The Best Choices for Heating Your Solar Home | And The Worst!

March 17, 2015 · 15 comments

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The largest energy consumer of any home-built in the northern hemisphere is the heating system.

Designing the correct heating system is critical in the success of the off grid home. Build it wrong and nothing else will matter. Almost all heating systems require some form of electricity to operate whether it for the fans (oil, wood or gas hot air furnace), circulating pumps (oil, wood or gas boiler), thermostatic and safety controls (almost every system) or auger (wood pellet stove). The worst part is this extra electricity is needed most when the days are the shortest and the sunshine is scarce. Check out our favorite heating system.

Heating the Soar HomeHeating systems in “off the power grid” homes are often the weak link in the system. The conventional “plumbing and heating” installer will insist there is only one way of doing things and try to force you into following the building codes.

Unfortunately the building codes are often outdated, unrealistic and will not work for the solar-powered home.

First, there are a few heating options that are NOT AVAILABLE  for the off grid home.

  1. Electric Heat
  2. Oil Furnace/Boiler
  3. Heat Pump/Geothermal

The above heating methods are out of reach for 99% of those deciding to live off of the grid. They require far too much electricity.

Using electric heat is not practical for the solar home.Electric Heat

Using electric space heaters, baseboard heaters, boilers and/or low wattage under floor radiant heating systems consume HUGE amounts of electricity. Any heating load, whether an electric heater, a hot water heater or electric range, is too large to even consider for all but a few off the grid homes.

If you are planning on making your own electricity using solar panels, wind turbines or a gas/diesel generator it is impossible to make enough electricity to power heat loads (resistive loads). There may be times when you have enough electricity to operate a heater as in a dump load but the extra power is usually in the summer.

The one exception is the home owner fortunate enough to have a massive resource of falling water. A micro hydro powered home might be able to operate some electric heat as a dump load but it is very rare.

oil boilerOil Furnace/Boiler

Although heating oil is the primary source of heat in the above heating systems there are also some large electrical requirements as well. Oil burners use high pressure pumps to force the oil through a fine nozzle to vaporize the oil enough to burn efficiently.

They also use electricity to ignite the fuel and a fan to make a clean and aggressive flame. In addition to the boiler, there is either a large fan (furnace) or circulating pumps and zone valves (boiler) to move the heat where it is most needed.

Last but not least, is the thermostatic and safety controls which are usually operated with  transformers that consume energy 24 hours per day. Anything that uses electricity 24 hours is of particular concern for the solar home. Some solar power systems are designed to sleep at night in an attempt to conserve electricity until it is required, as in the case of a light being turned on or the refrigerator compressor starting.

The thermostatic controls/safety controls will keep the system awake at night (phantom load) draining the batteries/battery bank.

Heat Pump/Geothermal

Although geothermal heating systems are very efficient by today’s standards, they are not suitable for the typical off grid home. A good heat pump system will consume about 1/3 the electricity an electric heater will use.

heat pumpA small well insulated home might use 1500-2000 kWh per month just for electric heat. To heat that same home with geothermal, 500-667 kWh will need to be generated per month. If your electricity is produced with solar modules you would need to purchase another 16000-22000  watts of solar ($16,000-$22,000) and up to 52 more batteries (Trojan L16 – $15,600))  just to run the heat pump system. These numbers are based on getting 1 sun hour per day in December and January. It is just not affordable for the average homesteader. Just like electric heat, you might be able to operate a heat pump with a large water turbine. For the rest of us, we will need a less electricity dependent heating system.

UPDATE AUGUST 2015: As solar modules are getting less expensive and some homes are super insulated it is possible to heat your home with a heat pump. It will still cost a lot up front but it is possible for some.

What are the good choices for heating a solar home?

As our electricity consumption needs to be as low as possible, we will need to do things differently than our neighbors. Even something as insignificant as a circulating pump and some zone valves can use more electricity than we can spare.

