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The cost of owning and operating a residential heat pump system in
Canada
NATIONAL RESEARCH COUNCIL OF CANADA
DIVISION OF BUILDING RESEARCH
THE COST OF OWNING AND OPERATING A RESIDENTIAL
HEAT PUMP SYSTEM IN CANADA
R.L.D. Cane
DBR Paper No. 905
of the
Division of Building Research
THE COST OF OWNING AND OPERATING A RESIDENTIAL
HEAT PUMP SYSTEM IN CANADA
by R.L.D. Cane
This paper outlines the operational characteristics of various
i
residential heat pumps and compares the costs of owning and operating
I
such equipment with conventional furnaces. The comparison is made
for nine Canadian cities and for a range of heating energy demands.
I
The data presented will allow the consumer to select a heating system,
for retrofit or replacement of an existing system or for new construction,
on the basis of life-cycle cost.
LES
C O ~ T S
DE POSSESSION ET D'EXPLOITATION DtUNE
POMPE
A CHALEUR R~SIDENTIELLE
AU CANADA
par R.L.D. Cane
R ~ S U M ~
Cet article dBcrit les caracteristiques d'operation de diverses
pompes
3chaleur residentielles et compare les coQts de possession
et d'operation de cet equipement avec les chaudisres traditionelles.
La comparaison est dressee pour neuf villes canadiennes et pour une
g a m e de demandes en Bnergie calorifique. Ltinformation
presentee
permettra au consommateur de choisir
unsystsme de chauffage, pour
ameliorer ou remplacer un systsme existant ou pour une nouvelle con-
struction, sur la base du coQt de la d u d e utile.
PREFACE
Homeowners i n Canada today a r e c o n s i d e r i n g p o s s i b l e a l t e r n a t i v e s t o conventional o i l and gas f u r n a c e s , with t h e r i s i n g p r i c e s of f o s s i l f u e l and t h e p r e d i c t e d s h o r t a g e s of o i l i n t h e n e a r f u t u r e . One h e a t i n g system t h a t has been on t h e market f o r s e v e r a l y e a r s , which i s becoming more a t t r a c t i v e a s f o s s i l f u e l p r i c e s i n c r e a s e , i s t h e e l e c t r i c h e a t
pump. To d a t e , t h e consumer has only had t h e claims of h e a t pump manu-
f a c t u r e r s t o i n d i c a t e p o t e n t i a l savings i n energy and i n h e a t i n g c o s t . This paper was prepared t o provide unbiased information on t h e economic worth o f h e a t pumps compared with conventional b e a t i n g systems.
Recognized methods a r e used t o p r e d i c t t h e performance and energy requirements o f t h e v a r i o u s a l t e r n a t i v e h e a t i n g systems. C a p i t a l and maintenance c o s t s were obtained from i n s t a l l a t i o n c o n t r a c t o r s and a r e considered t o be r e p r e s e n t a t i v e of a c t u a l p r e v a i l i n g c o s t s . For an
economic a n a l y s i s , however, f u t u r e t r e n d s i n t h e f o s s i l f u e l and e l e c t r i - c i t y p r i c e s had t o be assumed. P r i c e s a r e obviously s u b j e c t t o change because of s e v e r a l u n p r e d i c t a b l e f a c t o r s i n c l u d i n g f u t u r e government energy p o l i c i e s .
T h i s paper w i l l a l s o provide t h e consumer with some of t h e informa- t i o n r e q u i r e d f o r t h e r a t i o n a l s e l e c t i o n of a h e a t i n g system, whether it be f o r new c o n s t r u c t i o n o r f o r replacement of an e x i s t i n g furnace. The Division would welcome comments on t h e methods and/or assumptions used i n t h i s a n a l y s i s .
Ottawa A p r i l 1980
C
.
B. CrawfordTHE COST OF OWNING AND OPERATING
A RESIDENTIAL HEAT PUMP SYSTEM IN CANADA
R . L . D . Cane
INTRODUCTION
Most homeowners have had t o d e c i d e whether t o r e p a i r o r r e p l a c e a f u r n a c e . Depending on t h e t y p e o f f u e l b e i n g used, t h e owner might c o n s i d e r changing f u e l and/or t y p e o f h e a t i n g system i f t h i s would save him some money. However, reduced o p e r a t i n g c o s t s must be c o n s i d e r e d i n c o n j u n c t i o n w i t h t h e f i r s t c o s t o f t h e h e a t i n g system c o n v e r s i o n o r up- g r a d i n g ; t h e c r i t e r i o n should be t h e t o t a l l i f e - c y c l e c o s t .
T h i s p a p e r p r e s e n t s a comparison o f t h e t o t a l c o s t o f owning and o p e r a t i n g v a r i o u s a i r - t o - a i r h e a t pump systems and c o n v e n t i o n a l o i l , g a s and e l e c t r i c f u r n a c e s . The comparison i s made f o r a range o f h e a t - i n g l o a d s i n n i n e c i t i e s whose c l i m a t e s a r e r e p r e s e n t a t i v e o f t h e
v a r i o u s r e g i o n s o f Canada. The f a c t o r s o f c l i m a t e , r e g i o n a l f u e l c o s t and a v a i l a b i l i t y have a s t r o n g i n f l u e n c e on t h e b e s t c h o i c e of a new h e a t i n g system.
Although a h e a t pump i s c a p a b l e of p r o v i d i n g c o o l i n g i n summer, t h e e s t i m a t e o f b e n e f i t from a h e a t pump i s based e n t i r e l y on h e a t i n g - energy c o s t s a v i n g s . The r e s u l t s a r e p r e s e n t e d i n a format t h a t w i l l p e r m i t t h e r e a d e r t o determine t h e a d d i t i o n a l v a l u e t h a t must be a s s i g n e d f o r a i r c o n d i t i o n i n g i f t h e h e a t pump i s t o be c o m p e t i t i v e w i t h t h e low- e s t c o s t a l t e r n a t i v e h e a t i n g system.
