ISO/TS 23099:2026

Technical
Specification
ISO/TS 23099
First edition
Large yachts — A methodologic
2026-03
framework to assess large yachts
(30m+) on their environmental
performance and credentials
Grands yachts — cadre méthodologique pour évaluer les
qualifications et les performances environnementales des grands
yachts (30 m et plus)
Reference number
© ISO 2026
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Operational profile . 5
4.1 General .5
4.2 Speed profile .5
4.3 Shore power availability .6
4.4 Sailing correction .6
4.5 Total operational profile .10
5 Propulsion power .11
6 Hotel power .11
6.1 Determination of hotel power . .11
6.2 Hotel power in various conditions . 12
6.3 Heat recovery systems . 13
6.4 Onboard sustainable power generation. 13
7 Matching power demand and supply .13
7.1 General . 13
7.2 Shore power use . 13
7.3 Diesel direct, hybrid and diesel electric systems .14
7.3.1 Diesel direct or hybrid propulsion .14
7.3.2 Diesel electric propulsion .14
7.3.3 Other propulsion systems .14
7.4 Matching procedure .14
7.5 Batteries . 15
7.6 Lack of factory specific emission data . 15
7.6.1 General . 15
7.6.2 Generic emissions . 15
7.6.3 Generic effect of exhaust treatment systems .16
8 Environmental impact . 17
8.1 General .17
8.2 Upstream (WtT) impact . .17
8.3 Downstream (TtW) impact .17
8.4 Use of alternative fuels .18
8.4.1 General .18
8.4.2 HVO .18
8.4.3 Methanol .18
9 Fleet reference lines . 19
Annex A (informative) Sail power calculation, P .20
s,eff
Annex B (informative) Calculation example .23
Bibliography .28

iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
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with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
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This document was prepared by Technical Committee ISO/TC 8, Ships and marine technology, Subcommittee
SC 12, Ships and marine technology - Large yachts.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
This document has been developed in response to growing industry demand for a realistic and transparent
methodology to assess and compare large yachts regarding their environmental performance while in
operation. Increasingly, yachts are being promoted as “green” or “sustainable” without quantifiable criteria,
while simultaneously more clients are looking for references to understand the environmental footprint of
yachts.
The International Maritime Organization (IMO), with the International Convention for the Prevention
[18]
of Pollution from Ships (MARPOL) Annex VI Energy Efficiency Design Index (EEDI), has developed an
instrument for ships, however yachts are generally not subject to EEDI. Based on voluntary attempts, the
EEDI was determined to be inadequate for the specific application to large yachts due to its narrow scope
and different operational assumptions.
Elaborating on results of a five-years joint industry project, the document draws on collaboration between
major shipyards, naval architects, classification, environmental experts and research institutes. It provides
a framework with requirements not covered by legislation for yachts over 30 m and below 5 000 Gross
Tonnage (GT), and complementary for yachts over 5 000 GT. It can be seen as pro-active self-regulation to set
new industry standards, providing a sector specific, goal-driven approach.
Specifically, the EEDI methodology presumes continuous vessel movement, whereas yachts typically
[1]
spend approximately 90 % of operational time anchored or docked in harbour. The substantial energy
consumption occurring during these stationary periods cannot be neglected, as propulsion typically
accounts for about only half of a yacht's annual energy use and hotel power the other half. Therefore, it
was necessary to develop a robust method, starting with a realistic, standardized operational profile for
large yachts. The approach is system-based rather than behaviour-based, using installed equipment data
and verified performance across a fixed operational profile, ensuring a repeatable and verifiable calculation
method.
While EEDI focuses primarily on CO emissions during ship operation, other MARPOL regulations address
additional pollutants such as NOx and SOx. A comprehensive method based on life cycle assessment (LCA)
[19]
(see ISO 14040) has been used to accurately evaluate total environmental impacts, measuring both
downstream emissions (CO , NOx, SOx) and upstream processes including fuel production, shore-based
energy, and urea production. Although the current scope of this document emphasizes operational energy,
it is structured to allow future integration of yacht manufacturing, maintenance, and end-of-life stages. This
document aligns with MARPOL Annex VI and the IMO Life-Cycle GHG guidelines by accounting for both Well-
to-Tank (WtT) and Tank-to-Wake (TtW) contributions to a yacht’s total Well-to-Wake (WtW) impact. In
general terms, the calculation of the well-to-wake impact follows the formula below.
Well-to-Wake impact = power demand × operational profile × (specific Well-to-Tank impact + specific Tank-
to-Wake impact)
The power demand is based on vessel specific propulsion and auxiliary power input, thus rewarding yachts
with either improved naval architecture or improved onboard systems with less environmental impact, or
both.
The subsequent environmental impact is expressed in terms of “ecopoints” a common environmental
indicator when applying Life Cycle Assessments (LCA) incorporating various environmental parameters
including CO , NOx, particulate matter (PM) and more. Alternatively, the impact can be translated into
CO eq, a broader recognized metric.
[20]
Since 2019, a joint industry project and other index initiatives have emerged to address yacht specific
environmental assessments. This document includes elements of these methods and aims to provide the
yachting sector with a single methodology and reference for clarity, unity and most importantly to accelerate
progress with assessing and subsequently improving the environmental performance of both the existing
fleet and new build projects.
Use of this document enables early, consensus-based use of a maturing method and allows timely updates as
data availability and alternative fuels evolve.

