Location-Based Solar Production Calculator
Estimate monthly and annual photovoltaic energy production from a ZIP code, postcode, city, or coordinates using system design inputs and the NLR PVWatts V8 model.
What the Location-Based Solar Production Calculator does
The location based solar production calculator is designed for homeowners, installers, researchers, and energy-conscious buyers who need a transparent planning estimate rather than a hidden sales number. It converts the values entered above into a result that can be checked, changed, and discussed. The calculator is intended to support array design, production expectations, inverter selection, storage planning, and project economics. It does not replace an equipment datasheet, a site survey, a utility tariff, or a professional design.
Estimate monthly and annual photovoltaic energy production from a ZIP code, postcode, city, or coordinates using system design inputs and the NLR PVWatts V8 model. The result is most useful when every input comes from the same project boundary and time period. For example, annual energy should not be combined casually with one exceptional day, and a DC equipment rating should not be treated as an AC delivered value unless the conversion is included. The page shows the governing relationship, explains every field, and identifies the assumptions that normally cause the largest uncertainty.
People often reach this page using related searches such as solar calculator by zip code, solar output calculator by postcode, PVWatts calculator, solar production estimate by location, solar irradiance calculator. Those phrases describe similar questions, but they are not always mathematically identical. This guide keeps the differences visible so a user does not mistake one metric for another. A calculation can be numerically correct and still be unsuitable if the wrong system boundary was chosen.
The tool is built for the broader context of a residential photovoltaic system. That context matters because equipment does not operate in isolation. Loads, weather, controls, tariffs, user behavior, safety limits, and manufacturer settings interact. Use the result as one layer in a documented decision process, then verify the important assumptions using electricity bills, module and inverter datasheets, roof measurements, shade observations, local weather records, and interval production data.
Home Energy Desk presents the result as an estimate with units, explanatory notes, and related tools. Save the inputs with the date, equipment model, firmware or tariff version where relevant, and the source of each value. That simple record makes the estimate easier to audit when a project changes.
Formula and calculation boundary
The central relationship used by this calculator is:
The formula is intentionally visible. A visible formula lets a reader identify whether the calculator addresses energy, power, current, capacity, time, cost, efficiency, or another quantity. It also makes unit conversion errors easier to find. Inputs are converted only where the displayed calculation requires it, and results are rounded for readability rather than to imply laboratory precision.
A calculation boundary defines what is included. For this tool, the boundary follows the fields shown in the form and the assumptions stated below. Items not represented by an input are not automatically modeled. Depending on the topic, that may include standby consumption, degradation, temperature derating, taxes, utility demand charges, equipment downtime, maintenance, startup transients, shading, snow, or control behavior.
Do not add a general loss percentage when the same loss has already been included in a measured efficiency or net energy value. Conversely, do not use an ideal nameplate value when the purpose is to estimate delivered performance unless the appropriate derating factors are included. Double counting and missing losses are two of the most common reasons online calculator results disagree.
The calculator reports a planning value rather than a certified design value. More decimal places would not remove uncertainty in the assumptions. A sound estimate normally uses realistic ranges, keeps units consistent, and compares the calculated result with an independent benchmark such as a utility bill, manufacturer design tool, commissioning report, or measured operating record.
How to enter every input correctly
The quality of a location based solar production calculator result depends more on input quality than on arithmetic. Work through the fields in order, and do not leave a default value unchanged merely because it looks reasonable. Defaults are examples for demonstrating the form; they are not recommendations for a particular home, country, climate, or product.
1. ZIP code, postcode, city, or address
ZIP code, postcode, city, or address. Enter the numeric value that describes the real project rather than a sales assumption. Enter a location or provide coordinates below. Keep the source beside the calculation so the result can be reproduced and updated later.
