How Were Our Energy Predictions? An Analysis of the First Year Energy Use: Solar and Energy Performance

bwhouse

We had spent a lot of time planning and designing a house that would be energy efficient, aesthetically pleasing, and cost effective. This is a fine balance to try to find. However, it really is a big guessing game until you actually live in the space and track it’s performance. You can run all of the computer programs you want, but you really don’t know how things will be until you’re in and living your normal life.

We had installed PV solar panels on the house to combat some of our energy use with the hope that someday we could work towards a Net Zero home, but this too, seemed to be a big guess as to how well it would perform.

In the planning and designing stages of the house we ran a couple different energy models on the house. The first is called the “HOT2000” program. “HOT2000 is an energy simulation and design tool for low-rise residential buildings.  This software is widely used across Canada to support program, policy and regulatory development and implementation.  HOT2000 is developed and managed by the Office of Energy Efficiency at Natural Resources Canada” (NRCAN). It was originally designed for use with the R2000 energy efficiency program, which was an early promoter of green home building in Canada.

We later used the Passive House Planning Package (PHPP), which is now the widely used software program for building highly efficient homes worldwide.

My intent with this article is to report the varying predictions of the these two programs, as well as our predicted solar generation, and also to show our actual energy use for the year of 2016 – our first full year in the new house. I’ll also report some considerations and possible options for the future.


1: PRE-BUILD ENERGY MODELLING

I had been very curious about this when we were in the early stages of planning the house. Most of what I read was the predictions of various homes, but I’d only come across one house that actually tracked and reported its energy use – that being the Mill Creek Net Zero House in Edmonton, AB, Canada. Which, although using exceptionally little energy, did not meet it’s net zero target. That being said, it was very close.

I fully did not expect our home to be anywhere close to net zero, but we hoped that over the next number of years we could gradually build our solar panel array (as costs come down) to eventually reach our goal.

OK, let’s get to the numbers:

HOT2000 Predictions:

Annual Space Heating Energy Consumption: 7159 kWh

Annual Domestic Hot Water (DHW) Energy Consumption: 3409 kWh

Annual Appliance Energy Consumption: 8760 kWh

TOTAL = 19,328 kWh/year

PHPP Predictions:

Annual Space Heating Energy Consumption: 7584 kWh

Annual DHW Energy Consumption: 3974 kWh

Annual Appliance Energy Consumption: 11,310 kWh

TOTAL = 22,868 kWh/year

PV Array Predictions (6.2 KW)

PHPP Estimation: 7321 kWh/year

Solar Installer’s Estimation: 9300 kWh/year

So obviously there are discrepancies between the HOT2000 and the PHPP. Although their prediction of Heating and DHW are quite close, surprisingly the Appliance use was significantly different. Also, surprising was the discrepancy in the solar predictions – I was a bit disconcerted by the drastic difference of 2000 kWh/year!!

For comparison’s sake, according to Stats Canada website’s most recent 2011 home energy use data, a Saskatchewan home consumes an average of 30,555 kWh/year (110 GJ), of which electricity for appliance use is 8889 kWh/year (32 GJ).

Drum roll please.

… Actually first, some clarifications. All I have is our actual overall energy use. I cannot separate out Heating vs. DHW vs. Appliances unfortunately, although this would be interesting. The following information is taken from the solar panel’s generation and the Electrical meter. I tracked each month and have recorded it below.

OK, now the drum roll.

solar


2. ACTUAL ENERGY CONSUMPTION AND PV GENERATION:

January: Solar generated = 315 kWh vs. Energy Use = 3323 kWh

  • Yikes! I was a pretty worried when I saw this. That being said, January was very cold and has very short, dark days (-20° to -30°Celsius most days. We kept the house around 71°F).

February: Solar generated = 553 kWh vs. Energy Use = 2706 kWh

  • February is always a cold month. Although you can see the solar was getting a bit more sunlight already as the days lengthened.

March: Solar generated = 603 kWh vs. Energy Use = 1716 kWh

  • This was getting a bit better still. I lowered the house temperature to 69°F. It was getting warmer outside and more solar gain.

April: Solar generated = 979 kWh vs. Energy Use = 1385 kWh

  • April was warm and sunny. Nice spring weather. Started to not need the in-floor heat on at all during the day, but still ran it during the night.

May: Solar generated = 960 kWh vs. Energy Use = 1029 kWh

  • Almost net zero for the month. It was a very nice month. We were running our river pump frequently to water new grass, which I think increased energy use quite a lot.

June: Solar generated = 1434 kWh vs. Energy Use = 989 kWh

  • Net Positive in a big way. Beautiful month. Obviously the longest days of the year.