CALCULATION OF HEATING ENERGY REQUIREMENTS
A number o f f a c t o r s i n f l u e n c e t h e purchased h e a t i n g energy r e q u i r e - ments o f a d w e l l i n g . The t o t a l amount o f purchased energy used t o h e a t a d w e l l i n g depends on t h e h e a t l o s s c h a r a c t e r i s t i c o f t h e house, t h e c l i m a t e o f t h e l o c a l e under c o n s i d e r a t i o n , and t h e amount of h e a t ob- t a i n e d from p e o p l e , a p p l i a n c e s and s o l a r g a i n . The t o t a l h e a t l o s s r a t e
( 9 ~ 0 ~ ) i s d i r e c t l y p r o p o r t i o n a l t o t h e indoor-outdoor t e m p e r a t u r e d i f - f e r e n c e (AT), t h a t is: The p r o p o r t i o n a l i t y c o n s t a n t K i s sometimes r e f e r r e d t o a s t h e t o t a l h e a t l o s s c h a r a c t e r i s t i c o f a d w e l l i n g , having t h e u n i t s w a t t s / " ~ . From E q . (1) i t i s e v i d e n t t h a t f o r a given v a l u e o f K t h e t o t a l h e a t l o s s r a t e i n c r e a s e s l i n e a r l y w i t h i n c r e a s i n g AT.
The weather d a t a f o r c a l c u l a t i n g t h e h e a t i n g energy r e q u i r e m e n t s a r e shown i n F i g u r e 1. T h i s p l o t shows frequency d i s t r i b u t i o n s o f o u t - door t e m p e r a t u r e f o r t h e f o u r main r e g i o n s i n Canada; t h e d i s t r i b u t i o n s a r e f o r t h e c i t i e s i n d i c a t e d . T h i s f i g u r e c l e a r l y shows t h a t h e a t i n g
energy requirements vary considcrably from region to region.
The British Columbia region is characterized by few extremes,
with the bulk of the heating hours above 5°C. The average indoor-
outdoor temperature difference is small; of the regions considered,
British Columbia requires the least amount of heating energy for a given
value of K. At the other extreme, the Prairie region is characterized
by a relatively flat distribution over the entire outdoor temperature
range. With a large number of heating hours at low temperature, the
heating energy requirements will be greatest for a given value of
K.
The Maritime distribution resembles in many ways that shown for British
Columbia, but the majority of the heating hours are distributed about
0°C. The Ontario-Quebec distribution is intermediate to that of the
Prairie and Maritime regions, and heating energy requirements reflect
this.
In this study a range of heat loss characteristics was used. A
house of standard frame construction was selected as the model residence
To investigate the effects of varying loads on the heating system, the
levels of insulation in the ceiling and walls were varied. The heat
loss characteristics for the different levels of insulation are summarized
in Table 1. The last 4 columns in the Table are the component heat loss
characteristics for the insulation level shown at the head of the column.
For example, (12-10-7) indicates that R12, R10 and R7 insulation was app-
lied to the ceiling, walls and below-grade walls respectively.
The tabulated values of the total heat loss characteristic, together
with the frequency distribution of outdoor temperature data were used
in a modified "bin" method to calculate the total annual heat loss from
the houses. Allowance was made for both solar and internal heat gains
in arriving at an average heatin load on the equipment. The details of
this method have been published.
f
!
EQUIPMENT PERFORMANCE
Heating systems respond to the heating load in different ways. A
fossil fuel furnace delivers heat to the dwelling at essentially a con-
stant rate while it is operating. The heat output is varied by cycling
the burner on and off in response to a thermostat. An electric resis-
tance furnace, with a number of stages of resistance heaters, operates
on and off in response to a space thermostat. The heating capacity of
conventional furnaces, therefore, can be considered to be independent of
the outdoor and indoor conditions.
On the other hand, the heating capacity of an air-to-air heat pump
largely depends on outdoor condition and to a lesser extent on indoor
conditions. As the indoor-outdoor temperature difference increases, the
heating capacity of the heat pump decreases, mainly because less heat
can be extracted from the outdoor air at lower temperatures (Figure
2).The seasonal utilization efficiency of fossil fuel furnaces, unlike
capacity, is dependent on the load. Over a large portion of the heating
season, the capacity of an oil or gas furnace greatly exceeds the load
on the system. This results in short burner l1onl1
periods and long 'loffff
periods, with attendant heat losses up the chimney during the off cycle.
This chimney action increases the heat loss due to infiltration, which
is reflected in a reduced efficiency value for the furnace under low-
load conditions.
Even at full-load conditions, the combustion efficiency of a furnace
is less than 100%. In fact, bonnet efficiency, defined as heat delivered
to the supply air divided by energy content of fuel burned, rarely ex-
ceeds 80%. To account for part-load inefficiency and off-cycle chimney
heat losses, a part-load correction factor is commonly used. Figure 3
shows the part-load correction factor, CF, to be a function of the fur-
nace oversizing in relation to the design heat loss rate.2 For this
study the high efficiency correction factor was employed. The part-load
correction factor is related to the seasonal utilization efficiency
(S.U.E.) as follows:
IIs.
s
S.U.E.
=-
x 100%
F
S.U.E.
=the seasonal utilization efficiency for a combustion
furnace,
%'Is-
s
=full-load or steady-state bonnet efficiency, assumed equal
to 0.8 for both oil and gas furnaces
CF
=part-load correction factor (Figure
3)The seasonal utilization efficiency of an electric resistance furnace
was assumed equal to loo%, which implies that the purchased energy
equalled the heating energy required.
In the case of a heat pump, the
ratio of heating energy delivered to the house to the amount of energy
that was purchased is referred to as the Coefficient of Performance (COP),
and is usually greater than 1, and in most circumstances approaches 2.
The COP is a
function of outdoor temperature, as shown in Figure 2.
