Solar Panels vs. the Stock Market: Which Is the Better Investment in Hawaii?

A financial advisor will evaluate any investment on four dimensions: return, risk, tax treatment, and liquidity. Most solar-versus-stocks comparisons only look at return, which makes them incomplete and a little dishonest. Here is the full picture, using real Hawaii numbers.

The scenario: you have $30,000 to invest. Option A is a rooftop solar panel system on your Oahu home. Option B is an S&P 500 index fund. We track both for 25 years.

The Solar Investment

Thirty thousand dollars buys a roughly 8–10 kW system on Oahu after the Hawaii state tax credit ($5,000). That system produces approximately 12,000–15,000 kWh per year, offsetting most or all of a typical household's electricity consumption. (The federal residential solar ITC expired at the end of 2025, so these are post-expiration economics. If you add battery storage, the federal battery ITC at 30% still applies through 2032.)

At Hawaii's current average rate of about $0.45/kWh^[2], a system producing 13,000 kWh/year saves $5,850 in year one. That is a 19.5% return on a $30,000 investment. In the first year.

But electricity rates do not stand still. With a conservative 3% annual escalation — the historical average is closer to 3–5%^[6] — your savings grow automatically:

• Year 5: $6,586 saved (22.0% return)
• Year 10: $7,635 saved (25.5% return)
• Year 15: $8,850 saved (29.5% return)
• Year 25: $11,893 saved (39.6% return)

Panel degradation — typically 0.25–0.5% per year^[3] — slightly reduces production over time, but rising rates more than compensate. Your annual return actually increases every year you own the system. Over 25 years, with 3% rate escalation and 0.4% annual degradation, total electricity savings come to approximately $145,000–$155,000. On a $30,000 outlay, that is roughly 400–420% cumulative return.

The Stock Market Investment

The S&P 500 has delivered about 10% nominal annual return (roughly 7% inflation-adjusted) averaged over several decades, dividends reinvested.^[1] Here is what $30,000 looks like at 10% compounded:

• Year 5: $48,315
• Year 10: $77,812
• Year 15: $125,341
• Year 25: $325,087

The portfolio grows to roughly $325,000 — a $295,000 gain, or about 983% return. On raw cumulative return, stocks win. But that number is a fantasy until you account for what happens when you actually try to spend it.

Taxes Change Everything

Solar savings are tax-free. When you avoid a $450 electric bill, nobody at the IRS cares. You do not owe federal income tax, state income tax, or capital gains tax on electricity you never bought.

Stock market gains are taxable. Long-term capital gains face 15–20% federal tax plus Hawaii state capital gains tax of up to 7.25%.^[4] Dividends get taxed annually. After 25 years, that $295,000 in stock gains nets roughly $220,000–$240,000 after the government takes its cut.

Metric	Solar	S&P 500
25-year gross return	~$150,000	~$295,000
Taxes owed	$0	~$55,000–$75,000
After-tax return	~$150,000	~$220,000–$240,000

The gap narrows considerably. And we have not talked about risk yet.

Risk Is Where Solar Dominates

The sun will rise tomorrow. Your panels will produce electricity. HECO will charge high rates for the power you no longer need to buy. The only variables are weather patterns (which average out reliably over years) and panel degradation (which is warrantied and well-understood). In financial terms, solar has a Sharpe ratio approaching infinity — meaningful returns with near-zero variance.

The S&P 500's 10% average includes years of +30% and years of -40%. The 2008 financial crisis cut portfolio values in half. The COVID crash in March 2020 erased 34% in five weeks.^[1] A customer we spoke with last year put it well: "I lost $80,000 in my brokerage account during COVID. My solar panels kept making electricity the entire time. They did not care about the pandemic."

If you need your stock market money during a downturn, you realize those losses. Solar savings arrive every month regardless of what the market is doing.

Cash Flow, Inflation, and Your Home

Solar provides immediate monthly cash flow from day one. Your first post-installation electric bill shows the savings. You can budget around it. Stock returns are realized only when you sell (aside from dividends), which triggers taxes and reduces your capital.

Solar is a natural inflation hedge. As electricity rates rise — and in Hawaii, they rise faster than general inflation thanks to the structural cost factors — your savings increase proportionally. You do nothing. Your returns adjust upward automatically. Stocks are a mixed hedge: companies can raise prices, but high inflation often brings higher interest rates that compress valuations. The 1970s demonstrated that stocks can underperform inflation for an entire decade.

And solar adds roughly $15,000–$25,000 to a Hawaii home's resale value, according to Lawrence Berkeley National Laboratory research.^[5] That is an additional return that does not show up in the electricity savings calculation. Stocks in a brokerage account do not make your house worth more.

Where Stocks Win

Liquidity. Full stop.

You can sell stocks any day the market is open and have cash in your account within days. Solar panels are illiquid — you cannot peel off half your system when you need cash. The value comes through monthly savings or at home sale. If there is any realistic chance you will need that $30,000 back within the next 5–7 years for something unrelated to your home, the stock market offers flexibility solar cannot match.

The Right Answer: Solar First, Then Stocks

For Hawaii homeowners, the optimal strategy is not one or the other. It is sequential.

Invest in solar first. It delivers guaranteed, tax-free, inflation-protected returns of 15–20%+ annually — a risk-adjusted return no other investment available to individual households can touch. Then take the $300–$500/month you are no longer sending to HECO and put it into an S&P 500 index fund. Now you are earning both returns simultaneously.

After 25 years under this strategy, you have $150,000 in cumulative tax-free electricity savings already spent on living expenses (freeing other income), a stock portfolio built from reinvested monthly savings, a home worth $15,000–$25,000 more, and complete independence from oil price volatility.

This Math Only Works in Hawaii

On the mainland at $0.14–0.18/kWh, solar returns run 6–9% annually — competitive with stocks but not clearly superior once you account for the compound growth advantage. In Hawaii at $0.40–0.52/kWh, solar returns hit 15–25%+. At those numbers, solar is not competing with the stock market. It is in a different category entirely. The single highest-return, lowest-risk investment available to Hawaii households.

Alternate Energy Hawaii has been helping homeowners make this investment since 1993. In over 30 years, not one customer has lost money on solar. The stock market cannot say the same.