Can Hawaii go 100% Renewable?

Hawaii’s Renewables Portfolio Standard commits it to obtaining 100% of its energy from renewables by 2045, and Hawaii proposes to do this by wholesale replacement of fossil fuel generation with solar. This approach is theoretically possible, but only if there is enough energy storage (approximately 10GWh) to match day-night solar fluctuations of over 3GW to a substantially flat ~800MW load curve and if grid stability can be mantained with dominant solar generation. The Renewables Portfolio Standard also covers only electricity generation, which presently supplies only about a third of Hawaii’s energy needs, so even if it’s met Hawaii will still fall well short of its 100% renewable energy target.

Sources of data

Data for Hawaii are limited but adequate for a preliminary review. The main source of backup data for the 100% renewables claim is The Hawaiian Electric Companies 2016 Power Supply Improvement Plan . This is a four-book document that defies analysis because of its length (book four alone contains over 800 pages) and the Executive Summary provides little in the way of hard data. Other sources were:

Adequacy of supply reports

Hawaii PUC energy reports

Hawaiian Electric power facts

EIA generation and installed capacity data

There are no publically-available grid data available for Hawaii, or at least none that I could find.

Hawaii’s electrical generation system

Hawaii is a chain of islands unconnected by submarine cables. Electricity is supplied by three utilities, of which HECO, which serves Honolulu, is by far the largest.

  • Hawaian Electric Company (HECO): Island of Oahu, installed capacity 2,197MW
  • Maui Electric Company (MECO): Island of Maui and surrounding islands, installed capacity 424MW
  • Hawai’i Electric Light Company (HELCO): Island of Hawaii, installed capacity 397MW

Kaui generates only a small amount of electricity and is not considered in this review.

Figure 1: Hawaii’s utility service territories. Note that there are no interconnections between the islands

Details of installed 2016 capacity are given in Figure 2. Note that Hawaiian utilities do not include intermittent renewables as “firm capacity”, meaning that they don’t get counted in “adequacy of supply” analyses. Other jurisdictions might take note:

Figure 2: Hawaii’s 2016 installed capacity by type. Data from Hawaiian Electric Power Facts

The table below lists Hawaii’s 2014 generation by source. Oil and coal dominate. Solar will be underestimated because distributed generation is not taken into account and because the data, the most recent I can find, are for 2014. According to Figure 2 total distributed solar capacity in 2016 was 465MW, which would generate around 750,000 MWh/year, or about 7% of total generation assuming no significant curtailment. The data are from the U.S. Energy Information Administration, Form EIA-923, “Power Plant Operations Report” and predecessor forms.

About 8% of total generation comes from a mixed bag of “other” sources, which EIA describes as follows: Other includes non-biogenic municipal solid waste, batteries, chemicals, hydrogen, pitch, purchased steam, sulfur, tire-derived fuels, waste heat and miscellaneous technologies Other biomass includes agricultural byproducts, landfill gas, biogenic municipal solid waste, other biomass (solid, liquid and gas) and sludge waste. Other gases includes blast furnace gas, and other manufactured and waste gases derived from fossil fuels.

The question now arises, how does Hawaii get from this fossil-fuel dominated generation mix to 100% renewables by 2045 (or maybe 2040)? Simple. It adds solar – a lot of it. In 2045, in the E3 Plan, there is approximately 2,100 MW of distributed generation PV, over 2,000 MW of grid-scale PV, 200 MW of offshore wind, 68 MW of waste to energy, and 160 MW of onshore wind. This gives a total of at least 4,500MW installed compared to the current 3,000MW, and 90% of the capacity is now solar. Figure 3 compares projected output from this generation mix against demand for Oahu in 2045. 82% of gross generation is solar, 14% wind and 4% “firm renewable”, presumably mostly biomass:

Figure 3: Monthly renewable generation versus load, Oahu 2045: Graphic from 2016 Power Source Improvement Plan

Will this approach work?

To give it every chance I changed the rules. The plan shown in Figure 3 is derived from a complex computer model designed to minimize costs, and it still shows significant solar curtailment. However, just a little more solar would remove the gray winter “shortfall” areas and eliminate the need for seasonal storage, which as discussed in a potential solution to the problem of storing solar energy – don’t store it is the simplest and cheapest option at 20 degrees north latitude. Once we eliminate seasonal storage we have to consider only the storage needed to handle daily and other short-term variations in solar output, which are normally more manageable.

