Sun hours

[J.P.M.]

You seem to have a huge array! Thanks for posting about your adventures.

I'm contemplating switching from gas furnace to heat pump. My house is twice as big as yours,
and LA has ~1200 heating degree days + 1200 cooling degree days / year
vs. Chicago's 6500 hdd's and 850 cdd's, so if our houses are similarly leaky/uninsulated,
I'll be using 2400/7400 x 2 = 1.5 times as much energy as you = 45,000 KWH/year.
I think I can fit a 10KW array that should generate about 15,000 KWH/year, about half yours...
which suggests it'll only cover about a third of my energy needs
I hope that's a pessimistic estimate, and my nice Craftsman deep eaves plus opening
windows for breeze at night will cut the cooling bills (and that blindly estimating with
hdd's and cdd's like that is wrong).

Still, I'd better get busy insulating and plugging leaks!

1.) Check your math. The heating/cooling DD's are in the ballpark. The load calc is a bit unusual and in any case, the math is wrong. Aside from that, what's your current annual usage ?

2.) As before adding solar, tighten up/insulate/conserve before consideration of new/diff. HVAC equip., and if you proceed w/new equipment, just like solar, don't oversize it.

3.) For the relatively small HVAC loads imposed by low # heating/cooling DD, and also after considerations for load reductions, new equipment may be hard to justify from a cost effective standpoint.

[bcroe]

You seem to have a huge array! Thanks for posting about your adventures.

I'm contemplating switching from gas furnace to heat pump. My house is twice as big as yours,
and LA has ~1200 heating degree days + 1200 cooling degree days / year
vs. Chicago's 6500 hdd's and 850 cdd's, so if our houses are similarly leaky/uninsulated,
I'll be using 2400/7400 x 2 = 1.5 times as much energy as you = 45,000 KWH/year.
I think I can fit a 10KW array that should generate about 15,000 KWH/year, about half yours...
which suggests it'll only cover about a third of my energy needs
I hope that's a pessimistic estimate, and my nice Craftsman deep eaves plus opening
windows for breeze at night will cut the cooling bills (and that blindly estimating with
hdd's and cdd's like that is wrong).

Still, I'd better get busy insulating and plugging leaks!

Thanks for the comments. Plugging leaks is the most effective thing you can do.
Don't remove the gas furnace, its your backup. Heat pumps switching to resistance
heat are terrible.

Check your arithmetic, I estimate you will need 0.65 times as much energy as
used here. However a ranch is the least energy efficient, and outside surface
doesn't go up as fast as square feet, so maybe you only need 0.5 times as much.
If so 15,000 KWH would be in the ballpark. You will ALSO have the advantage
that your heat pump will typically run at higher efficiency in your temperatures,
and backup heat such as I used (resistance heating) can be avoided.

My array has many extra panels to keep up serious production even under some
level of clouds; its rarely clear here. AND, they are oriented to stretch the effective
length of a sunny day, without increasing the size of the rest of the plant.
Bruce Roe

[SunEagle]

You seem to have a huge array! Thanks for posting about your adventures.

I'm contemplating switching from gas furnace to heat pump. My house is twice as big as yours,
and LA has ~1200 heating degree days + 1200 cooling degree days / year
vs. Chicago's 6500 hdd's and 850 cdd's, so if our houses are similarly leaky/uninsulated,
I'll be using 2400/7400 x 2 = 1.5 times as much energy as you = 45,000 KWH/year.
I think I can fit a 10KW array that should generate about 15,000 KWH/year, about half yours...
which suggests it'll only cover about a third of my energy needs
I hope that's a pessimistic estimate, and my nice Craftsman deep eaves plus opening
windows for breeze at night will cut the cooling bills (and that blindly estimating with
hdd's and cdd's like that is wrong).

Still, I'd better get busy insulating and plugging leaks!

Getting rid of the "leaks" is one of the best ways to save money.

I saw a significant decrease in my AC costs when I replaced all of the East and a few of the West facing windows with new ones that had a Low E coating to prevent heat intrusion. You could feel the heat a foot away from the window when the sun was shining directly on it before I installed the new ones.