The heat pump is also subject to part-load effects, although not to the
same extent as conventional fossil fuel furnaces. When the capacity of
the heat pump exceeded the heating load (i.e., above the balance point),
a correction factor recommended by Bullock and Reedy of Carrier Corpora-
tion3 was applied. Below the balance point the heat pump runs conti-
nuously and the supplementary heaters provide additional heat as required.
In this case part-load effects are non-existent.
DESCRIPTION OF THE VARIOUS HEAT PUMP SYSTEMS
There are basically two types of residential air-source heat pump
systems on the market today. One is the all-electric heat pump which
employs electric resistance heaters for supplementary heating when the
heating load exceeds the capacity of the heat pump. The other is com-
monly referred to as an "add-onf1
heat pump because it is primarily aimed
at the retrofit market, for application on existing oil and &as furnaces.
This add-on type does not have any supplementary electric resistance
heaters.
A l l - E l e c t r i c I-leat Pump
The system l a y o u t o f an a l l - e l e c t r i c h e a t pump i s i l l u s t r a t e d i n F i g u r e 4. The h e a t pump shown i s r e f e r r e d t o a s a s p l i t system, because t h e u n i t c o n s i s t s o f an outdoor and an i n d o o r s e c t i o n . The outdoor s e c t i o n c o n t a i n s t h e p r i n c i p l e components o f t h e h e a t pump, i n c l u d i n g t h e motor-compressor, outdoor h e a t exchanger, f a n , and r e v e r s i n g v a l v e . The i n d o o r s e c t i o n , which i s r e l a t i v e l y compact compared t o conventional f u r n a c e s , c o n t a i n s t h e i n d o o r h e a t exchanger, a i r c i r c u l a t i n g f a n and e l e c t r i c r e s i s t a n c e h e a t e r s . Both t h e i n d o o r and outdoor h e a t exchangers a r e equipped w i t h expansion v a l v e s , t o c o n t r o l t h e flow o f t h e l i q u i d r e - f r i g e r a n t , one on t h e h e a t i n g c y c l e , t h e o t h e r on t h e c o o l i n g c y c l e . The modes o f o p e r a t i o n a r e shown i n F i g u r e 4.
"Add-On" Heat Pumr,
I n many ways, t h e add-on h e a t pump i s s i m i l a r t o an a l l - e l e c t r i c system (Figure 5 ) . Both have t h e same h e a t pump components; t h e main d i f f e r e n c e s a r e t h e l o c a t i o n o f t h e i n d o o r h e a t exchanger, and t h e o i l f u r n a c e ( i l l u s t r a t e d h e r e ) which s u p p l i e s supplementary h e a t i n g below t h e b a l a n c e p o i n t .
The add-on h e a t exchanger i s l o c a t e d above t h e f u r n a c e i n t h e
supply a i r plenum. With t h i s arrangement, t h e h e a t pump and f u r n a c e can- n o t o p e r a t e s i m u l t a n e o u s l y a s i n t h e a l l - e l e c t r i c system. T h i s i s t o a v o i d abnormally h i g h p r e s s u r e s i n t h e h e a t pump condenser caused by t h e h i g h t e m p e r a t u r e o f t h e a i r l e a v i n g t h e f u r n a c e h e a t exchanger. Two t y p e s o f add-on systems a r e commercially a v a i l a b l e a s d e s c r i b e d i n F i g u r e 5. One a l l o w s h e a t pump o p e r a t i o n below t h e b a l a n c e p o i n t , whereas t h e o t h e r s h u t s o f f and t h e f u r n a c e p r o v i d e s a l l t h e h e a t i n g a t outdoor t e m p e r a t u r e s below t h e b a l a n c e p o i n t . The add-on h e a t pump c o n s i d e r e d i n t h i s s t u d y was of t h e l a t t e r t y p e .
The concept of combining two f u e l t y p e s i n one h e a t i n g system h a s a d v a n t a g e s , p a r t i c u l a r l y i f t h e two f u e l s a r e o i l and e l e c t r i c i t y . In t h e c a s e of a h e a t pump - o i l f u r n a c e combination, t h e e l e c t r i c u t i l i t y l o a d i s reduced c o n s i d e r a b l y d u r i n g t h e c o l d weather compared t o a11 a l l - c l e c t r i c h c a t pump. Thc compressor and f m ~ s J c m i ~ ~ ~ d r c l i l t i v e l y 1 i t t l c
powcr a t low outdoor tcml)cr:lrll rcs, i i S i l l ~ s t r;~tcll i 11 I: i !!~lrc~ 2
Cayac i t y
(I'owcr = -
COP
) 'The supplementary energy i s o b t a i n c d from t h c o i lt a n k , t h e r e b y reducing t h e demand on t h e e l e c t r i c u t i l i t y d u r i n g t h e c o l d e s t weather when t h e t o t a l demand f o r e l e c t r i c i t y i s a t i t s maximum. In f a c t , t h e load f a c t o r on t h e e l e c t r i c power system i s s u b s t a n t i a l l y improved, w i t h t h e r e l a t i v e l y f l a t power demand o v e r t h e e n t i r e outdoor t e m p e r a t u r e range. More i m p o r t a n t l y , however, t h i s combination u s e s l e s s o i l t h a n an o i l f u r n a c e o p e r a t i n g a l o n e . Energy d e r i v e d from hydro, uranium o r c o a l i s used i n p l a c e o f o i l , t h u s c o n t r i b u t i n g t o t h e n a t i o n a l g o a l o f becoming s e l f s u f f i c i e n t i n o i l .
