Love the candor of the writeup, for example admitting that they are effectively double-dipping.
Though I think they are actually triple-dipping or even quadruple-dipping.
1-2. Net-metering and credits
3. Reduced contribution to infrastructure
There are times when their PV setup produces very little or no electricity at all. At those times, they are 100% reliant on the grid to supply them with all their electricity needs. A large part of the cost of electricity supply is the fixed cost of infrastructure, whether used or not, which is paid off by the variable supply of electricity. Since they are 100% reliant on the grid at least some time, they haven't reduced the need for the fixed-cost infrastructure, but have reduced their contribution to that infrastructure.
I guess this could be alleviated by capping the amount of electricity you are allowed to take from the grid?
4. Increased variability
The addition of variable suppliers like PV reduces grid stability and increases the requirements for and cost of measures to stabilize the grid. Battery backup could obviously alleviate this, but if not done carefully it could just stretch out the destabilizing events and then make those fewer events worse.
While I really, really like the idea of rooftop solar, (partial) energy independence, and a more distributed grid, I think we do have to figure these things out. I don't see how it makes sense at the moment.
> The addition of variable suppliers like PV reduces grid stability
True, that's why large p.v. farm should be BANNED not incentivized. But it's the opposite for self-consumption. I self consume (in France, I do not know how that's regulated in USA) meaning I have the interest to do my best shifting loads on p.v. as much as I can, as a result I reduce my total energy consumption from the grid (about 50% per year, being all electric) and much reduce my consumption during peak period when the grid is stressed. I do not reduce my demand only in the coldest part of the winter where the grid is strained due the growing amount of electrical heating but I do reduce to zero in summer where air conditioning demand strain the grid (here nights are fresh so no need to cool artificially at night) witch is a much welcomed thing for the grid. In the future IF battery prices fell here like in China I might also absorb much less for heating, so far batteries are just expensive personal backups. In the future we might add a grid scale data channel to the inverters, like the one we already have (mandatory by law) to allow the grid cutting/regulating EV recharging during peak demand) allowing to inject to the grid only when the grid like it.
At the moment p.v. self consumption IMO and IME makes sense both for individuals and for the grid. In the future we can be more integrated, but still the base is the same.
It is a good write-up. I partially agree with some of your points. I have some alternatives that I think might be useful.
1-2. I'm not bothered by net metering. I don't think symmetrical metering is appropriate, and the difference between buying and selling price should be used to fund infrastructure contributions. I suspect it'll just get used as dividends for shareholders.
3. That's where a reserve charge would be appropriate. In case I'm using the wrong term, a reserve charge is a fee assessed to pay for excess capacity on the grid in case you cannot provide it yourself.
4. Variability is an important issue. To me, accept the variability of lots of small-scale producers because any one of them going down has a much smaller impact on the grid. A single hailstorm can take out a utility-scale solar installation. If rooftop solar is distributed over a greater geographic region and is much less vulnerable to localized damage.
However, I think we're missing an opportunity to improve local power resilience by emphasizing and planning for virtual power plants constructed out of rooftop solar and local batteries. In my perfect world, municipalities would have rooftop solar on every city-owned building where it's practical. There would be multiple battery sites distributed on municipal properties. City residents would be encouraged to put in their own rooftop solar and house batteries to contribute to the virtual power plant run by the municipality.
There would still need to be a reserve charge to pay for the grid, distributed among all the municipal residents, and then a usage charge for what they actually consume.
We used to have municipal power companies, and some communities around here still do. While they don't generate power, they do a much better job handling lines and restoring service after weather-based outages. We should look to the past to learn how to build a distributed future for renewable energy power systems.
I don't think the expectation that you can save money with rooftop solar will be economically sustainable in medium or long term. Energy (and nearly everything) produced at scale is simply cheaper whether thermal, solar PV, wind, etc.
Having rooftop solar should be viewed as analogous to having a home diesel generator (without being filthy for the environment). The goal isn't to save money by "doing it yourself at home" but there are other benefits like energy independence, redundancy, backup, etc.