v
Technical Specification ISO/TS 23099:2026(en)
Large yachts — A methodologic framework to assess large
yachts (30m+) on their environmental performance and
credentials
1 Scope
This document specifies a methodology to calculate the environmental impact of operational energy
use for large yachts and enables the comparative assessment of a yacht's environmental performance
against a defined baseline fleet. The method established herein is robust and based on the best available
data, with transparency and comparability across various yacht types and technical characteristics. This
document explicitly addresses operational energy consumption during the yacht's use phase, emphasizing
the efficiency of onboard systems benchmarked against the found average operational profile and the
environmental emissions coming from this energy, both upstream and downstream. It excludes behavioural
variables arising from individual yacht operation patterns. Additionally, the production and maintenance
materials and processes (upstream impacts), as well as yacht end-of-life considerations (part of downstream
impacts), are outside the scope of this document.
The operational profile specified in this document assumes that the yacht is professionally crewed year-
round and capable of independent transoceanic voyages.
NOTE For motor yachts, this operational assumption generally aligns with IMO MARPOL requirements, which
apply to ships exceeding 400 GT that must be surveyed and certified for MARPOL compliance. Sailing yachts typically
exhibit lower GT for equivalent length; however, their cruising behaviours align closely with motor yachts of
comparable length.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
battery
rechargeable electrical energy storage system comprising one or more modules and associated ancillary
equipment
3.2
ecopoint
single numerical indicator expressing annual environmental impacts arising from yacht (3.22) emissions
from fuel usage, and shore-based electricity consumption
Note 1 to entry: Ecopoints represent a weighted aggregate derived from 18 environmental indicators using the eco-
scarcity method. This method addresses multiple environmental impacts beyond typical legislative approaches
primarily limited to CO .
3.3
environmental impact calculation
complete calculation method used to quantify the annual environmental impacts arising from yacht (3.22)
operations
Note 1 to entry: This includes emissions coming from energy carriers use and shore-based electricity usage.
Note 2 to entry: This calculation forms the basis for determining ecopoints (3.2) or alternatively, the impact can be
expressed in CO equivalent (see Annex B).
Below the method is summarized in Formula (1), where Y represents yacht environmental performance.
n
o
YY (1)
k