' l H ~ b r i d l l Heat Pumr,
The c u r r e n t "add-on" systems do n o t t a k e f u l l advantage o f t h e h e a t pump. The I1hybridl1 system i l l u s t r a t e d i n F i g u r e 6 u s e s t h e h e a t pump
system t o i t s f u l l e s t e x t e n t . By l o c a t i n g t h e h e a t exchanger on t h e up- stream s i d e of t h e f u r n a c e , t h e h e a t pump can o p e r a t e c o n t i n u o u s l y below t h e b a l a n c e p o i n t . No complicated c o n t r o l s a r e r e q u i r e d t o c y c l e t h e compressor and f u r n a c e on and o f f . The f l h y b r i d l l i s a f u r n a c e - h e a t pump package designed t o o p e r a t e t o g e t h e r . S p e c i a l c o n s i d e r a t i o n s a r e g i v e n t o t h e d i f f e r e n t a i r flow r e q u i r e m e n t s o f t h e h e a t pump and f u r n a c e , and t o p o s s i b l e c o r r o s i o n o f t h e f u r n a c e h e a t exchanger brought on by summer c o o l i n g o p e r a t i o n . Such a h e a t pum f u e l f u r n a c e combination i s c u r - r e n t l y under development i n Canada.
{
-COMPARISON OF HEATING ENERGY COSTS
One of t h e most important f a c t o r s i n t h e c h o i c e of a h e a t i n g system
i s t h e a v a i l a b i l i t y and c o s t o f t h e a l t e r n a t i v e f u e l s . I n Canada, t h e r e a r e c o n s i d e r a b l e d i f f e r e n c e s i n t h e p r i c e s o f e l e c t r i c i t y and n a t u r a l g a s from r e g i o n t o r e g i o n . On t h e o t h e r hand, t h e p r i c e o f h e a t i n g o i l a s p e r c e i v e d by t h e consumer, i s r e l a t i v e l y uniform because of t h e f e d e r a l o i l - p r i c i n g p o l i c y . Table 2 shows t h e energy c o s t s employed i n t h i s s t u d y .
The c o s t o f h e a t i n g energy f o r b o t h h e a t pump and c o n v e n t i o n a l h e a t - i n g systems i s summarized i n F i g u r e s 7 t o 15 f o r t h e v a r i o u s c i t i e s . I n a l l c a s e s , t h e annual energy c o s t i n 1979 i s p l o t t e d a g a i n s t t h e h e a t i n g energy r e q u i r e d by t h e c o n v e n t i o n a l system. I n t h e c a s e o f new cons- t r u c t i o n , one must e s t i m a t e t h e h e a t i n g energy r e q u i r e d b e f o r e t h e s e graphs can be used. For r e t r o f i t o r a d d i t i o n t o an e x i s t i n g system, how- e v e r , t h e owner's p a s t u t i l i t y o r o i l h e a t i n g b i l l s w i l l p r o v i d e t h e i n - f o r m a t i o n r e q u i r e d t o e s t i m a t e t h e s a v i n g s with a p a r t i c u l a r h e a t pump system. I n Edmonton, where h e a t i n g o i l
i s
n o t used, a comparison has n o t been drawn between a h e a t pump system and o i l h e a t i n g . The l i m i t e d u s e o r u n a v a i l a b i l i t y of n a t u r a l gas i n t h e Maritimes has n o t allowed a comparison between t h e add-on o r h y b r i d systems and n a t u r a l g a s h e a t i n g . CAPITAL AND MAINTENANCE COSTSThe remaining components of t h e t o t a l c o s t which must be c o n s i d e r e d a r e t h e c o s t of i n s t a l l i n g t h e equipment and t h e a n t i c i p a t e d maintenance c o s t s . Table 3 summarizes t h e s e c o s t s f o r t h e systems under c o n s i d e r a t i o n Systems 1, 2 and 3 a r e t h e c o n v e n t i o n a l e l e c t r i c , o i l and g a s f u r n a c e s r e s p e c t i v e l y . System 4 i s t h e a l l - e l e c t r i c h e a t pump i l l u s t r a t e d i n Figure 4 . Systems 5a and 5b, t h e add-on h e a t pumps, a r e i l l u s t r a t e d i n Figure 5. System 5a i s an add-on t o an e x i s t i n g o i l f u r n a c e whereas 5b i s an add-on t o an e x i s t i n g e l e c t r i c f u r n a c e . Systems 6 and 7 a r e t h e g a s - and o i l - h y b r i d h e a t pumps i l l u s t r a t e d i n F i g u r e 6 . The l a s t system l i s t e d i n Table 3 i s a c o n v e n t i o n a l c e n t r a l a i r c o n d i t i o n e r . The l a y - o u t o f System 8 i s i d e n t i c a l t o t h a t o f t h e add-on i n F i g u r e 5 b u t i t s o p e r a t i o n i s r e s t r i c t e d t o c o o l i n g d u t y o n l y . The l a s t column o f Table
3 l i s t s t h e P r e s e n t Worth o f t h e C a p i t a l and Maintenance c o s t s ' a s ex- p l a i n e d i n t h e n e x t s e c t i o n . The c o s t s shown h e r e a r e r e p r e s e n t a t i v e of
t h o s e p r e v a i l i n g i n t h e Ottawa a r e a . The i n s t a l l e d c o s t may v a r y from one r e g i o n t o a n o t h e r and should be i n v e s t i g a t e d by t h e p r o s p e c t i v e owner.
The chimney c o s t i s i n c l u d e d f o r t h e g a s f u r n a c e . In t h e c a s e o f t h e o i l f u r n a c e b o t h t h e chimney and o i l t a n k a r e i n c l u d e d . These c o s t s would t h e n o n l y a p p l y i n t h e c a s e o f new c o n s t r u c t i o n .
