Run the numbers
Work it out yourself, before you talk to anyone.
This calculator shows every assumption it uses. Move the slider, change the aspect, and check the arithmetic against your own bill.
Run your own numbers
- System size
- 8.6 kW
- Annual production
- 12,212 kWh
- Installed cost
- $24,510
- After federal credit
- $17,157
- First-year savings
- $1,392
- Pays for itself in
- 12.3 years
- 25-year net
- $17,643
Every assumption this uses
- Installed cost per watt
- $2.85
- Federal credit applied
- 30%
- Utility rate per kWh
- $0.114
- Production per kW, south-facing
- 1,420 kWh/yr
- Sizing heuristic
- $17.5/mo per kW
This is an estimate built from Triangle averages, not a quote. Your real figures depend on your roof, your shading and your actual usage. Incentives change with legislation — confirm the current federal credit with your tax advisor before relying on it.
Why we publish the assumptions
Every solar company can produce a savings figure. Almost none will tell you the utility rate, the production factor or the installed cost per watt they used to get there, which makes the figure unfalsifiable and therefore worthless.
Ours are listed under the result. If you think our rate assumption is optimistic, you can say so and we can have a real conversation about it. That is the whole point.
This is an estimate from Triangle averages, not a quote. Your real numbers depend on your roof, your shading and your actual twelve months of usage — which is what the site visit is for.
What the calculator cannot see
Shading is the big one. A single mature oak on the south side of a Chapel Hill lot can take a third off annual production, and no slider on a web page knows it is there.
Roof condition matters too. If your shingles have five years left, they should be replaced before an array goes on top of them, and that cost belongs in the payback calculation.
Both are things we check on site, for free, before quoting.