Sizing a Solar System for Your Home After the Net Billing Changes
System sizing used to be relatively simple, size for your peak usage and let any excess export at full value, that logic no longer holds under net billing, getting your sizing right now requires actually understanding your own consumption pattern, not just your peak demand.
Size your solar system primarily around your typical daytime consumption, the electricity you'll actually use as it's generated, rather than your total daily usage, since exported surplus is now bought back at a considerably lower rate than what you pay to import, pairing a more modestly sized solar array with adequate battery storage to shift your self-generated power into evening hours generally makes more financial sense than a larger system designed to export heavily during the day.
Why oversizing no longer makes the same financial sense
Under the old net metering structure, a system sized larger than your immediate needs still made sense, since the surplus exported during peak sun hours was credited at full value against your usage at other times, under net billing, that same surplus is now worth considerably less when exported, meaning an oversized system generates value at a meaningfully lower rate for anything beyond what you directly consume as it's produced.
Understanding your actual consumption pattern, not just your total usage
Review your electricity bills to understand not just your total monthly usage, but roughly when during the day you actually consume electricity, a household that's largely empty during daytime working hours has a very different optimal system design than one with significant daytime usage, air conditioning, work-from-home equipment, this pattern matters more now than it did under the old export-friendly structure.
The shifted role of battery storage in sizing decisions
Since exporting surplus is now considerably less valuable, storing that surplus for your own evening use through battery storage has become proportionally more valuable than it was previously, factor battery storage into your sizing decision from the start rather than treating it as a purely optional add-on, the batteries and generation capacity should be considered together as one design decision.
Working with your installer on a genuinely tailored design
Given how much the optimal sizing approach has shifted, work with your installer specifically on a design tailored to your actual consumption pattern, rather than accepting a generic sizing recommendation that might reflect outdated, pre-net-billing assumptions, ask directly how your proposed system size and battery capacity account for the current net billing economics.
A realistic approach to load-shedding backup versus grid export optimization
If your primary motivation is genuine backup power during load shedding rather than maximizing grid export value, your sizing priorities shift further toward battery capacity and reliable backup coverage for your essential loads, rather than the largest possible solar array, clarify your own primary goal, cost savings through self-consumption, or backup reliability, since this meaningfully shapes the right sizing approach for your specific situation.
Reviewing your sizing decision periodically as your household's usage evolves
Your household's consumption pattern may shift over time, a growing family, a home office setup, additional appliances, periodically reviewing whether your original sizing assumptions still match your actual current usage helps you identify whether adding capacity or storage later would genuinely improve your system's value. Our guide on Net Metering to Net Billing: What Changed covers a closely related question, worth checking if it applies to your situation. A related question, Solar Battery Storage Guide, is covered in its own dedicated guide.
A knowledgeable installer should be able to walk you through how they've accounted for these seasonal patterns.
This kind of forward planning is worth a specific conversation rather than an afterthought.
Frequently asked questions
This depends heavily on your specific consumption pattern and how well the smaller system is sized to your actual self-consumption, a well-matched smaller system can genuinely offer a better payback period than an oversized one under current net billing economics.
Yes, but treat it as a modest additional benefit rather than the primary economic driver it once was, your core savings now come predominantly from self-consumption offsetting expensive grid electricity.
Not necessarily, a well-sized smaller system focused on self-consumption can still offer genuine savings, the key is accurate sizing to your actual usage pattern rather than assuming any specific home size automatically determines whether solar makes sense.
Yes, seasonal variation in sunlight hours and your own usage patterns, higher cooling loads in summer, for example, are worth factoring into a genuinely well-tailored sizing decision.
If you have concrete plans for a significant future load increase, discuss this with your installer, some system designs accommodate easier future expansion better than others.