GUIDANCE NOTE 10
DEFINING GOOD QUALITY CHP- CRITERIA FOR GOOD QUALITY
CHP
GN10.1
In assessing the quality of CHP Schemes, and qualification as Good Quality CHP for
all or part of their inputs, outputs and capacity, there are a number of key criteria:

For Fuel Inputs under Annual and Initial Operation:
Normally, a Scheme that qualifies as Good Quality CHP for its entire annual
energy inputs is one where the power efficiency equals or exceeds 20%.

For Power Outputs under Annual Operation:
A Scheme that qualifies, as Good Quality CHP for its entire annual power
output is one where the Quality Index equals or exceeds 100. Normally, the QI
Threshold is based on Annual Operation, but can be based on other periods, for
example on the Heating Season in the case of Residential Community Heating
(RCH) Schemes

For Power Outputs under Initial Operation:
A Scheme that qualifies as Good Quality CHP for its entire annual power output
is one where the Quality Index equals or exceeds 95. Normally, the QI
Threshold is based on Annual Operation, but it can be based on other periods,
for example on the Heating Season in the case of RCH Schemes

For Power Capacity under Annual Operation:
An existing Scheme that qualifies as Good Quality CHP for its entire Capacity is
one which achieves a QI of at least 100 at its Maximum Heat Output under
Normal Operating Conditions

For Proposed New Power Capacity:
A proposed Scheme that qualifies as Good Quality CHP for its entire Capacity
is one which at design, specification, tendering and approvals stages, achieves
QI  105 based on Design Max Heat conditions and Power Efficiency  20%,
under Annual Operation. Max Heat operation is based on operation at the heat
output that is expected to be exceeded for the hours specified in the CHPQA
Standard and further explained in GN27 depending on the use of the CHP heat
output.
GN10.2
The Quality Index (QI) provides a means of assessing the quality of CHP Schemes
which takes account of the fact that power supplied is more valuable than heat
supplied. It compares CHP to separate power-only and heat-only alternatives. The
QI therefore offers scope for a major improvement over conventional methods of
assessment, which are based simply on overall efficiency. The Quality Index of a
CHP Scheme is calculated using formulae shown in Table GN10-1. The X&Y values
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were modified to accommodate the EU Cogeneration Directive’s Harmonised
Reference Values and comply with Article 12.2, see CHPQA Standard issue 3.
Following a December 2012 Government consultation (and January 2013
supplementary questions) that reviewed the qualification criteria for renewable CHP
schemes (the ‘CHPQA Review’), new QI formulae are being introduced for the
purposes of obtaining a CHPQA Guidance Note 44 certificate by new schemes e.g.
for obtaining ROCs.
The CHPQA Standard specifies different Quality Index formulae for the purposes of
determining eligibility for other benefits. These formulae have been more stringent
than those in Guidance Note 44. However in some cases, as a result of the CHPQA
review, the new Guidance Note 44 formulae are now more stringent than those in
Issue 3 of the CHPQA Standard (this is the case for <25MW schemes only). In these
cases these formulae have been used to replace those previously in the Standard.
The new X&Y values now shown in Table GN10-1 have been modified to
accommodate this revision. The revised arrangements will be applied by the
CHPQA programme from 1st January 2014.

Refer to GN24 for guidance on determination of Scheme Quality.
QI Methodology and Treatment of Different Plant
GN10.3
The QI methodology ensures validity across a broad spectrum of CHP plant and
applications, considering all sizes, fuel and types of CHP technology. A suite of QI
formulas have been developed and tested based around a simple general Form (see
GN10.6).
GN10.4
The methodology reflects the technical factors affecting the selection of CHP plant in
different applications and circumstances. These factors include:

Alternative power supply options to CHP, taking account of the generating
technology that would otherwise be employed

The improvement in generating efficiency that can be achieved with increasing
scale

Reduced transmission and distribution (T&D) losses for smaller embedded
generating plant, as compared to larger, network-connected generating plant

