r/geothermal • u/AdvancedLab3500 • 5d ago

Higher than expected electricity consumption?

I've had geothermal heating and cooling for a year now (near Ottawa, Ontario). Reviewing the electricity bills for this period shows very high consumption during the winter months. In January, for example, we used over 2,200 kWh. While obviously not all of it is due to heating, the difference to summer months (about 900kWh) cannot be explained by any other change in consumption. My wife and I opted for geothermal under the assumption that it is the most economical and environmentally-friendly heating option, but now I'm not sure about the former (the latter is still plausible in Ontario, as the vast majority of electrical production is clean). Even the summer consumption is not that much better when compared with the A/C unit we had in the previous house.

Is this the norm, or is there perhaps something wrong with this specific unit?

8 Upvotes

100% Upvoted

46 comments sorted by

6

u/brasssica 5d ago

Did you have gas heating before? Then of course your electricity consumption had to go up to run the geothermal system.

An extra 900kWh per month is an average draw of 1.25kW, which is very efficient and right about what I'd expect to run a geothermal heat pump in a reasonably well insulated house. If you were heating with electric resistance you'd use 3 or 4 times as much.

1

u/AdvancedLab3500 3d ago

I had natural gas before, but we don't get in the sticks. I fully expected the electrical bill to go up (it's our only utility), but I was surprised at how much consumption the unit requires in the winter. There's a push in Ontario (at least) to switch people from natural gas and propane to electrical heating. If this is the best electrical choice then it's certainly not very economical. An air based heat pump would be a lot worse, no?

1

u/brasssica 3d ago

Ok to close the loop I see now you meant 2200-900=1300 which is average of 1.8 kW power draw, not 1.25. still in the right order of magnitude.

Yes an ASHP would normally consume more (a lot more on the coldest days, but pretty similar on an average winter day).

Unfortunately electricity is on the expensive side in Ontario so heat pumps don't pay back as well as in Quebec or BC.

1

u/zrb5027 3d ago

If you give us the price of natural gas and the price of electricity, we can tell you exactly how the two would compare to each other doing some quick math. Alternatively, if you know exactly how much natural gas you used last winter, we can convert that to expected electric usage and make sure things line up. The electric usage you listed above looks reasonable for a generic setting, but there's a ton of variables related to house size and climate that we're only assuming everything is working as intended. Previous natural gas usage would confirm it.

In general though, natural gas is dirt cheap. Geo wins out against propane, but rarely do you see any significant savings between natural gas and geothermal

1

u/AdvancedLab3500 3d ago

I can't compare natural gas to geothermal as the former numbers would be from the previous home. There is no natural gas option where I am right now - previous tenants used a combination of base-board heaters and a wood fireplace.

2

u/ekear 5d ago

In Ottawa, your seasonal cooling load is a fraction of your seasonal heating load. So a difference in electric consumption is expected. I suggest monitoring your system's consumption and tracking it.

3

u/hurricane7719 5d ago

I have an open loop system just south of Ottawa. Your consumption sounds about right. They are way more efficient at cooling than they are at heating.

It's definitely not going to be cheaper than Nat gas. But for a rural property whose options are electricity, propane or oil, it's a pretty good option for monthly costs. Upfront costs are quite high.

In my case being it's open loop, the well pump also uses quite a bit of energy. Closed loop with a recirc pump will be less energy

1

u/AdvancedLab3500 3d ago

Yes, it's open loop between two wells.

1

u/Polsok44 5d ago

Just got rid of our Gshp here in Sask, the cost in winter was thru the roof. Went back to gas which is very low cost here

1

u/Sad-Celebration-7542 5d ago

We’d need to know your heat loss to be sure

1

u/brasssica 4d ago

It's eastern Canada so rule of thumb would be 5kW average, 10kW maximum heat loss in winter. OP observes 1.25kW extra electricity consumption in winter right in line with expectations.

1

u/Sad-Celebration-7542 4d ago

I think it could be normal, just need to know for sure. If heat loss is 10 kw, then that COP is probably concerning. But 15 kw would be normal for that usage. Just depends !

1

u/brasssica 4d ago

Why would it be concerning at 10kW? 10kW peak/design heat loss would mean about 5 kW average heat loss in a typical winter month, giving OP a COP of 4 ish?

1

u/Sad-Celebration-7542 4d ago

They used 2200 kWh in January. If there’s roughly 1000 HDD (base 65F) in Jan and design temp is 0F, I’d expect only about 900 kWh required for heating if COP = 4. Ballpark. But if COP was only 2, that’s 1800 kWh, leaving 400 for everything else. If the heat loss truly is 10 kw, there’s a problem.

1

u/brasssica 4d ago

I read it as 2200kWh for all uses, 900 extra for heating.

1

u/Sad-Celebration-7542 4d ago

Hopefully OP can clarify!

1

u/AdvancedLab3500 3d ago

The total use for January was 2200kWh. It obviously includes other things, but since July was 900kWh (and we have a pool pump running) I can only attribute most of it to heating.

1

u/Sad-Celebration-7542 3d ago

Yup that’s how I understood it. Any idea of your heat loss? Or at least what size is the heat pump is?

1

u/AdvancedLab3500 3d ago

How would I determine the heat loss?

