How the checker works
Wi-Fi. We convert your spot into an "effective distance": the real distance plus a penalty for each wall. Wood, vinyl and ordinary glass cost about 20 ft each in our rule of thumb; brick, stone, stucco and low-E coated glass cost about 45 ft, because dense and metal-coated materials absorb far more 2.4 GHz signal. Under about 60 ft effective is usually fine, 60–100 ft is marginal, and beyond that expect drop-outs. These are heuristics, not measurements: routers, antennas and interference vary enormously, so always confirm with your phone at the spot. If a feeder's maker gives a limit (Perky-Pet says 50 ft from the router), we flag it.
Solar. We multiply the panel's rated watts by your hours of direct sun and a season factor (half in late fall and winter, when the sun is lower and days are shorter) to get a "sun index", then compare it with what reviewers reported: in partial sun MacRumors' Birdfy feeder never dropped below 90%, a wooded one hovered near 50%, and The Gadgeteer's 4.4 W Kiwibit stayed at 70–95% in Texas spring sun. We don't publish battery-life figures because makers don't measure them the same way and bird traffic changes everything.
Cornell Lab advice: feeders within 3 feet of a window (or on it) are safest, because birds can't build up speed; beyond 30 feet is also fine. In between is where collisions happen.
Close enough to shrubs or trees for birds to dash to safety, far enough that squirrels and cats can't use them as a launch pad (Project FeederWatch).
Check signal at the exact spot with your phone before mounting. Most camera feeders use 2.4 GHz only, and every wall between you and the router costs range.
A solar panel wants several hours of direct sun. A feeder in shade can sit in shade if the panel's cable reaches a sunny spot.
Check your own spot in the Wi-Fi & solar placement checker.
A worked example
The defaults describe a feeder 40 ft from the router through one wood-frame wall, with 4 hours of sun in summer. That's an effective 60 ft, right at the edge of "usually fine", so check with your phone. With a 3 W panel the sun index is 12, in line with the reviewer setups that rarely needed charging. Switch the season to winter and the index halves to 6: expect to charge it during long gray spells. Change the wall to brick and the effective distance jumps to 85 ft (marginal), so a mesh node or outdoor access point near that wall is the fix, or a feeder with a microSD slot that keeps recording through drop-outs.
More help: where to place a bird feeder camera, smart bird feeder Wi-Fi problems and do smart bird feeders work in winter?