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 Manufacturing GmbH are grantors. As of March 31, 2025 and December 31, 2024, such custodial accounts also included noncurrent restricted cash and cash equivalents balances of $2.8 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 three months ended March 31, 2025, we purchased $5.0 million of restricted marketable securities as part of our ongoing management of the custodial accounts.

See Note 8. “Fair Value Measurements” to our condensed 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 March 31, 2025 and December 31, 2024 (in thousands):


	As of March 31, 2025
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
U.S. debt	$	144,193	$	—	$	31,145	$	113,048
Foreign government obligations	63,972		—		13,380		50,592
Supranational debt	30,287		14		2,183		28,118
U.S. government obligations	24,344		—		5,547		18,797
Total	$	262,796	$	14	$	52,255	$	210,555


	As of December 31, 2024
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
U.S. debt	$	144,652	$	—	$	35,497	$	109,155
Foreign government obligations	62,595		—		13,571		49,024
Supranational debt	25,351		—		2,542		22,809
U.S. government obligations	24,368		—		6,220		18,148
Total	$	256,966	$	—	$	57,830	$	199,136

As of March 31, 2025, the contractual maturities of these securities were between 6 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.