Solar panels in Nampa, ID

Roofs in Nampa get about 1,677 hours of usable sunlight a year — more than 71% of the cities we've measured. Here's what that means in cost, savings and payback, using real rooftop data rather than a national average.

Check your specific roof in Nampa → City averages are a starting point; your own roof's size, pitch and shading change the answer a lot.

What a typical Nampa solar system costs

A 19-panel system (7.6 kW) is about right for an average Nampa home using 10,800 kWh a year. It would produce roughly 10,833 kWh annually and offset 100% of that usage.

How we worked this out for Nampa

Every number on this page comes from these seven steps. Nothing is a national average — the sunlight figure is measured from Nampa rooftops.

Step 6 matters more than it looks. Only 35% of what a system this size produces in Nampa is used the moment it is generated; the other 7,053 kWh is exported and credited one-for-one under net metering. Because exports here are credited at or near retail, that split changes the payback very little — 12.5 years against the 12.5 we show. In places where exports pay a fraction of retail the same split moves payback by years, which is why we model it explicitly rather than assuming.

Assumptions: 400W panels, 15% system losses (inverter, wiring, heat, soiling), $2.85/W installed, 10,800 kWh typical annual household use, 11.2¢/kWh electricity. Change any of those and every figure above moves — which is exactly why a single national "solar costs X" number is misleading.

Notice that payback barely improves as systems get bigger, and eventually gets worse. That's because you can only save money on electricity you were going to buy anyway. Once a system covers your usage, extra panels mostly generate exports at a much lower rate.

Why Nampa gets 1,677 sun hours

That figure comes from Google's analysis of real rooftops across Nampa — it already accounts for shading from trees, chimneys and neighbouring buildings, which is why it's lower than the raw "hours of daylight" figures you'll see elsewhere. An unusually open, unshaded roof in Nampa reaches about 1,715 hours, roughly 2% better than typical.

The numbers behind this page

When Nampa actually produces

Annual totals hide the thing that catches people out: 38% of Nampa's yearly sunlight arrives in May–July, and just 12% across November–January.

Nampa produces about 3.6× as much in Jun as in Dec — a normal mid-latitude swing. Expect real winter shortfall and summer surplus rather than steady year-round output.

The annual total is measured from Google's rooftop imagery. Its split across months is calculated from solar geometry at Nampa's latitude, not separately measured, so treat the monthly figures as the shape of a typical year rather than a forecast.

How Nampa compares to the other 788 cities

What actually stands out about Nampa:

• Unusually open roofs. Only 2% of available sunlight is lost to obstruction in Nampa — better than all but 87 of the 788 cities measured. Most roofs here get close to their theoretical maximum.
• Cheap electricity is the headwind. Idaho power costs about 11.2¢/kWh. Low rates are good news generally, but they lengthen solar payback — there is simply less bill to displace.

Cities with almost the same sunlight

These are the closest matches to Nampa's 1,677 usable sun hours from other states and provinces. Same sunlight, different electricity prices — which is usually what decides whether solar is worth it.

Nearby cities

See all of Idaho → statewide sunlight, rates, incentives and every city we've measured.

Nampa solar questions

Worth reading before you buy

Estimates only, generated 2026-08-22 from Google Solar API rooftop samples and average Idaho electricity rates. Not a quote and not financial advice. Your roof, usage, utility plan and local incentives will change these numbers — get real quotes before buying.