k1
E
C
n n P  n  n  
S,ij
f emsf,i e
s
fP t tf f Pt  f
   
j ii ss  j  ii a
j11i 6 j1 i 11
1000 1000
1E
   
Y 
k
1000
where
for each defined operational condition, Y shall be calculated;
k
n is the number of energy carriers;
f
f is the fuel or emission intensity factor [-], according to 8.2 and 8.3;
j
P is the engine loading, expressed in electrical kilowatts kWe, of each respective engine at the appli-
i
cable operational condition, according to Clause 7;
P is the shore power, expressed in kilowatt hours (kWh), according to 7.2;
s
t is time, expressed in hours (h), per year of each respective engine running (operational profile),
i
according to Clause 4;
t is the shore power time, expressed in hours (h), according to 4.1;
s
f is the emission factor of shore power according to 8.2;
s
C is the specific fuel consumption, expressed in grams per kilowatt hour (g/kWh), of each respective
sf,i
engine at the applicable operational condition;
E is the specific emission, expressed in g/kWh, of each respective engine at the applicable operational
S,ij
condition;
n is the number of engines;
e
t is the time connected to shore power, expressed in h;
s
f is the shore power impact factor;
s
n is the number of emissions’ types;
m
n is the operational mode as per Table 1;
o
f is the factor of after-treatment systems, as per 7.6.3.
a
Note 3 to entry: The Y score represents the environmental Well-To-Wake intensity of a yacht based on the standard
operational profile (3.13). Well-To-Tank intensity includes fuel and shore power energy consumption multiplied by
their respective intensity factors. Tank-To-Wake intensity includes engine emissions mass multiplied by emission
intensity factors and adjusted by the after-treatment factor.

3.4
engine
device converting fuel into mechanical energy, typically employed for propulsion or electrical power
generation
Note 1 to entry: An internal combustion engine (ICE) is normally utilized, though gas turbines or steam turbines may
also be included. Fuel conversion efficiency is load-dependent, resulting in specific emissions varying accordingly.
3.5
generator set
unit comprising an engine (3.4) and an alternator that supplies electric power to the main switchboard
Note 1 to entry: Specific fuel consumption and emissions are determined accounting for losses up to the main
switchboard (e.g. rectifiers, alternator efficiency).
Note 2 to entry: Fuel cells or reformer/fuel-cell combinations are considered within this definition with their
characteristic efficiencies and emissions.
3.6
gross tonnage
GT
measure of a ship's total internal volume used to express the vessel's overall size, rather than mass
3.7
hotel power
all onboard power consumption excluding propulsion power
Note 1 to entry: Loads include engine-room ventilation, steering, and cooling pumps, which vary across the operational
profile (3.13).
3.8
hydrogeneration
recovery and conversion of excess sail power from a high-performance sailing rig into electrical energy by
means of the yacht's (3.22) propellers
3.9
length waterline
value determined at half-load condition as employed within the vessel's stability calculations, representing
average operational load conditions
3.10
life cycle assessment
LCA
compilation and evaluation of inputs, outputs, and potential environmental impacts of a product system
throughout its life cycle
[SOURCE: ISO 14040:2006, 3.2]
3.11
main switchboard
junction point connecting electrical power supply systems, such as generators and power take-off units
(PTOs), with electrical consumers associated with propulsion and auxiliary power demands onboard
3.12
motor yacht
yacht (3.22) utilizing exclusively engines (3.4) or generator sets for propulsion purposes
3.13
operational profile
standardized description of average annual yacht (3.22) operation used for comparative assessment
Note 1 to entry: A user-specific profile can be used to calculate impact for a specific operator; such results are not
intended for fleet comparison.

