Delaware Solar Savings Calculator: 2026 Updated

Delaware Solar Savings Calculator

Calculate Delaware solar costs, 2026 federal tax-credit status, retail net metering, SREC revenue, payback period, and 25-year savings.

Delaware 2026 rules: No state income tax credit for solar. The federal Section 25D credit ended for systems placed in service after December 31, 2025. Delaware mandates retail-rate net metering with annual true-up. Delaware has no state sales tax. There is no statewide solar property tax exemption. Registered systems may earn SREC revenue.

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Estimates only. Verify utility rates, net metering true-up terms, SREC eligibility, and federal tax status with your utility, installer, and tax professional.

What Is the Delaware Solar Savings Calculator?

The Delaware Solar Savings Calculator is a residential solar cost and savings estimation tool. It calculates the gross installation cost, subtracts entered incentives, estimates solar electricity generation, and projects savings over a 25-year period.

The calculator estimates how long a Delaware solar installation may take to recover its initial cost and how much it could save over 25 years. It uses installation costs, electricity rates, solar production, self-consumption, export credits, annual utility fees, SREC revenue, and entered incentives to calculate the financial results.

Its main outputs are the Payback Period and 25-Year Net Savings. The payback period identifies the first modeled year when accumulated savings recover the net system cost. The 25-year result represents total projected financial benefits minus the initial investment.

The tool also estimates first-year electricity production, annual household usage, solar offset percentage, and a 25-year carbon dioxide (CO2) offset.

Results depend on your inputs and the calculator’s fixed assumptions. They are estimates, not guaranteed electricity production figures or financial returns.

How the Delaware Solar Savings Calculation Works

The calculator combines installation costs, estimated electricity production, utility compensation, SREC revenue, and other entered financial adjustments. It then calculates annual savings over 25 years to determine the estimated payback period and net financial result.

1. Calculate the Gross Solar Installation Cost

The gross system cost equals the installed solar capacity in kilowatts multiplied by 1,000 to convert it into watts, then multiplied by the entered installed cost per watt.

G=K\times1000\times W

Where:

G = Gross solar installation cost in dollars.
K = Solar system capacity in kilowatts (kW).
W = Installed cost per watt in dollars.

For example, an 8 kW system installed at $3.10 per watt has a gross installation cost of:

8\times1000\times3.10=\$24,800

2. Subtract Federal Credits, State Credits, and Rebates

The calculator subtracts any entered federal credit percentage, Delaware state credit percentage, and upfront rebate amount. Both credit percentages are calculated independently from the original gross system cost.

N=\max\left(0,G-\frac{Gf}{100}-\frac{Gs}{100}-R\right)

Here, N is the net installation cost, f is the entered federal credit percentage, s is the entered Delaware state credit percentage, and R is the upfront rebate amount in dollars.

The calculated net cost cannot fall below zero. The federal credit, state credit, and rebate fields all default to zero. These amounts are user-entered assumptions, and the calculator does not determine whether a homeowner legally qualifies for a particular incentive.

3. Estimate Annual Solar Electricity Production

The calculator uses a fixed Delaware solar production assumption of 1,300 kilowatt-hours (kWh) per installed kilowatt (kW) during the first year.

P_1=K\times1300

Here, P₁ is first-year solar generation in kWh, and K is installed system capacity in kW.

For an 8 kW system, estimated first-year production is:

8\times1300=10,400\text{ kWh}

For later years, the calculator applies a fixed annual solar production degradation rate of 0.5%.

P_y=P_1\times(0.995)^{y-1}

In this formula, Pᵧ represents estimated solar electricity production in year y.

The calculator distributes each year’s solar production across 12 months using fixed monthly percentages. These seasonal production assumptions affect the modeled amount of solar electricity used at home and exported to the utility.

4. Calculate Self-Consumed and Exported Solar Electricity

The calculator values solar electricity used directly in the home at the entered retail electricity rate. Electricity treated as exported receives the entered export credit rate.

First, it estimates annual household electricity usage from your monthly bill and electricity rate.

