Model your electric bill, solar system, battery and payback using current California utility data — with the assumptions, rates and official sources shown behind every result. No sign-up.
Does a home battery pay off without solar?
Updated August 7, 2026 · a time-of-use arbitrage model at 365 cycles per year · by Cali Energy
Does a home battery pay for itself without solar? Usually slowly. On a typical time-of-use spread (~$0.45 peak, $0.28 off-peak), shifting ~10 kWh a night saves about $500 a year — a 25+ year payback on a $13,500 battery. Without solar, the real value is backup power and any SGIP incentive, not arbitrage.
✓ A real arbitrage model — it computes savings from your rates, not a number you guess. See every figure it uses ↓
Time-of-use arbitrage: charge cheap off-peak, discharge at the peak rate.
Arbitrage-only model at 365 cycles/year. It excludes backup value, demand charges, degradation and rate escalation. Without solar, battery economics usually lean on backup power and SGIP more than on arbitrage.
The rates and figures this calculator usestap to verify
This is an arbitrage model: it charges the battery at your off-peak rate and discharges at your peak rate, 365 times a year, and computes the savings for you. Every rate and quantity is your input; the two fixed assumptions are below.
| Cycles per year | 365 (one charge/discharge per night) |
| Round-trip efficiency | 0.90 default (your input) |
| Peak / off-peak rate | $0.45 / $0.28 per kWh |
| Shifted kWh per night | 10 |
| Installed cost / incentive | $13,500 / $0 (SGIP varies) |
| Per-cycle savings | kWh × peak − (kWh ÷ efficiency) × off-peak |
| Annual savings | × 365 |
| Payback | (cost − incentive) ÷ annual savings |
This models time-of-use arbitrage only — charging cheap and discharging at peak. It deliberately excludes backup value, demand charges, degradation and rate escalation, and assumes one cycle a night (365/year). The default rates and $13,500 cost reflect 2026 California ranges (a Powerwall installs near $13–17k; SGIP incentives vary and can be significant for some customers). The honest takeaway: without solar, arbitrage alone rarely pays back within a battery’s warranty — the real value is backup power during outages and any SGIP incentive.
Example results you can reproduce
Each row sets the six inputs shown — enter the same values above to reproduce it.
| Scenario | Annual savings | Payback | 10-yr net |
|---|---|---|---|
| Default ($0.45/$0.28, 10 kWh, $13,500) | $507 | 26.6 yr | −$8,431 |
| + $5,000 SGIP incentive | $507 | 16.8 yr | −$3,431 |
| Bigger spread ($0.55/$0.22, 12 kWh) | $1,338 | 10.1 yr | −$117 |
How this calculator works
Each night the battery stores cheap off-peak energy and discharges it at the peak rate. Per-cycle savings are the peak value of the energy delivered minus the off-peak cost of charging it (grossed up by your round-trip efficiency, since you must charge a bit more than you deliver). Multiply by 365 for annual savings, then divide the net cost by that for simple payback. Because it’s arbitrage-only, a negative 10-year net simply means the battery hasn’t paid for itself on rate-shifting in a decade — which is the usual result without solar.
How to read your result
A long payback here is the honest answer, not a bug: on typical spreads, arbitrage saves a few hundred dollars a year against a five-figure battery. The number that changes the verdict most is the SGIP incentive, followed by the rate spread. If arbitrage alone doesn’t pay back, that doesn’t mean the battery is a bad buy — it means you’re buying it for backup, and the arbitrage is a bonus.
What moves the result the most
The peak-to-off-peak spread — a wide spread (steep TOU plan) roughly doubles annual savings versus a narrow one. Then the SGIP incentive (which cuts the net cost directly), how many kWh you shift each night, and the installed cost. Round-trip efficiency matters a little: a less efficient battery wastes more of the cheap energy it stored.
Common questions
What do I need to use this calculator?
Your peak and off-peak rates (from your bill), how many kWh you’d shift each night, the battery’s round-trip efficiency, and its installed cost and any incentive.
Why is the payback so long?
Because a typical rate spread earns only a dollar or two per cycle. Over 365 nights that’s a few hundred dollars a year against a $13,500 battery — hence 20+ years on arbitrage alone.
What is SGIP?
California’s Self-Generation Incentive Program, which can rebate part of a battery’s cost — sometimes substantially for eligible or resiliency customers. Enter it as the incentive to see how much it shortens payback.
Does backup value count here?
No — this model is arbitrage-only. The value of keeping power on during an outage is real but personal, so it’s left out of the dollar payback and noted separately.
What is round-trip efficiency?
The share of stored energy you get back out — around 90% for a modern battery. The other ~10% is lost charging and discharging, which is why you charge slightly more than you deliver.
Is it different with solar?
Yes — with solar, the battery stores your own free daytime energy instead of buying off-peak, which changes the economics. See is solar worth it with the battery option.
Sources
- CPUC — Self-Generation Incentive Program (SGIP)
- SGIP Statewide — live program metrics (SelfGenCA)
- IRS — OBBB FAQ: Residential Clean Energy Credit (Section 25D)
- DOE — Solar Integration: Solar Energy and Storage Basics
Estimates only, not a quote. Assumptions, rates, incentives and program rules can change — confirm current details with your utility, the program administrator or a licensed professional.
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