| Without a battery | With a battery | |
|---|---|---|
| Initial cost | { sans.coutTexte } | { avec.coutTexte } |
| Self-consumption rate | { sans.tauxTexte } | { avec.tauxTexte } |
| Self-consumed energy | { sans.autoconsoTexte } | { avec.autoconsoTexte } |
| Surplus sold | { sans.surplusTexte } | { avec.surplusTexte } |
| Bill savings / year | { sans.economieFactureTexte } | { avec.economieFactureTexte } |
| Surplus sales / year | { sans.gainReventeTexte } | { avec.gainReventeTexte } |
| Total annual gain | { sans.gainAnnuelTexte } | { avec.gainAnnuelTexte } |
| Payback time | { sans.amortissementTexte } | { avec.amortissementTexte } |
| Net profit over 20 years | { sans.benefice20ansTexte } | { avec.benefice20ansTexte } |
| Size | Cost w/o batt. | Cost w/ batt. | Gain/yr w/o | Gain/yr w/ | Payback w/o | Payback w/ | Profit 20yr w/o | Profit 20yr w/ | Note |
| {y} |
Calculate the Return on Solar Panels — With or Without a Battery
This simulator calculates the return on a solar panel (photovoltaic) system: annual bill savings, surplus sale earnings, payback time and net profit over 20 years.
Its key feature: it automatically compares, side by side, a system without a battery and the same system with a storage battery. You immediately see which option is more advantageous for your situation.
How is the return calculated?
The calculation happens in three steps.
Step 1: annual production
Annual production (kWh) = Size (kW) × Production per kW
In the United States, 1 kW installed produces an average of about 1,400 kWh per year. This value varies by region: around 1,100 kWh/kW in the cloudy Northeast, up to 1,800 kWh/kW in the sunny Southwest. The "Production" field suggests these reference values.
This production is split into two parts: the self-consumed energy (used directly by the home) and the surplus fed into the grid (sold).
Step 2: annual gains
Bill savings = Self-consumed energy × Price of a kWh bought
Sale earnings = Surplus sold × Buyback rate
Total annual gain = Bill savings + Sale earnings
Note: the simulator caps the self-consumed energy at the home's annual consumption, since you can't self-consume more than you use.
Step 3: payback time (return on investment)
Payback time (years) = Total project cost ÷ Total annual gain
The total project cost is the system cost minus incentives (federal tax credit, local rebates…), plus the battery cost for the storage option.
The simulator refines this calculation by factoring in the annual increase in the electricity price (3% per year by default, adjustable with the slider): bill savings grow each year, which shortens the payback compared with a fixed-price calculation.
With or without a battery: the financial paradox
Without a battery
The upfront investment is lower. The self-consumption rate is limited (usually between 30% and 40%), because the panels produce during the day while part of the consumption happens in the evening. The surplus is sold, but at a rate lower than the price of a kWh bought. Despite this, the payback time is often shorter: about 8 to 12 years.
With a battery
The self-consumption rate climbs between 70% and 85%: the energy produced during the day is stored to be used at night, and you buy almost nothing from the grid. The annual savings are therefore higher. However, the cost of the battery (and its potential replacement after 10 to 15 years) often lengthens the overall payback time: sometimes 14 to 18 years.
That is the whole point of the comparison table: depending on your consumption, your electricity price and the battery cost, the conclusion can flip. Vary the values to find your break-even point.
Which surplus buyback rate to use?
The surplus is bought back under your utility's net metering or net billing program. This rate varies widely by state and utility: under full retail net metering, the surplus is credited at the same price you pay (around $0.16/kWh); under net billing or avoided-cost rates, it can be much lower (around $0.03 to $0.10/kWh). Check the rate offered by your utility and adjust the "Surplus buyback rate" field.
The lower the buyback rate, the more attractive self-consumption (and therefore possibly a battery) becomes compared with selling the surplus.
How to use this simulator?
The fields are pre-filled with typical US values: a 6 kW system at $18,000, a battery at $10,000, a kWh at $0.16 and a consumption of 10,500 kWh per year. The result appears immediately.
Most fields have a slider to quickly vary the value and see its effect on the return; the associated field also lets you type a precise value (for example the exact amount from a quote). Only the price of a kWh and the buyback rate are typed by keyboard, because they are precise rate values.
- Size (kW): the peak size of the planned system (often 4, 6 or 10 kW for a home).
- Install cost ($): the total cost of the panels, equipment and installation, excluding the battery.
- Battery cost ($): the cost of the storage battery alone.
- Incentives / rebates ($): the amount of incentives you receive (federal solar tax credit, local rebates…). It is deducted from the system cost. Leave 0 if you don't get any.
- Annual consumption (kWh): shown on your electricity bill.
- Price of a kWh bought ($): the rate you currently pay.
- Self-consumption rate: the share of the production you use yourself, set with the sliders. Leave the default values (35% without a battery, 80% with) if you don't know them.
The comparison table and the "Which to choose?" analysis update automatically with each change.
Frequently asked questions about solar returns
What is the average payback time for solar panels in the US?
For a properly sized system without a battery, the payback time is generally between 8 and 12 years, for a panel lifespan of 25 to 30 years. With a battery, the payback is often longer (14 to 18 years), but the annual savings are higher.
Is a solar battery worth it?
It depends on the price of the battery, your electricity price and the surplus buyback rate. As buyback rates fall (net billing replacing full retail net metering in many states) and electricity prices rise, storing your energy becomes increasingly worthwhile. Use this simulator's comparison table to check your specific case.
What is the self-consumption rate?
It is the share of the solar production you use directly at home, instead of feeding it into the grid. Without a battery, it is between 30% and 40%. With a battery, it rises between 70% and 85%, because the energy produced during the day is stored for the night.
How much does a solar panel produce per year?
In the United States, 1 kW installed produces an average of about 1,400 kWh per year. The range goes from about 1,100 kWh/kW in the cloudy Northeast to 1,800 kWh/kW in the sunny Southwest. A 6 kW system therefore produces about 8,400 kWh per year on the national average.
Should incentives be counted in the calculation?
Yes: the federal solar tax credit (currently 30% of the system cost) and other rebates reduce the real cost of your project. Enter their amount in the "Incentives / rebates" field: it is automatically deducted from the system cost to get a realistic payback time.
Keyboard shortcuts
m ⇝ Reset
f ⇝ Save
Save the data in a table
You can save your simulations (Save button) and record them in a table to compare several scenarios (sizes, costs, regions), then export them in PDF or CSV format.