This is impressive -- Google sheets stalls out for me all the time with data sets that are pretty small, all things considered. What was your trick for making it so much faster inside the same browser? Anything design decision that stands out?
Matrices isn't editable (sort of by design) and works best for columns that are all of the same type. It then uses arrow for fast in-memory analytics.
Google sheets has to serve a much broader array of use cases, so I think they can only do so much to improve the performance. It can't always rely on having consistent rows and columns.
Yes i think this is interesting because there are people who like to plan trips and people who just want to go on them. My parents just fwd me an itinerary for 2 weeks in Scotland. One of their friends loves to plan it. The enthusiasm comes across in the email she fwd me. So it’s interesting that this platform could be almost like a creator platform for those who like to plan trips. Would be super cool to be able to reserve blocks of flights, rooms, tickets etc in advance to be able to confirm the price up front. If guests could simply tap to join and have everything booked and paid for would be cool. Especially would be good now for 3 or 4 day weekend trips for remote workers
Great suggestion -- HPH was a stab at making more sophisticated tools like that more approachable for homeowners, but for folks able and inclined to use the more powerful software out there (including energy plus and open studio), it could be really useful.
One thing we've built but not yet included in the site is a way to back into a more precise heating/cooling load for the home using past utility bills. That could be useful even for folks going down the more bottoms-up modeling route as a way to help with the 'garbage in / garbage out' problem of having to estimate insulation, window heat transfer, etc. etc.
Hi! Yes, couple of primary things that would drive that answer:
1/ Right now, if you select "No A/C", we still include the cost+emissions of cooling from the heat pump. It's on the backlog to add a "heat vs. heat only" comparison. In part, we're assuming that if you have cooling capability, you'll probably use it (and therefore wanted to include that in the emissions impact), but also that homes without A/C today will have small cooling loads to begin with, so it wouldn't change the answer too dramatically. For now, I'd suggest looking at the monthly costs in the summer on the bar chart and mentally adjusting the headline number for those. Sorry that's not smoother!
2/ Natural gas is indeed way cheaper here -- dramatically so this year, but previously as well. The backtest shown on the site is Feb '21 to Feb '22 -- natural gas prices this coming winter are bound to be much higher than they were last year, so savings numbers will definitely change going forward. It's on our list to (a) make that dynamic clearer on the site, and (b) explore a more forward-looking savings number. Right now, the annual energy costs are "what you would have saved _last year_ vs. your existing equipment", instead of what you might expect, thinking that would be more convincing / less controversial, albeit potentially conservative.
Thrilled to hear you're 6mo into life with a heat pump! Is it air-to-water and still using water/steam radiators, or forced air now?
> Thrilled to hear you're 6mo into life with a heat pump!
It was the logical thing to do. Even before the war in Ukraine, the ROI of the heat pump was 8-10 years compared to natural gas. With current conditions, shortage of natural gas, inflation and more, the ROI is around 4 years.
> Is it air-to-water and still using water/steam radiators, or forced air now?
Pretty much everything regarding heat in (northern) Europe is based on water, with the exception of hotels that usually use either only air or a combination of air/water.
Our particular installation is from the 1970s, meaning it's 1 string and made for much higher flow temperatures than the houses from 2000 and onwards, so instead of a 35C flow temperature we instead have a 55C flow temperature, which reduces the COP value of the heat pump.
I've coupled mine with radiator thermostats from Tado (https://www.tado.com/gb-en/products) which use geofencing to lower the temperature when nobody is home, and they also have a "sensor/control unit" for the heat pump control itself, allowing fine grained control of the heat pump. One of their upcoming features is to try to optimize heat pump usage for when electricity is cheap.
Hi! Yes, the simulation is all server-side. It does take a while today -- we aren't using the beefiest machines for the site, but even locally it's a >5s process.
Some of the things driving speed:
- Fetching hourly weather data -- we use binned data for the 15-30 years used for equipment sizing and selection, but for the 12 month backtest to get savings and emissions, we're going hour by hour through the last year for the simulation.
- Loading + merging emissions data -- same deal for hourly grid emissions for your local grid, to get emissions from electricity usage (though we do make some assumptions about the grid decarbonizing when we show expected lifetime emissions figures).
- Simulating thermostat behavior -- we do some extra processing before the core simulation to model realistic human behavior on thermostat setting, so that you don't get lots of flipping between heat+cool in shoulder months or the furnace kicking on in June just because it hits 68dF in the middle of the night.
- Heat pump equipment selection -- we're doing a slightly simplified version of the backtest over 15-30 years of historical data for ~2k heat pump units (depending on ducting type) as a bake-off to choose the most efficient-but-properly-sized heat pump for the home. There's more optimization to be done there, but it's about 2-3s of the total time currently.
