Hot tubs consume a lot of energy and you might want to explore the possibility of solar water heating as a standby. It can not only reduce energy bills but also help you contribute to reducing carbon emissions. Solar power can be converted into electricity using Photovoltaic (PV) cells and this electricity can be either stored in batteries or used immediately for heating water or operating the water pump.
Alternatively, you can use a solar collector that heats water in a series of small diameter pipes in the collector. While the heated water in the collector rises to the top of the hot tub, the colder water at the bottom flows down into the collector. This constant circulation can provide hot water for the tub when sunlight is available.
By using thermally insulated hot tubs and hot tub covers that reduce heat loss, the water in the hot tub can be kept warm for longer periods.
In places where sunlight is not continuously available, it might be impractical to depend entirely on solar power. Hence, the solar option typically involves separate plumbing. The original hot tub system powered by conventional electric power is retained and the solar powered system is used as a standby.
You can look around for pre-plumbed solar water heating panels that can be used with your existing hot tub. For example, your existing water pump will pump the water through the collector, where the water is heated, and return hot water to the tub through the outlet. Models that allow several heaters to be linked together to provide additional heating are also available.
PV panels that generate electricity that can be used to power even your pump that circulates the water through the solar heater. Going even beyond, solar energy can be used to power UV bulbs that sanitize your water and the jets that provide the great hot tub experience. While these might be off the mainstream for now, solar water heating is a feasible and even cost effective solution worth exploring.