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I recently replaced my [central, ducted] heat pump, and the new one is rated with a 4.981 SCOP. It's fairly efficient, but not the most efficient on the market.
-40% for the duct heat loss
In a house I own in Melbourne, Australia, I just replaced an old gas central heating system with 3 new top of the line Daikin mini split heat pumps. The new units can heat the entire house for the same amount of electrical energy that was used to run the FAN in the old gas unit. They are crazy efficient. Ducts are dead. The Daikin Alira X is the gold-plated option and cost $8k AUD for 2x2.5kw and 1x7.1kw units includ…
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Loads of countries have effective power grids which go down incredibly rarely. I can't even remember the last power cut I had - maybe a few years ago? It's certainly rare enough that I don't need my main source of cooking and heat to take it into account. My parents live in rural Scotland and use a ground source heat pump for heat and an induction stove for cooking. Power outages happen more often - but still pretty…
And when the grid goes down, then what will you do? How will the utility compensate you for your death when they find you frozen? This is not an academic question, especially in North America. The weather here can be very harsh. We lost power earlier this year as the temparature dropped to 0F (-18C). Our contingency (oil heat, oil generator) kicked in and we were fine, but many people were not. After power was restor…
I haven’t had a power outage lasting over an hour for as long as I can remember (years), but that doesn’t mean I’m not considering that scenario. There could be wars or sabotage or whatever. One should always be able to manage for a week or so without power and that will require some form of backup such as a combustion heater of some sort. But having a backup solution that keeps you alive for a week isn’t so expensive. You don’t need two completely separate and redundant heating methods simply because one of them relies on the power grid.
When will air source heat pumps be ready for service in cold weather climates without gas backup?
They are now. In Vermont, we are in our first year with heat pumps. Have a wood stove as backup and supplement when we want to go pantsless mode. The original oil burner is currently turned off, out of commission waiting on some parts. We could go without the wood stove, and have done so for stretches. We installed Mistubishi Hyperheats, 3 external units, 5 heads. Zero interest financing by installer, for about 21k a…
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I paid real money to have my ducts removed. They cause issues installing comprehensive insulation and caused hot/cold spots on the ceiling.
Honest question: Why would one care about cold or hot spots on the ceiling? I don't spend much time up there.
In a house I own in Melbourne, Australia, I just replaced an old gas central heating system with 3 new top of the line Daikin mini split heat pumps. The new units can heat the entire house for the same amount of electrical energy that was used to run the FAN in the old gas unit. They are crazy efficient. Ducts are dead. The Daikin Alira X is the gold-plated option and cost $8k AUD for 2x2.5kw and 1x7.1kw units includ…
I got a similar setup for my house as well. Being able to selectively cool rooms that are in use is great. However, I do wish the insulation was far better. Unfortunately I’ve noticed that Melbourne houses are usually very poorly constructed due to expensive raw materials and labour.
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I always joke that in winter all appliances are 100% efficient (I know they're not). Some look at me funny but the ones who pay the gas bill get usually get it.
I think 100% is pretty accurate for most devices, except for washing machines and other gadgets connected to the sewer. Where else would the energy go? Your fridge has the potential to go even higher than 100%, as it's a heat pump. But for more than a temporary effect you'd have to keep replacing the stuff inside it with stuff warmed up to outside temperate, which would have to be between fridge temperature and room…
I really enjoyed reading The Homemade Heatpump Manifesto on Ecorenovator. https://ecorenovator.org/forum/showthread.php?t=484
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Why wouldn't you just lay insulation on the ducts, same as you do with water pipes?
US and Australian units are different for insulation, but in my terms the insulation around the best ducts is R1.5, but good ceiling insulation is R6. 4x difference Edit: not to mention the huge difference in surface area. Ducts can expose your conditioned air to a huge, poorly insulated surface. Bad for efficiency.
They also recently undid a long held myth about ducts buried in insulation leading to condensation issues. Most areas now allow ducts to be buried as long as you have R19 above and below, or R30 above. When I just installed a ducted mini for 3 upstairs bedrooms, I surrounded my R8 flex duct with R30 insulation.
> heat pumps: electrical devices Just to be pedantic, but not exactly. The typical design in a domestic heating unit, or refrigerator is mechanical. A fluid is pumped and cyclically compressed/expanded. While electric motors are usually used, they can be driven by any source of mechanical energy; driven directly by a combustion engine is not too unusual. There are also heat pump cycles that can be driven directly wit…
But that is the introductory paragraph, the author is defining what they mean by "heat pump": a device for heating a house which is powered by electricity. You could power it with something else, but the point is to replace natural gas furnaces.