Plug-In Solar Savings Calculator (feedback prototype)

Your estimated savings

solar energy per year

What if electricity rates rise? Try 3% per year, about the US average increase over the past decade. This is a scenario, not a forecast.

Your average monthly electric bill ($, optional)

Add this to see about how much of your bill solar could offset.

Your electricity rate ($ per kWh)

Your exact rate is on a recent power bill, usually in cents per kWh.

Your ZIP code (optional)

Average peak sun hours per day

The prefilled value is a US starting estimate: one city per state plus DC, weighted by state population (PVWatts typical-year model, at the tilt of the selected mounting). It describes the default above, not a ZIP result. Enter a ZIP for a local value, or edit the number yourself.

Solar panels (watts)

Inverter output limit (watts AC)

The most power the system can feed into your home at once. Some kits ship with a lower setting you can raise in the manufacturer's app.

Balcony or ground mount?

Ground assumes a sunny, unshaded 35-degree angle facing south; Balcony assumes vertical panels facing south.

Production factor (%)

Production-side losses only: equipment, wiring, temperature and sun angle at your location. Entering a ZIP sets this from the same PVWatts run as the sun hours; you can edit it afterwards. The published OwnWatts guides model these losses hour by hour (11.42% system losses, 96% inverter efficiency, premium panels): the system-loss and inverter-efficiency settings multiply to 85%, and hourly temperature and sun-angle effects bring the modeled figure to about 78 to 81 percent in the guide cities. Power your home does not use is handled separately below.

Share of solar your home uses (%)

The share of the solar power your home absorbs while it is being made. Any solar not used at home earns no savings or export credit in this estimate.

How we estimate this

Yearly solar energy comes from an hour-by-hour model: the PVWatts Version 8 engine (NREL's open solar model) simulates a typical year of real weather at your location with your panel watts, inverter limit, a 96% assumed inverter efficiency and no rear-side (bifacial) gain. With no ZIP, a simple daily estimate is used instead: peak sun hours x 365 x system size x production factor, capped at the inverter limit. Savings count only the share your home uses: savings = used energy x your electricity rate. Any solar your home does not use earns no savings or export credit in this estimate. Ground mounting assumes a sunny, unshaded 35-degree tilt facing south; a balcony assumes vertical panels on a south-facing railing. Sun data uses the free NREL demo key with per-visitor rate limits, so heavy repeat use may pause lookups for an hour. Disclosure: this calculator was built by Teresa Russell, founder of OwnWatts, a plug-in solar shop. This is a feedback prototype - no products are sold or linked here.

Panel watts and inverter output are yours to edit: the hourly model applies the inverter limit hour by hour, so oversizing panels past the inverter clips the peak but keeps morning and evening production.
Mount sets the geometry the estimate assumes: Ground is a sunny, unshaded 35-degree tilt facing south; Balcony is vertical panels on a south-facing railing with no rear-side gain, since the back faces the railing.
If a ZIP lookup fails or the sun-data service is busy, the estimate falls back to the simple daily estimate, labeled below the results - never a misleading zero.