The gridscale/utility market in PV is absolutely booming - "Solar and battery storage to make up 81% of new U.S. electric-generating capacity in 2024"[1] and is constrained by supply of batteries and PV panels. As someone deeply concerned about global warming, I'd rather any available PV panels be used in the most effective way to reduce CO2 emissions and that is in a grid-scale installation.
There might have been a case for direct and indirect incentives for homeowners to install PV 10 years ago to help boost overall demand for PV panels but there is no such need these days - the industry is booming and supply is a bigger issue than demand.
We save in stability: p.v. and co vary it's output far quicker than classic big power plant, this means that on grid we have more and more frequency stability issues. To compensate we need a smart grid witch is an IT nightmare and in any case it's not there.
At home, in self consumption, we are in a small smart-grid. So we can do our best to shift loads on p.v. using the grid let's say "for the base load", as a result individually we spend less and have (in case of batteries) backups, at grid scale peak demand is less intense and happen less.
That's the "issue" with p.v.: utilities do not want semi-autonomous homes, they do want to own, leaving others with nothing but subscriptions, paid services, this is incompatible with current state of tech while the current state of tech is perfectly compatible with small scale self-consumption.
Now try to imaging a hypothetical society where people living in reasonably sunny part of earth have p.v. and batteries. On scale it's probably not doable today, but we can definitively start. We still need a grid or some other backup, but we do not need an UPGRADED grid in capacity terms because most of the loads, the biggest one at least, happen locally. Surely without seasonal storage being autonomous it's a myth, but technically we can pass most day-to-day needs in largest slice of the Earth who happen to be the most inhabited as well. This means we can converge to electricity as main energy without consuming much more than today from the grid.
I think you are right, and what's happening with rooftop solar in urban environments like DC (as in OP) is a case in point. By and large, the rooftop solar here is directly integrated with the grid and net metered. It is not off grid whatsoever like a diesel generator would be. It's possible to install a backup battery and inverter, but if the power goes out, you don't get to use your solar directly.
Energy companies in DC, are incentivized by the govt to produce energy from renewable sources. They have to pay a penalty for SRECs they fail to produce, so they have good reason to convince consumers to put solar panels on their roofs and then buy SRECs from them at a rate lower than the value of the penalty.
Home PV + batteries could at least help tame the duck curve and at least moderate the cost of grid expansion which ultimately is a cost born disproportionately by low income homes which are already energy burdened. But yes I mostly agree with you in re: grid-scale PV (+ wind and storage) being much more significant.
I live in DC like the author and went solar in 2020. I want to emphasize that DC's energy credit (SREC) prices are the only reason that solar makes financial sense here - perhaps anywhere.
Without SRECs, we would be losing money. Our SREC payouts have averaged $380/MWh over the past four years. When last I checked, this was by far the best price on offer in the US. I've seen "solar is a scam" posts across the Internet. Given the numbers, I'm inclined to believe that's true wherever SREC prices are below, say, $250/MWh.
I keep a detailed spreadsheet and have been meaning to write a similar blog post. The short story is that we have made more money overall from SRECs than from savings on our monthly bill.
Rooftop solar can't be economically efficient without subsidies of some sort. How could it outcompete the economies of scale of putting an extra 10 panels in a utility-scale installation 50 miles away?
SREC is one such subsidy - which looks enormous, twice as big as the actual retail cost of the electricity! - and the author also mentions a federal tax credit for 26% of the cost.
Note that net metering is yet another subsidy. Try to sell electricity on commercial terms at "we will provide you with energy when it's sunny and withdraw when we want, at the same price" and see how quickly you get laughed out of the room. Granted, in a climate like DC peak usage (AC) is pretty close to peak solar production so it's not quite as bad as that, but batteries cost order-of-magnitude the same as solar panels, and this is asking the grid to serve as a giant battery.
All these subsidies have clearly had a positive effect - rooftop solar is better than none at all, and perhaps there are some secondary benefits in job creation, environmental awareness, etc. But this is one area where the tax breaks would have been more efficiently spent enriching big businesses rather than sent directly to middle-class home owners.
