Why Would a Larger Battery Have Less Savings?

Summary

There are many factors that influence the difference in total savings in a comparison between two batteries. A larger battery can indeed lead to less savings in a PV system due to the cost and specific energy profile of the user.

• Cost: Generally the larger the battery the more expensive
  • Larger Upfront Costs: Cost generally increases as the amount of kWh increases and the installation cost is generally higher.
  • Operating Costs: If a larger battery is less efficient or not suited for the system it can mean the battery needs to be replaced earlier. 
  • Incentives and Financing:
    • Incentives Cap: Some government or utility incentives are capped by system size or capacity, so a larger battery might not qualify for proportionally more benefits.
    • Financing Costs: Larger systems require higher financing amounts (if not paid upfront), leading to increased interest payments over time.
• Energy Storage vs Demand: A larger battery can store more energy but if it is not suited for a specific energy usage pattern, the extra storage becomes underutilized.
• Maximising Solar Self Consumption: A battery should be chosen that matches the size of your solar system to store excess generation for later use. If the battery is significantly larger than peak generation the battery might not fully be utilized and storage could more efficiently be achieved with a smaller one 

Ultimately OpenSolar provides a solution for this in the Battery Design Assistant in which savings can be maximized. If the user intends to manually select the battery consider:

• Peak and off-peak consumption - how much energy you use during high-cost (peak) and low-cost (off-peak) times.
• Understand your objectives: What are you trying to maximise, self consumption, or lower energy bills
• The warranty and efficiency of the battery