LADWP solar bill calculator, built for installers
Model the customer’s LADWP bill before and after solar the way LADWP actually bills — two-month periods, usage tiers, Zone 1 and 2, and the rollover credit — then put it in a branded proposal.
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Demo home · Imagery © Google
Why LADWP breaks generic solar calculators
An average $/kWh misses the three things that decide an LADWP solar bill. Cali-Graf models each one explicitly.
Two-month billing periods
LADWP bills every two months, and solar nets against usage inside each period — one to one. The same yearly production splits differently across periods, and the bill changes with it.
Tiers by zone
Zone 1 and Zone 2 give each home a different allowance of cheaper kWh per period. Cali-Graf takes the zone from LADWP’s ZIP list and shows it under the address, so you can check it against the bill.
Credit that rolls, never pays out
Surplus solar becomes a dollar credit that carries to later bills — LADWP never writes a check. An oversized system earns credit it can never spend, and Cali-Graf says so before the customer pays for extra panels.
A worked example, end to end
The fictional demo home from the in-app tutorial — an LADWP Zone 2 home using 9,600 kWh a year, with a 9.46 kW system of 22 panels and a 10 kWh battery, at $3.10 per watt cash.
- Electric bill today$3,106 / yr
- Bill with solar, year one$145 / yr
- First-year savings$2,961 · −95%
- Solar covers140% of usage
- Payback from bill savings11.9 years
- Net savings over 25 years$69,029
At 140% coverage the calculator also warns: about $966 of credit is left over after year one and keeps rolling forward — roughly 6 panels could come off with little loss in savings. That honesty is the point.
See this example as a proposal
Fictional demo home — results depend on usage, rates and the roof
How the LADWP calculation works
- Hourly production first. A typical weather year (NSRDB), the sun’s path on each roof face and Google’s shade data at each panel give production for every hour.
- Netting per billing period. Solar offsets usage one to one inside each two-month period; tier prices follow the published rates and the days of each period.
- Credit and charges, like the bill. Surplus becomes rollover credit at the published prices; the credit pays base energy rates and the access charge, not taxes.
- City tax shown separately. The utility users tax is listed under the result — today and with solar — instead of hiding inside the bill.
The full method, in plain words, is public: How the LADWP bill with solar works and how production is calculated.
Validated against 64 real LADWP bills
During development the engine recalculated 64 real LADWP customer bills from 2023–2026: every one within 3 cents of the printed bill, 23 to the exact cent. Credit use and surplus on real solar bills were reproduced to the cent and within 2 cents. Validation results and methodology.
Honest about batteries
Under one-to-one netting, storing solar usually doesn’t change an LADWP bill. Cali-Graf simulates the battery hour by hour and says plainly when its value is backup power, not savings. Battery modes.
What’s not covered yet
The calculator uses LADWP’s standard residential rate (R-1 Rate A). The time-of-use rate R-1B, the EZ-SAVE and Lifeline discounts, and homes outside LADWP and SCE territory aren’t supported yet — the full list is public in What Cali-Graf doesn’t do yet.
LADWP solar questions
What happens to extra solar under LADWP net metering?
Within each two-month period, solar offsets usage one to one. Surplus becomes a dollar credit that rolls forward to later bills — LADWP never pays it out. Cali-Graf shows the credit carried after year one and warns when a system is oversized.
What is the difference between Zone 1 and Zone 2?
The zone, from LADWP’s ZIP code list, sets how many kWh in each billing period are charged at the lower tier prices. Cali-Graf finds the zone from the address and shows it so you can check it against the bill — see how the utility and zone are found.
Does a battery lower an LADWP bill?
Usually not: solar sent to the grid is already credited like solar used at home, so storing it rarely changes the bill. The battery’s honest value for LADWP homes is backup power, and the proposal says so.
Which LADWP rates are supported?
The standard residential rate (R-1 Rate A) with Zone 1 and 2 tiers and the published adjustment factors. R-1B time-of-use and the EZ-SAVE and Lifeline discounts aren’t supported yet.
Is the calculator really free?
Yes — roof design, the bill calculation and branded PDF proposals, with daily fair-use limits. No subscription, no credit card. The details.
Model your next LADWP bill properly.
Start with the property address — the utility, zone and roof come up in seconds.
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