What percentage of my electricity can solar offset?

Most homeowners design their solar systems to offset 80–100% of their annual electricity use. The actual offset depends on your roof size and orientation, local sunlight hours, your daily usage, and whether you add battery storage. Aiming for 100% offset on average means you'll overproduce in summer and underproduce in winter.

Does 100% solar offset mean a $0 electric bill?

Not exactly. Even with 100% production offset, most utilities charge a minimum connection fee or base charge of $5–$20/month. Net metering credits can eliminate most consumption charges, but utility fees usually remain. Battery storage allows you to reduce grid dependence further.

What solar offset percentage should I aim for?

Most homeowners target 80–100% offset — generating enough solar energy to cover 80–100% of their annual electricity consumption. Going above 100% can be less cost-effective unless you have a battery or very favorable net metering rates. 80–90% is often the sweet spot balancing system cost and bill elimination.

What factors affect my solar electricity offset?

Key factors include your roof's orientation (south-facing is optimal), tilt angle, shading from trees or structures, your geographic location and peak sun hours, panel efficiency, and system size. A professional site assessment accounts for all of these to give you an accurate offset estimate.

Electricity Offset Calculator

Calculate what percentage of your electricity your solar system covers, how much you save per month, and what your effective electricity cost becomes after solar production is factored in.

Monthly Bill ($)

Solar Production (kWh/mo)

Electricity Rate (¢/kWh)

About This Calculator

The Electricity Offset Calculator measures how much of your home's electricity demand is covered by your solar panels. Solar offset — expressed as a percentage — is one of the most fundamental metrics in solar system design. A 90% offset means your panels cover 9 out of every 10 kWh you consume, with only 10% still coming from the grid. This calculator goes further, showing you the dollar value of that offset, your remaining grid cost, and your new effective electricity rate — the blended cost per kWh when you account for both solar and remaining grid purchases.

The relationship between solar production and monthly usage determines your offset directly: if you produce 900 kWh and use 900 kWh, your offset is 100%. But "offset" at the monthly level can be misleading — if you produce 900 kWh at noon on sunny days but consume heavily in the evening, your actual self-consumption without a battery may be much lower. Net metering policies blur this distinction by treating monthly production vs. consumption on a net basis. For a more granular view, the Net Metering Calculator handles the self-consumption vs. export breakdown.

To use this calculator accurately, enter your average monthly kWh usage from your utility bill (12-month total divided by 12 works best, since summer and winter usage differ greatly). For solar production, use your installer's projected monthly output figures or the Solar Energy Production Calculator. Your electricity rate should be your effective rate — total bill divided by total kWh — rather than the base rate alone, since delivery and distribution charges are also eliminated by solar production in most net metering arrangements.

Tracking your actual offset after installation helps you verify your system is performing as designed. A meaningful drop in offset percentage over time (beyond expected panel degradation) can signal inverter issues, soiling, or shading from new tree growth — making this a useful ongoing monitoring metric as well as a pre-installation planning tool.

Calculations based on NREL solar modeling data and industry-standard assumptions, built and maintained by the independent SolarToolsOnline research team.

Estimates only — not financial, tax, or legal advice. Verify important results with a licensed solar installer or financial professional before making decisions.