Understanding your utility bill after Semper Solaris solar.

Solar production vs. what your home uses

Solar panels produce the most power around midday. Many households use the most power in the late afternoon and evening — cooking, laundry, air conditioning, EV charging — when panels produce little or nothing.

Whatever your panels don't cover at that moment is pulled from the grid (an import). Extra power your panels make when you're not using it goes back to the grid (an export). Your utility bill is built from those imports, exports, the rate plan you're on, and fixed charges.

Where a home battery fits in

At a high level, a home battery can store solar power produced during the day and use it later, such as in the evening, instead of importing that power from the grid. It may also provide backup power during an outage.

How much a battery affects your bill depends on how it's set up (for example, backup-only versus time-based use), its size, your usage and your rate plan. If a battery's settings changed, or it's reserving most of its charge for backup, your grid imports may be higher than you expect.

Rate-plan considerations

Your utility's billing plan (for example, legacy net energy metering or a newer Solar Billing Plan) and time-of-use rate decide how imports are priced and exports are credited. If your plan changed — such as when a legacy period ends — your bill pattern can change too.

Why you can still get a bill after going solar

• Evening and nighttime use

  Power you use when the sun is down usually comes from the grid unless a battery covers it.

• Fixed charges and fees

  Some monthly charges can't be offset by solar credits. SDG&E, for example, notes that NEM customers may still owe fixed charges and fees even when they generate more than they use.

• Time-of-use pricing

  Power imported during higher-priced hours costs more, while exports may be credited at different values depending on your billing plan.

• Seasonal changes

  Shorter winter days mean less production; hot summers can mean more AC use than panels cover.

• Usage that grew

  A new EV, pool pump, heat pump or more people at home can outpace what the system was sized for.

• Billing-plan cycles

  Depending on your plan, some charges may settle monthly or on a longer cycle, such as an annual true-up statement.

A step-by-step solar bill check

• 1. Confirm which billing plan you're on

  Your bill or online account should show whether you're on a legacy net energy metering (NEM) plan or a newer plan such as a Solar Billing Plan, and your time-of-use rate.

• 2. Compare the same month last year

  Look at total grid imports, exports and billing days — not just the dollar amount.

• 3. Check your system's production

  Use your installer's or equipment maker's monitoring app to see whether production dropped (shading, dirt, an error or an inverter issue).

• 4. Look at when you use power

  Heavy use between late afternoon and evening often costs more on time-of-use plans.

• 5. Review your battery settings

  If you have a battery, check its mode and backup reserve in the app.

• 6. Separate fixed charges from usage

  Identify which charges would appear no matter how much solar you produce.

• 7. Write down your questions

  Equipment questions go to your installer; billing and rate questions go to your utility.

Semper Solaris vs. your utility: who handles what

• Ask Semper Solaris about

  Your panels, inverter, battery, monitoring app, production that seems low, error messages, warranty, service visits and the terms of your purchase, loan or lease.

• Ask your utility about

  Your billing plan, rate plan, meter readings, import and export amounts, credits, fixed charges, true-up or billing cycle, and payment options.

• Utility Bill Advocates can help with

  Understanding the utility-bill side in plain language and preparing clear questions — we don't service equipment or change your account.

Questions to ask

• For your installer

  Is my system producing what it's expected to for this time of year? Are there any alerts or errors? How is my battery configured? Did any settings change after an update or service visit?

• For your utility

  Which billing plan and rate plan am I on? How are my exports credited? Which charges can't be offset by solar credits? When does my billing cycle or true-up settle? Is there a rate plan that better fits my usage?

Where to reach each

For installation, equipment, battery or service questions, use Semper Solaris's official contact page or help center. For billing and rate questions, contact the utility listed on your bill. If you have a Tesla Powerwall, Tesla also provides Powerwall support.

Common questions