SIA Blog

What the numbers actually say about home solar

Original research and plain-English explainers on residential solar economics. We publish the method and the data alongside the conclusion.

Latest research Measured annual sunlight on a Fall River, Massachusetts roof, with the modelled panel layout outlined.

Research 26 September 202620 min read

Is solar worth it in Massachusetts? We modelled 62 real homes to find out

Massachusetts still has what California gave up: full retail net metering, the SMART incentive and a state tax credit, stacked on some of the highest power prices in the country. 61 of 62 homes come out ahead, the typical one at a 15% tax-free return. SMART adds another ~$3,400 — on the 56% of roofs that clear its 80% shading bar — and strip net metering to a California-style export rule and payback nearly doubles.

7.0 yrsMedian payback
14.7%Median return
55/62Rated good
Measured annual sunlight on a Lancaster, California roof in SCE territory, with the modelled panel layout outlined.

Research 20 September 202618 min read

Is solar worth it in SCE territory? We modelled 67 real homes to find out

Every one of 67 Southern California Edison homes came out ahead — not most, all. The surprise is the tariff: SCE moves new solar customers onto TOU-D-PRIME, and on that rate the typical home pays back in 5.0 years at a 21.4% return, close to the old NEM 2.0 regime everyone says was killed off. A battery paid back on none of them.

5.0 yrsMedian payback
21.4%Median return
67/67Rated good
Measured annual sunlight on a Santa Ana, California roof in SCE territory, with the modelled panel layout outlined.

Research 20 September 202615 min read

Solar when you can’t pay cash: what a lease or PPA is really worth in SCE territory

We found a price line for lease and PPA deals in PG&E territory. Does it travel? We modelled 29 homes in low-income Southern California Edison neighbourhoods to find out. It does not. SCE households can afford to pay more than PG&E ones and still come out ahead — and the deal they are typically offered is priced at three times what the system costs to finance, a worse markup than PG&E customers see.

−43%Solar’s value on CARE
11.5¢PPA worth signing
2.4×What you’re offered
Measured annual sunlight on a Stockton, California roof in PG&E territory, with the modelled panel layout outlined.

Research 20 September 202615 min read

Solar when you can’t pay cash: what a lease or PPA is really worth in PG&E territory

Most solar advice assumes you can write a cheque for $14,000. We took 29 homes in low-income PG&E neighbourhoods and asked what “no money down” is actually worth. Being on CARE cuts what solar saves you by 45%. And there is a price line for a lease or PPA: just below it, 28 of 29 homes come out ahead; a third higher, only 8 do. The deal most people are offered sits on the wrong side.

−47%Solar’s value on CARE
10.7¢PPA worth signing
28/29Work at that price
Measured annual sunlight on a Richmond, California roof, with the modelled panel layout outlined.

Research 8 September 202621 min read

Is solar worth it in PG&E territory? We modelled 56 real homes to find out

California gets a quarter more sun than Illinois and charges nearly twice as much for electricity. Every one of 56 roofs came out ahead even after NEM 3.0, and 24 cleared our bar for a good investment. What you pay the installer can add two and a half years to the payback. Every roof measured individually, nothing hand-picked.

10.4 yrsMedian payback
9.3%Median return
24/56Rated good
Measured annual sunlight on a Peoria, Illinois roof, with the modelled panel layout outlined.

Research 7 September 202625 min read

Is solar worth it in Illinois? We modelled 46 real homes to find out

Every house outside the most-shaded quarter came out ahead. Illinois Shines carries the result almost single-handed — and leases and PPAs now leave the typical household worse off than doing nothing.

10.1 yrsMedian payback
8.6%Median return
20/46Rated good

Explainers

Explainers & method

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