Solar Savings Calculator
Estimate how much money solar panels will save you per year, and how long they take to pay back.
What this tool does
A solar savings calculator estimates how much money a solar panel system will save you on your electricity bill. Enter your average monthly electricity bill, the system size in kW, the peak sun hours for your location, your electricity rate, and the percentage of solar generation you expect to use on site. The calculator estimates annual generation, converts it to a bill saving, and divides the system cost by the annual saving to give a simple payback period in years.
Estimates annual solar generation in kWh from system size, peak sun hours and system efficiency.
Converts generation into a bill saving using your electricity rate and on-site usage percentage.
Estimates the payback period by dividing the system cost by the annual saving.
Shows the saving over 10, 20 and 25 years alongside the payback.
How to use it
- Enter your average monthly electricity bill.
- Enter the solar system size in kilowatts.
- Enter the peak sun hours for your location.
- Enter your electricity price per kWh.
- Enter the expected system cost and the percentage of generation you will use on site.
- Read the annual saving and the payback period.
Why use this calculator
Shows the saving over 10, 20 and 25 years alongside the payback, because the annual saving alone does not tell you whether the system is a good investment. A system that saves $1,000 per year and costs $10,000 pays back in 10 years and then produces free electricity for another 15 years. Seeing the cumulative saving next to the cost makes the long-term value clear.
Why we built it
We built the solar savings calculator to take the output of the solar generation calculator and turn it into money, because generation in kWh is abstract but a dollar saving is concrete. The solar panel system size calculator works out the size you need, and the electricity bill calculator shows what you currently pay.
If your task goes further, try the energy consumption calculator to understand your usage, and the ROI calculator to compare solar against other investments.
Who this tool is for
- Homeowners weighing up whether solar is worth the upfront cost
- Buyers comparing quotes with different prices and system sizes
- Anyone who wants to know how long solar takes to pay for itself
- People checking whether solar can cover their electricity bill
When to use it
- Comparing solar quotes on a like-for-like saving basis.
- Deciding whether to invest in solar or pay down other debts.
- Estimating how much of a future electricity bill solar will cover.
- Checking whether a larger system pays back faster than a smaller one.
How it is calculated
Annual generation in kWh = system size in kW × peak sun hours × 365 × system efficiency. Annual saving = annual generation × electricity rate × on-site usage percentage. Payback in years = system cost ÷ annual saving.
Worked example: a 6 kW system with 4.5 peak sun hours, 80% efficiency, an electricity rate of $0.28 per kWh and 80% on-site usage. Annual generation = 6 × 4.5 × 365 × 0.80 = 7,884 kWh. Annual saving = 7,884 × 0.28 × 0.80 = $1,766. A system costing $12,000 pays back in 12,000 ÷ 1,766 = 6.8 years. Over 25 years the saving is about $44,150.
On-site usage matters because many tariffs pay less for exported solar than they charge for imported electricity. If you export a lot, your real saving is lower than the full generation value.
What you enter, and what you get back
| Item | Details |
|---|---|
| Monthly bill | Your average electricity bill, for context. |
| System size | The solar array size in kilowatts. |
| Peak sun hours | The equivalent hours of full-power sunlight per day. |
| Electricity rate | Your price per kWh. |
| System cost | The upfront cost of the system. |
| Result | Annual saving, payback period and cumulative saving. |
Issues you may run into
| What you see | Why it happens | What to do |
|---|---|---|
| Saving is lower than expected | A low on-site usage percentage was used. | Check your tariff's export rate. |
| Payback seems long | Electricity rates are low in your area. | Check whether rates are likely to rise. |
| System cost unknown | A quote has not been obtained. | Use a typical price per kW for your region. |
A worked example
These are the values the calculator opens with, so you can see exactly what it does with them. Change any value on the page and the result updates; the figures below come from the same calculation.
| Input | Value |
|---|---|
| Currency symbol | $ (dollar) |
| Monthly bill | $150 |
| System size | 6 kW |
| Peak sun hours | 4.5 hours |
| Electricity rate | $0.28 per kWh |
| System cost | $12,000 |
| On-site usage | 80% |
With those inputs, the calculator returns:
- Annual generation: 7,884 kWh
- Annual saving: $1,766
- Payback period: 6.8 years
- 25-year saving: $44,150
Assumptions and limitations
- A simple payback that does not include the time value of money, tax incentives or rising electricity prices.
- Assumes a constant electricity rate and system output over the whole period.
- Does not model panel degradation, inverter replacement or maintenance costs.
- On-site usage percentage must be estimated from your tariff's export rate.
- A planning aid, not a financial forecast.
Frequently asked questions
How do I calculate solar savings?
Estimate annual generation in kWh by multiplying system size in kW by peak sun hours by 365 by system efficiency. Multiply the generation by your electricity rate and the percentage you use on site to get the annual saving. Divide the system cost by the annual saving for a simple payback period.
How long do solar panels take to pay back?
A typical residential solar system pays back in 6 to 12 years depending on system cost, local electricity rates and available sunlight. After the payback period, the electricity produced is essentially free for the remaining life of the panels, which is often 25 years or more.
What affects how much solar saves me?
The biggest factors are your local electricity rate, the amount of sunlight your location receives, the system size, how much of the generation you use on site rather than export, and the upfront cost after any incentives or rebates.
Do solar panels work in cloudy weather?
Yes - solar panels generate electricity from daylight, not direct sunshine. On a cloudy day they typically produce 10% to 25% of their rated output. They do not need bright sunshine to work, which is why solar is viable even in relatively cloudy climates.
How much does a solar system reduce my bill?
A correctly sized system can offset 60% to 100% of a household's electricity bill, depending on system size, usage patterns and how much generation is used on site. The exact reduction depends on your tariff's export rate and when you use electricity during the day.