Where to Start: The California Homeowner’s Honest Guide to Home Efficiency

You’ve probably been told to get solar. Maybe you’ve gotten a quote. Maybe the number made you close the browser tab.

Here’s what the solar salesperson didn’t mention: for most California homeowners, solar is not the first thing to do. In many cases, it’s not even the second or third.

This guide explains the actual priority order — based on ROI, not on what someone has a financial incentive to sell you. We’ll also deal honestly with the timeline problem (“we might move in five years”), the current incentive landscape, and what to make of all the exotic options you’ve seen on YouTube.

The mental model nobody explains

Home energy efficiency falls into three layers, and they have a natural order:

1. Reduce the load — less energy needed in the first place (insulation, air sealing, passive design)
2. Efficient systems — when you do use energy, use it efficiently (heat pumps, LED lighting, etc.)
3. Generate your own — solar PV, solar thermal, etc.

Almost all professional advice starts at layer 3. The industry that wants to sell you a $30,000 solar installation has no incentive to tell you to air seal your attic first.

But the honest order is 1 → 2 → 3. A more efficient house needs a smaller, cheaper solar system. Skipping steps doesn’t save money — it costs it.

Where your energy is actually going

Air leaks don’t feel dramatic. They’re not visible. Nobody makes a sales pitch about them. But they account for a larger fraction of most homes’ energy loss than windows, appliances, or anything else people typically fix first.

Where the leaks actually are, in order of impact:

• Attic bypasses — where walls meet the attic, around plumbing and electrical penetrations (usually the worst)
• Rim joist — where the house framing meets the foundation
• Recessed lights — older can lights are direct air channels into the attic
• Windows and doors — obvious, but usually not the biggest problem

The honest priority order

For a California homeowner — especially one uncertain about timeline — this is the sequence that maximizes ROI:

1. 1

   Get a free energy audit

   PG&E, SCE, and SDG&E all offer free or subsidized audits. This tells you what’s actually wrong with your specific house. Don’t guess — measure.

   PG&E: 1-800-743-5000  ·  SCE: 1-800-655-4555  ·  SDG&E: 1-800-411-7343

2. 2

   Air sealing

   Especially attic bypasses and the rim joist. This is the unsexy, highest-ROI step that most people skip entirely because nobody sells it.

   DIY: $200–$500  ·  Professional: $1,000–$3,000  ·  Payback: 2–4 years

3. 3

   Attic insulation (if under-insulated)

   California climate zones 3–4 should have R-38 to R-49. Many homes built before 1990 have R-11 or less. Blown cellulose is cheap, effective, and DIY-able.

   ~$0.50/sq ft  ·  Payback: 2–5 years  ·  Adds home value

4. 4

   Heat pump water heater

   If you have a gas water heater, this is the next highest-impact switch. Uses a third of the energy. PG&E and TECH Clean California offer rebates.

   $1,000–$1,800 installed  ·  Saves $200–$550/year  ·  Payback: 3–7 years

5. 5

   Heat pump HVAC (when yours dies)

   When your current system reaches end of life, replace it with a heat pump, not another gas furnace. Don’t replace early — let it die naturally. Modern heat pumps work in cold climates down to −13°F.

   $4,000–$8,000 installed  ·  2–3× more efficient than resistance heat

6. 6

   Solar PV — only after the above

   A more efficient home needs a smaller, cheaper system. Get everything else right first. And understand NEM 3.0 before you sign anything — the economics changed significantly in 2023.

   $2.50–$3.50/W installed  ·  Payback: 8–14 years under NEM 3.0

The timeline problem

“We might move in five years” is a real constraint that most energy advice ignores. Here’s the honest take for each step:

• Air sealing and insulation: High ROI even in 2–3 years. Adds measurable home value. Do it regardless of timeline.
• Heat pump water heater: Pays back in 3–7 years. Transfers to the next owner as a selling point on disclosure.
• Full solar installation: Probably doesn’t pencil out in 5 years at post-NEM-3.0 rates, unless you’re running a $400+/month bill. Calculate before committing.
• Plug-in solar (balcony or window kits): Low cost, no installation required, take it with you when you move. Worth considering as a starter while you decide on the larger picture.

What about the exotic stuff?

Earth tubes. Rocket mass heaters. Trombe walls. Earthships. You’ve probably found these in YouTube rabbit holes. The honest take:

• Earth tubes (earth-air heat exchangers): Real technology. Uses the earth’s stable ~55°F temperature to pre-cool summer air. Works best in new construction or major renovation. Requires careful design to prevent condensation and microbial growth. Not banned.
• Rocket mass heaters: Dramatically more efficient than conventional wood stoves — the 80–90% wood savings claim is plausible based on builder reports, though not independently verified by DOE. Hard to permit. Not your first move.
• Trombe walls: Passive solar heating that actually functions in sunny, cold climates (high-altitude Colorado, New Mexico). Requires a proper overhang to prevent summer overheating. Not applicable in overcast climates.
• Evaporative cooling walls: Only works in dry, low-humidity climates. Useless in the Bay Area or coastal California. Genuinely effective in the Central Valley or Southwest.

All of these are worth understanding. None of them are your first move for an existing California home.

The one thing to do this week

Call your utility and ask about a free home energy audit.

• PG&E: 1-800-743-5000
• SCE: 1-800-655-4555
• SDG&E: 1-800-411-7343

It costs nothing. It takes an hour. It tells you exactly where to start for your specific house, in your specific climate zone, with your specific problems.

Everything else flows from that.