Use site-specific information. Rounding a location or environmental input can be acceptable for early screening, but a final design should use the actual site, local design conditions, and the correct sign or directional convention. This input works together with the other fields, so changing it in isolation may create an internally inconsistent scenario. For a decision involving purchase, installation, safety, or a warranty, compare the entered value with electricity bills, module and inverter datasheets, roof measurements, shade observations, local weather records, and interval production data.
2. Optional country code
Optional country code. Enter the numeric value that describes the real project rather than a sales assumption. Two-letter ISO code such as US, GB, CA, AU, or NZ to reduce ambiguous location matches. Keep the source beside the calculation so the result can be reproduced and updated later.
The value should be consistent with the other inputs used for this location-based solar production calculator. If it is uncertain, calculate a conservative case and a more favorable case instead of hiding uncertainty inside one number. This input works together with the other fields, so changing it in isolation may create an internally inconsistent scenario. For a decision involving purchase, installation, safety, or a warranty, compare the entered value with electricity bills, module and inverter datasheets, roof measurements, shade observations, local weather records, and interval production data.
3. Optional Open-Meteo customer API key
Optional Open-Meteo customer API key. Enter the numeric value that describes the real project rather than a sales assumption. For commercial production use, enter the customer key and verify the current Open-Meteo license. Leave blank only for testing where permitted. Keep the source beside the calculation so the result can be reproduced and updated later.
The value should be consistent with the other inputs used for this location-based solar production calculator. If it is uncertain, calculate a conservative case and a more favorable case instead of hiding uncertainty inside one number. This input works together with the other fields, so changing it in isolation may create an internally inconsistent scenario. For a decision involving purchase, installation, safety, or a warranty, compare the entered value with electricity bills, module and inverter datasheets, roof measurements, shade observations, local weather records, and interval production data.
4. Latitude
Latitude. Enter the numeric value that describes the real project rather than a sales assumption. The field is expressed in degrees. Optional when a location is entered. Use decimal degrees, north positive. Keep the source beside the calculation so the result can be reproduced and updated later.
Use site-specific information. Rounding a location or environmental input can be acceptable for early screening, but a final design should use the actual site, local design conditions, and the correct sign or directional convention. This input works together with the other fields, so changing it in isolation may create an internally inconsistent scenario. For a decision involving purchase, installation, safety, or a warranty, compare the entered value with electricity bills, module and inverter datasheets, roof measurements, shade observations, local weather records, and interval production data.
5. Longitude
Longitude. Enter the numeric value that describes the real project rather than a sales assumption. The field is expressed in degrees. Optional when a location is entered. Use decimal degrees, east positive. Keep the source beside the calculation so the result can be reproduced and updated later.
Use site-specific information. Rounding a location or environmental input can be acceptable for early screening, but a final design should use the actual site, local design conditions, and the correct sign or directional convention. This input works together with the other fields, so changing it in isolation may create an internally inconsistent scenario. For a decision involving purchase, installation, safety, or a warranty, compare the entered value with electricity bills, module and inverter datasheets, roof measurements, shade observations, local weather records, and interval production data.
6. Weather dataset
Weather dataset. Enter the choice that describes the real project rather than a sales assumption. Use the default NSRDB where available or select an international station dataset. Keep the source beside the calculation so the result can be reproduced and updated later.
The value should be consistent with the other inputs used for this location-based solar production calculator. If it is uncertain, calculate a conservative case and a more favorable case instead of hiding uncertainty inside one number. This input works together with the other fields, so changing it in isolation may create an internally inconsistent scenario. For a decision involving purchase, installation, safety, or a warranty, compare the entered value with electricity bills, module and inverter datasheets, roof measurements, shade observations, local weather records, and interval production data.
7. Weather-station search radius
Weather-station search radius. Enter the numeric value that describes the real project rather than a sales assumption. The field is expressed in miles. Use 0 to allow the closest station regardless of distance. Keep the source beside the calculation so the result can be reproduced and updated later.