> Rooftop solar can't be economically efficient without subsidies of some sort. How could it outcompete the economies of scale of putting an extra 10 panels in a utility-scale installation 50 miles away?
By not using expensive land (since it's on top of a building that existed anyways).
There's likely to be a document somewhere where they calculated that SREC value and justified it by savings on health and other negative externalities of the grid energy that it displaced.
My understanding is that in the DC case, the SREC values are anchored by DC's Solar Alternative Compliance Payment (SACP). This is a penalty energy companies must pay if they don't produce their quota of SRECs. Currently, the penalty is $480 per SREC, so the energy co.s save some money paying $350-400 vs. the penalty.
In tandem with this, DC is small, meaning rooftops are really the only place you can put panels, and DC requires that the SRECs are generated by systems located in DC:
"The D.C. City Council passed a law in July 2011 preventing out-of-state systems registered after January 31, 2011 from participating in the DC SREC Market, further limiting supply."
This program has benefited me and other DC residents individually, but I would be much more at ease knowing that this is actually globally good policy. I'll admit I don't really know.
I'm not sure there's too much oil revenue flowing into the coffers of the dudes in Peshawar and Kandahar, but it doesn't stop them knocking the s*t out of each other and anybody else there.
I think energy independence is more important than not potentially financing terrorists.
I don’t understand how not everyone can be on board with renewable energy and EVs. Even if your country exports more oil than it produces, like USA, it can still be dependent on oil production from the Middle East due to the logistics and differences in the type of oil produced.
Even if you live ICE you should support EVs with all your heart. The less people are using oil for fuel the more gasoline the less likely it is that fuel will get more and more expensive, and the more likely it is that your country won’t be completely incapacitated when the next oil crisis hits.
Do people love so much being slaves to Middle Eastern autocracies?
The contribution of SREC to the income ROI calculation is high. That aside, with load shifting into peak production time and some judicious non battery time shifting (hot water) it's possible to reduce billable kW consumption.
In oz what's happened is the SREC equivalent is now much lower and the unavoidable network and systems costs to the energy supply company went up. It's still worth having, and if you can afford the capex then arbitrage of battery can earn higher marginal return quite aside from extending your non consumption window significantly.
If you spend $25K on a solar installation, does the value of your home increase by $25K?
This angle isn't mentioned in the article. Overall the profitability of the installation seems shaky and depends on various government interventions that probably won't be around forever.
If we model the solar installation as a conversion of cash into home equity however, the calculus changes. You are buying home equity and getting reduced energy bills in the process. You almost certainly come out ahead, the panels are in a sense free, other than costing you some liquidity.
Googling around a Zillow study says solar installations increase the value of a home by 4% on average.
The article also didn't touch on maintenance costs.
> If you spend $25K on a solar installation, does the value of your home increase by $25K?
I spent $25k to install solar in 2020 (also in DC like OP). The solar company estimated that my home value increased by $14K.
As part of the install, I bundled a "heavy-up" for $5K, which is an upgrade my house needed, but not strictly part of the renewable energy system. So total cash outlay was $30K.
I immediately got back 26% in a federal tax credit: $7.8K
So on balance, my system cost $8K cash, which was paid down by energy savings and SRECs within three years. The SRECs made the biggest impact.
I agree V2G will be huge, but rolling it out will be hard, especially somewhere like the US without major financial incentives (for both the infrastructure and getting people to accept the idea that they might not fully control their rolling castle’s battery). Conceptually though, I think it’s one of the coolest ideas in sustainable tech - distributed prosumer/battery networks. There’s also some cool P2P topologies.
When we went solar in DC (like the OP), the solar company offered a zero-cost option. The way this works is that the solar company owns the panels, while the customer enjoys the energy savings and IIRC a small slice of the SRECs.
This is good, PV panels can ammortize themselves even quicker when electricity costs are higher.
> Topping out at 56 kWh in a day is pretty good... The best summer days generate almost twice as much energy as the best winter day
It was really worthwhile seeing the stats put in order like this, thank you.
