System size isn't one-size-fits-all, and the 'average' isn't necessarily right for you. Here's how to actually land on the right number.
Start with usage, then check against roof and budget
Your annual kWh usage sets the target size for full offset — see the solar panel calculator for that starting point. From there, check whether your roof has enough usable space (the roof size calculator helps here) and whether the resulting cost fits your budget or financing plan.
We've broken out common sizes for reference
To make cost concrete at different scales, we've built dedicated pages from a 3kW system up through a 20kW system — each showing typical cost, production, and payback at that specific size, reflecting real economies of scale in cost per watt.
It's fine to undersize intentionally
Not everyone needs or wants 100% offset — some homeowners deliberately size smaller to fit a tighter budget, accepting a partial offset and a smaller electric bill rather than none at all. This is a completely reasonable choice, not a mistake, as long as it's intentional rather than accidental.
Plan for future electrification if it's likely
If an EV, heat pump, or other major electric load is a realistic near-term addition, sizing with some room for that future usage avoids a more expensive add-on system later. See our electrification priorities guide for how to think through that planning.
Frequently asked questions
Should I size for 100% of my current usage?
It's a common target under net metering, but not required — sizing smaller for budget reasons, or larger to cover planned future electrification, are both reasonable choices depending on your specific goals.
Does a bigger system always have a better payback period?
Not necessarily — while larger systems often have a lower cost per watt, payback period depends on how well the system size matches your actual usage and export value, not size alone.