3.14
propulsion power
mechanical or electrical power used to propel the yacht (3.22) at speeds (3.21) defined in the operational
profile (3.13) under half-load conditions
Note 1 to entry: For diesel-direct systems, losses up to the engine flywheel (shaft line, thrust bearing, gearbox) are
included (brake power).
Note 2 to entry: For electric propulsion, losses up to the main switchboard (shafts, gears, motor, frequency drive) are
included.
3.15
sailing yacht
vessel designed to carry sail, whether as a sole means of propulsion or as a supplementary means
3.16
sea margin
correction factor accounting for additional propulsive power demand due to weather and fouling
[2]
Note 1 to entry: For this document, a value of +15 % is applied, as per the ITTC Guidelines.
3.17
sea trial
test conducted at yacht (3.22) delivery to verify (3.23) calm-water propulsion performance at half-load
conditions
Note 1 to entry: See ISO 15016 for further guidance.
3.18
shore power
electrical power supplied from marina facilities to satisfy yacht (3.22) auxiliary power demands, allowing
onboard generators to be shut down
Note 1 to entry: Typically, shore power usage results in reduced environmental impact due to efficiencies and
renewable energy sources utilized in large-scale electrical generation facilities.
3.19
specific emissions
emissions produced by an operating engine (3.4), discharged via exhaust gases
Note 1 to entry: Specific emissions depend on engine type, efficiency, and operational load, typically including
greenhouse gases such as carbon dioxide (CO ) and methane (CH ), as well as pollutants like nitrogen oxides (NOx),
2 4
sulfur oxides (SOx), particulate matter (PM), and ammonia (NH ). Specific emissions for each engine type are
determined through factory bench tests or onboard measurements.
Note 2 to entry: Emission control systems such as selective catalytic reduction (SCR) and diesel particulate filters
(DPF) are often installed to reduce emissions. If designed to operate continuously whenever the engine runs, such
systems may be considered permanently active.
3.20
specific fuel consumption
measurement of an engine's (3.4) fuel efficiency expressed as fuel mass consumed per hour for given engine
load conditions, expressed in grams per kilowatt hour (g/kWh)
Note 1 to entry: Specific fuel consumption values are provided by engine manufacturers, performance diagrams based
on factory bench testing, or actual measurements obtained during onboard harbour or sea trials (3.17).
3.21
speed
velocity of the yacht (3.22) relative to the water, measured in knots

3.22
yacht
vessel of 24 m or more in length, used for sport or pleasure, in private or commercial use
Note 1 to entry: The method in this document is applicable to a yacht over 30 metres in length, that is professionally
crewed year-round and capable of independent transoceanic voyages.
3.23
verify
confirm, by provision of objective evidence, that specified requirements have been fulfilled
4 Operational profile
4.1 General
The operational profile contains the following operational conditions, which are divided over the year with
a fixed number of hours per year each:
NOTE The hours division was developed by analysing 297 years of Automatic Identification System (AIS) data of
[1]
109 yachts.
— 10 % of time moving;
— 34 % of time on anchor;
— 56 % of time in port.
The parametric operational profile is further detailed by using the following parameters:
— length waterline (m);
— maximum speed (kn);
— hotel power, harbour condition (kW);
— rig characteristics (sailing yachts only) (m).
4.2 Speed profile
[1]
The speed profile has been developed using the same AIS data set. The length waterline parameter has a
greater impact than top speed in defining the speed profile, as the latter is rarely reached by yachts. This
impact on the speed profile was validated for conventional displacement motor yachts, fast motor yachts
and sailing yachts alike. The operational profile contains the following speeds.
Maximum speed, V , equals the maximum attainable speed achieved at sea trials, with full propulsive
max
power, corrected for the predefined 15 % sea margin.
Cruising speed defined as the speed sailed most often, derived from the AIS data set (see Figure 1), is
defined in Formula (2), manoeuvring speed is defined in Formula (3), and fast cruising speed is defined in
Formula (4):
0,252 1
VL4,4706  (2)
cr wl
VV05,  (3)
mancr
V = (V + V )/2 (4)
fcr max cr
[1]
Time division between these speeds as per AIS analysis (percentage of whole year ) is as follows:

V 1,5 %
man
V 7,6 %
cr
V 0,8 %
fcr
V 0,1 %
max
Key
V cruising speed [kn]
cr
L length waterline [m]
wl
NOTE During analysis it was noted that fast yachts (planing/semiplaning motor yachts) tended to sail usually
at somewhat higher speed, but still not near their maximum speed. However, the sailing hours were lower than
displacement yachts. This led to the conclusion that for fast yachts the same speed profile as displacement yachts
could be used, since energy spent (=power × hours) was about equal to that of displacement yachts.
Figure 1 — AIS cruising speed data analysis
4.3 Shore power availability
The availability of shore power decreases as power demand rises, due to limitations of marina facilities. A
[3]
marina survey and analysis were performed by Water Revolution Foundation to describe the relation. The
total time in harbour is divided between with and without shore power by the shore power availability, e.g
a shore power availability of 75 % results in 75 % of the harbour time on shore power and 25 % of harbour
time on the yacht’s own power supply.
Formula (5) for shore power availability is given below, maximized at 100 % (occurring around 50 kW):
Se^,0 00330P  ,15 100 (5)