A=\frac{12B}{U}

Where A is annual household electricity usage in kWh, B is the monthly electricity bill in dollars, and U is the electricity rate in dollars per kWh.

For each month, the calculator determines self-consumed solar electricity using the smaller of two values: the entered self-consumption percentage of monthly solar generation or one-twelfth of estimated annual household usage.

D_m=\min\left(\frac{M_mq}{100},\frac{A}{12}\right)

X_m=\max(0,M_m-D_m)

Here, Mₘ is monthly solar production, q is the entered daytime self-consumption percentage, Dₘ is self-consumed solar electricity, and Xₘ is exported electricity.

The calculator values all modeled exported electricity using the entered export credit rate. Although its explanatory notes describe Delaware net metering and annual true-up arrangements, the calculation does not separately model monthly credit balances or an annual avoided-cost settlement.

5. Calculate Annual Electricity Savings and SREC Revenue

For each year, the calculator adds the financial value of self-consumed and exported electricity. It then subtracts annual utility solar fees and adds entered property tax savings and annual SREC revenue.

V_y=\sum_{m=1}^{12}\left(D_{y,m}U_y+X_{y,m}E_y\right)-F+T+S

Where:

Vᵧ = Calculated financial savings for year y.
Dᵧ,ₘ = Self-consumed solar electricity during month m of year y.
Xᵧ,ₘ = Exported solar electricity during month m of year y.
Uᵧ = Retail electricity rate for year y.
Eᵧ = Export credit rate for year y.
F = Annual utility solar fees.
T = Entered annual property tax savings.
S = Entered annual SREC revenue.

The calculator increases both the retail electricity rate and export credit rate each year using the entered Annual Utility Rate Increase percentage.

U_y=U_1(1+i)^{y-1}

E_y=E_1(1+i)^{y-1}

Here, i is the entered annual rate increase expressed as a decimal.

Annual SREC revenue is added as a fixed dollar amount each year. The calculator does not increase or decrease that amount based on electricity production, certificate prices, or market conditions.

6. Calculate Solar Payback Period and 25-Year Net Savings

The payback period is the first whole year in which accumulated annual financial savings equal or exceed the net installation cost.

\sum_{y=1}^{n}V_y\ge N

Here, n is the earliest year when this condition is satisfied. The calculator checks up to 25 years. If the net installation cost is zero, the payback result is Immediate. If savings do not recover the cost within 25 years, the result is 25+ Years.

The 25-year net savings calculation subtracts the original net installation cost from the sum of all 25 years of calculated financial benefits.

\text{25-Year Net Savings}=\sum_{y=1}^{25}V_y-N

7. Worked Example Using the Calculator’s Default Values

Consider a hypothetical Delaware solar installation using the calculator’s default values.

Input	Value
Monthly Electric Bill	$135
Electricity Rate	$0.145/kWh
System Size	8 kW
Installed Cost per Watt	$3.10
Export Credit	$0.145/kWh
Daytime Self-Consumption	30%
Annual Utility Rate Increase	3.5%
Annual Utility Solar Fees	$0
Federal and State Credits	0%
Upfront Rebates	$0
Property Tax Savings	$0/year
Annual SREC Revenue	$0

The estimated gross installation cost is $24,800. With no entered credits or rebates, the net installation cost is also $24,800.

First-year solar production is 10,400 kWh. Based on the monthly electricity bill and rate, annual household electricity usage is approximately 11,172 kWh.

During the first simulated year, the calculator assigns 3,120 kWh to self-consumption and 7,280 kWh to exports. Because both categories are valued at $0.145/kWh, the calculated first-year electricity savings are:

(3120\times0.145)+(7280\times0.145)=\$1,508

With no additional revenue, fees, or annual property tax savings entered, first-year financial savings are $1,508.

Extending the calculation over 25 years, including annual electricity rate increases of 3.5% and solar production degradation of 0.5%, produces these results:

Gross System Cost: $24,800.
Net System Cost: $24,800.
Payback Period: 14 Years.
25-Year Net Savings: Approximately $30,054.
Solar Offset: Approximately 93%.
25-Year CO2 Offset: Approximately 110.2 tons.