The most obvious options are:

Solar Hot Water

At first it might seem like solar hot water is the obvious choice for heating your renewable energy home.

solar heaterIt is green, renewable and downright sexy but also very expensive, high maintenance and complicated. It is one thing to install a photovoltaic module, run some wire and connect to a charge controller. It is a whole different process for solar heating. Solar hot water collectors are often heavy, fragile and cumbersome to mount. Installing the plumbing, controls, heat exchangers, hot water storage tanks, pumps and thermostats is beyond the scope of the average homesteader. Not to say it can’t be done. It is just more than the average do-it-yourself homesteader will be ready for.

There are also major considerations such as:

  • How many sun hours will I get per day in the middle of winter?
  • How large of a storage tank will I require?
  • Will I need to use a double wall heat exchanger or will a single wall meet code approval?
  • How many collectors will I require?
  • How will I keep the heat transfer fluid from freezing?
  • Should I design a closed loop, open loo, drain-back, direct or indirect system?
  • What will I do if the sun doesn’t shine for a a day, a week, two weeks?
  • What am I going to do with the abundance of hot water I generate in the summer?

The biggest problem with a solar hot water heating system that it is required the most when it is able to produce the least.

In the middle of January, the sun rarely shines while it is one of the coldest months of the year. In the east coast of Canada we average 1 sun hour per day in late December and early January.

Undoubtedly you will need some type of ‘backup heating system for those cloudy days or very short days. Even though it is possible to design a solar hot water heating system that will work flawlessly and completely, it would be unwise to not incorporate some type of backup system. More about solar hot water to come later.

UPDATE AUGUST 2015: I have seen a few solar hot water systems that were able to provide 100% of the heat for large homes in the New England States as well as in Canada. Each of these systems cost well over $100,000 and were massive, containing up to 20 hot water collectors and storage tanks as large as 1600 gallons(6000 liters). One in particular has been operating for over ten years and the water in the storage tank (according to the owner) has never gone below 190 degrees F (88 degrees C). Pretty impressive but out of reach for me and most other homesteaders.

Wood

Burning wood is by far the most common heating method for the solar homesteader. Wood is hard work and dirty but most folks who decide to live off the grid are not deterred by a little work and dirt.

wood heatThe simplest wood heating system with the lowest electricity  requirement is the common wood stove. The majority of wood stoves operate with no electricity or fancy controls making them ideal for renewable energy homes. However they might not be the best choice as they only heat a small area, can be very inefficient and require the addition of firewood constantly.

Other options include the wood hot air furnace (fan uses a huge amount of electricity), indoor and outdoor wood boiler (go here for efficient circulating pump setup), pellet stove (auger and fan consume a lot of electricity) and rocket stove/rocket mass heater (impossible to get building code approval).

Propane/Natural Gas

Polaris propane or natural gas hot water heater / boiler.The beauty of gas is the ease of handling and the ability to store massive amounts on your property with little effort. If you are living off the grid, you will likely use gas for cooking and/or hot water. Adding a propane/natural gas heating system is the logical next step. There is a lot of variety when looking for a gas heating system. Some are good, while some are horribly inefficient.

If you go to your local home improvement store and buy the cheapest propane heater you can get you should expect an efficiency of about 50%. For every liter of propane you purchase and consume, one half goes into home heating and the other half goes out the chimney.

The better option is purchasing a high end propane boiler/water heater like the Polaris made by American Water Heaters, USA. It boasts an efficiency of 96%.

You can quickly assess the efficiency of a gas heater by looking at the chimney or venting system. If the gas heater requires a steel vent or full blown chimney, you can expect it to waste a lot of propane/natural gas. If it is vented by a small plastic (ABS or PVC) vent you can be pretty sure it will be efficient. Less heat going out the vent means more heat in your home.

Propane/Natural gas heating systems can be hot water boilers(like the Polaris) , hot air furnaces (van uses a lot of power), water heaters, vented space heaters, fireplaces and non vented space heaters (most require no electricity and are 100% efficient). The efficiencies can vary widely between any of the above heaters except the non vented space heater. As it is non vented, all of the heat stays in your home making it as close to 100% efficient as possible. Check out the different propane/natural gas heating systems before making a decision.

