If you’re thinking about installing solar in Bangladesh, one of the first questions you’ll probably ask is:
“How much money will I actually save on my electricity bill?”
You may find different answers from different solar companies.
One installer may say you’ll save ৳5,000 per month.
Another may say ৳8,000.
An online calculator may give you a completely different number.
So which one should you trust?
The best approach is to understand the basic calculation yourself.
You don’t need a complicated financial model to get a useful first estimate.
You mainly need:
- Your monthly electricity consumption in kWh
- Your electricity rate
- Your location’s average peak sun hours
- Your expected solar system size
- Your solar installation cost
- Your expected annual generation
- Net-metering assumptions, if applicable
Once you understand these numbers, you can check whether a solar quotation makes financial sense for your home or business.
The Quick Solar Savings Formula
For a simple first estimate, start with your monthly electricity usage.
Step 1
Monthly kWh ÷ 30 = Average Daily Electricity Usage
Step 2
Daily kWh ÷ Peak Sun Hours = Approximate Solar System Size
Step 3
Calculate your expected annual solar generation.
Step 4
Compare the electricity generated by solar with the electricity you would otherwise purchase from the grid.
Step 5
Calculate your annual savings.
Step 6
Finally:
Payback Period = Total Solar Investment ÷ Annual Savings
This is a simplified calculation.
A proper financial model should also consider system losses, degradation, maintenance, financing, inverter replacement, electricity tariff changes and the treatment of surplus electricity.
The attached source similarly emphasises that the formula is a starting estimate rather than a guaranteed result.
Step 1: Find Your Actual Electricity Consumption
Before calculating solar savings, don’t start with your monthly bill amount.
Start with:
kWh
Kilowatt-hours tell you how much electricity you actually consume.
Your bill may show:
৳8,000
but that doesn’t tell you directly how much electricity you used.
You might have consumed:
600 kWh
or:
800 kWh
depending on your applicable electricity rate and charges.
That’s why solar calculations should be based primarily on kWh consumption, not only the amount of your bill.
The attached source makes the same distinction between the monetary bill amount and actual monthly kWh usage.
Where to Find Your Monthly kWh
Check your electricity bill for:
- Current reading
- Previous reading
- Total units
- kWh consumption
You can also collect your previous bills and create a simple 12-month usage history.
This is better than using only one month’s bill because electricity consumption can change throughout the year.
For example, your usage may increase because of:
- Air conditioners
- Fans
- Water pumps
- Refrigerators
- Freezers
- Office equipment
- Factory machinery
Step 2: Calculate Your Average Daily Usage
Suppose your home uses:
600 kWh per month
A simple daily estimate is:
600 ÷ 30 = 20 kWh/day
So your average electricity consumption is approximately:
20 kWh per day
This is the starting point for calculating the required solar capacity.
Step 3: Determine Peak Sun Hours
The next number you need is:
Peak Sun Hours
Peak sun hours are not simply the number of hours the sun is visible.
They represent the equivalent amount of strong solar radiation available during an average day.
The actual value varies depending on:
- Location
- Season
- Weather
- Solar radiation
- Roof orientation
- Shading
For a Bangladesh planning example, let’s assume:
4.5 peak sun hours/day
This is an illustrative assumption, not a universal number for every location in Bangladesh.
For an actual project, the solar resource should be evaluated for the property’s specific location.
Step 4: Estimate the Solar System Size
Now use:
Daily electricity usage ÷ Peak Sun Hours = Approximate System Size
Our example:
20 kWh/day ÷ 4.5
= 4.44 kW
So you would need approximately:
4.4–4.5 kW
of solar capacity as a basic starting estimate.
However, real solar systems experience losses from:
- Inverter conversion
- Wiring
- Temperature
- Dust
- Shading
- Other system losses
So a practical design may need some additional capacity.
For example, after allowing for reasonable system losses, an installer might recommend something around:
5 kW
depending on the actual site conditions.