A range of alternative heat-supply options. In industrial applications CHP will
typically displace boilers across a range of sizes, fuels, and thermal efficiencies.
In Residential Community Heating, communal boilers, electric heating and small
individual boilers are displaced by heat from CHP
GN10.5
In addition to these technical factors, it is essential to ensure that under all
circumstances:
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
CHP provides significant ‘environmental and other benefits’ compared to
the best available energy supply alternatives

The QI provides an incentive to improve environmental performance
The primary energy savings generated by GQCHP should ensure compliance with
Article 12(2) of the European Union Directive 2004/008/EC- Promotion of
Cogeneration based on a useful heat demand in the Internal Energy Market. QI
formulae have been derived such that GQCHP Schemes with total installed capacity
of



<1MWe – should provide > 0% primary energy savings compared with the
Directive’s harmonized reference values for separate production of heat
and electricity;
1MWe – should provide 10% primary energy savings compared with
the Directive’s harmonized reference values for separate production of
heat and electricity;
>25MWe – should have an overall efficiency of above 70% (based on Net
Calorific Value).
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THE GENERAL FORM
GN10.6
The general Form of the QI calculation is:
QI = X * Power Efficiency + Y x Heat Efficiency
Where:
Power Efficiency (Power) = Total Power Output (MWhe) / Total Fuel Input (MWh)
Heat Efficiency ( Heat) = Qualifying Heat Output (MWhth) / Total Fuel Input (MWh)
X is a factor for power, related to alternative electricity supply options. Y is a factor
for heat supply, related to alternative heat supply options. These factors vary to
reflect particular classes of CHP plant and to guarantee primary energy savings
when compared with alternative options.

Total Power Output (CHPTPO) is the total registered annual power generation
from a CHP Scheme (MWhe) as measured at the generator terminals

Qualifying Heat Output (CHPQHO) is the total registered amount of useful heat
supplied annually from a CHP Scheme (MWhth). It is the total heat output that
is demonstrably utilised to displace heat that would otherwise be supplied from
other sources

Total Fuel Input (CHPTFI) is the total registered annual fuel input to a CHP
Scheme (MWh)

All figures are based on Gross Calorific Value (GCV)
QUALITY INDEX FORMULA(S)
GN10.7
The Quality Index formulas set down in the CHPQA Standard cover the full range of
CHP Scheme applications, sizes (CHPTPC), technologies and fuels (see Table GN101).
Transitional Arrangements
The CHPQA Standard specifies different Quality Index formulae for the purposes of
determining eligibility for benefits other than ROCs. These formulae are more
stringent than those currently used in CHPQA Guidance Note 44 for determining
eligibility for ROCs.
DECC consulted from December 2012 to March 2013 on amendments to Guidance
Note 44, and consequential amendments to other CHPQA documents, proposing
tightening the Guidance Note 44 requirements to reflect improvements in the
efficiency of renewable CHP schemes since Guidance Note 44 was first developed.
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The Government’s response, setting out the changes which would be implemented,
was published on 12th July 2013.
In some cases the revised formulae are now more stringent than those in Issue 3 of
the CHPQA Standard (this is the case for <25MW schemes only) and have been
used in Issue 5 of the Standard and here (in Table 10-1), to replace those currently
in Issue 3 of the Standard.
However, with CHPQA certification based on scheme performance over the previous
calendar year, Issue 3 of the Standard formulae will be used for the 2014 certification
of existing schemes. This will allow these schemes to reconcile their 2013
performance using the old formulae. Issue 5 of the Standard formulae will apply from
1st January 2014 and will be used for the 2015 certification of existing schemes. This
will allow these schemes to reconcile their 2014 performance using the new
formulae.
For schemes not previously certified, there is no reconciliation over the previous
calendar year and Issue 5 of the CHPQA Standard formulae will both apply and be
used for the 2014 certification of new schemes from 1st January 2014.
CHP SCHEME SIZE:
CHP Total Power Capacity (CHPTPC): the registered maximum power generation
capacity of the CHP Scheme (MW e), at International Standard Atmosphere
conditions. It defines the size of the CHP Scheme for the purpose of selecting the
appropriate Quality Index formula.
Where there is more than one electrical generator in a Scheme, CHPTPC shall
include the total electrical capacity of all generators that can run together, i.e. the
actual maximum generation capacity. Where a Scheme includes mechanical power
outputs, this shall be converted to an equivalent power output and included in
CHPTPC.
CHP Scheme Fuel Type:
 For schemes that burn a mixture of fuels, separate QI formula for each type of
fuel should be entered, with the X & Y coefficients weighted for each fuel
fraction. These are then summated to produce the overall weighted QI
formula to be applied.
 Qualifying recovered heat (waste heat) imported into the CHP Scheme is
classed as an alternative fuel.



