You want a portable power station that keeps your gear running for years, not one that dies after two seasons. Buying the right capacity upfront means you only buy once.
Tech companies drop new models on a predictable cycle, which is good news for your wallet. When the latest version hits stores, last year's model gets marked down even though it does the exact same job.
That intro window is a firm deadline, not free money. If you still have a balance left when those 15 months run out, you will get hit with interest on the original amount.