What a Year of Solar and Batteries Saved Us

• by Petabite
solarenergysustainabilitydata

What a Year of Solar and Batteries Saved Us

One year ago, I installed 8kW of solar panels and a 13.5kWh battery on my house. Here are the real numbers, unfiltered.

The Setup

  • Solar: 8kW (20x 400W panels)
  • Battery: Tesla Powerwall 2 (13.5kWh usable)
  • Inverter: Built into Powerwall
  • Cost: $18,500 after federal tax credit
  • Location: Northern California (good sun, high electricity prices)

The Numbers

Energy Production

Total generated: 11,245 kWh
Monthly average: 937 kWh
Peak month (June): 1,384 kWh
Worst month (December): 425 kWh

Energy Consumption

Total used: 9,876 kWh
From solar: 7,234 kWh (73%)
From grid: 2,642 kWh (27%)
Exported to grid: 4,011 kWh

Financial

Electricity cost without solar: $3,456/year @ $0.35/kWh
Actual cost with solar: $924/year (grid imports)
Net savings: $2,532/year

Plus export credits: $802/year @ $0.20/kWh
Total benefit: $3,334/year

Payback period: 5.5 years

What Worked

1. The Battery Changed Everything

Without battery:

  • Use solar during day
  • Export excess (paid less than import cost)
  • Buy from grid at night (expensive)

With battery:

  • Charge battery during day
  • Use battery at night
  • Only import on cloudy days

The battery increased self-consumption from 58% to 73%. Worth the extra $10k.

2. Time-of-Use Optimization

My utility has time-of-use pricing:

  • Off-peak (midnight-3pm): $0.28/kWh
  • Peak (3pm-9pm): $0.52/kWh
  • Super off-peak (9pm-midnight): $0.22/kWh

The battery targets this:

1. Charge from solar (12pm-4pm)
2. Discharge during peak (4pm-9pm) - avoiding $0.52/kWh
3. Charge from grid if needed (9pm-12am) @ $0.22/kWh
4. Discharge overnight (12am-6am)

Saved an extra $600/year just from time-shifting.

3. Outage Protection

We had 3 power outages this year (Pacific storms). The battery kept us running:

  • Refrigerator
  • Internet/WiFi
  • Lights
  • Laptop charging

Not running:

  • EV charger (too much power)
  • Dryer (ditto)
  • Air conditioning (can run but drains fast)

Peace of mind has value.

What Didn’t Work

1. Export Rates Suck

I generate more than I use (114% coverage). The excess goes to the grid.

  • Import rate: $0.35/kWh
  • Export rate: $0.20/kWh

They buy low, sell high. I “lost” $602 this year to the spread.

Solution: size your system to match consumption, not maximize production.

2. Winter Is Rough

December through February:

Average generation: 450 kWh/month
Average consumption: 890 kWh/month
Grid import: 440 kWh/month = $154

Solar is a summer game in northern climates.

3. Installation Delays

Permit approval: 6 weeks (should be 2) Utility interconnection: 12 weeks (should be 4) Total time from contract to online: 5 months

Bureaucracy, not technology, is the bottleneck.

Unexpected Benefits

Energy Awareness

The app shows real-time production and consumption. I became obsessed with:

  • Running dishwasher during solar peak
  • Pre-cooling house at 2pm (before peak rates)
  • Charging EV overnight (cheap rates)

We reduced consumption 12% just from awareness.

Blackout Indifference

When the power goes out, I get a notification. But the house just… keeps working. Lights stay on. Internet stays up.

Neighbors frantically check their phones. I pour coffee and work.

Neighbor Effect

Four neighbors installed solar after seeing my numbers. The economics are compelling when electricity is $0.35+/kWh.

Would I Do It Again?

Yes, but differently:

What I’d Change

  1. Size smaller: 6kW would match my usage better
  2. More battery: 2x Powerwalls for 27kWh (cover 2-3 days)
  3. Wait for prices to drop: Solar costs fell 15% this year

What I’d Keep

  • Battery is essential (don’t do solar without storage)
  • Time-of-use optimization is huge
  • Outage protection is worth it

The Real ROI

Financial: 5.5 year payback, then 20+ years of cheap electricity.

But also:

  • Energy independence
  • Blackout resilience
  • Reduced carbon footprint (3.2 tons CO2/year)
  • Smug feeling when electricity rates increase

Should You Go Solar?

Run the numbers:

annual_consumption_kwh = 10000  # Your usage
electricity_rate = 0.35  # Your rate
system_cost = 18500  # After incentives
annual_savings = annual_consumption_kwh * electricity_rate * 0.75
payback = system_cost / annual_savings

print(f"Payback period: {payback:.1f} years")

If payback < 8 years: probably worth it If payback > 12 years: wait for prices to drop

In California with $0.35/kWh rates? No-brainer.

In Mississippi with $0.11/kWh rates? Marginal.

One Year Later

I check the app every day. I’ve become that person who talks about their solar panels at parties. No regrets.

The future is distributed energy. Might as well get started.