8/14/2019 Val Prest Payback Calculations

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HEATING my NEW HOME & RE-CAPTURE of CAPITALBy Lynwood V. Prest, P.E., 11 Highland Road, Groton, MA 01450

for a Farenheit temperature difference of -2 outside to 70 degrees inside = 72 degrees.

Assume a more seasonal, average temperature difference of 25 to 69 degrees = 44 degr

Then my Heating load is 79,847 x (44/72) = 48,795 BtuH

Operating 24 hrs/day for 30 days per month the total Btu = 48,795 x 24 x 30 = 35,136,6

Heating oil contains 138,690 BTU's per gallon. (From kirotv.com, "The Facts About Heatin

Therefore oil usage per month would be 35,136,680 BTU/138,690 BTU per gallon = 253.3

Heating Oil costs $3.46 per gallon as of Feb. 27, 2008 according to the Energy Informatio(Official Energy Statistics from the U.S. Government)

Energy-Star-Rated lighting and appliances, except for the radiant heating in the worksho

house - Geothermal HVAC, ventilation system, lighting, appliances, tools, radios, stereo s

What would separate electricity cost?

Though that included some air conditioning I will ignore it and use that cost for the separ

for Dec., Jan. & Feb.

Apply 1/2 the oil costs + electricity for Oct., Nov., March and April = $876.48/2 + $124.0

Let us further assume that for the other 5 months there is no savings (Not quite true bec

heating water is ignored.).

Diff. = $3,593

Water Energy Distributors, Plaistow, NH calculated the Heating Load = 79,847 BtuH,

Bill Wenzel Heating & Air Conditioning designed and built the Geothermal HVAC sytem to

Therefore, if I used oil heat, its cost would have been 253.32 gallons x $3.46/gallon = $8

This would not include electricity for lights and appliances. My new home has all high-eff

My largest invoice from Groton Electric was $346.38 for January, 2008 which includes ev

For August, 2007, our 1st month in the home, the electric bill that came on 9/1/2007 was

SO, assuming oil-fired heat, monthly cost would have been $876.48 + $124.09 = $1,000

Annual cost would have been 3 x $1000.57 + 4 x $562.33 + 5 x $124.09 =

Projected Actual Annual cost in new house = 3 x $346 + 4 x $155 + 5 x $12

Time to re-capture excess capital cost for Geothermal HVAC system = $20990/$3593 =

8/14/2019 Val Prest Payback Calculations

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OST

es

0 Btu

g Oil".)

2 gallons/month

Administration,

.

stems, etc.

te electricity.

= $562.33/mnth

use AC and

/yr

do that.

6.48/mnth

iciency,

erything in the

$124.09.

.57mnth

$5,871.48

=$2,278

6 years