Choosing the right solar system configuration involves balancing upfront cost, usable energy storage, projected savings, and long-term financial return. The comparison tool above lets you model up to four distinct configurations and evaluate them side-by-side across every key metric.
Battery chemistry choice is one of the biggest factors in system comparison. Here is how they differ in practical terms:
| Factor | Lithium LiFePO4 | Lead-Acid AGM/Gel |
|---|---|---|
| Depth of Discharge | 90% | 50% |
| Round-Trip Efficiency | 95–98% | 80–85% |
| Cycle Life | 3,000–5,000+ | 500–1,000 |
| Expected Lifespan | 10–15 years | 3–5 years |
| Self-Discharge Rate | ~2–3% per month | ~5–15% per month |
| Weight (per kWh) | ~10 kg/kWh | ~25–35 kg/kWh |
| Upfront Cost (per kWh) | Higher (~$300–600/kWh) | Lower (~$100–200/kWh) |
| Replacements in 10 Years | 0–1 | 2–3 |
For most permanent off-grid installations, lithium offers lower total cost of ownership over 10+ years. Lead-acid may be preferred for temporary setups, tight budgets, or when weight is not a concern and replacement labor is cheap.
System voltage determines the fundamental architecture of your solar installation. While any voltage can technically run the same loads through an inverter, higher voltage systems have real efficiency and cost advantages at scale.
Power (Watts) = Voltage × Current (Amps). For the same wattage, higher voltage means lower current. Lower current means less heat loss and smaller required wire gauge — which is significantly cheaper. A 48V system at 5kW draws 104A; the same system at 12V draws 417A, requiring four times the conductor capacity.
All financial projections assume constant electricity rates and panel output. Actual results will vary based on location, shading, and battery degradation. For educational use only.
Enter each system's panel wattage, battery capacity, system voltage, upfront cost, and your local utility rate. The tool calculates usable energy, annual yield, payback years, and 25-year net savings for each configuration so you can compare them directly side-by-side.
A payback period of 6–10 years is typical for residential off-grid solar systems. Systems in high-sun locations with higher electricity rates can pay back in 4–6 years. Lead-acid battery systems tend to have longer payback periods due to replacement costs every 3–5 years — use the 10-Year Cost tool to model this accurately.
In most cases, yes. A lead-acid system typically requires 2–3 complete battery replacements over a 10-year period, often making the total cost comparable to or higher than an equivalent lithium system. Use the 10-Year Cost Comparison tool to calculate the exact crossover point for your specific budget and usage.