Step 5: Calculate the Number of Panels
Suppose you choose:
550 W solar panels
A 5 kW system would require approximately:
5,000 ÷ 550 = 9.1 panels
Since you cannot install 0.1 of a panel, you would typically need a practical configuration such as:
10 × 550 W panels
Total capacity:
10 × 550 = 5,500 W
or:
5.5 kW DC
The final panel count depends on the inverter design, roof layout and equipment specifications.
Step 6: Estimate Annual Solar Generation
Now we need to estimate how much electricity the system can produce.
Suppose our example system is:
5.5 kW
and the planning assumption is:
4.5 peak sun hours/day
A simplified calculation is:
5.5 × 4.5 × 365
= approximately:
9,034 kWh/year
But this is a theoretical estimate before accounting for real-world losses.
After considering system losses, shading, temperature, inverter efficiency and other factors, actual annual production would be lower.
For example, if we use an illustrative overall performance factor of 80%:
9,034 × 0.80
≈ 7,227 kWh/year
So the system might produce roughly:
7,200 kWh/year
in this simplified example.
The actual production must be based on a proper site-specific solar assessment.
Step 7: Calculate Your Electricity Savings
Now we need an electricity rate.
Suppose, purely for this example, the effective value of the electricity being offset is:
৳12 per kWh
And the solar system produces:
7,200 kWh/year
Then:
7,200 × ৳12
= ৳86,400/year
So the estimated annual electricity saving is approximately:
৳86,400
or:
৳7,200/month on average
Again, this is an illustrative calculation, not a guaranteed saving.
Your actual savings depend on your applicable electricity tariff, how much solar electricity you consume directly, and how surplus electricity is treated.
Why Your Solar Savings May Not Equal Solar Generation × Electricity Rate
This is an important point.
You might generate:
7,200 kWh/year
but that doesn’t automatically mean you save:
7,200 × your highest electricity rate
There are several reasons.
Your solar electricity can be:
Used Directly
Solar power is consumed by your home or business while the panels are producing electricity.
This can directly reduce electricity purchased from the grid.
Exported to the Grid
If your system generates more than you are using at that moment and your project is eligible for net metering, surplus electricity may be exported according to the applicable rules.
The financial value of that exported electricity depends on the applicable arrangement.
Lost Due to System Limitations
Some energy may not be used or exported depending on system design and grid/net-metering conditions.
Therefore, a proper solar savings calculation should distinguish between:
Self-consumed solar electricity
and
Exported solar electricity
Step 8: Understand Net Metering
Net metering can have a major impact on solar savings.
Imagine your solar panels generate electricity during the middle of the day.
But your home is using relatively little electricity at that time.
Your solar system may produce:
10 kWh
while your home consumes:
6 kWh
The remaining:
4 kWh
may potentially be exported to the grid under an applicable net-metering arrangement.
That exported electricity needs to be treated according to the current applicable rules.
This is why you should never calculate your solar savings without understanding how surplus generation will be handled.
The attached source similarly identifies net metering as one of the major variables that can materially change the savings calculation.
Step 9: Calculate Your Solar Investment
Now let’s assume our 5.5 kW system costs:
৳4,40,000
This is an illustrative example only.
Actual solar installation prices in Bangladesh vary depending on:
- Panel brand
- Panel wattage
- Inverter brand
- Mounting structure
- Installation
- Protection equipment
- Cable length
- Roof condition
- Net-metering work
- System type
- Battery inclusion
So always use your actual quotation for the final calculation.
Step 10: Calculate the Simple Payback Period
Our example:
Solar investment = ৳4,40,000
Annual savings = ৳86,400
Therefore:
৳4,40,000 ÷ ৳86,400
≈ 5.1 years
So the simple estimated payback period is approximately:
5 years
After that point, the system could continue generating electricity and providing savings for the remainder of its useful life, subject to maintenance, degradation and other costs.
A More Realistic Example
Let’s make the calculation slightly more realistic.
Suppose:
Solar system size: 5.5 kW
Initial investment: ৳4,40,000
Estimated first-year generation: 7,200 kWh
Effective electricity value: ৳12/kWh
First-Year Savings
7,200 × ৳12
= ৳86,400
Simple Payback
৳4,40,000 ÷ ৳86,400
= approximately 5.1 years
But don’t stop here.