-
For t h e e l e c t r i c f u r n a c e and t h e a l l - e l e c t r i c h e a t pump t h e i n c r e m e n t a l c o s t o f a 200 As e r v i c e h a s been t a k e n i n t o account f o r new c o n s t r u c t i o n o n l y . The h y b r i d systems, a l t h o u g h n o t commercially a v a i l a b l e a t t h i s t i m e , a r e i n t e n d e d f o r replacement o f e x i s t i n g o i l o r g a s f u r n a c e s , o r f o r new c o n s t r u c t i o n . For t h i s r e a s o n , t h e c a p i t a l c o s t i n c l u d e s t h e c o s t o f h e a t pump and f u r n a c e components ( i n c l u d i n g chimney and/or f u e l t a n k ) a s w e l l a s t h e maintenance c o s t s f o r t h e complete system. The add-on h e a t pump i s i n t e n d e d f o r
a d d i t i o n t o an e x i s t i n g f u r n a c e (both o i l (5a) and e l e c t r i c ( 5 b ) ) , and t h e r e f o r e r e f l e c t s o n l y t h e c o s t o f t h e h e a t pump. With t h e h y b r i d and add-on systems, t h e r e i s no requirement f o r a 200 A e l e c t r i c a l s e r v i c e
( i . e . , no r e s i s t a n c e h e a t e r s ) and t h u s t h e c a p i t a l c o s t i s lower t h a n f o r t h e a l l - e l e c t r i c h e a t pump. A c e n t r a l a i r - c o n d i t i o n e r i s i n c l u d e d f o r t h e c a s e where a combined h e a t i n g - c o o l i n g system i s d e s i r e d by t h e home- owner. In t h i s s i t u a t i o n , t h e c a p i t a l c o s t f o r t h e a i r - c o n d i t i o n e r must be added t o t h e c a p i t a l c o s t o f t h e c o n v e n t i o n a l h e a t i n g system.
TOTAL LIFE-CYCLE HEATING COST
The p r e s e n t worth o r t h e t o t a l l i f e - c y c l e c o s t o f h e a t i n g i s t h e amount o f money t h a t a consumer would have t o i n v e s t t o d a y , a t some i n t e r e s t r a t e , t o pay f o r t h e equipment, maintenance and energy r e q u i r e d by t h e system o v e r t h e s e r v i c e l i f e . T o t a l l i f e - c y c l e c o s t i n 1979 d o l l a r s = PWF (cost o f h e a t i n g energy E i n 1979) + PWFM
-
( c o s t of maintenance i n 1979) + i n s t a l l e d c o s t o f h e a t i n g system where PWFE = p r e s e n t worth f a c t o r f o r energy c o s tPWFM = p r e s e n t worth f a c t o r f o r maintenance c o s t n 1 + e 1 +e where PWF = [(-)
-
111
[(=)- 11
1+1 e = e s c a l a t i o n r a t e on f u e l o r maintenance i = i n t e r e s t r a t eFor t h i s s t u d y , it h a s been assumed t h a t t h e c o s t o f e l e c t r i c i t y and n a t u r a l g a s w i l l e s c a l a t e a t a r a t e o f 2% above i n f l a t i o n on o t h e r goods and s e r v i c e s . I n t h e c a s e o f h e a t i n g o i l , t h e e s c a l a t i o n r a t e h a s been assumed t o be 4% above t h e g e n e r a l r a t e o f i n f l a t i o n . T h i s s c e n a r i o was assumed t o a p p l y o v e r t h e n e x t 1 2 y e a r s , which was assumed a s t h e u s e - f u l s e r v i c e l i f e o f a h e a t pump. A r e a l i n t e r e s t r a t e of 2% was con- s i d e r e d t o be r e p r e s e n t a t i v e o f t h e r a t e o f r e t u r n a v a i l a b l e t o t h e
average consumer (i.e., the cost of residential mortgages) and hence was
employed to calculate the following present worth factors:
PWFoil
=14
PWF
--
PWFelect
=12
gas
PWFM
=10.75
.The total life-cycle costs are summarized in Figure 16 for new
construction and in Figure 17 for the case of retrofit or replacement
of an existing system. In Figure 17 comparison should be made between
competing systems (i.e., 1 and 5b; 2 and 5a;
2and 7).
DISCUSSION OF RESULTS
New Construction
Space heating with natural gas is by far the most economical choice
in Saskatoon and Edmonton, and for this reason these cities have not been
included in Figure 16. In other regions of Canada where natural gas is
generally available (i.e., Vancouver, Windsor, Toronto, Ottawa), it is
the lowest cost choice for space heating today in new construction. For
areas within these regions where natural gas is not available, the
most economical choice would appear to be electric resistance (electric
furnace) or an all-electric heat pump, depending on the amount of annual
purchased energy. The oil hybrid (System 7) is competitive with the
electric heat pump, in spite of its relatively high capital cost.
In Montreal, electric resistance heating offers the lowest cost
in new construction, with the all-electric heat pump competitive at high
levels of purchased energy. Natural gas space heating is not competitive
in this region owing to its high cost compared to that of electricity.
In Fredericton, all systems are competitive (with the exception of
natural gas) over a wide range of purchased energy. The electric furnace
and oil furnace are the economic choices at low consumption levels,
whereas at the other end of the scale, the heat pump systems (4 and 7)
appear to be the best choices.
In Halifax, the high cost of electricity eliminates the electric
heating systems as desirable choices. Ilere an oil furnace offers the
lowest cost to the consumer.
This discussion has dealt with the selection of the most cost ef-
fective heating systems. Where the homeowner wants a combination heating-
cooling system, the cost of a central air-conditioner (System 8)
must be
added to the conventional furnace systems. This would make the electric
heat pump the most cost effective heating-cooling system in Vancouver,
followed closely by the gas hybrid (System 6).
In Windsor, Toronto, and
Ottawa, the gas hybrid would be the most cost effective heating-cooling
system. Where natural gas is not available, an electric heat pump would
be the economic choice.
In Montreal, the electric heat pump would appcar to be the most
cost effective heating-cooling system. In Fredericton, the homeowner
could choose between the oil-hybrid or electric heat pump, because of
the competitive nature of the two systems in this region. If air condi-
tioning were desired in Halifax, the oil hybrid would be the economic
choice followed closely by the combination of an oil furnace and a
central air-conditioner.
REPLACEMENT OR RETROFIT OF
AN
EXISTING HEATING SYSTEM
It was emphasized that natural gas, where available (with the ex-
ception of ~ontreal), was the most cost effective way of providing space
heating in new construction. This situation will probably apply in the
case where an existing oil furnace needs replacement. Here the installed
cost of a new oil furnace must be compared with the installed cost of a
gas furnace and the cost of upgrading the chimney. The installed costs,
together with the energy and maintenance costs are used in a calculation
similar to that presented in the previous section.