The value should be consistent with the other inputs used for this location-based solar production calculator. If it is uncertain, calculate a conservative case and a more favorable case instead of hiding uncertainty inside one number. This input works together with the other fields, so changing it in isolation may create an internally inconsistent scenario. For a decision involving purchase, installation, safety, or a warranty, compare the entered value with electricity bills, module and inverter datasheets, roof measurements, shade observations, local weather records, and interval production data.
8. Solar array DC capacity
Solar array DC capacity. Enter the numeric value that describes the real project rather than a sales assumption. The field is expressed in kW. Total module nameplate capacity. Keep the source beside the calculation so the result can be reproduced and updated later.
Nameplate and real operating values are not always identical. Continuous capability, short-duration surge capability, thermal derating, voltage range, and manufacturer limits should be considered separately when they apply. This input works together with the other fields, so changing it in isolation may create an internally inconsistent scenario. For a decision involving purchase, installation, safety, or a warranty, compare the entered value with electricity bills, module and inverter datasheets, roof measurements, shade observations, local weather records, and interval production data.
9. Module type
Module type. Enter the choice that describes the real project rather than a sales assumption. Select the module performance class. Keep the source beside the calculation so the result can be reproduced and updated later.
The value should be consistent with the other inputs used for this location-based solar production calculator. If it is uncertain, calculate a conservative case and a more favorable case instead of hiding uncertainty inside one number. This input works together with the other fields, so changing it in isolation may create an internally inconsistent scenario. For a decision involving purchase, installation, safety, or a warranty, compare the entered value with electricity bills, module and inverter datasheets, roof measurements, shade observations, local weather records, and interval production data.
10. Array type
Array type. Enter the choice that describes the real project rather than a sales assumption. Choose the mounting/tracking configuration. Keep the source beside the calculation so the result can be reproduced and updated later.
The value should be consistent with the other inputs used for this location-based solar production calculator. If it is uncertain, calculate a conservative case and a more favorable case instead of hiding uncertainty inside one number. This input works together with the other fields, so changing it in isolation may create an internally inconsistent scenario. For a decision involving purchase, installation, safety, or a warranty, compare the entered value with electricity bills, module and inverter datasheets, roof measurements, shade observations, local weather records, and interval production data.
11. Ground coverage ratio
Ground coverage ratio. Enter the numeric value that describes the real project rather than a sales assumption. Module surface area divided by ground/roof area occupied by the array. Keep the source beside the calculation so the result can be reproduced and updated later.
The value should be consistent with the other inputs used for this location-based solar production calculator. If it is uncertain, calculate a conservative case and a more favorable case instead of hiding uncertainty inside one number. This input works together with the other fields, so changing it in isolation may create an internally inconsistent scenario. For a decision involving purchase, installation, safety, or a warranty, compare the entered value with electricity bills, module and inverter datasheets, roof measurements, shade observations, local weather records, and interval production data.
12. Roof or array tilt
Roof or array tilt. Enter the numeric value that describes the real project rather than a sales assumption. The field is expressed in degrees. Zero is horizontal; 90 is vertical. Keep the source beside the calculation so the result can be reproduced and updated later.
Use site-specific information. Rounding a location or environmental input can be acceptable for early screening, but a final design should use the actual site, local design conditions, and the correct sign or directional convention. This input works together with the other fields, so changing it in isolation may create an internally inconsistent scenario. For a decision involving purchase, installation, safety, or a warranty, compare the entered value with electricity bills, module and inverter datasheets, roof measurements, shade observations, local weather records, and interval production data.
13. Roof or array azimuth
Roof or array azimuth. Enter the numeric value that describes the real project rather than a sales assumption. The field is expressed in degrees. 180° is south, 90° east, 270° west in the northern hemisphere. Keep the source beside the calculation so the result can be reproduced and updated later.