These results follow the calculator’s mathematical assumptions. They are not installation quotes, expected market returns, or guarantees of future savings.

How to Use the Delaware Solar Savings Calculator

Enter your monthly electricity bill. Type the dollar amount under Monthly Electric Bill ($). The default value is $135.
Enter your electricity rate. Provide Electricity Rate ($/kWh). The default is $0.145/kWh. Use a value greater than zero because annual usage is calculated by dividing by this rate.
Enter the system size. Adjust System Size (kW) to the solar capacity you want to evaluate. The default is 8 kW.
Enter your installation price. Set Installed Cost per Watt ($) using the price you want to model.
Select your utility. Choose Delmarva Power, Delaware Electric Cooperative, Municipal Utility, or Other Utility. This selection does not independently change the mathematical calculation.
Adjust export and self-consumption assumptions. Enter Export Credit ($/kWh) and Daytime Self-Consumption (%). The self-consumption field accepts values from 0% to 100%.
Enter future utility cost assumptions. Adjust Annual Utility Rate Increase (%) and Annual Utility Solar Fees ($).
Review incentive amounts. Enter any applicable Direct Federal Credit (%), Delaware State Credit (%), Upfront Rebates ($), and Property Tax Savings ($/yr).
Enter annual SREC revenue. Use Annual SREC Revenue ($) to include an assumed yearly certificate payment. Leave the field at $0 if you do not want to include this revenue.
Calculate your savings. Click Calculate Savings to display your estimated costs, payback period, 25-year savings, and electricity production figures.

The calculator also includes a Battery storage or high daytime self-use checkbox. Selecting it does not independently modify the calculation. To model different solar self-consumption, adjust the Daytime Self-Consumption (%) field directly.

Use Reset to restore the default inputs and hide the previous results. You can then enter another set of values to explore a different scenario.

Understanding Your Solar Savings Results and Assumptions

Gross System Cost and Net Cost

Gross System Cost shows the installation price before entered incentives. Net Cost shows the remaining amount after federal and state credit percentages and upfront rebates are deducted.

The calculator’s accompanying 2026 notes state that the residential federal Section 25D credit ended for systems placed in service after December 31, 2025, and that Delaware does not offer a state solar income tax credit. The calculator therefore defaults both credit fields to zero.

These are statements included in the calculator’s explanatory text, not separate checks of your tax situation. Confirm applicable rules and eligibility before entering nonzero credit percentages.

Annual SREC Revenue

A Solar Renewable Energy Certificate, or SREC, represents an eligible amount of solar electricity generation under an applicable certificate program. Its potential financial value is separate from the electricity savings associated with using or exporting solar power.

The calculator provides an Annual SREC Revenue ($) field, initially set to zero. If you enter a positive amount, the results display a separate Annual SREC Revenue row, and the amount is added to projected savings every year for 25 years.

The tool does not calculate how many certificates a system qualifies to earn, determine registration eligibility, or forecast certificate prices. It also does not reduce SREC revenue automatically as modeled solar production declines. Enter an annual revenue assumption supported by your circumstances.

Net Metering and Electricity Export Credits

The calculator’s Delaware notes describe retail-rate net metering, monthly credit rollover, and annual true-up arrangements. Its calculation, however, uses the numeric Export Credit ($/kWh) field to value all modeled exported electricity.

It does not independently apply different utility tariffs or account for credit expiration and annual settlement rates. Changing the utility dropdown without changing the numeric export credit does not affect the calculated savings.

For a more relevant estimate, use an export credit rate consistent with your actual utility arrangement.

Solar Offset and Estimated Environmental Impact

Solar Offset compares estimated first-year solar electricity generation with estimated annual household electricity usage.

\text{Solar Offset (\%)}=\frac{P_1}{A}\times100

A solar offset above 100% means modeled first-year solar production exceeds estimated annual household electricity consumption. It does not mean that all electricity is consumed directly in the home.