To evaluate this option I first went to the Sunny Portal website and downloaded operating data for four solar PV installations on Oahu – Hawaii National Bank, Kalanimoku, Kaimuki and Coffee Systems Hawaii – converted the output into monthly capacity factors and plotted them up with the results shown in Figure 4. The plots match quite well, showing an average capacity factor of around 19% and a winter/summer range from about 14% to 22%:

Figure 4: Monthly solar generation from four operating installations on Oahu expressed as capacity factors.

The next step was to factor the generation from these systems up to match the December minimum in the monthly load curve. (I found that 5.9GW of solar, not 4.1GW, was needed to do this at the capacity factors shown in Figure 4.) The results show curtailment levels ranging from 35% in June down to zero in December and overall curtailment of 23%, which is not unacceptable considering that the curtailed generation has a fuel cost of zero.

Figure 5: 2045 generation mix after scaling to match solar generation to December demand. Wind and “firm renewable” are scaled off Figure 4

Figure 6 plots solar generation for a winter month (January 2015) and a summer month (July 2015) using scaled-up data from Figure 4. There is little difference between the two, with both showing night-day ranges of over 3GW. Demand, however, remains generally within the 0.7-1.1GW range. Clearly a significant amount of flexible and robust storage will be needed to match daily and other short-term solar generation fluctuations to demand:

Figure 6: January and July 2015 hourly solar generation scaled up from Figure 3 data

Figure 7 shows how much winter storage would be needed based on the Oahu demand curve for January 25, 2016 published by the EIA , which was the only demand curve for Oahu I could find. January solar generation is matched to demand for the day and the differences between generation and demand are accumulated to define storage requirements. I have assumed that wind and “firm” generation are constant and that all the variability is a result of solar:

Figure 7: Storage inflows and outflows needed to match solar generation to Oahu demand, January 2016

According to these results over 6GWh of storage would be needed to match solar generation to demand on this particular day, but 10GWh or more would probably be needed to handle the deficits during days of low solar generation, such as January 14 and 29 (Figure 6). The storage would also have to be robust to tolerate being charged and discharged each day at high ramp rates. The results also make it clear that demand side management will have no significant impact on the amount of storage needed.

Where is Hawaii to get this storage from? The emphasis is presently on batteries, but in the MWh or kWh, not the GWh range. In 2014 HECO put out an RFP for 200MWh of energy storage which has resulted in a few small projects in the pipeline but only one operating system – a 250kWh battery storage system on Oahu . Sights will have to be set much higher to achieve the amount of storage needed in 2045, but it’s impossible to know whether battery technology will have advanced by 2045 to the point where 10GWh of battery storage would be technically and economically feasible.

There is also the question of grid stability. Can a grid that handles such large swings in solar input and which is supported by hardly any conventional generation maintain frequency between Hawaii’s 59.3 – 60.5 hz limits? Grid stability experts with time on their hands are invited to skim through Book 4 and express an opinion.

And there is another fly in the ointment. MECO and HELCO report no problems, but HECO on Oahu already has doubts as to whether it will be able to keep the lights on after 2018:

Hawaiian Electric’s reserve capacity, which does not include intermittent energy sources such as wind and solar, may not be sufficient to meet the Company’s generating system reliability guideline in 2018 and beyond, assuming Waiau Units 3 and 4 are deactivated at the end of 2017 and the Schofield Generating Station is in service from 2018. Hawaiian Electric may seek to mitigate reserve capacity shortfalls in 2018 and beyond by deferring future deactivation of units, implementing additional Demand Response Programs, optimizing maintenance schedules, reactivating units that are currently deactivated (i.e., Honolulu Units 8 and 9), installing temporary distributed generation, increasing the capacity of existing utility or non-utility units, or acquiring additional firm capacity.

Outages for planned work and maintenance will continue to be more numerous and longer in duration than in previous years. Maintenance will continue to be a challenge for the existing units. As the generating units age they will need to be maintained more often and for longer periods of time. As the demand on existing generating units change to mitigate different resources on the system such as variable generation resources, the generating units operate harder to counteract the increasingly dynamic changes, which increase the likelihood of unscheduled (forced) outages and operations at derated power levels.

