🏭 Tank Sizing
💰 Seasonal Cost Comparison
| Heating Source | Annual Energy | Seasonal Cost (CAD) | Cost/GJ Delivered |
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Full Calculation Breakdown
| Parameter | Value | Notes |
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How to Use the Propane Boiler Calculator
Standard atmospheric propane boilers typically achieve 80% AFUE. Mid-efficiency units with induced-draft fans reach 90%. Condensing propane boilers hit 95–98% AFUE when return water stays below 55°C - use the outdoor reset calculator to maintain low return temperatures. Higher AFUE directly reduces how much expensive propane you burn each season.
The boiler input rating is needed for the tank vaporisation check - propane must boil fast enough to meet the burner's demand at the coldest outdoor temperature. Building heat loss drives seasonal consumption; use the heat load calculator for a precise figure. HDD and design outdoor temperature are pre-filled when you select a location preset.
Rural propane delivery routes in Canada often run every 30–60 days in peak heating season. The calculator determines the minimum tank capacity needed so you don't run out between scheduled deliveries. The fill level at delivery (80% is the code-mandated maximum) and your safety reserve level (typically 20%) set the usable capacity per delivery cycle.
The tank diagram shows the minimum recommended capacity and how full it needs to be at delivery. A separate vaporisation rate check confirms the tank is large enough to supply the boiler's full input rate at your design outdoor temperature. Propane vaporises more slowly as temperature drops - a tank that works fine at -10°C may restrict boiler input at -33°C.
The comparison table shows seasonal cost for propane, fuel oil, and a heat pump side by side on a cost-per-GJ-delivered basis. This lets you evaluate whether switching fuels or installing a heat pump for base-load heating while keeping propane for peak cold days makes economic sense for your property.
Propane Heating for Rural Canadian Properties
Propane - liquefied petroleum gas (LPG) - is the primary heating fuel for hundreds of thousands of rural Canadian properties that sit beyond the reach of natural gas distribution networks. Understanding propane's energy content, tank sizing requirements, and true cost per unit of heat delivered helps rural property owners make informed decisions about their heating systems and whether alternatives make financial sense.
Propane Energy Properties
Liquid propane has a higher heating value of approximately 25.3 MJ/L (91,500 BTU/US gallon). This is considerably higher per litre than fuel oil's 38.7 MJ/L but propane's lower density means you need a larger volume for the same energy. When comparing fuels, always use cost per GJ of heat delivered after accounting for boiler AFUE - not raw price per litre. At $1.00/L and 90% AFUE, propane delivers heat at roughly $44/GJ. Compare this using the boiler output calculator to verify effective output at your operating conditions.
Tank Sizing: Two Separate Calculations
Getting the right propane tank requires two independent calculations that both constrain the minimum tank size. The first is storage capacity: the tank must hold enough propane to last the full delivery interval, from fill level down to the safety reserve, even during the coldest stretch of weather. The second is vaporisation rate: liquid propane must evaporate inside the tank to become the gas the burner consumes, and this evaporation rate depends on tank surface area, the temperature gradient between the liquid propane and the outside air, and the fill level. A cold, nearly empty tank vaporises propane much more slowly than a warm, nearly full one. At -30°C, a 420-litre (420L) tank may only be able to supply about 1.0–1.5 kg/h, limiting the boiler to roughly 13–20 kW input. Boilers larger than this in cold climates need bigger tanks, tandem tanks, or electric vaporisers.
The 80% Fill Rule
Propane tanks are never filled to 100%. A 15–20% vapour space must be maintained to allow for liquid expansion as outdoor temperature rises. During a warm summer day, propane in a full tank expands enough to potentially rupture an overfilled container. Propane delivery trucks are regulated under CSA B149.2 to fill residential tanks to a maximum of 80% capacity. This is why the "fill level at delivery" in this calculator defaults to 80%, and it's why a 420L tank only delivers 336L of usable propane per fill. Always account for the 80% rule when sizing storage capacity.
Propane vs. Fuel Oil in Rural Canada
Both propane and fuel oil are delivered by truck to rural properties. On a per-GJ-delivered basis, they tend to run within 15–30% of each other in most Canadian markets, with propane sometimes cheaper and sometimes more expensive depending on regional supply chains and delivery distances. Propane has some advantages: cleaner combustion, no risk of tank corrosion from acidic condensate like older oil tanks, and compatibility with condensing boilers down to very high efficiencies. Fuel oil offers higher energy density - you store more BTUs per litre, which matters when tank placement space is limited. Use the fuel oil calculator with identical inputs to compare both fuels side by side at your local prices.
Condensing Propane Boilers
High-efficiency condensing propane boilers reach 95–98% AFUE, dramatically cutting fuel use compared to an 80% standard unit. At $1.00/L propane, moving from 80% to 95% AFUE saves 15.8% of fuel - at 3,000 L/year consumption that's about $474/year. The payback on a condensing boiler depends on installed cost minus any rebates, but most provincial programs extend incentives to propane equipment. The key requirement is keeping return water below 55°C for consistent condensing; the condensing boiler calculator models this in detail.
Heat Pump as Propane Offset
Air-source heat pumps are increasingly viable in rural Canada as an alternative to running on propane alone. A cold-climate heat pump sized to handle 80–85% of the building's heating hours operates on electricity at a COP of 2.0–3.0 even at -20°C, delivering heat at a cost that frequently undercuts propane at $1.00+/L. The propane boiler remains for the coldest days when heat pump capacity drops. At electricity rates of $0.10–$0.13/kWh (common in Quebec, Manitoba, and BC), heat pump heating costs roughly $12–$20/GJ delivered - significantly below propane. Where electricity rates are higher (Ontario $0.15–0.18/kWh, Atlantic Canada $0.155/kWh), the comparison tightens but propane still often loses. Federal and provincial rebates for cold-climate heat pumps in rural Canada frequently reach $5,000–$10,000, changing the payback calculation substantially.
Frequently Asked Questions
Tank sizing requires two separate checks. First, storage capacity: the tank must hold enough propane to last between deliveries while maintaining a 20% safety reserve. At 80% fill, a 420L tank provides 336L usable minus 20% reserve = 252L per cycle. Second, vaporisation rate: at your design outdoor temperature, the tank must evaporate propane fast enough to meet the boiler's rated input. Cold temperatures and low fill levels both reduce vaporisation rate. A boiler needing more than about 20 kW input in prairie climate conditions (-30°C) typically needs a tank larger than 420L. This calculator checks both constraints and recommends the minimum tank size based on your specific inputs.
Propane costs substantially more per GJ of heat delivered than natural gas in most Canadian markets. At $1.00/L propane and 90% AFUE, heat costs roughly $44/GJ. Natural gas at $10/GJ and 90% AFUE delivers heat at about $11/GJ - four times cheaper. However, propane is only relevant where natural gas infrastructure doesn't exist. In those areas the comparison is between propane, fuel oil, electricity (for heat pumps), and wood. Use the fuel oil calculator to compare propane against oil at your local prices, and the fuel comparison table in this calculator for a quick three-way cost comparison.