Offgrid Solar Calculator

Find out if your solar panels and battery bank can provide enough energy for your daily power needs.

Enter your solar capacity, daily electrical load, peak sun hours and battery details. The calculator will estimate solar energy production, usable battery storage, backup period, energy coverage and any remaining grid demand or shortfall.

What does the off-grid solar calculator show?

The calculator compares your daily electricity demand to the energy available from your solar panels and battery bank.

It can estimate:

•  Daily solar energy production
•  Monthly solar generation
•  Annual solar generation
•  Solar energy production compared to your daily load
•  Total battery storage in kWh
•  Usable battery energy
•  Expected nighttime battery backup
•  Solar energy contribution to your daily load
•  Battery contribution
•  Rest of the grid needs or energy shortages
•  The battery capacity required for your chosen autonomy.
•  Recommended solar panel capacity

These results can help you compare different system configurations before selecting equipment. The final design of an off-grid system should also consider peak power demand, equipment start-up loads, seasonal sunlight, inverter capacity, charge controller range, shading, and the characteristics of the equipment to be installed.

How to use the off-grid solar calculator?

1. Enter your solar PV capacity.

Enter the total DC capacity of your solar panels in kilowatts.

For example:

•  3 kilowatts = 3,000 watts of solar panels
•  5 kilowatts = 5,000 watts
•  10 kilowatts = 10,000 watts

If you already have a solar system, enter its installed panel capacity. If you are reviewing a proposed installation, enter the solar capacity shown in the quotation.

2. Enter your daily electricity load.

Enter the total amount of electricity your appliances use during a typical day.

Daily energy consumption is measured in:

• Kilowatts per day

This is different from the maximum number of watts your appliances can use at one moment.

How to calculate daily appliance consumption.

Multiply the wattage of each appliance by the number of hours it has been running. For example, a 100W device running for 5 hours uses:

• 100W × 5 hours = 500Wh

Convert watt hours to kilowatt hours:

• 500 ÷ 1,000 = 0.5 kWh per day

Repeat this calculation for the devices you need to run and add the results together. If you have several devices, a solar load calculator can make this step easier.

3. Enter peak sun times.

Peak sun times show the amount of useful solar energy available at your location. They are not equal to the total number of hours between sunrise and sunset.

Changes with available solar energy:

•  Location
•  Weather
•  Weather
•  Shading
•  Panel direction
•  Panel tilt

For a system operating without grid support, it is important to consider periods of low solar availability rather than designing around harsh summer conditions.

4. Set the performance ratio.

The efficiency ratio accounts for the difference between theoretical solar panel output and expected real-world generation.

What can reduce solar energy production?

Common disadvantages may include:

•  High panel temperature
•  Inverter replacement
•  Electrical wiring
•  Dust and dirt
•  Minor shading
•  Other operating losses

Use a realistic efficiency ratio instead of assuming that the solar array will consistently produce its full rated capacity.

5. Choose your battery type.

Select the battery technology you want to use. The calculator currently supports:

•  Lithium batteries
•  Tubular batteries

The battery type matters because the calculator applies different depths of discharge when determining usable battery energy. Actual usable capacity may vary depending on battery chemistry, model, age, temperature, battery management settings, and manufacturer recommendations.

6. Enter the battery voltage and capacity.

Enter your battery-bank voltage and capacity in ampere-hours (Ah). The calculator converts these values into stored energy.

For example, one:

• 48V 200Ah Battery Bank

Contains:

• 48 × 200 ÷ 1,000 = 9.6 kWh

Nominal battery energy.

Only a portion of this energy may be available for regular use when considering the depth of discharge of the battery.

7. Choose your desired battery autonomy.

Battery autonomy defines how long you want stored energy to meet your electricity needs when solar energy is unavailable or insufficient. Greater autonomy usually requires a larger battery bank. For example, a remote property without a grid connection may require more storage than a property that has a generator or utility supply available as backup.

8. Enter your nighttime battery usage.

Enter the number of hours at night during which you expect the battery to supply your load. The duration of the backup depends on both: Time and Electrical load. Running a small load for eight hours requires much less stored energy than running several high-power appliances for the same period.

9. Select whether grid power is available.

Select No. If you are evaluating a fully stand-alone solar system without utility grid backup. Select Yes if grid power is available when solar power generation and battery storage are insufficient .

Off-grid vs. grid-backed systems

A system that intentionally relies on utility electricity when solar and battery energy are insufficient is better described as a hybrid or grid-backed solar system . A true off-grid system must be able to support the required load without relying on the utility grid.

10. Calculate your off-grid system.

Select Calculate Off-Grid System to see your estimate :

•  Solar generation
•  Battery storage
•  Usable battery energy
•  Backup duration
•  Energy coverage
•  Remaining deficit
•  Required battery capacity
•  Recommended solar capacity

Change individual values to compare different solar panel and battery configurations.

How is an off-grid solar system calculated?

The calculator uses your daily electricity requirement along with your solar and battery specifications.