p,av hs
where
P is input value (expressed in kW) as defined in 6.2;
hs
S  is shore power availability.
p,av
4.4 Sailing correction
Sailing yachts benefit from reduced propulsion loads by including motor sailing and pure sailing conditions
into the operational profile, depending on the size of the rig. As the cruising speed condition contains most

of the propulsive energy, the sailing correction splits this condition into pure motor operation, motor-
sailing operation and pure sailing operation. This results in reduced propulsive power requirement and thus
reduced yearly impact.
NOTE 1 Very little data exists on the time sailing yachts spend under sail, since the status contained within AIS
data is not automated but manual entry. Due to the lack of data and the complexity of the correction method, only the
cruising speed part of the operational profile has been included. Example calculations using this method have resulted
in realistic figures of sail timeshare and power in the opinion of expert sailing yacht designers.
The method to calculate the reduced propulsive power as a result of sails is based on the IMO EEDI wind
[17]
assistance model. In short, the power produced by the sails is calculated for the yacht at cruising speed
for tabulated true wind speed (TWS) and true wind angle (TWA) combinations, also known as a Polar table.
These results are multiplied with a table containing the standardized probability of occurrence of the wind
[17]
speed and angle combinations over the most common shipping routes, also known as the availability
factor, F . The sum of the resulting table is the probabilistic power contribution of the sail system.
eff
NOTE 2 The method described below is based upon conventional sail plans. The use of kites or other non-
conventional wind assistance/propulsion is expected to be assessed using coefficients based upon direct calculations.
As the IMO EEDI wind assistance method is developed for low power sail plans (only assisting engine power,
not fully replacing) some type-specific applications to the method are incorporated:
— The EEDI wind assistance method ignores the hydrodynamic drag due to the side force generated by the
rig. For yachts, this is an oversimplification, so this shall be taken into account when determining the
[5]
power contribution of the sail system. The lifting line theory by Lex Keuning is used to quantify the
added resistance.
— A reef factor is introduced which decreases sail area in high winds.
— The propulsive efficiency of 0,7 as per MEPC circulars is decreased to 0,6 to conform to yachting
standards.
— A hydrogeneration procedure is introduced, whereby excess sail energy can be harvested by the propeller.
— The effective sail power limit is raised from 100 % (MEPC) to 250 % of P . This provides the option
cr
to harvest the excess power using hydrogeneration systems, with the limitation of 250 % intended to
represent the physical limitations of the hydrogeneration system (usually the yacht’s propeller with
either a PTO on the shaft or electric drive engine converting hydro power to electricity).
The detailed wind assistance procedure to calculate the effective wind power P for each combination of
s,eff
wind angle and wind speed is described in Annex A. The procedure is represented in Figure 2.