And yet another fly. The explosive growth in rooftop solar in 2013 and 2014 threatened to overwhelm a number of local grids, prompting the Hawaii Public Utilities Commission to cancel net metering provisions in 2015 and replace them with fixed price contracts that make rooftop solar a lot less financially attractive. This has had a negative impact on the distributed solar growth rate.

And one final fly. Like many other jurisdictions Hawaii has difficulty distinguishing between energy and electricity. (“Our Power Supply Improvement Plan accelerates the pace on the path to 100 percent renewable energy.”) But the Power Supply Improvement Plan concentrates entirely on decarbonizing the electricity sector, which according to the 2014 State of Hawaii Energy Data and Trends supplies only about a third of Hawaii’s energy needs:

Figure 8: Hawaii energy use by sector. Data from 2014 State of Hawaii Energy Data and Trends

So even if Hawaii were to achieve its goal of 100% renewable electricity tomorrow it would still be dependent on fossil fuels for about two-thirds of its total energy supply.


There are a number of isolated islands other than Hawaii that are currently planning to go “100% renewable” but they are small (El Hierro, the largest of them, has a peak demand of about 7 MW). Hawaii is much larger (peak demand on Oahu in 2015 was 1,232 MW) and is therefore a better example of how 100% renewable energy might work on the large scale. At this point the prospects for 100% renewable electricity by 2045 look shaky and the prospects for 100% renewable energy remote. Yet Hawaii utilities remain confident in their ability not only to meet their electricity goal but to surpass it:

Figure 9: Showing how Hawaii’s utilities plan to exceed the Renewable Portfolio Standard of 100% renewable electricity before the 2045 target data. Graphic from the Power Supply Improvement Plan

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50 Responses to Can Hawaii go 100% Renewable?

  1. Dave Rutledge says:

    Hi Roger,

    Thank you for a thoughtful summary. Are any of these companies thinking about bringing synchronous capacitors on line to help stabilize the grid? I believe that we did this in Southern California when the San Onofre nuclear plant was shut down.


  2. Tom Bates says:

    Interesting example of the wackos who push this renewal energy idea without wondering how to store the power. What is interesting about Hawaii is why they are not going more to geothermal. They have a large heat source spiting out lava every day. While they do also have limited fresh water, the ocean is right there with unlimited water they could inject into the hot rock. Since the bigger islands are not that far apart it may be possible to lay cable between them to distribute power though since the trench between some islands is pretty deep it would be the deepest cable network as far as I know in the world if put in place. Since as you point out the electrical power is only a small part of overall energy demand, they are going to need a whole lot more solar and storage if they force people to go to electric cars which considering how small the islands are would actually be practical as it is pretty hard to put 100 miles on your car in a day.

    • Roger Andrews says:

      The problem with geothermal on Hawaii is that most if not all of the untapped potential is on the “Big Island” of Hawaii while most of the demand is on Oahu 200 miles to the north. There also seems to be a lot of public resistance to building more geothermal plants.

    • meliorismnow says:

      They’ll actually need much less storage because EV owners will take advantage of time of use plans, smoothing demand. Some (particularly Uber) will even use idle EVs to supply energy during peak rate times. There should be a BEV version of just about any kind of vehicle available by 2022 and low mileage variants should be price comparable to gas versions (in all categories) by 2025. By 2045, all intra and interisland transport should be electrified. Even electric ferries and planes will take advantage of ToU and location arbitrage (reducing the need for interconnects and the environmental impact that killed the Super Ferry). The main question is how quickly do city residents without a garage to charge their cars move to a service that does incorporate ToU (but it will certainly be standard everywhere by 2045).

      Roof mounted solar will also continue to spread as installation cost drops and local battery storage (ala powerwall) will be common to take full advantage of ToU plans and have less effect on grid stability.

      Obviously transport from the mainland or other countries will still use fossil fuels.

      • TimC says:

        Equally obvious is that all of the thousands of tons of manufactured material and equipment that Hawaii imports every year from the mainland and other countries, including EVs, BEVs, Powerwalls, etc., will still be made using fossil fuels.

  3. jfon says:

    Do you have any estimates for inter-island transport, or proposals for how to decarbonise it ?

  4. Alex says:

    It seems easier for Hawaii than for the UK, largely because solar power in the tropics is more reliable than wind power.

