What we found

About our test

We took four different types of ready-to-burn firelogs and compared the way they burn to clear, seasoned radiata firewood. We used the same low-emission woodburner for all the firelogs (and for the seasoned radiata).

For each fire we started with a hot ember bed, weighed the same quantity of fuel, and then burned it away completely. We noted how long the fuel burnt for - and, while it was burning, we continuously measured the heat output of the fire, the fire temperature, and the emissions going up the chimney.

Our results

Burn time

The Duncan Wattie Firelogs, Solid Energy HotLogs and the Lighthouse Firelogs tend to burn longer, but with less heat, than regular (radiata) firewood. This longer burn time despite having less heat output may be a desirable feature, because a radiata fire does tend to need reloading quite often.

The Solid Energy Ecoheat Bricks were closest to the burn time and heat output of radiata firewood.

Emissions

These were lowest with the radiata - which is not surprising, given that modern woodburners are "tuned" to burn this fuel.

All except the Lighthouse Firelogs produced emissions that were higher than the radiata's but still reasonable (between 2.7g and 3.3g per kg of fuel). These are similar to figures we got for macrocarpa and blue gum in last year's firewood burning test.

The Lighthouse Firelogs produced 5.8g per kg of fuel, which is a bit on the high side given that these are manufactured products.

Cost

Using radiata in a modern woodburner costs about 6 to 7c/kWh of heat produced. A portable electric heater comes in around 20c/kWh.

The Duncan Wattie Firelogs and Solid Energy HotLogs cost around 15c/kWh; and the Solid Energy Ecoheat Bricks cost about 19c/kWh - so using them is a bit cheaper than an electric heater.

Burning the Lighthouse Firelogs at 27c/kWh makes little sense.