Key
Θ true wind angle
V true wind speed
w
kW kilo watt
[17]
A IMO MEPC global wind probability table F in MEPC.1-Circ.896 Annex 2
eff
Each cell represents the probability of the Θ× V combination
w
The sum of all cells equals 100 %
B Yacht specific table of effective sail power, P
s,eff
Each cell contains the effective sail power belonging to the Θ ×V combination, calculated according to Annex A
w
C Available effective sail power table, P
s,av
Each cell contains the product of key reference A and B for each Θ ×V combination
w
Figure 2 — Wind assistance model
The key references A, B and C in Figure 2 can be split in three zones as shown in Figure 3:
— Zone 1: No additional power from the sails (i.e. unusable wind angle, power of sails less than additional
resistance, too little or much wind): in this case the yacht will be running on motor power only. The
summed occurrence (key reference A in Figure 3) of the “no sail power zone” determines the timeshare
of the motoring subcondition.
— Zone 2: The power of the sails is less than what is required for cruising speed. In this case the yacht will
be motor sailing, with the average power of the zone (key reference C in Figure 3) defining the sail power
assistance, and the summed occurrence (key reference A in Figure 3) determines the timeshare.
— Zone 3: The power of the sails is equal or higher than what is required for cruising speed: in this case the
yacht is in pure sailing condition, with average sail power (key reference C in Figure 3) and timeshare
(key reference A in Figure 3) calculated as before. If the yacht is fitted with a hydrogeneration system, the
excess power in the pure sailing condition can be harvested and used to power the hotel load, reducing
the generator loading in this condition (P ) as described in 6.2.
hot,sail
Key
Θ true wind angle
V true wind speed
w
1 Zone 1
2 Zone 2
3 Zone 3
Figure 3 — Zone divisions wind assistance method
To compensate for the effect that sailing yachts with high power rigs can use wind conditions which are
disregarded by the method above, a time compensation factor is introduced. For example, fast sailing yachts
can tack upwind with a resulting speed V (speed “made good” in a non-sailing direction) close to cruising
mg
speed. Since the MEPC method only incorporates steady-state sailing, it underestimates the use factor of the
rig. The compensation factor is determined by Formula (6).
PP
sa,,vc3 r
t  (6)
c
06, P
cr
where
t is the time correction factor for high powered sailing rig;
c
P is the sum of P in zone 3 in Table C of Figure 2 divided by ∑ f
s,av,3 s,av eff,zone3
P as defined in Clause 5;
cr
0,6 is the standardized tuning factor.
The time compensation factor is applied to reduce the motor condition (zone1), and increasing the motor
sailing and pure sailing conditions as shown in Formula (7), (8) and (9):
TfTT' 1 t  (7)

mmeffz, one1 mc
TT
 ms m
Tf TT t (8)
ms effz,2onemsms c
TT
ms s
Tf TTTT /TT t (9)
sceffz, ones3 ss mmss
where
T , T , T is the uncorrected timeshare of the cruising speed condition spent at the applicable subcon-
m ms s
dition, summed from Table A of Figure 2;
T , T , T is the corrected timeshare of the cruising speed condition spent at the applicable subcondition;
m’ ms’ s
NOTE For a motor yacht, the factors are automatically defined as T = 100 %, T = 0 % and T = 0 %.
m’ ms’ s’
f is the availability factor in the applicable zone.
eff,zone[x]
These numbers are used to divide the cruising speed condition hours in the three subconditions motor,
motorsailing and pure sailing in the operational profile.
4.5 Total operational profile
Adding up all of the results of 4.1 to 4.3, the total operational profile can be determined as shown in Table 1.
Table 1 — Total operational profile for yachts
Condition no. Condition Hours/year Speed Hotel load
1 Harbour, shore power 4906 S 0 P
p hs
2 Harbour, generator 0 P
4906 1 S hg

p
3 Anchor 2 978 0 P
ha
4 Slow cruise/manoeuvring 131 V P
man hm
5 Cruise, motor P
T 666
hm
m
T 666
6 Cruise, motorsailing V P
ms
cr hs
T 666
s
7 Cruise, sailing P
hs
8 Fast cruise 70 V P
fcr hm
9 Maximum speed 9 V P
max hm
Total 8 760
P   shore power
s
T   time motor
m
T   time motorsailing
ms
T   time sailing
s
V   manoeuvring speed
man
V    cruising speed
cr
V    fast cruising speed
fcr
V    maximum speed
max
P    hotel power [kW]
h
P    hotel power from shore power only
hs
P   hotel load on generator
hg
P   hotel load at anchor
ha
P   hotel load at manoeuvring
hm
P hotel power at a cruising and maximum speed operation
hmotor
P   hotel power while under sailing mode operation
hsail
5 Propulsion power
The propulsion power can be determined in the design stage using conventional naval architecture
(analytical method, CFD, model testing, including the efficiency of the propulsors like propellers, water jets,
azimuthing thrusters, etc.). For electric propulsion, it shall include factors such as the efficiency of propulsion
motors and frequency drive. The propulsion power calculation shall be verified at delivery during sea trials.
The predefined sea margin of 15 % shall be included in the power requirement. See Figure 4.
Key
P propulsion power in kW (diesel direct) or kWe (diesel electric)
V speed in knots
1 speed-power curve sea trial condition
2 speed power curve including 15 % sea margin
Figure 4 — determination of propulsion power
In case of a sailing yacht, the engine power at cruising speed P is reduced in the following operational sub-
cr
conditions:
P no reduction;
cr,motor
P reduce by the sum of P in zone 2 in key reference C in Figure 3;
cr,motor-sailing s,av
P reduce to zero.
cr,sailing
6 Hotel power
6.1 Determination of hotel power
For each condition a hotel load shall be determined. This load shall be based on all systems running in
normal operating conditions, with full crew and guest complement on board.
Heating, ventilation and air conditioning (HVAC) loads shall be based on:
— normal exterior conditions of 25° C/80 % Relative Humidity (RH);
— normal interior conditions 21° C/50 % RH;

