Much later than planned, but here it is. In summary, micro-CHP saves 5% to 10% of carbon in large inefficient houses but only if you use SAP’s flawed methodology and give yourself extra-extra credit for displacing grid electricity. A few of the key findings:

• The trial has demonstrated that the carbon and cost savings from Micro-CHP are generally better for buildings where they can operate for long and consistent heating periods.
• In small commercial applications, the field trial has shown that Micro-CHP systems can provide typical carbon savings of 15% to 20% when installed as the lead boiler in appropriate environments.
• The domestic Micro-CHP systems monitored in the trial have the potential to provide typical carbon savings of 5% to 10% for older, larger houses with high and consistent heat demands (over 20,000kWh/yr).

So since the last report, the Carbon Trust has toed the industry line that the 0.568 figure should be used.

But is the 0.568 figure to allow for displacing “marginal plant” as claimed in the CT report? Or is it to allow for displacing future generation capacity? If it’s the former than you should only be able to use the 0.568 figure during peak periods. But SAP lets you use 0.568 for renewables and CHP no matter what time they generate energy. If we’re getting funky, let’s at least be clear why.

There’s some very interesting output from the boiler field trials in the report as well. In particular, the boilers they’re monitoring are generally performing 4% to 5% below their SEDBUK rating.