    Scheme to consider:
    1. Don’t ditch the diesel. One day, it will be needed. If necessary, invest in diesel that can sit idle for a long time (see discussion on Ta’u and the problems of starting diesels after a few years idle).
    2. Build some big solar parks on the south slopes of Mauna Kea and Manua Kea-
    – Just below the snow line but above the moist Pacific air, forests, and where people live and farm- probably at about 2,000m – 2,500m altitude.
    – Orientate the panels for maximum winter sun – about 35 degrees off the horizontal. The mountain slope should reduce costs and area required.
    – That should give a high yield – not quite Chile – but good for the islands
    – Expect about 50% to come from here – perhaps 3GW capacity, or 15km2 of panels covering perhaps 30km2.
    3. You would think there’s good scope for pumped storage on the North Slope of Manua Kea. Only 20km from the sea, and you’re at 2,500m altitude. Could a feature like this,-155.3848527,15.79z/data=!5m1!1e4?hl=en have a wall built? Looks like scope for 1 to 2 million tons of sea water, or a store of well over 6GWh. The pumped storage will even out the load from Hawaii island. (Might have to cover the upper store – warm sea water might evaporate quite fast at 2,500m).
    4. Put a 1GW HVDC connection between the islands. This is not that easy as the water depth is up to 2,000m.
    5. For the rest, make sure the incentive scheme covers solar + battery, and not just solar.

    Not cheap!

    • Alex says:

      This item here:,-155.4252519,16z/data=!5m1!1e4?hl=en

      Looks ready made for storing 1 million m3 of sea water at 3,500m. Are these features volcanically active? seems Manua Kea is dormant, but Manua Loa is active.

    • gweberbv says:


      for the HVDC connections one might us such a scheme:
      Stormy weather might a challenge, but when this is possible for a car tunnel in Norway, it might be possible as well for a HVDC cable which probably has less strict mechanical requirements.

    • anon says:

      pumped storage in hawaii is almost certainly impractical from the geological point of view – hawaii is pretty much entirely made of porous volcanic rock. Youll notice there are no rivers or lakes even in areas with very high year-round rainfall- the water soaks right into the ground. .

      • Alex says:

        We’re talking about relatively small upper reservoirs. They can be lined quite easily (must be lined as we’re dealing with salt water).

        The bigger worry is volcanic disturbance. Maui is less volcanic and has sites for a water chamber that are 2400m up and just 9km from the coast.

    • Roberto says:

      ‘2. Build some big solar parks on the south slopes of Mauna Kea and Manua Kea-‘

      This you can forget it… Mauna Loa is a sacred mountain to local indigenous people, they just forced the astronomers’ community to scrap their plan for a new telescope, much smaller than a PV field.

      • Alex says:

        Tradition versus environmental issues! Always a problem. In the UK, old buildings are sacred and you can’t insulate them.

        Solar farms at 2,000m altitude though would be fairly unobtrusive – they’d be flat on the hillside just changing the colour of the mountain.

        Would volcanic ash be a problem? If so, perhaps best to focus on the next island.

  5. gweberbv says:

    Does anyone has an idea of the role of wind power in this scenario? I would expect that it will be more costly to operate on remote islands than on the mainland as experts and large equipment has to be brought to the islands on a regular basis. And I do not see any benefit compared to PV (when solar seasonal variations are small).

    Regarding storage: 1 GW/7 GWh are typical parameters for a large-scale pumped storage plant. Two of them will do the job. Of course, I have no idea if there are suitable locations. But on a much smaller scale this approach seems to be followed on one of the smaller islands:

    • Alex says:

      Hawaii has so much “head” – ie altitude close to the sea, that it should be possible to build dedicated caverns at altitude. At 2,000m, not much volume is needed.

    • Alex says:

      It’s the opposite scenario compared to the UK. A bit of wind will help as it’s counter cyclical, but solar will be cheaper. So maybe a 90/10 split in favour of solar.

      Hawaii isn’t really a “remote” island. It should be possible to get economies of scale so support costs are not that much greater than the mainland, and lower than for offshore.

      I suspect a bigger issue will be national parks and preserving iconic views.

      • gweberbv says:


        200 MW of offshore wind in the middle of nowhere will be *very* expensive. You need to build 10 GW and more in a small region (i. e. Northern Europe) to get the costs to an acceptable level.

        • Thinkstoomuch says:

          Have people even looked at the feasibility of offshore wind in Hawaii?

