Should You Size Your Solar System for an Electric Vehicle You Don't Own Yet?

Key Takeaways

• Most EVs add 30 to 50 percent to household electricity consumption

• Installing extra panels now costs less per panel than adding them in a second project later

• The federal solar tax credit applies to the full system when installed together

• Electrical service upgrades needed for EV charging can be coordinated with solar installation

• Phased installation options exist if you want flexibility without committing fully to future capacity

How Much Electricity Does an EV Actually Use?

Most electric vehicles consume between 0.25 and 0.35 kilowatt-hours per mile. If you drive 30 to 40 miles per day, an EV uses about 10 to 12 kWh daily. Over a year, around 3,600 to 4,400 kWh.

A typical Minnesota household uses 10,000 to 12,000 kWh annually. Adding an EV increases total consumption to roughly 13,500 to 16,500 kWh per year—a 30 to 40 percent increase. Your solar system needs significantly more capacity.

The Cost Trade-Off

Installing extra solar capacity today costs more upfront but often less per panel than a future expansion. Fixed costs include permitting, engineering, site preparation, and labor. If you install 20 panels now and 6 later, you pay fixed costs twice.

Adding panels in a separate project typically costs 20 to 40 percent more per panel.

The federal solar tax credit allows you to claim 30 percent of the total system cost. If you install a larger system now for future EV charging, the entire cost qualifies for the credit in the year of installation.

Panels you install now but do not fully utilize until you buy an EV have delayed ROI. Excess production gets exported to the grid at net metering rates, which currently provides good value in Minnesota.

Electrical Service and Panel Capacity

Most homeowners install a Level 2 EV charger, which draws 30 to 50 amps. Your electrical panel needs available capacity for this load. If your panel is near capacity, adding an EV charger might require an upgrade.

Installing solar often involves electrical work at your main panel. Evaluating your panel capacity now and upgrading during solar installation saves money compared to two separate projects.

Phased Installation Strategies

You do not have to choose between sizing fully now or not at all. Some installers design systems with two phases planned from the start. Phase one covers current usage. Phase two adds panels when you buy the vehicle.

You can also prepare for future expansion by running extra conduit, sizing the inverter to handle additional panels, and leaving roof space clear. These preparations cost little initially but save money later.

Minnesota-Specific Considerations

Solar production in Minnesota varies significantly by season. Systems produce much less in December and January than in June and July. EVs also use more electricity in winter for heating the cabin and battery.

Minnesota utilities currently offer net metering. If your solar system overproduces in summer, those credits can offset winter consumption including EV charging.

Making the Decision

If you plan to buy an EV within 12 months, sizing your solar system to include it makes strong sense. The cost advantages of installing everything together outweigh the short period of unused capacity.

If your EV purchase is three to five years away, you will pay for panels that sit underutilized. If you have no specific timeline, do not oversize your system. Design for actual current needs.

Ask your installer for two proposals: one sized for current usage, one including EV charging. Compare costs, tax credit benefits, and production estimates.

What Greenway Recommends

At Greenway Solar, our general guidance:

If you are buying an EV within a year, include it in your system design now. If your timeline is one to three years and you are confident about the purchase, we usually recommend sizing up now to capture the financial benefits of a single installation. If your timeline is uncertain or beyond three years, we recommend designing current needs and revisiting expansion later when your plans are clearer.

We can also design systems with built-in expansion capability, including inverters sized to handle more panels than you install initially, roof layout that leaves clear space for future panels, and electrical preparation so adding capacity later is simpler.

FAQs

How much does it cost to add panels later versus installing them now?  

Adding panels in a separate project typically costs 20 to 40 percent more per panel because fixed costs like permitting, site preparation, and labor apply to both installations.

Will my roof have space for more panels if I decide to expand later?  

This depends on your roof size, orientation, and shading conditions. Your installer can show you a layout that identifies areas suitable for panels and whether future expansion is possible.

Can I use the federal tax credit if I add panels later?  

Yes, the federal solar tax credit applies to system expansions. You claim the credit in the year you complete the expansion, though the credit percentage might change over time depending on federal policy.

Plan for What You Know, Prepare for What Might Happen

Sizing your solar system for a future EV depends on your timeline, your budget, your confidence in your plans, and your priorities around simplicity versus cost optimization.

At Greenway Solar, we work through these questions with every customer. We will show you the cost difference between options, the production estimates for each scenario, and the financial implications over the life of the system.

Ready to explore your options? We will design a solar system that fits your current needs and your future plans.

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