Solar Self-Sufficiency Calculator

Use this calculator to estimate how much of your electricity could be covered by solar panels, how a battery may change grid imports, and what the rough yearly savings might look like.

Solar calculator

Estimate solar production, battery impact, and savings

Start simple with panel power and sun hours. Open advanced settings if you want to adjust orientation, roof angle, shading, battery efficiency, and tariffs.

Simple inputs

Electricity use

Enter the kWh from your electricity bill.

Solar panel power

Example: balcony solar 0.8 kW. A larger home system may be 8 kW.

Full-sun hours per year Simple assumption. 800 W x 1000 h = about 800 kWh before losses. Usable battery size kWh usable storage. Use 0 if there is no battery. Use while panels are producing This estimates how much power you can use directly before sending extra solar to the grid or battery.

Money inputs

Electricity price price per kWh you avoid buying. Example: 0.25, not 25 or 250. Export credit credit per exported kWh, if applicable. Example: 0.05. Installed system cost optional rough cost for simple payback

35%

Estimated autarky

Self-sufficiency

Direct solar: 35% Battery: 0%

35% self-sufficiency with 1,950 kWh grid import 3,960 kWh/year produced. 1,050 kWh used by the home, 2,910 kWh exported.

System size5 kW

Annual use3,000 kWh

Solar production3,960 kWh

Direct solar1,050 kWh

Self-used solar1,050 kWh

Grid import1,950 kWh

Exported solar2,910 kWh

Estimated savings$408/yr

Simple payback14.7 years

Self-consumption27%

5 kW x 1,000 sun hours x 79% usable factor = 3,960 kWh/year

Key assumptions 79% usable production factor Simple mode uses 10% shading and 12% technical system losses.

Usage and tariffs Normal daytime use: 35% of demand while panels are producing. $0.25/kWh avoided purchase and $0.05/kWh export credit.

Seasonality Normal seasonality is selected.

Battery impact No battery contribution is counted.

Production 3,960 kWh

Self-used 1,050 kWh

Grid import 1,950 kWh

Meaningful export. A battery may help, depending on tariffs and use pattern.

Interactive scenario modeling needs JavaScript. The starter estimate is visible, but advanced inputs, PDF export, copy summary, and share actions need JavaScript enabled.

Your solar details stay in your browser. Nothing is uploaded while you model scenarios. The report and copied summary are generated locally from the values you enter.

Calculator ready.

Approximate planning tool only. Results depend on location, roof orientation, shading, tariffs, system design, battery behavior, taxes, incentives, installation cost, and local rules. This calculator is not financial, engineering, legal, or installation advice.

How to use the result

The calculator is useful for comparing scenarios. Try changing the solar size, battery size, daytime consumption share, and electricity price. If a small change creates a very different result, ask installers to explain which assumptions they are using.

What the calculator cannot know

Real solar performance depends on roof angle, shading, orientation, inverter design, weather, tariff rules, export limits, battery behavior, taxes, incentives, and installation quality. Treat the result as a planning estimate, not a guaranteed outcome.

What to ask a solar installer

What annual production estimate are you using?
How much shading loss did you assume?
What battery capacity is usable, not just nominal?
How are grid imports and exports modeled?
Which electricity price and export credit did you use?
What happens if my usage changes later?

Common questions

Is this solar calculator a quote or a guarantee?

No. It is a planning calculator for comparing scenarios. Real production and savings depend on roof layout, weather, tariffs, export rules, installer design, and local conditions.

Why does a battery not always make the result better?

A battery only helps when there is enough surplus solar, enough evening or nighttime demand, and enough usable storage capacity. Battery losses and seasonal production limits can reduce the benefit.

What does self-sufficiency mean here?

Self-sufficiency estimates the share of annual electricity use covered by solar used directly or through the battery. It does not mean the home is fully off-grid.