Why West-Facing Solar Beats South in San Diego

Aiming Your System at San Diego’s 4–9 PM Peak

First, why “when” matters so much in San Diego

SDG&E prices electricity by time of use. In summer, the 4–9 p.m. on-peak window runs about 69.65¢/kWh in 2026 — while midday super off-peak sits closer to 38¢ and off-peak around 46¢. That’s not a rounding difference; peak power can cost nearly double the midday rate.

On top of that, the value of the solar you export to the grid (under SDG&E’s Net Billing rules) is lower than the retail price you pay to pull power back. So two things are true at once: power is most expensive in the early evening, and your exported midday surplus is worth relatively little. Both facts push in the same direction — the most valuable solar is the solar you use yourself, especially during the peak.

The problem with a south-facing array in the evening

A south-facing array peaks around solar noon and tapers through the afternoon. By 5 or 6 p.m. it’s producing a fraction of its midday output.

The trouble is that 4–9 p.m. is exactly when SDG&E charges the most, and exactly when your home is hottest and the AC is grinding. So a south-facing system is fading right as your most expensive, most cooling-heavy hours begin. You generate a big midday surplus (credited at a lower export rate) and then buy pricey power in the evening. It still saves money — but it leaves value on the table during the hours that matter most.

Why west-facing panels line up with the peak

West-facing panels shift the production curve later in the day. They give up a little total annual output compared to south — often in the ballpark of 10–15% less over a year — but they keep generating deeper into that 4–7 p.m. stretch, powering your AC directly from the roof during the first, most expensive hours of the peak window instead of pulling from the grid.

In a world where you’re rewarded for using your own solar when power is expensive, that timing is worth real money. A west-leaning design trades a small amount of total production for output that lands in your highest-value hours. For a household that comes home in the late afternoon and runs the AC hard until bedtime, that trade often comes out ahead on the actual bill — which is what you care about, not the theoretical annual kilowatt-hour number.

South, west, or both?

This isn’t all-or-nothing. Many of the best San Diego designs are a blend:

• South for maximum total generation and the biggest midday surplus.
• West to carry production into the late-afternoon peak.
• Sometimes a split across roof planes to smooth the curve so you’re covered from late morning all the way toward sunset.

The right mix depends on your roof orientation, your shading, and — importantly — your evening usage. A household that’s empty until 6 p.m. and then blasts the AC has a very different ideal layout than one that cools all afternoon or works from home.

What actually drives the recommendation

• Your daily rhythm. When is your home occupied and cooling? Evening-heavy usage favors a west lean.
• Your roof. Which planes exist, how big they are, and how they’re shaded often decides what’s even possible before preference enters the picture.
• Whether you’re adding a battery. With storage in the mix, orientation matters a little less (the battery handles the evening); without it, orientation is your main lever on the peak.
• Your rate plan. TOU-DR1 and EV-TOU-5 have different peak definitions, and the best layout follows the plan you’re actually on.

Where a battery fits

Orientation gets you part of the way, but the sun still sets during the 4–9 p.m. window. Even a west-facing array can’t cover 8 or 9 p.m. on its own. That’s where storage comes in: bank your daytime solar and discharge it across the whole peak.

Panel orientation and a battery aren’t competing strategies — they work together. Smart orientation reduces how much you have to lean on the battery, and the battery covers what orientation can’t. A west-leaning array plus a battery is one of the most effective setups there is for beating SDG&E’s summer evenings: the panels carry you into the peak, and the battery carries you through the rest of it.

A couple of common questions

Won’t west-facing panels lose me money by producing less overall? They produce a little less total energy, but they produce more of it during expensive hours. On a time-of-use bill, the timing of production can matter more than the raw total — which is the whole reason to consider west.

Is south-facing ever still the right call? Absolutely — for some roofs, usage patterns, and battery setups, south (or a south-heavy split) is best. The point isn’t “west wins”; it’s that the decision should be made on purpose, against your rates and your usage.

What this means for your design

The takeaway isn’t “always go west.” It’s that in San Diego, a good solar design is planned around when you’ll use power and when it’s expensive — not just how many kilowatt-hours the roof can make in a year. Two systems with the same number of panels can save very different amounts depending on how they’re aimed.

When we design a system, we model your roof planes against your actual load shape and SDG&E’s peak window, so your production lands where it’s worth the most — in the expensive evening hours when your AC is running.

Curious whether a west-facing or split layout would beat a standard south-facing design on your roof and your usage? Stellar Solar has been San Diego’s trusted solar installer since 1998 — A+ rated with the BBB and a repeat winner of San Diego’s Best Solar in the Union-Tribune Readers Poll. Get a free design consultation at your free quote here or call 866.787.6527.

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How Much of Your Summer AC Can Solar Offset?

How Much Solar It Takes to Cover Your Summer AC

What your AC actually costs in a San Diego summer

A typical central AC compressor for a San Diego home draws somewhere between 3 and 5 kilowatts while it’s running. On a hot inland day it might run four to eight hours — and not always in one stretch, since it cycles on and off to hold your setpoint. Add it up and you’re looking at roughly 15 to 35 kWh of cooling in a single day, with the higher end common in places like El Cajon, Santee, Escondido, and the inland valleys where summer afternoons are genuinely hot.

