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Note 6. Restricted Marketable Securities (Notes)
 12 Months Ended
Dec. 31, 2025
Debt Securities, Available-for-Sale, Restricted [Abstract]  
Restricted Marketable Securities
6. Restricted Marketable Securities

Restricted marketable securities consisted of the following as of December 31, 2025 and 2024 (in thousands):
20252024
U.S. debt$115,350 $109,155 
Foreign government obligations54,156 49,024 
Supranational debt28,276 22,809 
U.S. government obligations19,390 18,148 
Total restricted marketable securities$217,172 $199,136 

Our restricted marketable securities represent long-term investments to fund the estimated future cost of collecting and recycling modules covered under our solar module collection and recycling program. We have established a trust under which funds are put into custodial accounts with an established and reputable bank, for which First Solar, Inc.; First Solar Malaysia Sdn. Bhd.; and First Solar Holdings GmbH are grantors. As of December 31, 2025 and 2024, such custodial accounts also included noncurrent restricted cash and cash equivalents balances of $6.9 million and $5.0 million, respectively, which were reported within “Other assets.” Trust funds may be disbursed for qualified module collection and recycling costs (including capital and facility related recycling costs), payments to customers for assuming collection and recycling obligations, and reimbursements of any overfunded amounts. Investments in the trust must meet certain investment quality criteria comparable to highly rated government or agency bonds. As necessary, we fund any incremental amounts for our estimated collection and recycling obligations on an annual basis based on the estimated costs of collecting and recycling covered modules, estimated rates of return on our restricted marketable securities, and an estimated solar module life of 25 years, less amounts already funded in prior years. During the year ended December 31, 2025 and 2024, we purchased $5.0 million and $7.9 million of restricted marketable securities, respectively, as part of our ongoing management of the custodial accounts.
See Note 11. “Fair Value Measurements” to our consolidated financial statements for information about the fair value of our restricted marketable securities.

The following tables summarize the unrealized gains and losses related to our restricted marketable securities, by major security type, as of December 31, 2025 and 2024 (in thousands):
 As of December 31, 2025
Amortized
Cost		Unrealized
Gains		Unrealized
Losses		Fair
Value
U.S. debt$142,790 $— $27,440 $115,350 
Foreign government obligations67,091 — 12,935 54,156 
Supranational debt30,123 59 1,906 28,276 
U.S. government obligations24,274 — 4,884 19,390 
Total$264,278 $59 $47,165 $217,172 
 As of December 31, 2024
Amortized
Cost		Unrealized
Gains		Unrealized
Losses		Fair
Value
U.S. debt$144,652 $— $35,497 $109,155 
Foreign government obligations62,595 — 13,571 49,024 
Supranational debt25,351 — 2,542 22,809 
U.S. government obligations24,368 — 6,220 18,148 
Total$256,966 $— $57,830 $199,136 

As of December 31, 2025, the contractual maturities of these securities were between 5 years and 14 years, and restricted marketable securities with unrealized losses had generally been in a loss position for a period of time greater than 12 months. The unrealized losses were primarily due to increases in interest rates relative to rates at the time of purchase, and, based on the underlying credit quality of the investments, we expect to hold such securities until we recover our cost basis.