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Sir Sparks
Sir Sparks, President/Owner/ Master Electrician
Category: Electrical
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Experience:  US State Certified & UK Electrical Contractor for all electrical fields/disciplines
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Approx how much energy in kW-hr/yr would a 4000 sq.ft house

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Approx how much energy in kW-hr/yr would a 4000 sq.ft house and a 2400 sq ft barn require to heat and operate in eastern massachusetts. Use some assumptions such as 10 ft ceilings in the house and 14 ft in the barn or what ever assumptions would be typical for a high end house. The barn would be maintained at 65

Sir Sparks :

A Master Electrician here to help. I am a double qualified; USA & UK electrician. Please give me a moment to formulate a reply.

Sir Sparks :

Perhaps the biggest unknown here is the degree of insulation. Also is this just conventional electric heat ?.

JACUSTOMER-us34k63l- :

Assume typical insulation and conventional electric heat.

JACUSTOMER-us34k63l- :

The barn would have some activity in the winter such as a garage.

JACUSTOMER-us34k63l- :

Where to hot air would escape.

Sir Sparks :

huh ?

With the amount of information supplied any estimate I gave would be little more than a wild guess. I will see if another expert can assist.
Customer: replied 6 years ago.

OK, I will try to approach this a little differently. Just let me know if you cant answer this. I use 2200 gal of propane for heat, hot water and range top. I also use 11,000 kW-hr per year for lights etc. I would like to build a 30ft x 80ft gable end barn and heat it. I would like to size a solar PV array to eliminate all my anticipated energy needs. How many kW-hrs should this solar array produce? Give me a range. Your answer will not significantly affect my decision because I am oversizing the array. I would just like to bounce this off of an expert. Will you answer this? huh?

I can get closer with this. IN MA you are likely to get an annual average of 400 watts per day from an 8 sq. ft $1000 Solar cell.
VERY roughly your Winter heating requirement with conventional electric heat for this 6,400 sq ft total will be 100 to 200 Kw per day So you will need 250 to 500 solar cells at a cost of $250,000 to $500,000 without any allowance for electronics or installation.

The roof space required will be about 2,000 to 4,000 square feet.
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Customer: replied 6 years ago.

Thanks. The news is not so bad. I am building a 60kW system and I want to backup my claim that it is for personal use and not commercial. Using your high end estimate of 200 kW per day or (200 kW-hrs per day)(365 days) = 73,000 kW-hrs per year. This is approx what the 60kW array will produce in a year. The ROI is a different matter.


PS, I am using your 200kW per day as an annual average and not a winter avg. Is the 200kW a winter avg or anual avg?



Bearing in mind that this is a rough estimate I meant an average when heating was required. I would expect Summer usage to be considerably less.However when considering all other non heating loads as well, I think your figure is fair as an annual average.

Edited by Sir Sparks on 1/30/2011 at 5:12 AM EST
Further research shows;
One gallon of propane (LPG) is equal to 27 Kw of electrical energy.
Therefore you annual usage of 2,200 gallons of propane for your present residence equates to 59,400 Kwhr per year. Add to this your 11,000 Kwhr "other loads" makes 69,400 Kwhr per year. So we are definitely in the right ball park here.

Also consider that although you will add 2,400 sq ft to this home size, your propane heating system is also not 100% efficient as is electrical heat.

Edited by Sir Sparks on 1/30/2011 at 6:06 AM EST
To be honest I am amazed at how close these two independent calculations correlated.
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