Savings and payback
See how much of a high electricity bill your system can realistically offset, and what size system it would take to cover the rest.
For planning purposes only, not financial or tax advice; confirm figures with a licensed installer or tax professional before making a purchase decision.
How it works
Step 1
Homes above roughly 15,000 kWh a year are considered high usage for solar sizing purposes. Not sure of your exact rate? The solar savings calculator walks through finding it.
Step 2
Not sure what size fits your usage? The solar panel calculator can help estimate a starting point.
Step 3
The tool shows both what your entered system covers and how much bigger a system would need to be to offset your usage completely.
A standard 6.5 kW system offsets only about 53% of an 18,000 kWh annual usage, leaving a remaining bill of roughly $1,362 a year even with $1,518 in savings. That's a meaningful gap compared to a typical-usage home, where the same system might offset close to 90% or more. The US Energy Information Administration's electricity data show how retail rates have moved, which is the starting point for any savings estimate.
For an 18,000 kWh annual usage at typical sun hours and derate, a system around 12.3 kW would be needed for full offset, nearly double the standard example size. That's a significant jump, and whether it's achievable depends on available roof space, budget, and local permitting rules. To size the array behind this number, the system size by annual kwh usage turns your usage into a kilowatt target.
Roof space is usually the limiting factor. Not every home has enough usable, well-oriented roof area for a system large enough to fully offset high usage, and some utilities cap system size relative to historical usage as well. Budget constraints also play a role, since a larger system costs proportionally more upfront. Adding an EV or other new load makes this gap even more relevant, as covered in the EV charging savings tool. For the official overview, the US Department of Energy's homeowner's guide to going solar covers buying, leasing, and system sizing.
In most cases, yes. The savings from a partial-offset system are still real, just applied against a smaller share of a larger bill. Run your specific numbers through the payback period calculator to see how the economics work out for your situation, or check the bill offset percentage calculator for more detail on the offset math itself. Output varies by roof and weather, and the real world vs nameplate output gap calculator shows what your site should produce in a typical year.
Questions
Usage above roughly 15,000 kWh a year is generally considered high, well above the typical 10,000 to 11,000 kWh most US homes use. A standard 6.5 kW system offsets only about 53% of an 18,000 kWh annual usage, leaving a meaningful remaining bill.
For an 18,000 kWh annual usage at typical sun hours and derate, a system around 12.3 kW would be needed for full offset, nearly double the standard 6.5 kW example. Roof space, budget, and local permitting all factor into whether that size is realistic.
Roof space is the most common limit, since not every home has enough usable area for a system large enough to fully offset high usage. Budget and some utilities' system size caps relative to historical usage can also constrain sizing below what full offset would require.
Often yes. Even a partial offset can produce a reasonable payback period, since the savings still apply, just against a smaller share of the total bill. Run the numbers through the payback period calculator using your specific system cost and savings figure to check.