I want to eliminate the long wait for hot water in my kitchen. I've ruled out a tankless unit there, so it's between a small storage-tank unit (6-12 gallons), or a recirculating pump (between the main 50 gallon conventional electric unit and the 20ft-distant kitchen).
Energy usage is my main concern, and that energy goes to one of three places: hot water used, hot water stranded in pipes after the faucet is turned off, and heat lost into the environment. Seems the first two are the similar for both the tank-style and the circulation pump. Heat loss is related to the surface area through which heat is lost (the tank surface area, or the surface area of the recirculation loop piping, since the pump essentially extends the surface area through which heat is lost), the temperature differential (hot water versus ambient), and the R-value (of the tank jacket, or of the piping). I wrote a little spreadsheet. For (both cases) a 60-degree temperature differential between the hot water and the ambient crawlspace, and R-8 insulation, a typical small tank has losses equal to about 22 watts, and a 20ft round-trip 1/2" pipe has a loss of about 12 watts. That's not much difference: less than $10/year at 10cents per kwh, or 100-200 pounds of carbon for typical electricity. Also, the pump uses some electricity - though of course it can be turned off a lot of the time with a timer, whereas even a turned-off tank heater is losing energy as the water cools off when the timer is off.
Also, the pump seems like more complexity, noise, and proneness to failure, and fairly similar in price.
Is my energy-efficiency analysis correct ? Are there other factors to consider ?