Solar Hot Water Heaters: Will They Work In The Winter?


For years I have been living off grid with Solar Hot Water Heaters as a primary source for heating water.  Through the cold winters of Vermont to months of rain in Hawai’i, I have used Solar Hot Water Heaters in some pretty adverse conditions.  If you have been wondering if Solar Hot Water Heaters work in the winter, you’ve come to the right place.

Solar Hot Water Heaters do work in the winter, but their efficiency is drastically reduced.  A properly designed solar hot water system can produce as much as 100% of your hot water in the summer, but that number can drop down to less than 25% during a really bad winter.

Luckily, there are ways that you can increase the efficiency during those long winter months to boost the performance of your water heater, just don’t expect it to do the job all by itself.

How Well Do Solar Hot Water Heaters Work In The Winter, Really?

Before I answer that question, you have to understand that Solar Hot Water Heaters can produce up to 60%-80% of the average household’s hot water needs for a year.  In Hawai’i, that’s a savings that can add up to a $1000 a year! Paying for itself in only 4 years time.

Solar hot water panels can produce all of your hot water in the summer, but that amount is cut dramatically in winter months.  It can still heat up during the winter on the sunniest of days, but the increased cloud cover and colder weather makes it much more difficult.

That is why a solar hot water heater is typically installed with a backup conventional water heater or on demand water heater when the water just can’t heat up.

My winters can be wet on my off grid homestead.  We average 150” of rain per year.  Sometimes it will rain for a month straight.  It’s hard for my Solar Hot Water Heater to heat up the water.  On some days the sun might creep out and heat the water up a little bit, but mostly it’s up to my little propane on-demand water heater to get the job done during those winter deluges.

This was the same when I lived in Vermont.  In fact, the system had to be designed with a separate mechanical heater line that ran coolant through the panels so that the water wouldn’t freeze.  For the most part, our water was heated by an on demand water heater as well.

There are some strategies to increase the efficiency of your solar hot water system that can extend the length of time hot water can be stored for those long cold spells.  I’ll expand upon that below.

Factors That Can Turn Your Solar Hot Water Heater Useless In The Winter

When it comes to heating water in the winter, solar hot water panels don’t perform very well.  This is because of a couple of factors:

  • The winter sun is lower in the sky, leading to indirect solar energy hitting the panels as opposed to directly, taking longer to heat up water.
  • The winter is typical of increased cloud cover and colder weather.  The sun just isn’t out as often.
  • Because of the cold weather, the water will be colder, adding to the inability for solar hot water panels to perform at peak levels.

If we can address some of these factors, we could make our solar hot water panels achieve optimum performance.


Make Your Solar Hot Water Heater Perform Better During The Winter

We can utilize a couple strategies to make our solar hot panels work better during the winter months.  These may not give us panels that heat water 100% of the time, but it will get us closer.  I don’t know about you, but I like the challenge of trying to get the best out of what I got.

Well Insulated Supplementary Hot Water Tank

You know those hot water tanks you find in a house behind some random door?  You can get an oversized version of one of those, locate it in a super insulated room while also adding insulation to the tank and connect it as a storage tank for the water heated by the solar hot water panels.

This can allow water heated on a Saturday, last until the following Saturday.  If it takes a week before the sun comes out again where it as able to heat the water, you’ll be ok because it’s still nice and hot, stored in your tank.

Use Well Water In The Coldest Climates 

Where water temperature drops below 55 degrees on a regular basis, you can help your solar hot water panels out by pumping well water through the system as opposed to water coming from near surface sources.

Water from a well is typically 55 degrees, but water from a surface water source can be much colder.  In the coldest places, the water might be freezing, but deep down in the ground your well water is nice and cozy at 55 degrees.

By utilizing the well water, you start the water off circulating at a higher temperature than from other sources.  Now our solar hot water panels can get that water to optimum temperature levels faster.

To take this one step further, install a storage tank with a heat exchanger.  Pump well water out of the ground to your storage tank, the water gets heated up a little more through the heat exchanger then gets to the panels at an even higher starting temperature.

Borrow Heat From Your Solar Panels

If you happen to have solar panels in addition to a solar hot water heater, you may be able to try this trick.

Solar panels put out a bit of heat as the convert the suns energy into energy we can use.  If we locate our solar hot water panels closer to our solar panels wherever the heat signature is higher, we can borrow some of that heat to help give our solar hot water panels a boost.

This won’t amount to too much, so don’t go reconfiguring your entire system, but you may get an extra couple of degrees, which is nice.

My Favorite Solar Hot Water Panel

I’m not going to beat around the bush, I like the SunBank Solar Hot Water Heaters. 

They are really easy to install, with basic plumbing skills you will have no problem. 

It has no moving parts, so there’s less to break.

The water heats up fast.  In fact it did it’s job so well that on a hot sunny day, I had water that was too hot in very little time.

Lastly, they’re easy to buy.  Just a simple visit over to Amazon and you’ll have a Solar Hot Water Heater delivered straight to your door.  They just make everything easy.

Best of all, it comes with a 10 year warranty.

Sean Jennings

Sean has been living simply Off-Grid in Hawai'i for over 18 years. He lives debt free on Hawai'i Island with his family and over 40 chickens. When he's not tinkering around the homestead, he's off exploring the shorelines for fish & surf.

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