One other situation exists where an oil furnace has a number of
years of useful service life remaining. A conversion gas burner can be
fitted with the idea of reducing energy costs. The energy cost saving
must be compared with the cost of the conversion burner and the cost of up-
grading the chimney. Depending on individual circumstances, a gas con-
version may be cost effective.
The following sections will examine the replacement or retrofitting
of existing oil and electric furnaces where natural gas is unavailable.
REPLACEMENT OR RETROFIT OF AN OIL FURNACE
Reu
1
acement
I-lomeowners
faced with the need to replace an oil furnace and who
are unable to obtain natural gas must make a choice between purchasing
a new oil furnace or switching to an electric heating system. Conversion
to an electric furnace requires an increase in the electrical service to
200 A. This involves an expenditure of approximately $700. This in it-
self makes the conversion to an electric furnace or all-electric heat
pump uneconomical on the basis of the assumptions used in the present
analysis.
The homeowner could install an oil hybrid such as System 7, or an
oil furnace together with electric resistance duct heaters up to the
limit of the existing electrical service. In this study only the former
system has been studied. The results are shown in Figure 17.
System 7 is competitive if not decisively more economical than oil
furnace heating in all the cities shown in Figure 17, with the exception
of Halifax. This conclusion is based on heating energy savings alone
and does not involve a capital allowance for air conditioning.
R e t r o f i t
Iiomeowners who have an o i l f u r n a c e w i t h a number of y e a r s of u s e f u l s e r v i c e l i f e remaining ( a t l e a s t 12) might look t o an add-on heat pump t o reduce o p e r a t i n g c o s t s o r provide summer a i r c o n d i t i o n i n g . In t h i s c a s e t h e c o s t of owning and o p e r a t i n g an add-on h e a t pump (System 5a) i s compared with t h e c o s t o f c o n t i n u i n g t o h e a t with o i l over t h e next 12 y e a r s . The r e s u l t s a r e p l o t t e d i n Figure 17 f o r a l l c i t i e s except H a l i f a x . With t h e e x c e p t i o n of Vancouver, t h e r e s u l t s i n d i c a t e t h a t t h e homeowner must be prepared t o p l a c e some v a l u e on having c e n t r a l a i r c o n d i t i o n i n g
i n o r d e r t o j u s t i f y t h e r e t r o f i t t i n g o f an o i l f u r n a c e with an add-on h e a t pump. I t should be emphasized t h a t t h e economics o f an add-on h e a t pump t h a t o p e r a t e s below t h e balance p o i n t would be between t h a t of t h e o i l - h y b r i d and t h e add-on systems c o n s i d e r e d h e r e .
R e t r o f i t o f an E l e c t r i c Furnace
One o t h e r p o s s i b l e r e t r o f i t s i t u a t i o n would be t h e a d d i t i o n o f a h e a t pump (System 5b) t o an e x i s t i n g e l e c t r i c f u r n a c e . The t o t a l c o s t of System 5b i s compared with t h a t of System 1 ( e l e c t r i c f u r n a c e ) i n Figure 17. I t
i s
e v i d e n t t h a t t h e a d d i t i o n o f a h e a t pump t o an e l e c t r i c furnace can be economically j u s t i f i e d i n some c a s e s without making a c a p i t a l allowance f o r a i r c o n d i t i o n i n g . The d e c i s i o n would depend on t h e amount o f energy c u r r e n t l y used by t h e e l e c t r i c f u r n a c e . The "break-even" annual consumption i s seen t o v a r y with l o c a l e . In Vancouver, Windsor, Toronto and F r e d e r i c t o n , circumstances a r e such t h a t an e l e c t r i c h e a t pump could be added t o an e l e c t r i c f u r n a c e and produce s a v i n g s f o r t h e homeowner over t h e s e r v i c e l i f e of t h e h e a t pump. T h i s conversion would not appear t o be a t t r a c t i v e i n Ottawa and Montreal a t t h i s time.In H a l i f a x , r e t r o f i t t i n g o f an e l e c t r i c f u r n a c e with a h e a t pump w i l l almost always r e s u l t i n a s a v i n g t o t h e owner. The p l o t f o r H a l i f a x shows t h e e f f e c t of a 3-ton h e a t pump (System 5b (3T)) on t h e t o t a l l i f e - c y c l e c o s t s . Even though t h e l a r g e r h e a t pump i s more expensive ( - $ b o o ) l e s s r e s i s t a n c e h e a t i n g i s r e q u i r e d and t h e energy s a v i n g s more t h a n o f f s e t t h e a d d i t i o n a l c a p i t a l c o s t . T h i s advantage w i l l o n l y be apparent i n c l i m a t i c r e g i o n s f a v o u r a b l e t o a i r - s o u r c e h e a t pump o p e r a t i o n and where e l e c t r i c i t y c o s t s a r e h i g h . In Ottawa, f o r example, a l a r g e r h e a t pump does not r e s u l t i n a lower t o t a l l i f e - c y c l e c o s t , because t h e incremental energy c o s t saving does not exceed t h e a d d i t i o n a l c a p i t a l c o s t .
IMPACT OF ASSUMPTIONS ON RESULTS
A number of assumptions, such a s f u t u r e energy p r i c e s and s e r v i c e l i f e of h e a t pumps, had t o be made i n o r d e r t o c a r r y o u t an a n a l y s i s o f t h e r e l a t i v e economics o f a i r - t o - a i r h e a t pump systems and conventional h e a t i n g systems. The a c t u a l t r e n d i n energy p r i c e s w i l l obviously have an e f f e c t on t h e r e s u l t s p r e s e n t e d h e r e , a s w i l l t h e e s t a b l i s h m e n t o f a p o l i c y favouring t h e u s e of some energy forms o v e r o t h e r s , such a s t h e use of n a t u r a l gas and e l e c t r i c i t y t o reduce consumption o f o i l .