Refer to GN12.16 for detailed guidance on selecting the QI formula (s).
Refer to GN14.6 & 14.7 for detailed guidance on Recovered Heat.
Refer to GN24.10 for guidance on mixed fuels.
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Table GN10-1 QI Formulae for Various Sizes and Types of existing CHP
Scheme (will be applied by the CHPQA programme from 1st January 2014).
Size Of Scheme (CHPTPC)
QI Definition
CONVENTIONAL FOSSIL FUELS SCHEMES
Natural gas (inc. Reciprocating Engines)
1MW e
>1 to 10MW e
>10 to 25MW e
>25 to 50MW e
>50 to 100MW e
>100 to 200MW e
>200 to 500MW e
>500MW e
QI =
QI =
QI =
QI =
QI =
QI =
QI =
QI =
249
195
191
186
179
176
173
172
x
x
x
x
x
x
x
x
power
power
power
power
power
power
power
power
+
+
+
+
+
+
+
+
115
115
115
115
115
115
115
115
x
x
x
x
x
x
x
x
heat
heat
heat
heat
heat
heat
heat
heat
QI =
QI =
QI =
249 x
191 x
176 x
power
power
power
+
+
+
115
115
115
x heat
x heat
x heat
QI =
QI =
QI =
249 x
191 x
176 x
power
power
power
+
+
+
115
115
115
x heat
x heat
x heat
Oil
1MWe
>1 to 25MWe
>25MWe
Coal
1MWe
>1 to 25MWe
>25MWe
SPECIAL CASES
FUEL CELL SCHEMES
QI =
180 x
power
+ 120
x heat
ALTERNATIVE FUEL SCHEMES1
Category A (e.g. AD gas, sewage gas, landfill gas)
1MWe
>1 to 25MWe
>25MWe
QI =
QI =
QI =
238 x
225 x
193 x
power
power
power
+ 120
+ 120
+ 120
x heat
x heat
x heat
QI =
QI =
QI =
275 x
251 x
193 x
power
power
power
+ 120
+ 120
+ 120
x heat
x heat
x heat
QI =
QI =
QI =
245 x
191 x
176 x
power
power
power
+ 120
+ 120
+ 120
x heat
x heat
x heat
QI =
QI =
QI =
245 x
226 x
176 x
power
power
power
+ 120
+ 120
+ 120
x heat
x heat
x heat
QI =
QI =
QI =
QI =
370
370
370
220
power
power
power
power
+
+
+
+
x
x
x
x
Category B (e.g. synthesis gas)
1MWe
>1 to 25MWe
>25MWe
Category C e.g. Fatty Acid Methyl Ester, Pyrolysis oil etc.)
1MWe
>1 to 25MWe
>25MWe
Category D (e.g. Tallow, Used Cooking Oil)
1MWe
>1 to 25MWe
>25MWe
Category E (e.g. Municipal waste, sewage sludge, paper
sludge etc.)
1MWe
>1 to 10MWe
>10 to 25MWe
>25MWe
x
x
x
x
120
120
120
120
heat
heat
heat
heat
1
In accordance with the EU Cogeneration Directive’s harmonised efficiency reference values and defined in the CHPQA
Guidance Notes.
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Category F (e.g. Logs, Energy crops, Agricultural
residues etc.)
QI =
QI =
QI =
QI =
348
348
348
220
x
x
x
x
power
power
power
power
+
+
+
+
130
130
130
120
x
x
x
x
heat
heat
heat
heat
QI =
QI =
QI =
QI =
352 x
338 x