Wood Pellet

Pellet stoves are not often talked about but they do have their place in the off grid home. They are very reliable, a lot cleaner than firewood, fairly efficient and able to be operate for long periods of time between fill ups. One of the problems with the pellet stove in the off grid home is the amount of electricity required for operation. The auger, ignition system and fan all use electricity. You must get all the details before purchasing your pellet stove. Some do not require much electricity and can operate in the event of a power outage. Some use a huge amount of electricity as their glow plug ignition system operates constantly using up to 1000 watts the whole the unit is operating.

pellet stoveMost wood pellet stoves take inside air for combustion of the pellets. This can be a problem as it is taking warm air from your home and dumping it outside. The air removed will be replaced with cold outside air making your home harder to heat. In a small, tight home (like an energy efficient off grid home) this can rob your home of oxygen. Fortunately you can get a pellet stove such as a Harman that uses outside air for combustion.

There is even a wood pellet stove (Harman PC45) that can burn many fuels including wheat, corn, cherry pits, sunflower seeds and others. Choosing the best wood pellet stove for your solar home can be a challenge.

Contact a reputable dealer and get a spec sheet before you make any decisions. You can even call the manufacturer to get the power requirements while the unit is operating and while it sits dormant. Some pellet stoves are a phantom load.


We need to think outside the box.Now we are getting away from the traditional home heating systems.

As off grid homesteaders we always need to think outside the box. We cannot waste energy like our neighbors. It is too precious and too expensive to make our decisions lightly.

Biomass

Biomass might be an option when designing your solar/off the grid home. It is relatively new and mostly misunderstood. The term biomass heating refers to generating heat from living organisms. Most of the time the living organisms are plant based as in wood chips, compost, corn, grains etc. However some biomass energy might be gathered from animals as in the collection of methane from cows. Sounds easier than it is!

Some of the simplest biomass heating systems are nothing more than a pile of manure, leaves, sawdust and small sticks with multiple coils of pipe inside use to heat water or a pile of compost inside a green house constantly generating heat.

Biomass heating system using compost as your heat source.

We are in the research and testing phase for a few types of biomass heating systems. As we get more facts and prove more concepts we will update our biomass home heating page.

Hybrid Generator Systems

The last form of heating system we will mention here is the hybrid generator heating system. Most of us will need to rely on a generator for electricity production at some point in time. Some of us have long periods without sun or very short days in the winter. A generator is just a fact of off grid life. One of the problems with a combustion engine generator is the poor efficiency. A large amount of fuel is consumed to make a small amount of electricity. In fact most of the fuel is turned into heat instead of electricity. A hybrid generator system captures that lost heat and uses it to heat your home.

Generator's waste a lot of heat that can be captured with a heat exchanger.

The most common method of capturing the heat is by rerouting the cooling system from the radiator to a heat exchanger like the one shown above, and from the heat exchanger to your home. The other method of heat capturing is by making a heat exchanger for your exhaust pipe and directing that heat into your home. The above heat exchanger would work for exhaust as well. Some systems do both.

We have seen homes that are making up to 50% of their home heating by simply recovering the heat from the fossil fueled generator. It makes sense and is not that hard to setup.

Leave a Comment

{ 15 comments… read them below or add one }

Dennis August 14, 2015 at 11:13 pm

I think you have made an error stating 500-667 kwh per day consumption by a heat pump this kwh is a month’s consumption. If for example we assume that a 12kw geothermal heat pump with an efficiency factor of 6 then the most electricity needed is 12/6*12 hrs=24kwh per day or 720 kwh per month. Are my assumption wrong?. Thanks

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Jody Graham August 15, 2015 at 10:56 am

Hi Dennis,
Thank you for pointing that out. You are completely correct. It should have stated 500-667 kWh per month for our particular example. It is now corrected and thank you for showing me my mistake. Take care…Jody

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Luke August 7, 2013 at 9:45 pm

What about solar heaters. You can buy them or make quite easily yourself. They could be passive or active systems.

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Lionel June 12, 2013 at 1:00 pm

Yes. There are 2 ways to do it.1. Off the grid. You buy it, you make it, you store it, you use it. Pro: you’ll still have lights in a bucokalt.Con: If you don’t make enough you sit in the dark. 2. On the grid. You have the equipment to generate power that is then sold to the power co. for storage and sale. They in turn sell you power. You have 2 meters, what you generate turns backward and what you use turns forward, you hope they net to 0 at the end of the month.Pro: you don’t need to have the storage on site (batteries) and the power co. will usually give you a partial subsidy for the equipment.Con: dependent on the grid.