Daily Solar Generation

The basic formula for solar generation is:

• Daily Solar Generation = Solar PV Capacity × Peak Sun Hours × Efficiency Ratio

For example:

• Solar power capacity: 5 kW
• Peak sun hours: 5.5
• Efficiency ratio: 0.80

Calculation:

• 5 × 5.5 × 0.80 = 22 kWh per day

Estimated daily generation:

• 22 kilowatt-hours

The actual daily generation will naturally change with sunlight, weather, and system conditions.

Total battery energy

Battery storage is calculated from battery voltage and Ah capacity:

• Total battery energy = battery voltage × Ah ÷ 1,000

For 48V 200Ah battery bank:

• 48 × 200 ÷ 1,000 = 9.6 kWh

Total battery energy:

• 9.6 kilowatt-hours

Usable battery energy

Not all of the battery’s nominal capacity is necessarily available for regular discharge. The calculator applies the depth of discharge associated with the selected battery type:

• Usable battery energy = Total battery energy × Depth of discharge

For example, if 85% DoD is applied:

• 9.6 × 0.85 = 8.16 kWh

Usable battery energy:

• 8.16 kilowatt-hours

For actual installation, check the recommended operating limits provided by the battery manufacturer.

Understanding your off-grid solar results

The results show how your proposed solar and battery setup compares to your entered electricity demand.

Daily Solar Generation

This is the estimate of what your solar array can generate over the course of a day based on the selected solar capacity, peak sun hours, and efficiency ratio.

Monthly and annual solar generation

These figures extend daily generation estimates over a long period of time. Actual monthly production varies throughout the year due to the changing weather and available sunlight.

Solar Generation vs Daily Load

It compares your estimated daily solar production with your daily electricity needs. For example, if your property needs:

• 10 kilowatts per day

And the estimated time of the formation of the solar system is:

• 12 kilowatts per day

The breed is equal to:

• 120% of the listed daily load

However, this does not automatically mean that the property can operate completely off-grid.

Why doesn’t solar guarantee more than 100% off-grid operation?

Energy must be available when needed. A system can produce more energy than the property uses on an average day but still suffer from a shortage because:

•  Nighttime consumption
•  Cloudy weather
•  Seasonal changes
•  Battery limitations
•  Peak load
•  Equipment Disadvantages

This is why solar generation and battery storage need to be considered together.

Total battery energy

This is the nominal energy stored in your battery bank based on voltage and Ah capacity.

Usable battery energy

This is the fraction of the nominal battery capacity available after the calculator applies the depth of discharge.

Expected night backup

This tells how long the battery can meet the nighttime requirement. Actual runtime may change due to:

•  Night burden
•  Inverter performance
•  Battery status
•  Temperature
•  Battery management settings

Solar, battery and grid shortages

The calculator shows how the entered daily power requirement is divided between solar energy, battery energy and any remaining grid requirement or energy shortfall. A battery does not create electricity. It stores previously generated electricity. If solar energy production remains below electricity consumption for several days, the battery will eventually need to be recharged:

•  Solar panels
•  Grid electricity
•  Generator
•  Another source of energy

Required battery bank

This result estimates the battery storage required to meet your chosen autonomy target. You can compare this to the battery capacity you entered to see if additional storage might be needed.

Recommended solar panel capacity

This figure estimates the power demand and the solar array capacity required for the incoming solar conditions. The exact number of panels will depend on the wattage of the panels you choose. For example, the required array capacity in kW can be converted to the quantity of panels once the wattage of each panel is known.

Off-grid solar vs. hybrid solar

Before sizing solar panels and batteries, it is important to understand the differences between these two systems.

What is an off-grid solar system?

A true off-grid system operates without relying on the public electricity grid.

This usually requires quite a bit:

•  Solar generation
•  Battery storage
•  Inverter capacity
•  Charge controller capacity
•  System margin

To support the required electrical load of the property.

What is a hybrid or grid-backed solar system?

The hybrid system can use another source of electricity when solar and battery energy are insufficient. Depending on the system, that backup source could be:

•  Utility grid
•  Generator
•  Another source of power

Because backup power is available, a grid-backed system may have different battery and reliability requirements than a completely off-grid installation.

Daily kWh vs. peak power

One of the most important parts of off-grid system design is understanding the difference between energy and power .

What does kWh per day tell you?

kWh/day tells you how much electrical energy your appliances require throughout the day. This helps determine solar generation and battery storage requirements.

What do kilowatts or watts tell you?

Watts or kilowatts represent the power required by equipment at a specific moment, whereas daily kWh indicates their total energy consumption. Water pumps are a prime example, as they may have low daily energy usage but require high startup power. This is a crucial factor when designing off-grid solar systems for agricultural pumping. You can use our solar irrigation calculator to estimate your irrigation energy requirements.

Why Startup Surge Matters

Motors and compressors may require a significant amount of power briefly when starting. Common examples include:

•  Water pumps
•  Refrigerators
•  Freezer
•  Air conditioner
•  Other motor-driven equipment

Before choosing an inverter, check both the maximum simultaneous load and startup surge requirements of these devices.

How to choose peak sun times in Pakistan?

The availability of solar energy is not uniform throughout Pakistan or throughout the year. Use solar resource information appropriate for your location whenever possible. 