Use site-specific information. Rounding a location or environmental input can be acceptable for early screening, but a final design should use the actual site, local design conditions, and the correct sign or directional convention. This input works together with the other fields, so changing it in isolation may create an internally inconsistent scenario. For a decision involving purchase, installation, safety, or a warranty, compare the entered value with electricity bills, module and inverter datasheets, roof measurements, shade observations, local weather records, and interval production data.
14. Total system losses
Total system losses. Enter the numeric value that describes the real project rather than a sales assumption. The field is expressed in %. Include soiling, shading, wiring, mismatch, availability, and other non-inverter losses. Keep the source beside the calculation so the result can be reproduced and updated later.
Percentages deserve particular attention because a small change can influence several downstream results. Confirm whether the source reports a fraction, percentage, AC value, DC value, gross value, or net value. Avoid counting the same loss twice. This input works together with the other fields, so changing it in isolation may create an internally inconsistent scenario. For a decision involving purchase, installation, safety, or a warranty, compare the entered value with electricity bills, module and inverter datasheets, roof measurements, shade observations, local weather records, and interval production data.
15. DC-to-AC ratio
DC-to-AC ratio. Enter the numeric value that describes the real project rather than a sales assumption. DC array rating divided by inverter AC rating. Keep the source beside the calculation so the result can be reproduced and updated later.
The value should be consistent with the other inputs used for this location-based solar production calculator. If it is uncertain, calculate a conservative case and a more favorable case instead of hiding uncertainty inside one number. This input works together with the other fields, so changing it in isolation may create an internally inconsistent scenario. For a decision involving purchase, installation, safety, or a warranty, compare the entered value with electricity bills, module and inverter datasheets, roof measurements, shade observations, local weather records, and interval production data.
16. Inverter efficiency
Inverter efficiency. Enter the numeric value that describes the real project rather than a sales assumption. The field is expressed in %. PVWatts accepts typical values between 90% and 99.5%. Keep the source beside the calculation so the result can be reproduced and updated later.
The value should be consistent with the other inputs used for this location-based solar production calculator. If it is uncertain, calculate a conservative case and a more favorable case instead of hiding uncertainty inside one number. This input works together with the other fields, so changing it in isolation may create an internally inconsistent scenario. For a decision involving purchase, installation, safety, or a warranty, compare the entered value with electricity bills, module and inverter datasheets, roof measurements, shade observations, local weather records, and interval production data.
17. Bifaciality
Bifaciality. Enter the numeric value that describes the real project rather than a sales assumption. Use 0 for monofacial modules; use a manufacturer-supported value for bifacial modules. Keep the source beside the calculation so the result can be reproduced and updated later.
The value should be consistent with the other inputs used for this location-based solar production calculator. If it is uncertain, calculate a conservative case and a more favorable case instead of hiding uncertainty inside one number. This input works together with the other fields, so changing it in isolation may create an internally inconsistent scenario. For a decision involving purchase, installation, safety, or a warranty, compare the entered value with electricity bills, module and inverter datasheets, roof measurements, shade observations, local weather records, and interval production data.
18. Ground reflectance
Ground reflectance. Enter the numeric value that describes the real project rather than a sales assumption. Typical values range from about 0.1 to 0.9. Keep the source beside the calculation so the result can be reproduced and updated later.
The value should be consistent with the other inputs used for this location-based solar production calculator. If it is uncertain, calculate a conservative case and a more favorable case instead of hiding uncertainty inside one number. This input works together with the other fields, so changing it in isolation may create an internally inconsistent scenario. For a decision involving purchase, installation, safety, or a warranty, compare the entered value with electricity bills, module and inverter datasheets, roof measurements, shade observations, local weather records, and interval production data.
19. NLR API key
NLR API key. Enter the numeric value that describes the real project rather than a sales assumption. DEMO_KEY is suitable for testing only. Obtain a free production key before regular public use. Keep the source beside the calculation so the result can be reproduced and updated later.
