Savings and payback
See the system size needed to fully offset your usage, plus an honest look at why fixed utility charges usually keep your bill from hitting a true $0.
How it works
Step 1
Use figures from a recent bill for the most accurate result, or see the bill offset percentage calculator if you already know your production.
Step 2
Look for a "customer charge" or "connection fee" line item on your bill. This figure sets your realistic bill floor, since it can't be offset by production no matter how large your system, as confirmed in the annual true-up payment estimator.
For 12,000 kWh of annual usage, a system around 8.2 kW would fully offset your usage-based charges under typical sun and derate assumptions, matching production to consumption over the year, similar to the sizing shown in the 1000 kWh a month calculator and the bill offset percentage calculator. Utility rates drive the whole savings calculation, and the US Energy Information Administration's electricity data track them state by state.
Most utilities charge a fixed monthly customer or connection fee, commonly $8 to $25 a month, that solar production can't offset since it isn't tied to usage. A $10 monthly fee still adds up to $120 a year even with perfect production matching, meaning a truly $0 bill is uncommon even for a well-sized system. The US Department of Energy's homeowner's guide to going solar walks through the same decision step by step.
The fixed charge covers grid connection and maintenance regardless of how much electricity you use or produce, so it applies even in a month where your system generates exactly as much as you consume. It's billed per connection, not per kWh, which is fundamentally different from the usage-based charges that solar production directly reduces. The system size by monthly kwh usage is the quickest way to check whether the system size behind this estimate fits your roof and usage.
Generally not, since the fixed charge exists specifically because it can't be offset by production, no matter how large the system. Oversizing to chase a literal $0 bill usually means paying for capacity that goes toward excess credits instead, a tradeoff covered further in the bill credit rollover calculator. If your production estimate feels uncertain, the real world vs nameplate output gap calculator gives you a second check on annual output.
Questions
For 12,000 kWh of annual usage, a system around 8.2 kW would fully offset your usage-based charges under typical sun and derate assumptions, matching production to consumption over the year.
Usually not quite. Most utilities charge a fixed monthly customer or connection fee, commonly $8 to $25 a month, that solar production can't offset since it isn't tied to usage. A $10 monthly fee still adds up to $120 a year even with perfect production matching.
The fixed charge covers grid connection and maintenance regardless of how much electricity you use or produce, so it applies even in a month where your system generates exactly as much as you consume. It's billed per connection, not per kWh.
Generally not, since the fixed charge exists specifically because it can't be offset by production, no matter how large the system. Oversizing to chase a literal $0 bill usually means paying for capacity that goes toward excess credits instead, which is rarely worth the extra upfront cost.