Cheapest way to heat up a pool?

[arold]

What about using evacuated glass? And trickle feeding the pool With a small dc pump?

[J.P.M.]

What about using evacuated glass? And trickle feeding the pool With a small dc pump?

Too much $$. Too high tech to make economic sense. Wrong application for evac. tubes. Evac. tubes can provide temp. approaching process heat applications like + 100 deg. Match the tool to the task. Bottom line: Start with a pool cover, use it and see the results. Then, get made for purpose pool water heaters for the remainder of the load as you see fit. Easiest, cheapest and probably most workable solution.