much as the bill total, since the same dollar amount means very different usage depending on how much your utility charges. Leave the rate blank and this tool uses the 2026 national average instead.

Step 2

Flag if it was a typical month, and add anything planned

An unusually high or low month gets corrected toward a representative baseline before sizing. If an EV, heat pump, or pool is coming, add its expected monthly load now. If you'd rather work from raw kWh directly instead of a dollar amount, the monthly usage tool skips the rate conversion entirely.

Step 3

Confirm your rate structure for the final buffer

Your net metering situation decides how much buffer above raw usage is worth building in. Check the net billing vs net metering comparison if you're not sure which structure your utility uses.

Why the rate you use changes the answer

The same bill can mean very different usage

A $166 monthly bill at the 2026 national average rate of 18.44 cents per kWh, close to the figure EIA's electric power monthly report tracks nationally, works out to about 900 kWh. That same $166 bill at a lower rate of 12 cents per kWh represents closer to 1,383 kWh, since the household is paying less per unit and therefore using more electricity for the same money. A tool that skips the rate entirely can't tell these two households apart.

Where your actual rate matters most

Rates vary widely by state, from around 12 cents per kWh in low-cost states to over 40 cents in the most expensive ones. If you're not sure of your exact rate, check a recent bill, it's usually printed per kWh or easy to back out from the total divided by usage shown on the same page. The Energy Information Administration's explainer on electricity prices breaks down what drives those differences between states.

Why this tool still checks if the month was typical

Once your bill is converted to a usage figure, an unusually high or low month can still skew the result the same way it would for a usage-based tool. This estimate adjusts an atypically high month down by about 15% and an atypically low one up by about 15% before sizing, correcting toward a representative baseline rather than taking one outlier bill at face value.

What this still doesn't capture

This estimate still relies on typical panel wattage and national average sun hours rather than your exact equipment and address. A bill amount hides the usage pattern behind the dollars, so for a fully custom result using your own panel choice and local sun hours, use the full solar panel calculator instead.

What to do with this number next

Take the system size from your bill amount to the payback period calculator to see what it might save you over time, and check what incentive programs apply to a system of this size before you get quotes.

Questions

Frequently asked

This tool divides your monthly bill by your rate per kWh to get your actual usage, then sizes from that the same way a usage-based tool would. A $166 bill at the national average rate of 18.44 cents per kWh works out to about 900 kWh, which needs roughly a 9.6 kW system with full net metering.

Check a recent bill for your rate, usually listed per kWh or as a total divided by usage. If you can't find it, the national residential average is about 18.44 cents per kWh as of 2026, though your actual rate could run from around 12 cents in low-cost states to over 40 cents in high-cost ones.

Many people know their bill amount by heart but don't track their kWh usage directly. This tool lets you start from what's most familiar, your bill total, and does the kWh conversion for you using your actual rate rather than a generic assumption.

Not necessarily. A higher rate means the same dollar bill represents less actual usage, so it needs a smaller system. A $200 bill at 30 cents per kWh (about 667 kWh) needs a smaller system than the same $200 bill at 15 cents per kWh (about 1,333 kWh), since the second home is using twice the electricity for the same money.

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