A proper long-term calculation should consider:
- Panel degradation
- Maintenance
- Inverter replacement
- Cleaning
- Electricity tariff changes
- Net-metering treatment
- Financing costs
- System downtime
That’s where a real solar financial model becomes more useful.
Panel Degradation Changes Your Savings
Solar panels don’t produce exactly the same amount of electricity every year.
Their output gradually decreases.
The attached source uses approximately 0.5% annual degradation as a planning assumption.
For example:
Year 1
7,200 kWh
Year 2
Approximately:
7,164 kWh
Year 3
Approximately:
7,128 kWh
The decline is small each year, but over 20–25 years it becomes meaningful.
So a serious solar savings model shouldn’t assume that the system produces exactly the same amount forever.
Electricity Price Changes Can Work in Your Favour
Here’s something many simple solar calculators don’t model properly.
Your electricity tariff may change over time.
Suppose your effective electricity cost today is:
৳12/kWh
If electricity costs increase in the future, the value of each unit of solar electricity you generate can also increase.
For example, if the effective avoided electricity cost eventually becomes:
৳14/kWh
then the same:
7,200 kWh
of annual solar generation would have a theoretical electricity value of:
7,200 × ৳14
= ৳1,00,800
This is why solar savings shouldn’t always be treated as a fixed amount for the next 20–25 years.
However, future tariff changes are uncertain, so they should be modelled using reasonable scenarios rather than guaranteed assumptions.
Roof Direction Can Change Your Savings
Two houses can have identical:
- Electricity consumption
- Solar capacity
- Panel brand
and still produce different amounts of electricity.
Why?
Because the roofs are different.
Roof Orientation
Panel orientation affects how much sunlight the system receives.
Roof Tilt
The angle of the panels can affect annual production.
Shading
Trees, nearby buildings, water tanks and rooftop structures can reduce generation.
Dust and Weather
Bangladesh’s environmental conditions can also affect real-world output.
The attached source similarly points out that roof direction, pitch, shading and local climate can cause actual production to differ from a basic calculator estimate.
Shading Can Reduce Your Solar Savings
Suppose your calculation says:
7,200 kWh/year
But a large portion of your roof becomes shaded during important production hours.
Actual production could be significantly lower.
That means:
Lower generation → Lower electricity savings → Longer payback
This is why a proper site survey is valuable.
Don’t buy a solar system based only on:
“Your house needs 5 kW.”
Ask:
“How many kWh will this exact system produce on my roof each year?”
That is a much more useful question.
Roof Condition Can Affect Your Payback
Suppose you install:
৳4.4 lakh solar system
but your roof needs major repair after five years.
If the solar panels need to be removed and reinstalled during the repair, additional costs can reduce your actual return.
So before installing rooftop solar, consider:
How long will my current roof remain suitable?
If major waterproofing or structural work is already required, complete that work before installing the solar system.
Don’t Forget Maintenance
Solar systems generally have relatively low operating costs, but they are not completely maintenance-free.
Potential costs include:
- Panel cleaning
- Electrical inspection
- Inverter maintenance
- Cable inspection
- Mounting inspection
- Repairs
- Monitoring
For a small home system, these costs may be relatively modest.
For a large commercial system, they can become more significant.
Inverter Replacement Can Change Long-Term Savings
Your solar panels may operate for decades.
But the inverter may need replacement earlier depending on the equipment and operating conditions.
Suppose your original solar investment is:
৳4,40,000
and several years later the inverter needs replacement.
If replacement costs:
৳80,000
your lifetime solar cost is no longer simply ৳4.4 lakh.
This is why a serious solar ROI model should include future equipment replacement.
Solar Savings vs Solar Payback
These are two different concepts.
Solar Savings
How much electricity cost you avoid over a particular period.
Solar Payback Period
How long it takes for cumulative savings to recover your initial investment.
For example:
Solar investment = ৳4,40,000
Annual savings = ৳86,400
Simple payback:
≈ 5.1 years
But the actual payback may be longer or shorter depending on:
- Electricity price
- Solar production
- Degradation
- Maintenance
- Financing
- Net metering
- System downtime
Solar Savings vs ROI
ROI goes one step further.