338 x
220 x
power
power
power
power
+
+
+
+
120
120
120
120
x
x
x
x
heat
heat
heat
heat
1MWe
QI =
329 x
power
+ 120
x heat
>1 to 10MWe
>10 to 25MWe
>25MWe
QI =
QI =
QI =
293 x
286 x
220 x
power
power
power
+ 120
+ 120
+ 120
x heat
x heat
x heat
QI =
QI =
QI =
294 x
221 x
193 x
power
power
power
+ 120
+ 120
+ 120
x heat
x heat
x heat
QI =
QI =
QI =
329 x
299 x
193 x
power
power
power
+ 120
+ 120
+ 120
x heat
x heat
x heat
QI =
QI =
QI =
275 x
260 x
176 x
power
power
power
+ 120
+ 120
+ 120
x heat
x heat
x heat
1MWe
>1 to 10MWe
>10 to 25MWe
>25MWe
Category G (e.g. Contaminated waste wood)
1MWe
>1 to 10MWe
>10 to 25MWe
>25MWe
Category H (e.g. Wood pellets, straw, clean waste wood
etc.)
Category I (e.g. by-product gases produced in industrial
processes)
1MWe
>1 to 25MWe
>25MWe
Category J (e.g. waste gases such as carbon monoxide,
or waste heat such as the exhaust gas from high temperature
processes, or as a product of exothermic chemical reactions).
1MWe
>1 to 25MWe
>25MWe
Category K (e.g. liquid waste-non-renewable)
1MWe
>1 to 25MWe
>25MWe
Note: Efficiencies are decimal fractions: i.e. 60% Efficiency = 0.60 for use in formulae
CRITERIA FOR CERTIFICATION OF ‘GOOD QUALITY’
GN10.8
Most calculations for Self-Assessment require three sets of annual data: fuel used,
power generated and heat supplied (all data are on a Gross Calorific Value or Higher
Heat Value basis). From these, Power Efficiency, Heat Efficiency and QI are
calculated.
GN10.9
Most CHP Schemes will meet the Good Quality CHP criteria for their entire capacity,
fuel input and energy output. Some CHP Schemes that generate power and recover
heat may not achieve either or both of the criteria identified in GN10.1. For such
CHP Schemes the power generation or fuel input qualifying as Good Quality CHP is
scaled back to recognise the reduced environmental benefits. These criteria will use
a series of formulae outlined below (GN10.10 to 10.16) so that it is clear what is, and
is not, defined as part of the CHP Scheme and eligible for benefits.
GN10.10
Schemes that do not achieve either or both the criteria necessary to qualify as Good
Quality CHP, fuel input and energy output, may be eligible for reduced benefits (See
GN10.11 to GN10.15).
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CHP Qualifying Fuel Input (CHPQFI)
GN10.11
Qualifying Fuel Input (CHPQFI) is the quantity of fuel that is considered to be used in
Good Quality CHP.