Really puts the spotlight on the technology to store the energy over longer periods (ie into the Winter). What is available on the market?
AFAIK standard home batteries empty out pretty quickly even without getting used. What about Vanadium-Redox? Hydrogen-Storage is too expensive and storying it via crypto-mining feels a bit like betting.
Looking at the chart before reading the article, I thought that their peak hourly output is just above 1.5kWh (sort of like you'd read a speed chart in {m|km}ph). Then the author says they have an 8.28kW system.
It'd have been useful to also share a normalised graph, sort of like "in the last 15 minutes we produced an equivalent of 6kWh". I had to infer it by counting the number of bars in a 3 hour interval.
Then ~6kWh during peak time in their peak month, seems more informative.
> Our 23 solar panels are rated to produce a total of 8.28 kilowatts (kW), but in reality energy production doesn’t get that high and maximum production is for a short part of the day. We peak at about 6.6 kW
kWh is energy, kW is power (which you probably know). The graph is in energy and you clearly computed it correctly. Just to clarify.
We had to go solar last year due to our two hour per day power outages - 3,1 Kw array with 10Kw battery storage.
I use about 800Kwh per month before solar was installed and now it is down to 400 Kwh - our biggest power usage is our water heater (geyser) but that is solar powered.
Coolant is heated in vacuum tubes on the roof and then the heat exchanged with the water in the cylinder.
I'd like to see some consideration of inflation. Maybe energy prices are expected to rise faster than inflation, that shortens the ROI time. Or maybe there's going to be so much renewables that electricity price regularly goes to zero and it will be carried over to consumers(like, no net metering around noon).
While the micro economic stats are interesting, the macro ones are mind blowing.
A powerful deflationary force that eliminates fuel price volatility and achieves efficiency gains of 75%, with paybacks in the Trillions is available to many nations right now and the main response is conspiracy theories.
I’m always astounded by other people’s electricity consumption. How does this person use over 50kWh per day? That’s almost as much as I use per month! Do aircons use that much power?
We live where we have to provide our own water pressure. So everytime we turn the tap on a 2400watt pump kicks in. We have 3 fridges, two normals ones and a mini fridge my homebrew lives in.
We have pool, which needs it's 2400watt pump to run for at least two hours a day.
We have 3 air-conditioning units (not counting the forth we have that can heat the pool), it's Winter in New Zealand so we run them most nights. We have 4 computers on pretty much all the time. We have a condenser tumble dryer we use quite regularly.
We are a family of four, our hot water is electric. My daughter spends years in there (which is also using that water pump...)
The big ticket items are the two pumps, the hot water, the fridges and the aircon units.
We also have electric heaters going in Winter.
It all adds up. We do 50kwh a day quite often. Sometimes 80 in summer when all the aircons are on and the pool heatpump is too.
Well, your setup is absolutely full of luxuries. Most people don't have 4x computers running all day, 3x fridges and a (heated) pool. Together lifestyle choices.
And then yes, you need to provide your own water pressure too.
Totally. We are extremely fortunate to have these things. That said, I still think even with the unnecessary fluff taken out, if you're heating your hot water with electricity you'll be using a lot of kWh.
When I visited the southern island of NZ in 2019 I was shocked how little insulated the houses I stayed in were, considering that the winters are quite cold. For example, most windows only had 1 pane tech. Whereas here in Europe modern windows use 3 panes for better insulation and sound filtering.
Yup! This house has little insulation. We got the downstairs windows double glazed after we moved in but upstairs is still single pane. One day we'll change that...
It's very bad for heating/cooling
They do indeed. For instance, Singapore uses the most energy per capita in the world (or top 3-4 depending on year)… and it’s mostly due to AC. Even with very high coefficients of performance (usually in the 2-4 range, meaning you can remove 2kWh-4kWh of thermal energy from a space with just a single kWh of electricity - remember ACs act as heat pumps essentially leveraging the refrigeration cycle), ACs are still total electricity hogs.