Suppose your system costs:
৳4,40,000
and over its useful life it generates enough electricity to provide:
৳12 lakh
of total gross electricity value.
That doesn’t mean your ROI is simply based on ৳12 lakh.
You must subtract:
- Initial investment
- Maintenance
- Repairs
- Inverter replacement
- Financing costs
- Other applicable expenses
This gives you a much more realistic long-term financial picture.
What If You Use a Solar Loan?
Financing changes the calculation.
Suppose:
Cash solar price = ৳4,40,000
But after financing costs, your total repayment becomes:
৳5,20,000
Your actual investment from a financial perspective is closer to:
৳5.2 lakh
not ৳4.4 lakh.
So when calculating payback, use the financing structure that actually applies to your project.
Don’t calculate ROI using the cash price if you’re paying significantly more because of financing.
What If You Add a Battery?
Battery storage can also change the economics significantly.
Suppose your basic on-grid system costs:
৳4.4 lakh
But you want backup power during outages.
You add:
Battery + hybrid inverter
Now your project may cost significantly more.
The battery can provide an important benefit—backup power—but that benefit isn’t simply the same as electricity bill savings.
This is why:
On-grid solar
and
Hybrid solar
should be evaluated separately.
When Solar Savings May Be Lower Than Expected
Your savings may be lower if:
Your Roof Is Shaded
Less sunlight means less generation.
Your Electricity Consumption Is Low
A large system may produce more electricity than you can economically use.
You Have Poor Solar Exposure
Orientation and roof conditions matter.
You Export a Large Amount of Electricity
If exported electricity has a lower financial value than electricity consumed directly, your effective savings can be lower.
The System Is Poorly Maintained
Reduced performance means reduced savings.
Your Actual System Cost Is Higher
Financing, electrical upgrades and other hidden costs can increase payback.
When Solar Savings Can Be Better Than Expected
The opposite can also happen.
Your savings can improve if:
- Your electricity consumption increases
- Electricity prices increase
- Your system produces more than expected
- You consume a high percentage of solar electricity directly
- Your system has excellent solar exposure
- Installation cost is lower than expected
This is why solar financial modelling should use realistic assumptions rather than a single guaranteed number.
Quick Bangladesh Solar Savings Example
Let’s summarise our example.
| Item | Example |
|---|---|
| Monthly electricity use | 600 kWh |
| Average daily use | 20 kWh |
| Peak sun hours | 4.5 hours |
| Approx. basic system size | 4.4 kW |
| Practical example system | 5.5 kW |
| Example annual generation | 7,200 kWh |
| Illustrative electricity value | ৳12/kWh |
| Estimated annual savings | ৳86,400 |
| Example system cost | ৳4,40,000 |
| Simple payback | ~5.1 years |
Important: These numbers are for demonstrating the calculation. They are not a guaranteed quotation, tariff or production estimate for every Bangladesh property.
How Much Could You Save Based on Your Usage?
The easiest way to estimate your potential savings is to start with your own electricity bill.
For example:
300 kWh/month
You use:
10 kWh/day
600 kWh/month
You use:
20 kWh/day
900 kWh/month
You use:
30 kWh/day
1,200 kWh/month
You use:
40 kWh/day
The required solar capacity then depends on your location’s solar resource and the actual system performance.
So don’t assume:
“I use 600 units, therefore I need exactly X kW.”
The roof and system design still matter.
A Simple Solar Savings Table
Using the same illustrative ৳12/kWh electricity value and assuming the solar system offsets electricity consumption effectively:
| Monthly Usage | Annual Usage | Annual Electricity Cost at ৳12/kWh |
|---|---|---|
| 300 kWh | 3,600 kWh | ৳43,200 |
| 600 kWh | 7,200 kWh | ৳86,400 |
| 900 kWh | 10,800 kWh | ৳1,29,600 |
| 1,200 kWh | 14,400 kWh | ৳1,72,800 |
| 1,500 kWh | 18,000 kWh | ৳2,16,000 |
This table is not a prediction of solar savings. It simply shows the annual electricity value at an illustrative rate of ৳12/kWh.
