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:
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
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.
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 Solar PV Generated = 8189 kWh
Actual Household Energy Consumed = 19,000 kWh
Actual Total Energy Used (consumption – PV) = 10,811 kWh
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.
This post was updated on March 4, 2017.
12 thoughts on “How Were Our Energy Predictions? An Analysis of the First Year Energy Use: Solar and Energy Performance”
Thank you so much for all the information that you have been sharing. For someone who is going through the same kind of adventure (finished planning and designing, about to start building), it is inspiring and very useful.
I was wondering if I could ask you for a bit more information concerning your PV array. You probably wrote about it before but I wasn’t able to find it.
Is it battery based? If not, do you consume directly the energy produced by the PV panels?
During daylight, the house energy supply, is it mainly from the PV panels? How does that work?
Thank you so much for your help.
All the best,
Hi Paulo- I’m glad this information has been helpful. Our PV array is not on a battery. When we were looking into it the cost was $15K which would last for ~12 hours. Instead how they hook it up is they run the PV array directly to the electrical meter. My understanding is that if it is sunny and you’re generating power from the panels then you will use that energy first. If you are generating more then you need then that will go back onto the grid. If you aren’t generating enough from the PV then you’ll draw from the grid instead. It’s a bit complicated really. In Saskatchewan they run a net metering system so that your meter keeps track of what you consume but also what you deliver to the grid. The solar array system keeps track of your pure PV generation.
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Thank you so much for the quick answer.
We too, for the very same reasons, are not choosing a battery based PV panels system.
I’m just trying to confirm if the PV panels (adequately dimensioned) are efficient enough so that, for the most part of a sunny day, we can be almost off-grid.
It looks to me like the heating accounts for about half of your energy costs – and if that were removed, your PV production would actually exceed your usage. Did I get that right? My next question – you mentioned that the annual Sask home consumes 35,000 kWh/year. But since most people have their furnaces gas powered – that seems a little high. Are you sure that number is correct? Thanks, Rylan.
Hi Rylan – yes that’s right. We are full electric here so you’re correct in saying that our PV basically meets our heating or our DHW/appliances. The 35,000 kWh is the energy conversion of 126 GJ which is what the Stats Canada link I referenced states is the total energy use for the average SK home (heating+cooling+DHW+appliances). You’re again correct to say that most homes are gas for heat. If they were all electric then that number would actually be much higher. But that’s the closest equivalent I could find. I’ve read as high as 45,000 kWh equivalent for the average house in Alberta but I couldn’t find anything for SK aside from the number I referenced
Hey Kent, I just check the stats Canada website, and on this page (http://www.statcan.gc.ca/pub/11-526-s/2010001/t004-eng.htm), it says the average electricity usage / household is 30 Gigajoules, which is the same as about 8,500 kWh. But… the catch is that the average house also uses 100 Gigajoules of gas, equivalent to 27,000 kWh. Add the two together and we get the 35,000 kWh that you found. So that number is actually a combined total of energy from gas and electricity. If you’re not using gas then you are far below the average energy usage, and your array takes you down further yet. 1/3 of the average!
I also want to mention that I’m the owner of solarpanelpower.ca and I would like to feature blueheronhaus in a new “Case Studies” page. How can I contact you for details? Can you send me a email to the one I’m leaving this comment with? Thanks!
Hi Rylan – yes that’s exactly right. Those are the same values I referenced. I’d be grateful to have our house featured. My email is firstname.lastname@example.org
Hey Kent, when you click your StatsCan page it says that this is not the most current data. The link below is for 2011’s average use per household http://www.statcan.gc.ca/pub/11-526-s/2013002/t004-eng.htm is 110 GJ or 30,555 kWh. So your house would be 37% more efficient than the 2011 sample average.
Thanks for the updated information Chris. I’ll amend the post. Thanks!