How to Correctly Size a Solar System for a Southern California Home

One of the most common mistakes homeowners make when shopping for solar is buying based on the size of the roof or the size of the sales pitch, not the size of their actual electricity usage. Under the current Solar Billing Plan, an oversized system rarely produces proportionally bigger savings, because excess exported energy is worth less than energy you use yourself.

Start With Your Actual Usage

A proper sizing conversation starts with 12 months of utility bills, not estimates. Seasonal swings, air conditioning load, and evening usage all matter. TM Electric & Solar reviews your interval data, not just your monthly totals, before recommending a system size.

Factor in Future Loads

• EV charging, since a single vehicle can add thousands of kWh per year
• Heat pumps or electric HVAC upgrades
• Pool equipment or spa heaters
• Backup power priorities that require compatible battery storage

If any of these are planned within the next few years, mention them now. Adding capacity during the original design is much cheaper than expanding a system later. This is especially true if you are also planning a home EV charger.

Roof Reality Check

Not every roof can hold the ideal system size. Shading, orientation, and structural condition all limit what actually fits. If your roof is nearing end of life, replacing it before installation is nearly always cheaper than removing and reinstalling panels later.

Common Sizing Mistakes

1. Sizing based on square footage instead of actual kWh usage
2. Ignoring future EV or heat pump loads
3. Overbuilding to try to zero out the bill, which does not work the same way under current billing rules
4. Underbuilding to hit a lower upfront price, then paying more per kWh from the grid for years

Talk to Tim Before You Sign Anything

A properly sized system saves more over 25 years than any discount at signing. Request your free estimate and Tim will pull your real usage and design a system that fits your home, not a template.