Methodology

Where prices come from

Once a day we record the price of every portable power station, expansion battery, and solar-generator bundle listed on the official online stores of Anker SOLIX, Jackery, BLUETTI, and EcoFlow — the same public product data their own storefronts serve. We identify our collector honestly in its User-Agent, fetch politely (about one request per second), and store every price we've ever seen — tracking began 2026-07-07. We do not track Amazon or other marketplace prices, so our numbers describe direct-from-brand pricing only; Amazon links on product pages are provided for convenience and carry no price claims.

Cost per Wh

$/Wh = price ÷ battery capacity in watt-hours. Capacity comes from the manufacturer's own stated watt-hour rating, hand-verified per model. Bundle listings (station + solar panels) are excluded from $/Wh rankings because panel value isn't battery capacity; bundles still appear on product pages.

Rated cycle-cost estimate

Rated cycle-cost estimate = price ÷ (capacity × manufacturer-rated cycle life). Manufacturers rate cycles to a capacity-retention threshold that varies by brand (typically 70–80% remaining). A battery rated for 3,000 cycles can deliver roughly 6× the lifetime energy of one rated for 500, which list prices don't reflect. We only compute this where the manufacturer publishes a cycle rating; treat it as a comparison tool, not a lifespan guarantee — real-world cycle life depends on usage and conditions.

Price-history verdicts

Each product's current price is compared to its own recorded history:

• Building price history — fewer than 30 tracked days.
• Unusually low — at least 10% below its trailing 90-day median.
• Below recent norm — 1–9% below its trailing 90-day median.
• Normal price — matches recorded low — at the recorded low while still within the normal range.
• Normal price — otherwise within the normal range.
• Above normal — more than 10% above its trailing 90-day median.

A recorded low remains a supporting fact: it is the lowest effective price in our daily record, not proof that today's price is unusual. Verdicts require at least 30 days of history. Where a store advertises a discount from a list price, we show that advertised percentage side by side with the discount measured against the product's own 90-day median, and let you draw your own conclusions.

Limitations

• US stores and USD only, for now.
• Daily snapshots can miss flash sales shorter than a day.
• Membership-only, coupon-gated, or cart-level discounts may not appear in listed prices.
• Specifications are hand-checked but corrections are welcome — tell us if you spot an error.