Is Heating with Wood Economical?
Heating with wood is supposed to be good – it uses renewable energy and is economical. Wood is cheap – but is it?
Heating with Wood – Benefits:
- Renewable resource
- Reduces use of fossil fuels
- Can be easily available
- Can be a cheap source of energy
- May require less equipment
- Lower installation costs
Heating with Wood -Disadvantages:
- Safety – fire and carbon monoxide.
- Tree felling can be dangerous
- Wood can be difficult to find
- Cost – if wood is purchased
- Time to cut, split, stack and cart
- Pollution from smoke – inside home and environment
- Not automatic – wood must be constantly added to stove / furnace
- Large area required to store wood
- Investment in equipment
Many people embarking on a minimalist adventure or considering moving into a tiny home and being self sufficient think of wood as a heat source. If you have not had the experience of heating a home with wood it is easy to imagine the rustic lifestyle, the feel-good effect of using renewable energy, the heady aroma of wood smoke wafting through your home. The thought of being bathed in waves of heat in front of a glowing fire in an open fireplace or wood stove on a cold winter’s night is the stuff of old Christmas stories. It sounds magical and it can be.
However, the reality can be quite different.
Living in a cold part of North America, I have been heating with wood for 14 winters. I have some experience of both the benefits and disadvantages. For several reasons, I have not yet made the transition to a tiny home. I live in a big farm house built in 1902. Although it has been fitted with modern double glazed windows, it is not well insulated.
There is a combined wood / oil furnace in the basement which heats the house by circulating warm air through ducting and registers in the same way as a natural gas or propane fuelled system.
How Much Wood is Needed?
I am often asked how much wood I burn each year. I have never taken the time to calculate it exactly until now. The amount of wood I cut and prepare is dictated by the time available and the weather conditions in spring and fall. I cut, split and stack as much as I can in the hopes that I will have enough for the next winter with more left over to dry for the following year.
Up until two years ago that somewhat unscientific system worked well. Neighbours who do not burn wood often ask me to take away fallen trees. Others need trees removed during the summer. For the last two summers, much of my time was taken up with helping my younger son start a vegetable business. I did not spend enough time cutting wood.
There is always the option of using oil. However, it is expensive. To reduce the consumption of fossil fuels, I use as little as possible. I set the oil thermostat to cut in at 15C. Then I know if I will be away the house will not freeze without wood being put in the furnace every 4 hours. In the 14 years in this house, the oil tank has only been filled twice. It’s still over one quarter full. The oil option is great for emergencies and a quick warm up on a very cold morning if I do not get up in the middle of the night to add wood.
Energy Requirement for Heating a House
Using data from calculator.net we can determine the amount of energy in the form of heat we need to maintain the temperature of a volume of 10 000 cubic feet (1000sq. ft floor area x 10ft ceiling). The amount of energy needed depends on the difference between the ambient and required temperatures.
In South Western Ontario where I live, we have many nights when the temperature drops to -15C (5F). Already this winter we have seen three consecutive nights of -25C. To maintain the temperature inside a 1000sq.ft.house at 20C (68F), a differential of 35C or 63F from the ambient temperature, we would need 80 640 British Thermal Units (BTU) or 23.633KW of energy per hour.
It does not stay that cold all day, every day for the entire winter, so I have also looked at the requirement if the outside temperature is a milder -5C or 23F.
Michigan State University have calculated that a standard cord (4′ x 4′ x 8′) of dry hardwood will contain the heat equivalent of 20 million BTU which is approximately the same as 145 US gallons of No. 2 Fuel oil or 215 gallons of LP gas. The article is a great resource for any one heating with wood.
We start using our furnace in September and generally stop early the following April around seven months or 30 weeks in total.
The energy requirement calculated above is affected by the design and efficiency of the insulation of the house. Using figures from Calculator.net here are the adjusted requirements for both temperature differentials and three levels of insulation.
How Much Wood is Needed for the Winter?
Every situation will be different, house design, number and size of windows, insulation efficiency, location and climate will affect the quantity of wood needed for winter.
Assumptions for ease of calculation:
- Small home of 1000 sq. ft. floor area with 10 ft height.
- Heating period 30 weeks
- Average temperature differential 25C
- Insulation quality – normal
- Type of wood – dry hardwood <20% moisture
- Heating equipment – high efficiency stove / furnace
From the calculations above, we will need to generate 57 600 BTU per hour or 1.382 million BTU per day. A cord of wood provides 20 million BTU, enough for 14.5 days. If we want to heat for 30 weeks (210 days), we will need 14.5 cords of wood.
Cost of Heating with Wood
Dry ready to burn hardwood is available in my area at CDN$80 (US$60) a face cord 4 x 8 x 1 or 32 cu ft. which is equivalent to CDN$320 (US$240) a standard cord.