July: Solar generated = 956 kWh vs. Energy Use = 511 kWh

  • The first two weeks of July were cloudy and rainy which is unusual for July.

August: Solar generated = 950 kWh vs. Energy Use = 645 kWh

  • This month was very rainy as well, which again, isnot normal. Usually August is very hot.

September: Solar generated = 778 kWh vs. Energy Use = 611 kWh

  • Cool and cloudy. I replanted grass seed and was running the river pump a lot again.

October: Solar generated = 315 kWh vs. Energy Use = 1478 kWh

  • October sucked!! 315 kWh is the same as January! It snowed on October 4th. We had to turn the heat back on. There were only 2-3 sunny days all month.

November: Solar generated = 390 kWh vs. Energy Use = 1750 kWh

  • Cloudy month, but had some mild days mid-month with above freezing temperatures. Still, we generated more solar in November then October, which should not happen.

December: Solar generated = 229 kWh vs. Energy Use = 2857 kWh

  • Shortest days of the year and extremely cold (-40°F). What do you expect?

ACTUAL TOTALS:

Actual Solar PV Generated = 8189 kWh

Actual Household Energy Consumed = 19,000 kWh

Actual Total Energy Used (consumption – PV) = 10,811 kWh


3. DISCUSSION

I’m extremely pleased with these numbers! I’ve been waiting for two and a half years to know what our actual energy use would be.

We actually used less overall energy then was predicted by both the HOT2000 (19,328 kWh/year, although it was close) and a LOT less then PHPP (22,868 kWh/year), which is surprising that it was so off… It makes me wonder how close we would be to meeting the Passive House standard given the actual energy use is 3868 kWh less then it predicted… Hmm. Maybe we should have tried to hit that airtightness target of 0.6 ACH after all. Oh well.

Nonetheless, the overall energy use of 19,000 kWh is very good (and such a nice round number too!). We did not do anything different in terms of our behaviour except to just be smart and not be wasteful. I still baked bread every weekend and we used our larger appliances just like we normally would. We have two refrigerators and two deep freezers in the house. All the lights are LEDs. We try to hang our clothes to dry. We used our wood stove occasionally, maybe 2-3 times per week, but mostly just for ambiance and occasionally on the extremely cold days. That being said, based on the predicted numbers, the heating energy likely accounts for about 50% of our overall energy use. Makes me wonder too how much better we could do if we burned wood a bit more often?

As for the actual solar PV generation (8189 kWh), it pretty well split the difference between the installer’s predicted 9300 kWh/year and the PHPP prediction of 7321 kWh/year. I think this past year was on the cloudier side for sure. We had a lot of rain in the Spring and even more in the Fall, which is very unusual. Followed by an extremely early snowfall which seriously cut into our PV generation (see October – brutal). It probably would be closer to the installer’s prediction on a typical year (will have to see what 2017 brings).

Still based on the actual numbers, our solar panels did cover nearly 45% of our overall energy use for 2016. We would however need to double our solar panels (add another 6.2 KW array) to meet Net Zero with consistency year to year. Who knows, maybe in the coming years the costs will drop more and perhaps government incentives will increase. One can hope.

Comparing our house to the average Saskatchewan home consumption of 30,555 kWh, we did very well. Using 37% less energy then the average home. And when you take into account the solar energy generated that drops us further to using 65% less energy then the average house! Sweetness.

Considering that we are completely on electric energy, it makes sense to make the house as energy efficient as possible. The cost of electricity for us is $0.12224/kWh (while cost for natural gas power is about $0.04/kWh equivalent), which works out to an electricity bill of $1321.54/year (10,811 kWh x 0.12224). We do however have to pay a basic service fee of $32.61/month (even when we are net positive in a month) which sucks and then 5% tax. That brings our absolute costs for the year to $1798.50/year or $149.88/month, which is about half the cost of our previous homes power and electricity bill. I’m ok with that.

throughthetrees

This post was updated on March 4, 2017. 