[DanKegel]

Its a 3 ton air to air, pretty quick & cheap but only half as efficient as a buried system,
and definitely limited in the coldest months. In a 2000 sq ft, not very well insulted ranch

You seem to have a huge array! Thanks for posting about your adventures.

I'm contemplating switching from gas furnace to heat pump. My house is twice as big as yours,
and LA has ~1200 heating degree days + 1200 cooling degree days / year
vs. Chicago's 6500 hdd's and 850 cdd's, so if our houses are similarly leaky/uninsulated,
I'll be using 2400/7400 x 2 = 1.5 times as much energy as you = 45,000 KWH/year.
I think I can fit a 10KW array that should generate about 15,000 KWH/year, about half yours...
which suggests it'll only cover about a third of my energy needs
[ EDIT: 1/3 x 2 = 2/3, not 1.5. I was asleep when I wrote that.
So this crude measure gives 20,000 KWH/year as my needs, so my array
should generate 75% of my needs, which isn't bad.]

I hope that's a pessimistic estimate, and my nice Craftsman deep eaves plus opening
windows for breeze at night will cut the cooling bills (and that blindly estimating with
hdd's and cdd's like that is wrong).

Still, I'd better get busy insulating and plugging leaks!

[bcroe]

They were very vague about that last year, net metering was a haphazard,
by hand operation. It was hard to tell what happened. But this year bills are regular again.

I believe they will reset 1 April or whenever they (manually) read the meter. The
plan was I get no credit for extra KWH, but A. I can burn extra heating the other
building, and B. It looks to be a very small amount anyway, which cost me nothing.
I can make 128 KWH in one sunny day. Or, I might run short, too close to call. Bruce

Finally the electric bill reflecting the end of my net metering year came. Last month
they didn't even send one until I requested a copy. Here is the curve of my KWH
reserve, being used up through the winter for electricity and heating the house.

Production for the year ending 1 April was about 28,000 KWH. What happened is
the reserve built up to about 12,400 KWH at the end of Oct, then consumption
exceeded generation. Would there be enough reserve to last the winter? Reserve
bottomed at 691 KWH 5 Mar, then it went up again. The POCO reset it to zero
1 April, I ended up giving them 728 KWH (that cost me nothing). So the reserve
made it with energy to spare. 12 months in a row with no electric energy charge.

This included 6 months use of a new heat pump. 15/16 will get 12 months use, so
the reserve might be even higher. If I can track it better, some may get diverted to
help keep the car shop above freezing. Bruce Roe

[gregvet]

Today was about 65 deg F, overnight lows hitting 35 to 45. Bruce Roe

Despite our highs around 60 to 75 degrees, our overnight lows have been around 28 degrees F.- Not necessarily conducive to normal heat pumps.

[SunEagle]

Today was about 65 deg F, overnight lows hitting 35 to 45. Bruce Roe

Can you put in a good word for warmer weather next week. I will be in Lincoln for a few days starting next Wednesday.

[bcroe]

What temps are you talking about?

Today was about 65 deg F, overnight lows hitting 35 to 45. Bruce Roe

[gregvet]

Meantime warmer days are here, the heat pump runs very little, and I'm already piling
up KWH reserve for the winter of 15/16. Bruce Roe

What temps are you talking about?

[bcroe]

Had a little problem this week, good weather, but the 3 ton heat pump just stopped. Still
covered after only 6 months (I didn't tell them how hard its been working). The main
machine seems just fine, plenty of F410A gas. Turns out the problem was no signal from
the new super fancy menu driven screen battery backup software imperiled thermostat.
A little program change and its all going again.

Can't say this surprises me much. In the vein that less complex is more reliable, I kept
my decades old environmentally illegal mercury tilt thermostat in place to run the
propane furnace; the new one just triggers the blower and heat pump. There just might
come a day when old reliable does everything.

