Solar planning guide
How to Read Your Utility Bill for Solar Planning
Find monthly kWh, fixed charges, export credits, and rate-plan clues on a residential utility bill before using a solar calculator.
Worked example: from a bill to panel count
Fictional California household, not a customer record. To keep the example reproducible, its energy price equals the June 2026 EIA state average. The $15 fixed charge and $7 tax are invented worksheet inputs, not an actual tariff.
1. Separate energy from other charges
- Energy charge for 900 kWh
- $312.66
- Full bill, including fixed charge and tax
- $334.66
($334.66 − $15 − $7) ÷ 900 kWh = $0.3474/kWh
Do not divide the full bill by an energy-only price: that overstates kWh. Prefer the printed usage. For a bill-only estimate, remove separately stated non-energy charges and verify that the chosen rate uses the same cost basis.
2. Use twelve billing periods
Period 1
700 kWh
Period 2
650 kWh
Period 3
720 kWh
Period 4
780 kWh
Period 5
900 kWh
Period 6
1100 kWh
Period 7
1250 kWh
Period 8
1200 kWh
Period 9
1000 kWh
Period 10
850 kWh
Period 11
780 kWh
Period 12
870 kWh
Annual total ÷ 12 → monthly input: 10,800 ÷ 12 = 900 kWh
3. Calculate with stated assumptions
California; 400 W panels; low shade; 100% annual energy target; 55% direct use; export at 35% of retail. No incentives.
6.8 kW · 17 panels · $13,405–$20,176
Open this editable example (English)Start with total kWh for the billing period
Solar sizing starts with how much electricity the home uses. A single monthly kWh number is usually enough for an early estimate.
Separate energy charges from fixed charges
Customer charges, meter fees, and minimum bills can remain after solar. Fixed charges matter for payback even when energy use drops.
Look for export or net-generation lines if you already have solar
Credits, banked kWh, NEM balances, or buy-all/sell-all lines explain why a bill may still be high with panels installed.
Check whether the rate plan is flat, time-of-use, or net billing
The label on the bill may not say everything. If the bill mentions peak/off-peak hours or export compensation, use the utility-aware calculator next.
SolarCalcNow provides planning estimates only. Results are not installer quotes, engineering designs, tax advice, financing recommendations, or utility interconnection approval.
What to do next
After you have monthly kWh or bill amount, compare the same assumptions against installer quotes and incentive claims.
FAQ
Common solar calculator questions
Where do I find monthly kWh on my bill?
Look for a line labeled kWh, energy use, or total usage for the billing period. Some bills show daily averages; multiply by days in the period if needed.
Can I use my dollar total instead of kWh?
Yes for early planning. SolarCalcNow can estimate kWh from bill amount and a state residential rate, but kWh is more accurate when fixed charges or tiered rates are large.
Does this page replace my utility rate plan documents?
No. Use it to collect the right numbers before running a calculator. Verify export credits, time-of-use periods, and net billing rules with your utility.
Evidence behind the estimate
- EIA — Measuring electricity
Units and measurement only
- FPL — Net Metering FAQs
FPL example: bill usage, export bank and minimum bill; other utilities differ
Source checked: 2026-09-04