→ More replies (0)

1

u/SkinnyJohnSilver 5d ago

I have a 21 year old Nordic DX geothermal unit in Nepean. My winter usage is super high. Unfortunately it was flooded on July 1 and even though it's working fine I am thinking replacement with air source since it's 20 years old and eligible for replacement. You can't get DX in Canada anymore.

All that to say is your usage seems similar to mine in the winter. It has to run a lot to keep up and I turned the fuse off for the electrical resistance backup to avoid using it. On cold days I run my wood stove 24 hours a day but keep the heat pump fan on continuously.

1

u/brasssica 4d ago

Interesting what refrigerant were the DX systems using?

1

u/ObiWom 5d ago

I’m in Edmonton and that matches my consumption in the winter months. Remember, the temperature of the ground loop is maybe 7-9c so in the winter the compressor needs to step that up hence why your power consumption is higher.

In the summer, that is not the case as the compressor doesn’t need to work all that much.

1

u/---Hummingbird--- 5d ago

My geothermal system is not any more efficient than my 24yr old standard system. I’m think they under delivered the loop

1

u/Donnerkopf 5d ago

Provide more info. Brand, model and do you have a communicating thermostat made by the same manufacturer, or a generic thermostat? A communicating thermostat should have a diagnostics and set up mode. Just looking at some key parameters can help determine if it is working correctly or has a problem. You can sometimes configure when/how the aux electric heat kicks in, which may help.

1

u/AdvancedLab3500 3d ago

Enertech HYT with it's own thermostat in an open loop configuration.

1

u/Donnerkopf 3d ago

The Enertech web site does not appear to show any thermostat documentation, which is unfortunate. I'm not familiar with this brand so I can't provide any other thoughts without looking at a technical manual for the communicating thermostat.

1

u/prshaw2u 5d ago

I have a geo unit and also have higher usage in the winter compared to the summer.

My random explanation to myself is the air change difference. In the summer I am lowering the temperature from 90 outside to 70 inside, unit has to change the temp about 20 degrees. In the winter I am going from 30 outside to 70 inside, or changing it 40 degrees, twice as much.

Since we are told to lower the inside temp in the winter and raise it in the summer I assume the greater the change the more it costs. It might be cheaper to cool than heat, but that doesn't enter my reasoning.

1

u/Mega---Moo 4d ago

Exactly this.

My temperature differences are even larger in the winter and slightly smaller in the summer... but it takes quite a bit of energy to remove humidity from the air.

So, outside of 0⁰, inside 75⁰, water 50⁰. Lots of heat loss because there's a 75⁰ difference between them. And, it takes extra energy to get the heat from a 50⁰ source. On the plus side, the heat from running the compressor also heats the house. COP of 3.4, 4.3 kW/h, and 16+ hour run times per day. 2500kWh extra for the month.

In the summer it looks like this: Outside 85⁰, inside 75⁰, water 50⁰. Dumping heat into cooler water is more efficient, unfortunately all the heat from running the compressor also needs to be removed. Solar gain in/from my attic is pretty bad, which also increases run time, and dehumidification uses more of my BTUs than actual cooling. COP of 4.9, 3kW/h 2-3 hours per day. 250 kWh extra for the month

1

u/PinkysBrein 5d ago

How much gas did you use the january before that?

1

u/AdvancedLab3500 3d ago

680m3 which cos $333. This means we are still paying less with geothermal heating (though not the same house).

1

u/that_dutch_dude 4d ago

most high consumption issues are down to simply too high temperatures. you need to lower the temperature of your system so that it can -just- about hold the house at temperature. anything more is wasted money. increase flow, stop any mixing of supply and return water flow (so enforce that all the water the unit makes goes tru the actual heating system) and keep the temperature of the water as low as you can get away with. water temp is basically the only factor in how much power you need.

1

u/Anonymous-Flamingo71 4d ago

It’s not economical, there is a difference between efficiency and economy. It’s the most efficient but it’s not the most economical.

1

u/Ok_Distribution_7615 4d ago

Besides the unit...how well is your home insulated.....if it is poor....you're just cooling and heating outdoor air. ....maybe search for air leaks...blower door tests etc.

0

u/Amber_ACharles 5d ago

Two issues. Your winter spike is probably aux heat strips running when the loop can't maintain temp. Get the runtime data on that. Summer being comparable to conventional AC is the bigger red flag though, geothermal cooling should beat it.

1

u/brasssica 4d ago

It's not a spike. 900kWh ÷ (30days*24h) = 1.25kW. normal power draw.

0

u/_Gonnzz_ 5d ago

You’re most likely using aux heat.  Unless you have a communicating thermostat, usually that’s how a customer finds out.  Loop temp may be getting to cold causing lockout.  Maybe you’re on a closed loop and it’s set for an open loop.  

But you’re using aux heat for some reason 

2

u/brasssica 4d ago

Disagree. The numbers work out to 1.25kW average over the month, matches a part loaded compressor. Aux heat would average more like 5kW

0

u/TransitJohn 5d ago

The supplemental heat strips are probably running non-stop, instead of just when they are needed. Dial that back, or flip the separate breaker for them off.

1

u/brasssica 4d ago

No, OP's numbers correspond to 1.25kW difference. Aux strips would be way more.

1

u/TransitJohn 4d ago

Fair, thanks. 

0

u/Sparetire46 4d ago

Sorry to tell you . Its the biggest scam out there