Therefore to heat a 1000sq ft house for the winter with wood purchased at current market rates would cost CDN$4640 (US$3480)
That sounds high when wood is supposed to be a cheap source of energy. Let’s explore what the cost would be if we cut our own wood.
Cost of Cutting Wood – My Experience
If you are fortunate enough as I am to have access to wood at no direct cost, your heating costs will be reduced a lot, but you still may not find it cheap.
Buying logs to cut and split yourself will also reduce costs.
Here is my experience having heated a 116 year old, 3500 sq ft farmhouse with wood for 14 winters.
We have enough trees on the farm that I only cut dead or dying trees (mainly Ash) and fallen trees. My major difficulty is access to the trees once the crops are planted in the adjacent field and when the ground is too wet or covered in deep snow and ice. I have two relatively short windows in late winter and early spring and again in the fall to get enough trees out of the bush and back to the yard.
In 2018, the ground did not freeze after the crops were harvested until after Christmas. Thawing and freezing created so much ice that I did not get my first trees out until the first week of March. Once the trees or logs are in the yard, I can take my time to cut, split and stack them for drying. My objective is to always have the following years supply cut, split and stacked before the end of the current winter. Two years would be a better period, but I have not got there yet.
My supply of trees is helped by neighbours asking me to remove dead or dying Ash trees and trees blown over by wind. I do not pay for the wood but need to use my own equipment to cut and transport it. A tree feller often brings me large logs he cannot process himself.
Based on my calculations above, I should use 50.75 cords, however, because of the poor insulation in the house, I know that is nearer 80 cords a year.
How many trees is that?
Last Saturday, I felled 6 Ash trees with butt diameters of between 12″ and 24″ and a usable length of 35 to 50 ft. Taking an average of 12″ diameter and 40′ length, a tree yields 125 cu.ft. or approximately 1 cord. I would need 80 of those size trees every year, fortunately, most of the trees I cut are much larger.
I guess I cut around 30 trees a year with the balance coming from neighbours.
A medium quality 20″ chain saw costing $300 lasts me 5 years. I also use a smaller 14″ saw for trimming and cutting smaller logs.
I have a 68 hp tractor with front end loader and a mounted hydraulic splitter. The tractor was purchased for moving hay bales, clearing snow and some field work, but it is essential for the amount of wood I need to cut and move. I use my road trailer behind the tractor or borrow a large wagon to move larger logs from more distant woodlots.
Tractor mounted hydraulic splitter
Every year I buy 2 or 3 new chains for the saws at a cost of around $40 each and a new bar every second year at another $40.00. I sharpen my own chains to save costs. I use a Dremel with sharpening stones and a guide.
My Costs for Heating with Wood
I don’t keep track of exact costs, but here is a summary of my expenses for my wood operation over the last year:
$763 is not bad for a winter’s heating cost for a large house, but it ignores the biggest cost – time.
Time Needed for Heating with Wood
As with the expenses, I do not keep a detailed record of the time I spend on wood. However, the considerable hours I do spend provide plenty of time to think about it. The most accurate estimation I can provide is that I seem to spend between an hour and a half to two hours cutting, splitting, loading and carting enough wood for 1 day’s heating.
So, heating for 30 weeks comes to 210 days which means I spend between 315 and 420 hours a year on wood. That’s a lot of hours with a huge opportunity cost. At minimum wage (in Ontario) of $15 an hour that’s between $4725 and $6300 a year on top of the equipment costs. Still a lot less than the over $10 000 it would cost to purchase wood ready cut, but not a lot less than using oil and more than propane or natural gas. In some areas, electricity from a utility would be a cheaper source of heat.
For a 1000 sq. ft. well insulated home, you could spend a quarter of the time I do each year. That would bring your hours down to between 80 and 110 a year with an annual cost at $15 an hour of $1200 to $1650.
Even if you enjoy cutting wood (which after a few years you won’t – believe me) and benefit from the exercise (which I do) that is a huge chunk of time to spend on a chore. It cuts into leisure time, family time and often for me as a self-employed person working from home, working time.
Given that I am able to generate more than minimum wage from my business, I should be employing someone else to do my wood.
2 days wood on the way to the basement
Wood is not necessarily the cheapest heating fuel, but it can be useful if you have access to trees or logs, plenty of time and a tight cash flow.
Cutting large trees is hard, dangerous work. Cutting and splitting large quantities of wood, even with the right equipment is hard on the back.
After the wood has been cut, split and stacked, it still needs to be moved to the furnace or stove. Sufficient indoor storage for a night’s wood may not always be available in a tiny home.
An outside furnace circulating hot water to an indoor heat exchanger system is a safer and cleaner option than an indoor stove or furnace but has a higher purchase cost.
Whether heating with wood would be the right choice for you depends on many factors, not just the cost in $ or hours. If you are fit and strong, have the right equipment and easy access to supplies of wood it can save you money.
The next post will compare heating costs of a range of fuel types
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