• For a grid-connected system, an annual average can be useful for estimating overall production. 
• For a true off-grid system, reliability becomes more important during periods of low sun.

Why are winter and low sun conditions important?

Designing around strong summer production alone can make an off-grid system more viable than during less favorable periods. If the property must operate without grid backup year-round, also check the system using lower peak-sun hour values. This helps to show whether additional panel capacity, battery storage or another backup source may be needed.

What is battery autonomy?

Battery autonomy defines how long your stored energy should support the required load when sufficient solar output is not available. Greater autonomy requires more usable battery storage. For example, a property requiring backup during extended cloudy conditions may require more storage than one that only requires overnight battery power.

Why big batteries alone don’t solve the energy shortage.

Adding battery capacity increases the amount of electricity you can store. It does not increase the amount of electricity your solar panels generate. After the batteries are discharged, the solar array should produce enough energy:

1. Provide the current burden of the property.

2. Recharge the battery bank.

If solar energy production is consistently less than electricity consumption, adding more batteries only delays the decline. Therefore, the capacity of the solar panel and the capacity of the battery must be sized together.

Lithium vs. Tubular Batteries for Off-Grid Solar

Different battery technologies can deliver different amounts of usable energy beyond their rated capacity. The calculator uses default Depth of Discharge values for its lithium and tubular options. These values are useful for comparison, but individual batteries should be evaluated using their actual characteristics.

What to check when choosing a battery

Overview:

•  Manufacturer’s recommended discharge depth
•  Rated cycle life
•  Maximum charge current
•  Maximum discharge current
•  Operating temperature range
•  Warranty Terms
•  Compatible inverter settings
•  Battery management requirements

The price of the battery alone doesn’t tell you how much usable storage or service life you’ll get.

Off-grid solar calculation example

Consider the following system:

Input	Value
Solar energy potential	5 kW
Daily electricity load	10 kilowatt-hour
Peak sun hours	5.5
Performance ratio	0.80
Battery voltage	48V
Battery capacity	200 AH
Battery type	Lithium
Depth of discharge	85%

Calculate Daily Solar Generation.

• 5 × 5.5 × 0.80 = 22 kWh per day

Estimated solar output:

• 22 kilowatts per day

Calculate the total battery energy.

• 48 × 200 ÷ 1,000 = 9.6 kWh

Total nominal battery storage:

• 9.6 kilowatt-hours

Calculate usable battery energy.

• 9.6 × 0.85 = 8.16 kWh

Estimated usable battery energy:

• 8.16 kilowatt-hours

The figures show that the proposed solar array can generate more than 10 kW of energy per day under selected solar conditions. However, this alone does not confirm that the system can operate reliably off-grid. Seasonal solar production, night-time consumption, peak power loads, inverter capacity, battery charging, and periods of inclement weather need to be considered.

What can affect off-grid solar performance?

Real-world performance may differ from calculated results for several reasons.

Seasonal sunlight

Solar energy production varies throughout the year. An off-grid system designed around average conditions may perform differently during low sun exposure.

Weather

Cloud cover, haze, and rain can reduce daily solar energy production. Several consecutive days of bad weather can have a much greater impact on an off-grid system than a single cloudy afternoon.

Shading

Trees, buildings, water tanks, and other objects can reduce panel output.

Panel orientation and tilt

The position of the solar array affects how much useful sunlight reaches the panels.

Battery status

Battery age, temperature, and operating history can affect usable capacity.

Inverter and power losses

Energy is lost during conversion and transmission through the system.

Electricity usage pattern

Two properties may use the same number of kWh per day but have very different demands on their solar and battery systems. A property with large evening loads will rely more on battery storage which uses most of its electricity during daylight hours.

When is an off-grid solar calculator useful?

Use this calculator when you want to:

•  Compare solar quotations with your daily electricity needs.
•  Test different solar panel capacities.
•  Compare lithium and tubular battery setups.
•  See how different sun hours affect breeding.
•  Estimate usable battery storage.
•  Compare battery autonomy options.
•  Identify potential energy shortages.
•  Check if grid or generator backup may still be needed.
•  Compare the current battery bank with your backup target.

This is especially useful before requesting a final system design because it helps you understand which solar and battery combinations are worth further investigation.

What is not included in the off-grid solar calculator?

The calculator focuses on energy production, battery storage and overall energy coverage.It does not provide a complete electrical design.

The calculation is not individual:

•  Hourly use of equipment
•  Battery charge status for several days
•  Increased startup of individual devices
•  Precise inverter performance
•  Inverter continuous rating
•  Inverter Surge Rating
•  Limitations of the charge controller
•  Solar panel voltage and current compatibility
•  Cable size
•  Voltage drop
•  Detailed shading
•  Precise panel orientation and tilt
•  Hourly weather conditions
•  Battery temperature
•  The battery is aging.
•  Generator operation
•  Equipment specific manufacturer limitations

Equipment prices can also change, so any cost figures displayed by the calculator should be checked against the current quotation.Before purchasing equipment, verify the final system against actual load measurements, site conditions, and manufacturer specifications.