Believe it or not, air conditioning systems sometimes even have to reheat the air! Sometimes you have to make the air much colder than desired just to dehumidify the air, and then you must reheat it to get it back to a reasonable temperature.
There are some cool innovations in alternatives that don’t rely on all this psychrometric chart hacking, like using membranes and dissidents to perform the dehumidification, or using direct/indirect evaporative cooling etc etc.
Edit: oh and of course space conditioning demands go up pretty linearly with total volume of air, which is in turn linear with total floor area. So could also just be a big home.
And I have seen people use mobile air conditioners without properly leading out the warm air that is created out of the building so they basically have a closed loop where the aircon fights itself. And even when properly letting out the warm air, new warm air from the outside is sucked in. Typically these types of air conditioners are just plain useless except for cooling one person who sits in the cool air blow.
It's also amazing how so many houses in warm countries are so poorly isolated and have bad window screens to avoid the sun heat up the inside of the building.
That's extremely low tbf. We're the same and use around 10 kWh/day. The average use per household in the UK is 7 kWh/day.
I'm really curious what people's base load is though. Mine is about 300W which seems very high and I can't figure out what would be using all that power. I guess we have 3 routers, an American style fridge and a Quooker tap, but even so... feels like it should be half that.
From the dates when we've been away from the house, ours is around 140 W. That's with a router and 4-bay NAS, a fridge, and whatever else is on standby mode (TV, microwave etc)
3 routers? Why? American style fridge-freezers are notoriously inefficient. When I worked in kitchens we'd try to put people off them most times. A side by side full-size European fridge and freezer is far better, more efficient and fits in our kitchens. The ones who got American style fridge-freezers were the ones for whom money was no concern. And bare in mind this was an upmarket kitchen place earth average overall cost between 20-30k per kitchen.
Ah ok.. not three routers then, but three pieces of network equipment. I have a similar set up (well, I have more like 10 things on including switches and NAS). I was speaking to a colleague the other day and he was saying how his network is annoying and it turned out he actually was using two routers. That second wireless AP should be just an access point, not a router (some have two modes).
Two separate appliances really was more efficient. The European models were vastly more efficient than the American ones (European ones were like A+ rating; American were like F with not much in between). I think the American style ones are a bit better now, though (they're probably European specific models).
FWIW, in my house, ~50% of the electricity is used by the electric water heater. This feels like lots of waste, given that we take at most 30 minutes of shower per day.
Aircon really does use a lot of power. Heating and cooling is the largest use of power in most western households. USA households use substantially more power than most nations, less efficiency focuses in goods and a lot of Aircon.
Same, i struggle to find a good explanation. 50 a month is definitely pretty low as well for where i come from, but the median for a family of four would still be around 20-25% of the numbers reported in the article. A couple consuming 1/6 of those 58kWh would be on the higher end. (Austria)
Also (Austria) - I live in a shared appartment in Vienna - We cook a lot, consumed about 1800kWh for the year, so 150kWh a month or 5kWh a day. 50kWh a day certainly seems Insane, but then again we have no AC.
A lot of places in Austria (esp. Vienna) are heated with burner Technology (gas/oil/pellets). The article states that this energy usage has been converted and is included in the total amount.
A quick search indicates that 1kg of pellets generates ~5kwh. So when burning 4to. of pellets in winter that adds about roughly 50kwh per day.
When using burner tech to heat, a good way to reduce the cost and profit from pv is to add a heating rod in the buffer tank of the heating system.
At the same time, the generated electricity also seems insane to me.
We live in a complex with 84 units, each with a solar roof, outputting about 12 kWh per unit per day. Maybe the owner just has a massive house, as they are outputting about 5x as much as our 2024 solar panel models …
It can definitely make a big difference. DC’s latitude is 38 degrees. That’s about the same gap to Miami (25 degrees). Think about shining a flashlight perpendicular to the ground vs at an angle.
Beyond the dynamics of direct irradiance, there’s also weather to consider- if you live in a significantly cloudier area (which might be possible, assuming you live in Canada or Germany/netherlands/etc based off that latitude), that will obviously affect output.
