Bill savings
Solar panel savings calculator: how bill savings are estimated
Solar panel savings depend on how much electricity the system produces, how much of that electricity is used in the home, how much is exported, and what your utility charges for imported power.
The two parts of solar savings
The first part is avoided electricity purchases. Every kilowatt-hour of solar power used directly by the home can reduce electricity bought from the grid. This is usually the most valuable part of the calculation because it offsets the full retail electricity price.
The second part is export value. When the system produces more than the home is using, surplus electricity may be exported to the grid. Exported electricity is valued at the feed-in tariff, export rate or net-metering credit that applies in your area. In many locations, exported solar is worth less than self-used solar.
Basic savings example
Assume a solar system produces 6,570 kWh per year. If the home uses 65% of that production directly, self-used solar equals 4,271 kWh. At an electricity price of 0.28 per kWh, that avoids about 1,196 in grid purchases. The remaining 2,299 kWh is exported. At an export tariff of 0.08 per kWh, that adds about 184. Total annual benefit is about 1,380.
Why self-consumption is important
Self-consumption is the share of solar generation that is used inside the home instead of exported. It is influenced by daytime occupancy, appliance timing, water heating, EV charging, battery storage and smart controls. Running flexible loads during sunny hours can improve savings without changing the solar system size.
System degradation and long-term savings
Solar panels normally lose a small amount of output each year. The calculator uses a degradation input so long-term savings are not treated as perfectly flat. This is a planning assumption, not a performance guarantee. Actual production also changes because of weather, shading, maintenance and equipment condition.
What the calculator cannot know automatically
An online calculator cannot see your roof, shade, wiring, utility rules or actual hourly consumption profile. It also cannot predict future tariff changes with certainty. For a stronger estimate, enter your actual tariff, a current installer quote, realistic peak sun hours and a conservative self-consumption percentage.
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Why annual consumption alone is not enough
Two homes can use the same number of kilowatt-hours per year and still have very different solar savings. The reason is timing. A household with significant daytime use may consume a large share of solar production directly. A household with most consumption after sunset may export more energy unless loads are shifted or storage is added.
Where your electricity provider offers interval data, review a typical weekday and weekend before choosing the self-consumption assumption. EV charging, water heating, pool pumps, dishwashers and laundry can sometimes be moved into solar hours without a battery. That can improve the value of the same array without increasing installed capacity.
Keep savings assumptions separate
Do not use the retail electricity price for exported energy unless your tariff genuinely credits exports at that value. The calculator deliberately separates import price and export tariff because combining them can materially overstate savings. Also avoid assuming that electricity prices will rise at a particular rate unless you are intentionally running a scenario; the base calculator keeps the estimate transparent by using the values you enter.
For a decision, compare first-year annual benefit with the 25-year estimate and remember that degradation, maintenance and tariff changes introduce uncertainty. A range of scenarios is more informative than a single headline savings figure.