Your actual savings depend on how much of your electricity consumption is offset by solar and the applicable tariff/net-metering treatment.
Why You Shouldn’t Use Your Bill Amount Alone
Suppose two businesses each pay:
৳50,000/month
That doesn’t necessarily mean they need the same solar system.
Their electricity consumption could be different because of:
- Different tariff structures
- Demand charges
- Commercial vs industrial rates
- Different consumption patterns
- Different billing components
So always ask:
“How many kWh did I consume?”
not only:
“How much was my bill?”
What About Businesses?
Solar savings can be particularly interesting for businesses because many businesses consume substantial electricity during daylight hours.
Examples include:
- Factories
- Offices
- Restaurants
- Hotels
- Shopping facilities
- Warehouses
- Hospitals
- Schools
- Commercial buildings
If a business uses electricity during the same hours when solar panels are generating electricity, a larger portion of the solar energy may be consumed directly.
That can improve the financial value of the system.
Daytime Consumption Matters
Imagine a factory generates:
100 kWh of solar electricity
during working hours.
If the factory is simultaneously consuming:
90 kWh
then most of the solar energy can potentially be used directly.
Now imagine a property generates the same:
100 kWh
but only consumes:
30 kWh
during those hours.
The remaining electricity may need to be exported or otherwise managed.
Therefore:
Solar generation + consumption timing
are both important.
Don’t Oversize Your Solar System Just to Generate More
A bigger system isn’t automatically a better investment.
Suppose your annual electricity consumption is:
7,200 kWh
and you install a system capable of producing:
15,000 kWh/year
That may be unnecessary unless you have a clear reason, such as:
- Future electricity demand
- Eligible surplus export
- EV charging
- New machinery
- Additional building loads
The goal is not:
Maximum solar capacity
The goal is:
Maximum useful financial value from the solar investment
What If You Plan to Add More Appliances?
Your future electricity consumption matters.
Suppose your current usage is:
600 kWh/month
but you’re planning to add:
- Two air conditioners
- An electric vehicle
- A larger water pump
- Additional refrigeration
Your future usage may become much higher.
In that case, designing the system only around today’s consumption could result in an undersized system.
The source similarly recommends considering future electricity use when evaluating a solar system.
When Solar May Not Be a Good Investment
Solar isn’t automatically the right financial decision for everyone.
It may be less attractive if:
- Your electricity usage is very low
- Your roof has severe shading
- Your roof requires major repair
- You plan to move soon
- The installation cost is unusually high
- Your solar production is poor
- The system is significantly oversized
- Financing costs are too high
The purpose of doing the calculation is not to prove that solar is always profitable.
It’s to determine whether it makes sense for your specific property.
The 5 Numbers You Need Before Buying Solar
Before asking for a solar quotation, collect these five numbers:
1. Annual Electricity Consumption
kWh/year
2. Average Daily Consumption
kWh/day
3. Expected Solar Generation
kWh/year
4. Total Installed Solar Cost
৳
5. Expected Annual Savings
৳/year
Once you have these, you can calculate:
Simple Payback = Solar Cost ÷ Annual Savings
And then build a more detailed ROI/LCOE model if necessary.
What to Ask Your Solar Installer
Before accepting a solar quotation, ask:
How many kWh will this system generate in the first year?
Not just:
“How many kW is the system?”
Then ask:
What assumptions did you use for peak sun hours?
How did you account for system losses?
What annual degradation rate did you assume?
How much of the generation do you expect me to consume directly?
How is surplus electricity handled?
Does the calculation include net metering?
What maintenance costs should I expect?
What happens when the inverter needs replacement?
These questions will give you much more useful information than simply asking:
“How much will I save?”
How Accurate Are Online Solar Calculators?
Online calculators can be useful for a quick estimate.