Meantime warmer days are here, the heat pump runs very little, and I'm already piling
up KWH reserve for the winter of 15/16. Bruce Roe

[bcroe]

This is the end of my first complete net metering year, the Po Co sets all back to zero. It
would be better if they did it on 28 Feb, because with longer days, fewer clouds, and lower
heating needs, March almost certainly will run a surplus. So the issue is, will I have a
surplus or deficit KWH reserve on the Feb meter reading date? The bill will tell, but it
doesn't come, and it doesn't come. Finally I call them and they say it was mailed 24 Mar
for $400.
1. I can ignore the $400 because the people answering cust service don't
see the net metering info; that is probably how much heating I did;
2. So why didn't the bill get mailed on 5 Mar?

So its a week and no bill. I call again; it was mailed 24 Mar but now its for $15.95, that
is the base amount if I don't buy any energy. Looks like I did it, no electric energy
purchases that year; hardly any propane. Also they read the meter on 5 Mar, not 28
Feb, probably behind due to weather and a short month. That just might have helped me
make a zero energy purchase year. The extra week into Mar ran an extra 683 KWH
generated, with reduced consumption. I requested another copy of the bill anyway, to
get all the details. Curve when available. Bruce Roe

[bcroe]

Nw il

Today was overcast, we saw no shadows, couldn't even tell exactly where the sun
was. But the "Illinois Array" turned in 113 KWH, I call that performance. Still
haven't seen an electric bill (to check reserve) from 28 Feb, guess that's Ill
performance too. Bruce Roe

[bcroe]

Bruce,
Not to get off topic, I have been contemplating a heat pump as well. Has it worked adequately in
this cold weather? Even with it working constantly, what is the kWh/day consumption?

Its a 3 ton air to air, pretty quick & cheap but only half as efficient as a buried system,
and definitely limited in the coldest months. In a 2000 sq ft, not very well insulted ranch,
its a big improvement over the previous (ancient) unit. It claims a SEER of 14.5, which I
estimate to be an energy multiplier (COP) of 3.7 in the warmer 6 months, dropping down
to 1 at 0 deg F. It uses 10A @ 240VAC, which at an estimated 0.9 power factor, comes to
52 KWH a day if running continuously. Add an estimated 8 KWH for the air blower. My
array can generate double that if the sun is shining even in Feb.

Haven't written much down, but it seems to pretty much handle everything down to
around 20 deg F by increasing run time and doing more frequent defrost cycles. Below
that it couldn't maintain the thermostat setting, so I start turning on some resistance
heat to help. This could add 50 or more KWH a day as the temp drops below zero, at
which point I would turn off the pump and run maybe 150 KWH resistance, -10 F I
might "exercise" the propane furnace that normally never runs. But that usually only
happens overnight, recovering well above zero the next day.

Its definitely paying for itself pretty quickly, a buried system would use considerably less
energy but even these can run out of steam in the most severe cold. And the buried coil
system would tear up the property, take quite an effort to restore. Certainly if building
from scratch a quite large buried coil heat pump with a lessor PV system would be more
ideal, but I am working on continuous upgrades from where I am. My PATHFINDER and
I will be surveying ways to avoid PV shading this year, to increase the 28,400 KWH annual
production. A quick (very cold) preliminary look was promising, should be able to actually
estimate the benefit before work. And house doors/windows/insulation are on the horizon.

Meantime Feb produced a lot more KWH than last year, and March is looking even better.
Bruce Roe

[gregvet]

One of the first things to notice about heating with a heat pump, the vent air isn't
very warm. Guess that agrees with the math, the energy doesn't come in great
big lumps like a propane furnace. In cold weather it pretty much keeps up, but
does so by running nearly continuously. Not that the blower uses much, but its
failure may be hastened. Perhaps I'd better get a spare blower motor and figure
out a quick change routine. Bruce Roe

Bruce,
Not to get off topic, I have been contemplating a heat pump as well. Has it worked adequately in this cold weather? Even with it working constantly, what is the kWh/day consumption?

[bcroe]

One of the first things to notice about heating with a heat pump, the vent air isn't
very warm. Guess that agrees with the math, the energy doesn't come in great
big lumps like a propane furnace. In cold weather it pretty much keeps up, but
does so by running nearly continuously. Not that the blower uses much, but its
failure may be hastened. Perhaps I'd better get a spare blower motor and figure
out a quick change routine. Bruce Roe