And then there is also things like building-to-building shading, in case you live in a dense area… lots of things can affect this kind of calculation.
Try playing around with the National Renewable Energy Laboratory’s PVWatts calculator:
It is indeed insane. It's amazing and scary what people can think is "normal". This person saves 3k credits per year on electricity. That's 3x the price of my entire year of energy and I'm sure the unit cost where I live (the UK) is higher. I pay attention to how much energy I use. Resist putting the heating on etc. While other people are leaving a footprint 10x as big and thinking nothing of it.
For what it's worth, my peak month this year was March at 169 kWh / month. I cook (electric) almost every day, I have a kid and I work mostly from home. Half of that energy is the (oversized) water heater. My winter months were actually a bit lower, but there's collective heating in my building, so that biases my consumption.
When I lived in an apartment in Australia, during winter we didn’t use the heater because it wasn’t so cold, when we moved to a landed house we couldn’t live without the heater! I don’t have any power bills from 20 years ago to know how much we used. But you’ve made me curious.
1000kwh/month in the winter and 350kwh in the summer. 4 people in central Europe. We use electricity for heating the house, warm water and everything else. We have an air-to-water heat pump.
50kWh/month is 68 watts; if there's no AC and if heating and cooking is non-electric, I can easily believe that.
Even a bit of microwave use won't eat much into that budget, as it's going to be 6-12 minutes per day at 1 kW, or an average of 4-8 watts.
Heating is the much harder one to find electric solutions for, but I'm sure there are plenty of examples of the right combination of temperate climates and good insulation/insolation design for that.
I have 6.5kW of solar PV and a 16kWh battery system in the UK. On a sunny day I’ll generate about 50kWh and export more than half of that to the grid. The rest is for charging my hybrid car (25kWh) and just general house use.
So far this year, our net grid import is 3000kWh and solar generation is 2500kWh. We have a 5kW heat pump and that uses quite a lot of electricity in winter when we don’t generate too much.
I have gone off the idea of solar at home. I’m on the octopus agile tariff where there are changing prices every 30 minutes. Given that sometimes I am paid to use electricity it would seem better to just buy a battery system and offset the usage.
Especially in the winter months when it’s blowing but not sunny. But I don’t see people selling this setup.
The aircons are far more efficient these days, but in mostly wooden hardly insulated houses often built in the US the costs are way higher.
A fully running aircon for a single room pulls around 1kw per hour, while it usually runs about 15 mins per hour in an efficient environments, depending in temps, humidity and insulation.
Our lowest consumption months (when the weather is nice) are 300 kWh/mo (10 kWh/day), and our highest are 900 kWh/mo (30 kWh/day), all depending on the heating and cooling needs. And this not counting cooking or hot water (which use gas)
Indeed. But that’s « only » 2kW constantly which makes sense if they leave AC 24/7 (that’s a reasonable assumption for a summer in DC) and the house isolation is not amazing (which unfortunately is the case with many houses in the US).
Though I think they are actually triple-dipping or even quadruple-dipping.
1-2. Net-metering and credits
3. Reduced contribution to infrastructure
There are times when their PV setup produces very little or no electricity at all. At those times, they are 100% reliant on the grid to supply them with all their electricity needs. A large part of the cost of electricity supply is the fixed cost of infrastructure, whether used or not, which is paid off by the variable supply of electricity. Since they are 100% reliant on the grid at least some time, they haven't reduced the need for the fixed-cost infrastructure, but have reduced their contribution to that infrastructure.
I guess this could be alleviated by capping the amount of electricity you are allowed to take from the grid?
4. Increased variability
The addition of variable suppliers like PV reduces grid stability and increases the requirements for and cost of measures to stabilize the grid. Battery backup could obviously alleviate this, but if not done carefully it could just stretch out the destabilizing events and then make those fewer events worse.
While I really, really like the idea of rooftop solar, (partial) energy independence, and a more distributed grid, I think we do have to figure these things out. I don't see how it makes sense at the moment.