- Backtest itself -- once we have the equipment chosen and the weather + thermostat scenarios created, we run the simulation itself for the last 12 months, twice (once for the status quo equipment, once for the heat pump configuration). That goes through each hour of the year, simulating heat load on the home (outside weather including cloud cover and solar positioning, humidity, wind speed, temperature, plus internal loads like appliances and the heat occupants give off), simulating equipment performance (for heat pumps, a function of output, outside temp, inside temp, outside humidity, altitude, and layering in backup heat as applicable/needed), plus accounting for surplus/deficit heat that needs to roll over to the next hour based on thermostat settings or insufficient conditioning, etc. etc.. With usage, we then compile and calculate the utility bills monthly (we have support for actual rate plans, TOU plans, etc., but for now we just use statewide marginal retail prices from the EIA for the site version, because those tend to be conservative) and also calculate emissions, which is time intensive for electricity given we're layering in actual emissions from the grid in the simulated hour.
Anyways, there's definitely a lot of optimization we could do to get the processing time down, but hope that gives you a sense of what's going on server-side. Also, the model we're running is more flexible than what's exposed on the site currently (e.g. arbitrary date ranges for the backtest), and if we made a more specialized version of it, we could do a lot more pre-computing.
You may or may not need backup heat, it depends on your particular home. Heat pumps DO still capture heat below freezing and down to temperatures much, much lower than they used to. Mitsubishi, for example, sells air source heat pumps that maintain 100% heating capacity down to 5 dF and can still heat (albeit at reduced capacity) down to -13 dF: https://www.mitsubishicomfort.com/articles/keep-warm-this-wi...
We model decreasing heat pump capacity and efficiency as the outside air temperature declines. Yes, heat pumps do lose capacity and efficiency the colder it gets, but they can still provide heat even when it's very cold out (there's heat energy in the air until absolute zero, or -273, after all!). You can see that declining efficiency if you expand the "Step 2: Choosing your ideal heat pump" section. We'll add a graph of capacity relative to outside air temperature as well.
Backup heat is still often necessary for many homes in cold climates, but it's necessary a lot less often than you might think. Note that in the results you'll see for the site, backup heat is included if necessary for single-zone centrally ducted heat pumps, but not for any other ducting types.
This is helpful -- we need to do a better job of guiding folks through a more complex set-up like you're describing. You're right that it's easiest for folks with centrally ducted A/C and furnaces.
If you're choosing 'multi-zone', "Heat pump: Number of units" corresponds to the number of _outdoor_ units, rather than indoor heads. For all other configurations, it maps to both outdoor and indoor (the others are all single zone). So, if you want to go with a multi-zone heat pump, I'd suggest entering 1 or 2 for "Heat pump: Number of units" (or just leaving it untouched, in which case the model will choose automatically based on home size).
> IMO you should just stick to calculate fuel costs for heat with gas, vs heat with electricity, and leave out the installation costs.
Roger that. We started out that way, and the cost-to-install was the number one thing that people asked us in follow-up questions, so we added some high-level guidance. I think the lack of transparency on upfront costs and pricing is a major issue for the transition broadly and a problem that needs to be solved -- that's high on our minds.
> That's really all I want to know: What costs less, heat with gas, or heat with electricity. Or maybe a hybrid.
Helpful! Related to the previous point, we want to make it easier for you, with a proposal from a contractor in hand or existing equipment already installed, to choose that equipment from among what we're analyzing (rather than only seeing cost savings for the most efficient unit that we choose automatically). In your case, you'd then be able to see exactly the cutoff points when your existing fossil fuel equipment is (a) necessary because of reduced heat pump capacity at lower temperatures, or (b) cheaper to run than the heat pump. FWIW, (b) is far rarer than we thought going into this exercise.
Thanks for the feedback! We can make those sliders better, thanks for the suggestions.
Yes, unfortunately we haven't seen great resources for the rest of the world, either. The same approach and core model here would work elsewhere, but we'll need to source historical data on housing stock, residential energy prices, grid emissions, weather to get it up and running elsewhere. If you know anyone that would be interested in taking that on, definitely let us know!
There are definitely still places in the U.S. where air-source heat pumps aren't economical. That said, two big things for most folks to keep in mind:
1. Air-source heat pumps are getting better and better, quickly, so that answer is changing
2. 93% of US homeowners would save money with air-source heat pumps vs. their existing equipment, and only 3% of homes would see an annual utility bill increase above $70. (these from backtesting the national sample of homes from the EIA's RECS survey)
A lot of people think "really really cold" means it hits zero a few times each winter. They don't know what living in Fairbanks is like :), and chances are that heat pumps can keep up with their local weather.
>A lot of people think "really really cold" means it hits zero a few times each winter
See this seems to me an illustration of something being hinky about the discussion.
"Hits zero a few times each winter" quite possibly is an accurate description of the climate where I live. I believe only one month had a below zero low recorded last winter.
But representing my climate with that particular factoid would gloss over that lows around freezing down to subzero are typical for like six months of the year, and the other six months, you don't need heat in the first place.
A lot of people in the CONUS really do live where winter is pretty harsh, not just North Dakota or something.
The important thing for saving on energy bills, which I don't ever see brought up in any online discussion about heat pumps, is how bimodal the climate is, not how extreme the winter lows are.
I can't say there is nowhere in the world where the temperature graaaaaaadually ramps up and down all year. But all I see is people taking for granted that's how it works and thus heat pumps spend a large amount of time in the optimal range.
