This New Zealand calculator compares the running cost of a wood burner against a heat pump to deliver the same heat over a season. Heat pumps are very efficient, while a wood burner's cost hinges on what you pay for firewood, so the cheaper option varies by household. You enter the heat needed, firewood and power prices and the efficiencies, and the tool shows the seasonal cost each way and which is cheaper for you.
A cord's heat energy and burner efficiency vary with wood type and the unit; the defaults are rough. Cheap or free wood shifts the result toward the burner. Beyond cost, weigh convenience, clean-air rules and power-cut resilience. Estimate only.
The calculator works out how much usable heat a cord of firewood gives once the burner's efficiency is applied, then the cords and cost needed to meet the season's heat. For the heat pump, it divides the heat needed by the heat pump's efficiency, its COP, to find the power used, then costs that at your power price. The high COP means a heat pump delivers several units of heat per unit of power, which is why it competes well with firewood.
To deliver 4,000 kWh of heat, a burner at 65% efficiency from cords giving 5,000 kWh each needs about 1.2 cords, roughly $220 at $180 a cord. A heat pump with a COP of 3.5 uses about 1,143 kWh of power, about $320 at 28 cents. Here firewood is cheaper, though cheaper power or pricier wood could flip it.
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