T h i s assumption i s probably u n r e a l i s t i c a s t h e e s c a l a t i o n r a t e w i l l depend on t h e f u e l used t o g e n e r a t e e l e c t r i c i t y ( i - c . , n u c l e a r , c o a l , hydro o r g a s ) and on o t h e r f a c t o r s .
I f n a t u r a l gas p r i c e s i n c r e a s e a t a r a t e g r e a t e r t h a n t h a t of e l e c t r i c i t y , t h e economics o f e l e c t r i c systems w i l l improve r e l a t i v e t o
t h a t o f t h e g a s f u r n a c e . The o p p o s i t e t r e n d would i n c r e a s e t h e c u r r e n t
c o s t gap between t h e e l e c t r i c and n a t u r a l gas h e a t i n g systems.
A h i g h e r e s c a l a t i o n r a t e f o r e l e c t r i c t y would improve t h e economics
o f t h e a l l - e l e c t r i c h e a t pump compared t o r e s i s t a n c e h e a t i n g , with t h e r e s u l t t h a t t h e e l e c t r i c h e a t pump would become t h e p r e f e r r e d system o f t h e two, without a c a p i t a l allowance f o r a i r c o n d i t i o n i n g .
T h i s s t u d y used t h e performance c h a r a c t e r i s t i c s o f h e a t pumps t h a t
have been on t h e market f o r s e v e r a l y e a r s . Newer, more e f f i c i e n t u n i t s
a r e a p p e a r i n g on t h e market, and depending on t h e a d d i t i o n a l c o s t , i f any, t h e y would i n d i c a t e a lower t o t a l l i f e - c y c l e c o s t f o r t h e h e a t pump systems.
CONCLUSIONS
Based on t h e assumptions made i n t h i s s t u d y , a n a t u r a l g a s f u r n a c e a p p e a r s t o be t h e most economical h e a t i n g system f o r new c o n s t r u c t i o n and f o r replacement o f o i l f u r n a c e s , where n a t u r a l g a s i s a v a i l a b l e .
I f a homeowner wants a combined h e a t i n g - c o o l i n g system, one o f t h e h e a t
pump systems could be t h e b e s t c h o i c e .
Where n a t u r a l g a s i s n o t a v a i l a b l e , a n e l e c t r i c f u r n a c e o r a h e a t
pump system, depending on t h e annual energy consumption, would be p r e - f e r r e d o v e r an o i l f u r n a c e i n new c o n s t r u c t i o n f o r a l l r e g i o n s except H a l i f a x , where t h e most economical h e a t i n g system a p p e a r s t o be t h e o i l f u r n a c e .
In r e g i o n s where n a t u r a l g a s i s u n a v a i l a b l e and an e x i s t i n g o i l f u r n a c e needs replacement, a o i l - h y b r i d h e a t pump can be j u s t i f i e d i n
many i n s t a n c e s without any c a p i t a l allowance f o r a i r c o n d i t i o n i n g . I f
t h e o i l f u r n a c e s t i l l h a s a number o f y e a r s o f s e r v i c e l i f e remaining, an a i r - c o n d i t i o n i n g c a p i t a l allowance i s r e q u i r e d t o j u s t i f y an add-on
h e a t pump of t h e t y p e analyzed f o r a l l c i t i e s e x c e p t Vancouver. I n most
c a s e s , it i s more economical f o r t h e homeowner t o c o n t i n u e u s i n g t h e
o i l f u r a n c e . Add-on h e a t pumps t h a t a l l o w o p e r a t i o n below t h e b a l a n c e
p o i n t were n o t c o n s i d e r e d i n t h i s s t u d y . In many c a s e s t h i s t y p e c o u l d
be an economic r e t r o f i t f o r t h e homeowner, without a c a p i t a l allowance f o r a i r c o n d i t i o n i n g .
I t should be emphasized t h a t t h e c a p i t a l c o s t s employed i n t h i s s t u d y may v a r y c o n s i d e r a b l y w i t h l o c a l e . The homeowner should i n v e s t i - g a t e v a r i a t i o n s i n h i s own a r e a and make a p p r o p r i a t e a d j u s t m e n t s t o t h e t o t a l l i f e - c y c l e c o s t s p r e s e n t e d .
The r e s u l t s p r e s e n t e d should be a p p l i c a b l e t o t h e r e g i o n s i n which
should be representative of heat pump performance in southcrn Ontario;
Ottawa for areas in eastern Ontario; Montreal for southern Quebec;
Fredericton and Halifax for the Maritime region. This of course assumes
that the electrical energy prices are uniform throughout the region.
REFERENCES
1. Cane, R.L.D. A llmodified'l
bin method for estimating annual heating
energy requirements of residential air source heat pumps. ASHRAE
Journal, Vol. 21, No. 9, Sept. 1979, pp 60-63.
2. Borg-Warner Corp., York Division. Seasonal performance factor and
operating cost calculation for heating. Application Data, Form
515.21-AD3-C.
3. Bullock, C.E. and Reedy, W.R. Heat pump cyclic performance and its
influence on seasonal operation. Proceedings of the 3rd Annual Heat
Pump Technology Conference, O.S.U., Stillwater, Oklahoma, April 10-11,
1978.
4.
Development of an innovative hybrid heat pump. DSS Contract No.
OSX78-00058 between Canadian Chromalox Co. Ltd. and the Division of
Building Research, National Research Council of Canada.
; (dux (..r LL~-~J.L.;
,/'
r i l s _ w & O.