That’s the part that stings under SDG&E’s rates. On the TOU-DR1 plan, summer on-peak power (4–9 p.m., June through September) runs about 69.65¢/kWh in 2026. Off-peak is around 46¢ and super off-peak about 38¢. So the same hour of cooling can cost you very different amounts depending on when the compressor runs — and unfortunately, late afternoon and early evening, right in that expensive 4–9 p.m. window, is exactly when homes are hottest and AC works hardest.

A quick worked example

Say your AC adds 25 kWh on a hot day, and about a third of that runs during the 4–9 p.m. peak. That’s roughly 8 kWh at ~70¢ (about $5.60) and 17 kWh across cheaper hours at, say, an average of 50¢ (about $8.50) — around $14 in cooling in a single day, or well over $400 across a hot month just for air conditioning. For a lot of San Diego homes, cooling is the single biggest reason the summer bill balloons, and it’s concentrated in exactly the hours SDG&E charges the most.

How much of that solar can offset

Here’s the good news: cooling season and solar season are the same season. Your panels produce the most in exactly the long, bright months your AC runs hardest. During the day, a properly sized system can run your AC directly on solar and send the excess to the grid.

For most San Diego homes, a well-designed system can offset the large majority of daytime cooling — often effectively all of it while the sun is up. The part solar doesn’t automatically cover is the 4–9 p.m. peak, when the sun is dropping but the house is still hot. That’s the gap a battery fills: you bank cheap midday solar and discharge it through the expensive evening window instead of buying 70-cent power.

So the honest answer is: solar can offset most of your summer AC, and solar plus a battery can offset nearly all of it, including the pricey evening hours.

Why the battery matters more under today’s rules

Under SDG&E’s current Net Billing structure, the surplus solar you export midday is credited at a relatively low rate, while the power you buy back at 6 p.m. is charged at that steep peak price. That spread is exactly what a battery captures. Instead of “selling low and buying high,” you store your own midday production and spend it during the peak — so a battery doesn’t just add backup, it directly protects the most expensive kilowatt-hours of your cooling load.

How many panels it takes

A modern residential panel is roughly 400 watts. As a rough planning number, each panel produces on the order of 1.5–2 kWh on a good San Diego summer day.

If your AC is adding, say, 20 kWh on a hot day, covering that load alone takes something like 10–14 panels’ worth of production on top of whatever the rest of your house uses. That’s why the sizing conversation matters: a system built only for your annual average usage can come up short in July and August, when cooling spikes your demand well above the yearly mean.

The fix is to size for the summer peak, not the average. When we design a system, we look at your actual highest-usage months and your afternoon load shape, so the array is big enough to carry the hot season instead of leaving you buying expensive top-up power exactly when rates are highest.

What changes the panel count for your home

• Your climate zone. A coastal home in Encinitas or Point Loma barely runs AC; an inland home in Ramona or Poway may run it for hours. Same house size, very different cooling load.
• Home efficiency. Insulation, windows, ductwork, and shade all change how hard the AC works — and therefore how many panels it takes to offset.
• AC type and age. An older single-stage unit draws more than a modern variable-speed or heat-pump system for the same comfort.
• Roof space and orientation. How many panels physically fit, and how they’re aimed, affects both the count and how much of the peak they can cover (a west lean helps into the evening).

The mistakes that leave AC savings on the table

• Sizing to the annual average. It looks efficient on paper but underperforms in the months you care about most.
• Ignoring the 4–9 p.m. window. Solar alone tapers in the evening. If beating the summer peak matters to you, plan for a battery.
• Forgetting future load. If an EV, a pool, or a heat pump is in your future, size for where you’re headed, not just where you are — adding panels later is more expensive than building the headroom in now.
• Chasing the cheapest quote. An undersized system is the most common way homeowners end up disappointed with “solar that didn’t lower my bill much.” It usually wasn’t solar’s fault — it was the sizing.

A few quick questions homeowners ask

Can solar run my AC by itself during the day? Yes — a correctly sized array can power your AC directly while the sun is up, sending any extra to the grid.

What about at night or during the 4–9 p.m. peak? That’s where a battery comes in. Panels can’t produce after sunset, so storage is what carries your cooling through the expensive evening hours.

Will one hot summer month wipe out my savings? Not if the system is sized for your summer peak. That’s the whole point of designing around your hot-season usage rather than a flat annual number.

The bottom line

In San Diego, solar and summer line up beautifully — the sun is strongest when your AC needs it most. A system sized to your actual hot-season usage can offset most of your cooling costs on its own, and adding a battery closes the gap on the expensive 4–9 p.m. evening hours. The key is designing around your summer peak and your afternoon load, not a flat yearly number.

Want to know exactly how many panels it would take to cover your AC on your roof? Stellar Solar has been San Diego’s trusted solar installer since 1998 — A+ rated with the BBB and a repeat winner of San Diego’s Best Solar in the Union-Tribune Readers Poll. Get a free, no-pressure system estimate built around your real summer usage at your free quote here or call 866.787.6527.

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