But they usually don’t know:
- Your exact roof
- Your actual shading
- Your exact electricity consumption pattern
- Your inverter configuration
- Your roof orientation
- Your local conditions
- Your applicable electricity tariff
- Your net-metering arrangement
So use them as a starting point.
A proper site assessment and detailed proposal are much more reliable.
The attached source makes the same distinction between online ballpark calculations and a site-specific installer assessment.
Frequently Asked Questions
How do I calculate solar savings?
Start with your electricity consumption in kWh, estimate the solar system’s annual generation, and determine how much of that generation will offset electricity purchased from the grid.
A simple starting formula is:
Annual Solar Generation × Effective Electricity Value = Estimated Annual Solar Savings
How do I calculate solar payback?
Use:
Solar Payback Period = Total Solar Investment ÷ Annual Savings
For example, if your system costs ৳4,40,000 and saves ৳86,400 per year:
৳4,40,000 ÷ ৳86,400 ≈ 5.1 years
Does a higher electricity bill mean I need more solar panels?
Usually, higher electricity consumption means a larger solar system may be required, but the bill amount alone isn’t enough. You should use your actual kWh consumption.
How many solar panels do I need for 600 kWh per month?
It depends on your location’s solar resource, panel wattage, system losses and roof conditions. As an illustrative example, 600 kWh/month is approximately 20 kWh/day, which could require around 4.4 kW before additional practical design allowances.
Does net metering affect solar savings?
Yes. How surplus solar electricity is treated can significantly affect the financial value of your system. Always include the applicable net-metering arrangement in your calculation.
Does shading reduce solar savings?
Yes. Shading can reduce the amount of electricity your panels generate, which directly reduces potential savings.
Do solar panels produce the same amount of electricity every year?
No. Solar panels gradually degrade, so annual production normally decreases over time. A long-term financial model should account for this.
Does solar still save money if electricity prices increase?
Potentially. If the cost of grid electricity increases, the value of electricity generated by your solar system can also increase. However, future tariff changes are uncertain and should not be treated as guaranteed.
Does battery storage increase solar savings?
Not necessarily. Batteries provide additional benefits such as backup power and energy shifting, but they also add significant upfront and replacement costs. Their financial value should be analysed separately.
Is solar payback the same as ROI?
No. Payback measures how long it takes to recover the initial investment. ROI considers the broader financial return over a defined period.
Should I use my current electricity bill to calculate solar savings?
Use your electricity bill to find your actual kWh consumption, but don’t rely only on the bill’s total ৳ amount. Your tariff structure and other charges can affect the final bill.
Can I calculate solar savings for a business?
Yes. The same basic approach works for businesses, but commercial projects often require a more detailed analysis of daytime consumption, demand charges, net metering, financing and system size.
What is the most important number to ask a solar installer?
Ask:
“How many kWh will this exact solar system generate in its first year?”
Then compare that number with your actual electricity consumption and the total installed cost.
That gives you a much better basis for judging the real financial value of the solar project.
Final Verdict
Calculating your solar savings doesn’t require a complicated calculator.
Start with your actual electricity consumption.
For example:
600 kWh/month
↓
20 kWh/day
↓
At an illustrative 4.5 peak sun hours/day
↓
Approximately 4.4 kW basic solar capacity
↓
A practical design may be around 5–5.5 kW, depending on losses and site conditions
↓
Estimate annual generation
↓
Multiply useful solar generation by the electricity value it replaces
↓
Calculate annual savings
↓
Then:
Payback Period = Total Solar Investment ÷ Annual Savings
But remember that this is only the starting point.
For a realistic Bangladesh solar investment decision, also consider:
- Net metering
- Self-consumption
- Panel degradation
- Shading
- Roof condition
- Maintenance
- Inverter replacement
- Battery costs
- Financing
- Future electricity consumption
At Muspana, we recommend looking beyond the headline number on a solar quotation.
Don’t ask only:
“How much will I save per month?”
Ask:
“How much electricity will this system actually generate, how much of that electricity will I use, what will it cost me over its lifetime, and when will the investment pay for itself?”
Once you understand those numbers, you’ll be in a much stronger position to compare solar quotations and make the right decision for your home or business in Bangladesh.