-, & 3 L TABLE 1 HEAT L O S S C H A R A C T E R I S T I C S U S E D I N S T U D YI
D E S I G N HEAT L O S S C H A R A C T E R I S T I C , W A T T S I ° C 1 2 3 4 COMPONENT'
(12-10-71' (20-12-81* 3 0 - 1 2 - 1 0 (30-20-101'-
CEILING 1 0 6 5 1 35 25 25 WALL (A. G. ) 1 1 7 6 5 4 8 4 8 3 3WALL AND SLAB (B.G. 2 0 9 1 5 6 5 4 4 7 '36
WINDOW (DOUBLE GLAZED) 2 0 6 2 6 2 6 2 6 2
DOORS 4 9 9 9 9
0.5 7 b
INFILTRATION (0.75 A.C. lh) 453"
*
1 1 4 1 1 4 1 1 4 1 1 4TOTAL HEAT LOSS CHARACTER1 ST1 C, Z" 5
WATTI°C 35 7 3 2 2 305 2 79
Y BRACKETED Q U A N T I T Y REFERS T O N O M I N A L I N S U L A T I O N ( I N BRITISH U N I T S ) A P P L I E D T O C E I L I N G , A B O V E GRADE WALLS A N D BELOW GRADE W A L L S , R E S P E C T I V E L Y . I N CASES 1 ,
2 , A N D 3 B A S E M E N T I N S U L A T I O N A P P L I E D T O T W O FEET BELOW G R A D E ; I N CASE 4 B A S E M E N T .WALL I N S U L A T I O N APPLIED T O F L O O R L E V E L . * * V O L U M E ( m 3 ) I N C L U D I N G B A S E M E N T i> L o ' ,
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TABLE 2 R E S I D E N T I A L FUEL A N D E L E C T R I C I T Y C O S T S ( E M R - J A N . 7 9 ) L O C A T l ON E L E C T R I C I T Y N A T U R A L G A S O I L $ l k ~ . h ( $ I G J ) t l ( S I G J ) ~ * l g a l ~ ( $ I G J ) ~ ~ ~ V A N C O U V E R 2 . 5 0 ( 6 . 9 4 ) 3 0 . 4 ( 2 . 8 8 ) 5 8 . 9 ( 3 . 3 4 ) EDMONTON 2. 3 0 ( 6 . 3 9 ) 2 0 . 2 ( 1 . 9 1 1 ( N . A . - S A S K A T O O N 2 . 5 0 ( 6 . 9 4 ) 2 7 . 4 ( 2 . 6 0 ) 5 8 . 9 ( 3 . 3 4 ) W I N D S O R 2 . 6 0 ( 7 . 2 2 ) 3 6 . 5 ( 3 . 4 6 ) 6 0 . 6 ( 3 . 4 4 ) TORONTO 2 . 6 0 ( 7 . 2 2 ) 3 6 . 5 ( 3 . 4 6 ) 6 0 . 6 ( 3 . 4 4 ) OTTAWA 2 . 5 5 ( 7 . 0 8 ) 3 6 . 5 ( 3 . 4 6 1 62. 2 ( 3 . 5 3 ) M O N T R E A L 1 . 9 0 (5. 2 8 ) 4 3 . 4 ( 4 . 11) 6 0 . 2 ( 3 . 4 2 ) F R E D E R I C T O N 2 . 6 5 ( 7 . 3 6 ) 5 0 . 0 ( 4 . 7 4 ) 6 1 . 2 ( 3 . 4 7 ) H A L l F A X 4. 15 ( 1 1 . 5 3 ) ( N . A.-
6 0 . 8 ( 3 . 4 5 )T A B L E 3 R E P R E S E N T A T I V E S Y S T E M C O S T S , 1 9 7 9 $ P R E S E N T W O R T H ( ' ) M A l N T E N A N C E OF C O S T S ( C A P I T A L C A P I T A L C O S T , A N D M A I N T E N A N C E l , N 0. S Y S T E M C O S T $ / y e a r $ 1 E L E C T R l C F U R N A C E 1 0 0 0 2 0 1 2 2 0
-
2 O I L F U R N A C E ( 2 ) 1 5 0 0 4 5 1 9 8 0 3 G A S F U R N A C E ( 3 ) 1 0 0 0 3 5 1 3 8 0 4 E L E C T R I C H E A T P U M P 2 7 0 0 5 0 3 2 4 0 ( 2 T O N ) 5a, b A D D - O N H E A T P U M P 2 0 0 0 5 0 2 5 4 0 ( 2 T O N ) 6 H Y B R I D ( G A S ) H E A T 2 7 0 0 6 0 3 3 4 0 P U M P ( 2 T O N ) 7 H Y B R I D ( O I L ) H E A T 3 0 0 0 6 0 3 6 4 0 P U M P ( 2 T O N ) 8 C E N T R A L A I R - 1 2 0 0 1 2 0 0 C O N D I T I O N E R ( 2 T O N ) ( 1 ) P W F M A I N T E N A N C E = 1 0 . 7 5 ( 2 ) I N C L U D E S C H I M N E Y A N D T A N K ( 3 ) I N C L U D E S C H I M N E Y1 1 1 , 1 1 1 1
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- 3 0 - 2 5 - 2 0 - 1 5 - 1 0 - 5 0 5 10 15 20 25 30 D R Y B U L B T E M P E R A T U R E , " CFigure 1. Frequency distribution of dry bulb temperatures in various Canadian regions (based on period 1957-1966)
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2 . I F H E A T PUMP U N A B L E T O S A T I S F Y D E M A N D S E C O N D S T A G E O F T H E R M O S T A T B R I N G S O N ELECTRIC R E S I S T A N C E HEATERS I N S E Q U E N C E U N T I L S E C O N D S T A G E I S S A T I S F I E D ( N O R M A L L Y \ T O 1.5OC D I F F E R E N T I A L BETWEEN FIRST A N D S E C O N D S T A G E )
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2 . OTHER A D D - O N H E A T PUMPS W I L L A L L O W O P E R A T I O N BELOW B A L A N C E P O I N T BY USE OF T W O S T A G E THERMOSTAT A N D OTHER C O N T R O L S . F U R N A C E A N D H E A T PUMP C A N N O T OPERATE S I M U L T A N E O U S L Y A N D H E A T PUMP I S N O R M A L L Y L O C K E D O U T BELOW -12OC T O A V O I D SHORT C Y C L I N G OF COMPRESSOR
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