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SolaCanadian March 18, 2013 at 12:20 am

Can I just say what a relief to find someone who in fact knows what theyre talking about. As an off gridder I have had many struggles trying to keep my home warm in the long cold winters in Canada. My home was designed by a so called “solar expert” but he made a heating system I couldn’t possibly run on my small solar system. Thanks for the good info…

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Tim Plearing March 17, 2013 at 11:39 pm

I am building an off grid home in the spring. You say electric heat is out of the question. Does that mean I can’t make any electric heat? Can I use a small space heater? What about a hair dryer? thanks…

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Jody Graham March 18, 2013 at 12:02 am

Hi Tim, thanks for your comments. It really is out of reach for most to operate heaters from solar PV. You might be able to run a space heater but keep in mind that a heater is required when there is very little sun. We use a 1500 watt heater as a dump load (we will adding info on dump loads soon) in the spring and fall when we have extra solar power. A hair dryer is fine as they are usually only operated for 10-15 minutes instead of hours like a space heater.

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Dilmervarteri March 17, 2013 at 4:58 pm

I believe that you should try your hardest to get away from fossil fuels instead of recommending propane or natural gas. I do really enjoy your website, I just think fossil fuels should be avoided. Cheers

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Juan June 12, 2013 at 9:17 am

Of course. Our house is on eteclric, powered by a 5kw solar system. The AC, dryer, refrigerator, water heater is all eteclric. Our heat is from a wood stove, but we could put in a whole house eteclric heating unit if we wanted. No problem. I don’t know much about wind energy, but I know a house can be powered solely by solar power. Putting in wind power would be another expense.You would have to pay up front, when the house is bring built, but the monthly costs would be next to nothing (depending on whether you’re hooked up to your eteclric company’s grid versus on rechargeable batteries out eteclric company changes us about $6/month for the privilege to be hooked up to their system).

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Jody Graham July 30, 2015 at 12:14 pm

Hi,
I agree. I dislike fossil fuels as well but we are addicted to them. Other than wood (which is getting harder as insurance companies do not like wood heat and many cities ban them because of the smoke pollution) we do not have much else. Solar heat is out of the range of most folk’s budget unfortunately. And in areas like Canada there is very little sun when the heat is needed most. It is easy to criticize each other for our use of fossil fuels but unless we go back to the stone ages (or subsidize renewable energy technologies like we do fossil fuels) we need fossil fuels. And I repeat, I do not like fossil fuels either. That is why my home is off the power grid (our grid is fueled by the dirtiest crude you can buy) and I do everything I can to minimize our use like driving a small hybrid car as much as I can with four children. Thanks so much for your comment.Jody

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GoingOffGrid March 15, 2013 at 4:06 am

Your blog is one of the best ones I found for good solid off grid information. I am building a homestead off the grid and will definitely be watching your website daily for updates.

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Jody Graham March 16, 2013 at 10:32 pm

Hi,thanks for the compliment. We do our best and we make lots of mistakes. If you ever need any advice please don’t hesitate to ask. Or if you discover something I don’t know please share.

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JSMfather March 15, 2013 at 2:34 am

Rather nice post, I absolutely love this site. Keep up the great work. It is hard to find info from real world solar expert and not someone who read a book or blog and thinks they’re an expert. I will keep recommending you!!!

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Jody Graham July 30, 2015 at 12:17 pm

Thank you so much for your comment. Thank you so much for your recommendation. We are trying our best to learn to live within our means and reduce our own impact on the earth and I must say we are failing. I like to live comfortably and drive a car and even fly in an airplane to Haiti once in a awhile. I consume more fossil fuels in one flight than most people in the world use in their lifetime. We are trying to get better though and there are so many others trying as well. Thanks again…Jody

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Solarman1399 March 12, 2013 at 2:53 am

I’m impressed, I must say. Honestly rarely do I encounter a weblog that is both educative and entertaining, and let me tell you, you’ve got hit the nail on the head. Everywhere I look I see the same generic info on home heating. It is nice to find someone who has experience with the challenges of living off the grid.

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