The value should be consistent with the other inputs used for this location-based solar production calculator. If it is uncertain, calculate a conservative case and a more favorable case instead of hiding uncertainty inside one number. This input works together with the other fields, so changing it in isolation may create an internally inconsistent scenario. For a decision involving purchase, installation, safety, or a warranty, compare the entered value with electricity bills, module and inverter datasheets, roof measurements, shade observations, local weather records, and interval production data.
Accuracy, uncertainty, and validation
The result is a planning estimate based on a typical-year weather dataset rather than a site survey or performance guarantee. Nearby shading, snow, curtailment, equipment downtime, export controls, roof geometry, module degradation, and local microclimate can materially change actual production. The optional location lookup uses Open-Meteo geocoding data based on GeoNames; a monetized production site should verify licensing and use the appropriate customer endpoint or require coordinates.
Accuracy should be discussed in layers. Arithmetic accuracy means the formula was applied correctly. Input accuracy means the entered values describe the project. Model accuracy means the simplified relationship represents real operation closely enough for the decision. A calculator can satisfy the first layer while remaining weak at the second or third.
Validate the result using at least one independent source. Suitable checks include electricity bills, module and inverter datasheets, roof measurements, shade observations, local weather records, and interval production data. For a new installation without measurements, compare multiple manufacturer tools or obtain a professional design. For an existing system, use interval data and known operating events rather than relying only on a monthly total.
Uncertainty is not a reason to avoid calculation. It is a reason to calculate a range. Identify the three inputs most likely to change, vary each one separately, and note whether the recommended decision changes. A stable decision that survives reasonable variation is stronger than a decision supported by one highly optimized scenario.
Seasonal and geographic differences matter. A value that is reasonable in one country may be unsuitable in another because voltage standards, climate, tariffs, utility rules, incentives, electrical codes, product versions, and user behavior differ. Localize every critical assumption.
Equipment updates also matter. Firmware, model revisions, battery compatibility lists, charger behavior, efficiency ratings, and tariff structures can change. Record the exact version or effective date whenever it affects the calculation.
Safety, code, and professional review
This calculator does not authorize installation or modification work. Relevant hazards can include high DC voltage, roof access, electrical shock, fire, arc faults, structural loading, code compliance, and utility interconnection. Do not open energized equipment, bypass protective devices, alter manufacturer settings outside approved ranges, or rely on an online estimate as the sole basis for hazardous work.
Final work may require a qualified solar designer, licensed electrician, structural professional, or local permitting authority. Requirements vary by jurisdiction, occupancy, equipment, utility, and installation method. Manufacturer instructions and local law take priority over the planning relationships shown here.
Stop and seek qualified assistance when there is heat damage, burning odor, visible arcing, repeated protective-device operation, battery swelling, fuel leakage, carbon-monoxide alarm, damaged insulation, water intrusion, refrigerant concerns, or an unexplained equipment shutdown.
Sources and further verification
Use primary sources whenever they are available. The following references provide background, standardized definitions, safety information, or model documentation relevant to this calculator. A source link does not mean that the organization endorses this page or its result.
Related Home Energy Desk calculators
A complete decision usually requires more than one calculation. Continue with the following tools and keep the same source assumptions across pages:
- Solar Shading Loss Calculator — Estimate annual energy lost from seasonal and time-of-day shading across multiple solar array zones.
- Solar Production Loss Calculator — Compare expected and measured solar generation to quantify energy shortfall, percentage loss, and estimated financial impact.
- Solar Panel Output Calculator — Estimate daily, monthly, and annual energy production for a solar array using panel rating, quantity, sun hours, and system losses.
- Solar Panel Temperature Loss Calculator — Estimate module operating temperature and photovoltaic power reduction caused by hot weather.
- PV Strings per MPPT Calculator — Estimate how many parallel photovoltaic strings can be connected to one inverter MPPT using input-current and short-circuit-current limits.
- Solar Panel Tilt and Orientation Calculator — Estimate a recommended fixed-array tilt and compare relative annual production for an entered roof tilt and azimuth.