— sea water 30 °C.
To compensate for the daily solar cycle, the effects of solar heat gain on surface temperature and radiation
through windows shall be reduced to 50 % of the values (see ISO 7547).
The hotel load shall be determined in (kWe) in one of the following verifiable manners:
— design values (load balance according to IMO EEDI principles);
— onboard monitoring (long-term monitoring in relevant conditions specified above, as well as post
processing).
Since monitoring involves registering the actual use of a single user/operator, care shall be taken not to
include exceptional use. This approach aims to assess average use. Long term monitoring shall include at
least one full year of use.
Where data are available and independently verified, monitoring results from onboard measurements shall
be used.
6.2 Hotel power in various conditions
Hotel power calculations are highly subjective and traditionally inaccurate. For this reason, it is acceptable to
use the average hotel load in all operational conditions and disregard the variations. At the anchor condition
with guests on board can be used as the average condition. When calculating systems that include waste
heat recovery, it is recommended to make sure to add the electric power to supply heat in the conditions
where no waste heat is available (shore power, battery operation).
If more detail in the calculation is preferred, condition dependent hotel power can be calculated, using the
guidance below to differentiate between the various conditions:
P Full luxury operation, including all heating loads. A suitably sized shore connection shall
hs
be fitted.
P Equal to P , but since this is based on generator use, the effect of waste heat recovery sys-
hh hs
tems shall be taken into account if fitted on board.
P P plus stabilizing power plus nav/com power.
ha hb
P P plus stabilizing power plus nav/com power plus steering power plus (bow), where the
hm hb
(bow) thruster power is the installed power of the thruster(s) multiplied by 5 % (assumed
per cent of the of operation) according to Formula (10).
P P plus stabilizing power plus nav/com power plus steering power plus engine room ven-
hmotor hh
tilation/cooling power
P P plus sail handling power. In case of the provision for energy regeneration from the
hsail hmotor
propeller this regenerated power may be deducted in the “sail only” condition. The power
of energy regeneration is determined according to Formula (10):
PPP  04, (10)

rg sa,,vc3 rd
in which
P is as per 4.3;
s,av,3
η is the propulsive efficiency, standardized at 0,6;
d
0,4 is the standardized efficiency of the hydro regeneration system from propeller to electricity;
or
P = P
rg PTO
in which P is the maximum power of the shaft’s power take off ( )
PTO PTO
or
P = P
rg hsail
whichever is the lowest.
6.3 Heat recovery systems
Heat recovery systems use waste heat in cooling systems or exhaust streams to enhance overall system
efficiency. Such a system may use low to medium temperature cooling water to supply heat to pool heating,
AC systems and other consumers to reduce the use of electric heating or may use high temperature exhaust
streams to power a steam turbine generator, increasing the electrical power of the generator. The effect of a
heat recovery system can be included in the environmental impact calculation by reducing the hotel power
in those conditions where low temperature waste heat is available (e.g. when generator engines are running,
and not when on shore power). Waste heat recovery generating electricity is usually expressed in higher
efficiency/lower emissions of the generator.
6.4 Onboard sustainable power generation
If applicable, the average produced power of any onboard power generation of solar cells, kites, wind
turbines etc. may be subtracted from the hotel load. For example, solar
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