The calculator also estimates a 25-Year CO2 Offset. It adds projected solar electricity production across 25 years and applies a fixed factor of 0.45 tons per 1,000 kWh.

\text{25-Year CO2 Offset}=\frac{0.45}{1000}\sum_{y=1}^{25}P_y

This is a simplified production-based environmental estimate rather than a direct measurement of avoided emissions.

Important Result-Label Limitations

Some displayed result labels differ from the quantities calculated in the current implementation. The rows labeled Year 1 Self-Use kWh and Year 1 Export kWh actually show the quantities remaining from the final simulated year, year 25, rather than the first year.

Similarly, the row labeled Net Year 1 Savings displays the positive portion of the calculated 25-year net savings amount, or $0 if that amount is negative. It does not display the savings generated during the first year.

The separate 25-Year Net Savings result shows the full calculated financial outcome, including negative values.

Dollar outputs are displayed in whole U.S. dollars. Electricity production and usage appear as whole kWh, Solar Offset is rounded to a whole percentage, and the CO2 offset is shown to one decimal place.

The Retail Net Metering and No State Sales Tax badges are informational. They do not verify individual utility eligibility or independently change the financial calculations.

Costs and Conditions Not Separately Modeled

The 25-year savings calculation does not separately include solar loan interest, financing payments, inverter replacement, maintenance expenses, insurance changes, or future equipment costs. Annual utility solar fees are deducted, but other expenses must be considered separately when evaluating actual project economics.

The model also does not discount future savings into present-day dollars. Its 25-year result is the sum of projected future dollar amounts minus the initial net installation cost.

Frequently Asked Questions

How much does an 8 kW solar system cost in Delaware?

Using the calculator’s default installed price of $3.10 per watt, an 8 kW solar system has an estimated gross cost of $24,800. The calculated net cost may be lower if applicable credits or upfront rebates are entered. The actual installation price depends on your quote, equipment, property conditions, and included services.

How much electricity can an 8 kW solar system produce?

The calculator estimates 10,400 kWh of electricity during the first year for an 8 kW solar system. It assumes 1,300 kWh of annual production per installed kW and reduces future generation by 0.5% each year. Actual electricity production depends on factors such as sunlight, shading, equipment, and panel orientation.

Does the Delaware solar calculator include SREC revenue?

Yes. The calculator includes an adjustable Annual SREC Revenue ($) field. Any entered amount is added to modeled savings every year and affects both payback period and 25-year net savings. The tool does not automatically calculate certificate eligibility, market prices, or the number of certificates generated. The field defaults to $0.

Does the calculator account for Delaware net metering?

The calculator includes an export credit field for estimating the financial value of solar electricity sent to the grid. Its notes describe Delaware retail net metering and annual true-up arrangements, but the model does not separately calculate a true-up settlement. Instead, it values exported electricity at the entered credit rate, adjusted by the assumed annual utility rate increase.

Does Delaware offer a solar tax credit in this calculator?

The calculator includes a Delaware State Credit (%) field that defaults to 0%. Its accompanying notes state that Delaware does not have a state solar income tax credit. The federal credit field also defaults to 0%, reflecting the calculator’s stated 2026 tax assumptions. Neither field automatically determines tax eligibility, so verify applicable rules before changing the values.

Why does the payback period show 25+ Years?

A result of 25+ Years means the calculator’s accumulated financial savings do not recover the net installation cost within its 25-year projection. Higher installation costs, lower electricity compensation, or greater recurring fees can contribute to that outcome. The tool does not calculate an exact payback year beyond the 25-year period.

Does selecting battery storage increase estimated savings?

No. Selecting the Battery storage or high daytime self-use checkbox does not independently change the calculator’s results. The calculation does not include separate battery costs, storage capacity, efficiency, or replacement expenses. You can adjust the daytime self-consumption percentage to explore another solar usage assumption, but this is not a full battery storage financial analysis.

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Delaware Solar Savings Calculator