If the CHP Scheme achieves the relevant Power Efficiency Threshold, all fuel
used is considered to be in Good Quality CHP

For CHP Schemes with Power Efficiency below the threshold, the fuel input that
is considered to be used in Good Quality CHP is the Total Fuel Input scaled
back to the level at which the CHP Scheme would have achieved the Power
Efficiency Threshold given the CHPTPO. The remainder is not considered to be
an input to Good Quality CHP


Refer to GN25 for guidance on calculating CHPQFI.
Refer to GN41 for guidance on Climate Change Levy (CCL) exemption.
GN10.12
Some Schemes use a mix of conventional fuels on which CCL may be due, and
alternative fuels, which are not subject to CCL. If such a Scheme does not meet the
relevant Power Efficiency Threshold, the CHPQFI will need to be calculated.


Refer to GN24.10 for guidance on mixed fuels.
Refer to GN4 for guidance on CCL exemption with mixed fuels.
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CHP Qualifying Power Output (CHPQPO)
GN10.13
Qualifying Power Output (CHPQPO) is the power that is considered to be generated in
Good Quality CHP.

If the CHP Scheme achieves the relevant QI Threshold, all power is considered
to be generated in Good Quality CHP

For CHP Schemes with a QI below the threshold, the Qualifying Power Output
is the power output (MWhe) from the CHP Scheme that would have achieved a
QI Threshold, given the CHPQHO. The remaining power is not considered to be
generated in Good Quality CHP

Refer to GN26 for guidance on calculating CHPQPO.
CHP Qualifying Power Capacity (CHPQPC)
GN10.14
CHP Qualifying Power Capacity (CHPQPC) is defined as follows:

For Power Capacity under Annual Operation:
An existing Scheme that qualifies as Good Quality CHP for its entire Capacity is
one which achieves a QI of at least 100 at its Maximum Heat Output under
Normal Operating Conditions

For Proposed New Power Capacity:
A proposed Scheme that qualifies as Good Quality CHP for its entire Capacity
is one which at design, specification, tendering and approvals stages, achieves,
QI  105 based on Design Max Heat conditions and Power Efficiency  20%
under Annual Operation
To qualify under Max Heat Conditions, the Maximum Heat Output shall be
maintained for an absolute minimum of not less than the following cumulative
periods during AO:

Industrial, commercial or institutional
1000 hours
(<10% CHPQHO to Residential Users)

Mixed residential, institutional, commercial or industrial 750 hours
( 10% residential)

Residential Community Heating (See GN30)
500 hours
For Schemes under AO, Max Heat shall be based on actual performance. For
proposed, new Schemes, evidence shall be required to support predictions of future
heat loads, for example, projected build-up of a Community Heating Scheme.
GN10.15
For CHP Schemes that do not meet the relevant QI threshold, CHPQPC needs to be
calculated. In simple terms, this calculation is the same method as for CHP QPO, but
using different data. Instead of being on the basis of fuel used, power output and
heat supplied all in MWh on an annual basis, the relevant data are fuel used (MW),
power capacity (MW) and heat capacity (MW), at Max Heat conditions.

Refer to GN27 for guidance on Calculating CHPQPC.
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Initial Operation (IO)
GN10.17
Initial Operation starts when the Responsible Person notifies the Administrator, in
writing, that the Scheme has begun operating. For a Scheme serving an individual
user or site IO ends after the first complete calendar year of AO. For a Scheme
serving Community Heating, IO ends after the first two complete AOs.
GN10.18
During Initial Operation, which starts when the Responsible Person notifies the
Administrator that the Scheme has begun operating, a reduced QI Threshold may
apply.

For Power Outputs under Initial Operation:
A Scheme that qualifies as Good Quality CHP for its entire annual energy
outputs is one where the Quality Index equals or exceeds 95. Normally, the QI
Threshold is based on Annual Operation, but can be based on other periods, for
example, on the Heating Season in the case of Residential Community Heating
Schemes.
Residential Community Heating (RCH)
GN10.19
Residential Community Heating (RCH) is the centralised supply of heat,
predominantly for Residential Users for space heating and domestic hot water.
Residential Use is defined by the Finance Act 2000.

Refer to GN30 for guidance on RCH Schemes.
GN10.20
For CHP Schemes serving Residential Community Heating with a CHPTPC of 2MW e
or greater, the Self-Assessment of QI in operation may be based on the sevenmonth Heating Season determined at the discretion of the Responsible Person,
provided that the seven-month Heating Season months fall within a single AO. This
could be January to April and October to December within a single AO.
GN10.21
Where such a Scheme does not meet the QI Threshold for Good Quality for all of its
power output, then the determination of CHPQPO shall be based on the same sevenmonth Heating Season. CHPQFI shall be determined on an annual basis, as normal.
GN10.22
Schemes below 2MW e serving Residential Community Heating can also be
assessed on a seven-month Heating Season, provided they comply with the normal
CHPQA metering and reporting requirements for CHP Schemes over 2MW e.
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