Solar water heaters | when they work best (Effects of weather)

Solar water heaters work best when installed with the solar panels facing the sun for the longest part of the day.

In the US and Canada, you want your solar water panels facing south – with no obstacles or as few as possible.

The brighter, clearer it is, and the more hours of sunlight you receive during the day, the more hot water your solar water heater will provide.

In this post, you will know when your solar water heater works best and what to do when the weather is not conducive for your water heater.

How night time affects the performance of solar water heaters

Solar water heaters need sunlight to heat water. During the night, your solar water heater is not able to heat water
using the sun’s energy anymore.

In this case, the solar water heater provides you with hot water heated during the day and kept hot in its well-insulated tank.

(Note: more and more solar water heaters now have an inbuilt electric element as a backup to heat water should your water temperature not be as high as you selected)

To have enough water during the night,

  • Select a solar water capacity (panels and storage tank) that is large enough for your family size and can heat the water hot enough for the sunlight hours your location receives
  • Install your solar water heater panels in locations to minimize shadows (ideally no shadows)
  • Get a solar water heater with an electric backup element or have a gas or purely electric heater as a backup.

How winter affects solar water heater performance

Yes, your solar water heater will still heat water during the winter months but it will not be as hot as during the summer.

This is because you generally have fewer hours of sunlight, lower air temperatures, and in some cases snow covering your panels during winter.

Note: solar panels are usually mounted angled so that the snow can slide off on its own).

To get as much hot water during the winter months

  • Always have an alternative water heating source to supplement your solar water heater. This could be an electric or gas-powered heater.
  • Clear any snow that may have piled up on your panels, if you can do so safely.

How solar water heaters perform during cloudy weather

Cloudy weather reduces the amount of sunlight reaching your panels.

Therefore your solar water heaters will not produce as much hot water with cloudy weather as during the bright, clear day.

To ensure that you have enough water during cloudy weather

  • Get a solar water heater with an electric backup element or
  • have a gas or purely electric heater as backup for those days when your water is not as hot as desired.
  • If aesthetics is not a deal breaker for you, use evacuated tube solar water heaters instead of the flat panels heaters.

Whereas the flat panel collectors tend to be preferred by more people because they blend nicely with the roof, the evacuated tube solar water heaters are more efficient collectors of heat energy.

The angle of orientation of the tubes is not as critical to how much hot water is generated as is the case with the flat panel solar water heaters.

How well solar water heaters work during the rainy season

During the rainy season, your solar water heater will still be able to heat water but not as much as during bright clear days.

This is because the clouds restrict the amount of sunlight reaching your solar water panels.

What to do about it:

  • Always have an alternative water heating source to supplement your solar water heater. This could be an electric or gas-powered heater.
  • If aesthetics is not a deal breaker for you, use evacuated tube solar water heaters instead of the flat panels heaters.

In summary, solar water heaters work best during bright, clear sunny days. Your solar water heaters will not provide as much hot water during winter, cloudy or overcast, or rainy weather.

To prepare for this, it is advisable to have an alternative water heater using electricity or gas. Also if aesthetics is not a big issue for you consider using an evacuated tube solar water heater instead of the flat panel solar water heaters.

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