Heating & energy
Compressed firelogs
Introduction
Why split firewood and have to store it, when you can buy dry firelogs anytime?
Tempting isn't it? Nice convenient packs of dry firewood, the right size, ready to burn, without the hassles of buying and storing firewood months in advance.
But how expensive are they to use? We tested four different ready-to-burn firelogs and compared their price, efficiency, and emissions to seasoned radiata firewood.
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.
Test results
The firelogs we tested
Duncan Wattie Firelogs (left), Solid Energy Ecoheat Bricks
.
Solid Energy Hotlogs (left), Lighthouse Firelogs.
Our advice
- Ready-to-burn firelogs provide good heat, with low emissions. But they are expensive to use - even if you have a modern efficient woodburner. With one of the logs we tested, plugging in an electric heater would be cheaper.
- Using seasoned radiata firewood in your woodburner is the cheapest way of heating your house (that's if you can't get free firewood).
- Compressed firelogs burn well and are convenient - but they are expensive to use other than as a back-up.
More information
Report by Bill Whitley