Solar panels – Good for the environment, good for your wallet

It wasn’t enough for us to simply reduce our carbon footprint through building a super-insulated eco-house. We wanted to come as close to eliminating our footprint completely by working towards a net zero standard. The house envelope, airtightness, passive solar design, and thermal mass of the house, would all have the effect of reducing our energy consumption by 75-80%. The rest of our energy for heating, domestic hot water, and appliances was purely electric based, with the exception of our wood burning stove. We have no natural gas to our property – and to be honest, even if we did, we would not have hooked it up. Burning fossil fuels for energy, despite it’s current affordability, is not a clean energy source nor is it sustainable. Still, despite what some people say, electricity – at least in Saskatchewan – is not sustainable nor is it clean either. Our electricity comes from a power plant that uses a combination of coal and natural gas. Really, in one of the windiest and sunniest places in the world, you’d think we should be able to have some capacity to utilize renewable energy sources. Unfortunately, this is often a top-down decision in the government and sadly, both our provincial and federal governments are heavily financed through their strong ties to the oil and gas industries in this country (no matter how much of a downturn there has been in the markets over the past year) and there is no sign of this changing anytime soon

Until such a time that the collective elite decide to recognize the need to shift away from non-renewables, it will continue to be left to the grassroots movements and local homeowners to decide if they care enough to make a commitment to renewable energy – despite the upfront costs of doing so.

But these times are changing. No longer is it purely a decision of environmentalism. Now the argument of the economics of renewable energy can be made. Let me present this in layman’s terms (as I am, of course, a layman myself).

Our projections for electrical energy consumption:

Estimated yearly energy use (DHW, appliances, heating) = 14,508 kWh (including regular wood stove use for heat)

Cost per kWH hour of electricity in Saskatchewan = $0.1456

Our projected electrical costs per year = 14,508 x 0.1456 = $2,112.36/year or $176.03/month

We worked with a company in Saskatoon, called MiEnergy, in sizing a choosing which solar array system would best suit our needs. We decided to purchased a 6.2 kW PV array. There was the option to upgrade to the 9.3 kW system but we felt that this would definitely be oversized for us at this point. The 6.2 kW system will be slightly under-sized but we can always add on more panels at a later date if we so choose.

6.2 kW system delivers an average of 775 kWh/month = 9330 kWh/year on average

That provides us an immediate saving of $1358.45 per year ($113.20/month) in energy costs. Expanded over the course of a 25 years this delivers $33,961 in electrical savings at the current electrical rates. (I found an interesting article on the energy outlook in the U.S. – there has been a $0.04 cent rise per kWh from 2003 to 2013. Extrapolating that, conservatively, over the next 25 years we should expect an upwards $0.08-0.10 rise per kWh. That equals between $0.22-0.24/kWh. The projections from MiEnergy pegs the 30 years saving at $58,067).

If you take the cost of the PV panels and roll this into a 25 year mortgage at a current 3.19% interest, this only costs a meagre $110/month. So essentially instead of giving $113.20/month (currently, which will increase) to the government to cover our extra electrical bill, we will invest $110/month towards the PV panels on our mortgage. After 25 years, they are paid for and we have money in our pocket (not to mention the fact that we’ve saved 233,250 kWh of energy from being generated at a polluting power plant). That’s a win for us and for Mother Nature.

IMG_3047

If you want the facts and economics only, then disregard the story that follows. Of course, I wish my post, could be that short and simple. But as I’ve learned with building the house – something always goes wrong – no matter how bizarre, stupid or impossible it might seem…

The above photo is the after shot. After I received the phone call at 6pm on a Friday night from Saskpower (the electrical company) asking why a large steel beam had been driven directly through their power line?

“Uh… I don’t… know?”

You see there is this thing called: “Call Before You Dig.” It’s a free service that most places have that asks that you please call them to mark your underground power and gas lines before digging so that you don’t kill, maim, electrocute or otherwise dismember yourself. Unfortunately, as we learned that night, it is not a perfect service.

The solar company had called and had the power line (note, the singular word: line) marked a couple of days before the planned installation. Unfortunately, there were in fact, two power lines running into our transformer, one from our neighbours place to ours and the other running from ours to about 60 houses over the next number of miles. Well, you guessed it, they hit the one running to the 60 houses (that was not marked), knocking out their power for the next 8 hours. Oopsy.

IMG_3040When I showed up to the house, you could see the one line that was marked (as it was prior) with the solar panel racking system 4-5 feet away, then you saw where they had discovered the 2nd line, lying directly underneath the 2nd row of racking (not previously marked). The Saskpower guys though were very good, they realized it was not the fault of the solar company, nor mine, the line simply had not been marked by the Call Before You Dig people. They were just glad that no one had been hurt. They were able to restore power to the 60-odd houses that had been affected and the next day they were back out to splice and move our newly rediscovered power line.

(Incidentally, this was a total blessing, had they actually marked both power lines previously, we would not have been able to put the solar panels where we had wanted them. We would have been forced to find another, less ideal spot a much greater distance away).

By the way, we have had a number of people ask us why we did not choose to utilize a solar thermal system for water heating. Basically, it was because of this article and this article on Green Building Advisor.