          Remember HI islands are of volcanic origin. That is the reason that as quoted above 20 km gets thousands of meters in elevation change. Thing about that facing the other way from said shoreline!

          Northern Europe, and for that matter the East Coast of the US, has an exact opposite bottom topography.

          Just off the cuff, I haven’t even looked at HI in this context. But offshore would seem an *extremely* limited application. For that matter onshore probably has huge limitations.

          Part of the reason nobody is seriously looking at offshore wind in CA. Unless it is floating and anchored which leads to an assortment of other issues.

          Also, gweberbv, we have different values of the middle of nowhere or at least how it is measured. Million and a half people and density of 200+ per square mile … (Wiki stats so take with a grain of salt)


          • Alex says:

            Offshore in Hawaii would mean floating – which is looking very expensive. On shore would be easier as there are plenty of 1,000m high ridges. However, I suspect Hawaiians won’t take kindly to their views being spoilt. Maybe the pass between Manua Loa and Manua Kea would be a good place?

    • Roger Andrews says:

      The plan calls for over 4,000MW of solar but only 260MW of wind,

  6. JerryC says:

    Decarbonising the electricity supply for an island chain in the middle of the Pacific Ocean that has an economy based on mainland tourism and mititary bases strikes me as just about the most pointless thing ever.

  7. disdaniel says:

    Hawaii would be a good place to test pumped hydro, where the hydro is stored in giant hollow shells underwater. Pump the water out to store energy, let the water in (and turn the attached turbine) to release the energy. Especially given how “tall” those islands are…Mauna Kea ~10km from base to summit.

  8. ristvan says:

    Cannot get there from here. In theory, grid inertia could be supplied by synchronous condensers. With a safety margin of 10%, about 4400Mw worth. The 2015 installed cost is about $1 million/mw per ipcbee. Siemens grid scale units). So a mere additional $4,400,000,000.
    Having worked in energy storage since the mid 1990’s, it is fairly certain batteries will not be grid capable on this scale either technically or financially. Grid scale (e.g 4Mw x 8 hour) sodium sulfur at Presidio Texas cost $25 million with a lifetime of 15 years and a RTE of only 75% (they run at a temp of 350C , a molten salt type battery). Your calculation shows a need of ~6GWh. Throw on an additional $ 4.7 billion and replace it in 15 years. Nope Would have to be pumped storage. Capital runs about $1000/kwh. A bargain at $6billion with a liftime >50 years.
    Now, since half the solar generation goes into storage (pumped is 75-80% efficient depending on head), the total installed solar needs to be about 2.5x what is supplied to the grid during daytime. You calculate 5.9 Gw needed. With storage, that is 14.8Gw of PV. First Solar is now getting 18.6% commercial efficiency, and says it can install grid scale arrays for $1/W. So another $14.8 billion.
    Total capital investment by 2040 (4.4+6+14.8) ~$25 billion.
    Now suppose instead each island installs one or more CCGT to replace everything. Efficiency ~doubles from ~32-34 to ~61%. Emissions more than halved. Total capital cost for ~3000Mw <$4.5 billion. Leaving $20 billion and change to buy the LNG. And it could all be done in three years.

  9. Thinkstoomuch says:

    Interesting article from Jan 10th on UtilityDive.

    I haven’t followed all the links but pretty timely for this post. Figured I would get smarter people than me looking at it.


    • ristvan says:

      T2M, am certain am not smarter. But the vendor is Solar City (now part of Tesla), the quoted price is why Solar City was going bankrupt until ‘rescued’ by Musk, and now guarantees that Tesla will soon also. Best short I have seen in over a decade.

    • Roger Andrews says:

      T2M: Indeed an interesting article. But it prompts a question. The four solar arrays I picked (at random) in the post all generate a maximum of only about 80% of their MWp rating during sunny days around the summer solstice. This seems too large a difference to be explained by inverter losses or by panel misalignment. Anyone have any ideas?

      • ristvan says:

        Yes. Solar City misrepresentation. Whyndo we suppose they state truth?

      • Thinkstoomuch says:


        A few thoughts from someone who is *too* anal retentive with too much time on on his hands.

        There are *reasons* that utility scale projects seem to use the 1.3:1 array to inverter ratio. Also for the Enphase micro inverters to be “undersized” for the panel. Facts pointed out to me by commenters here.

        I suspect the leading cause of that performance is cell temperature.

        The EROI study post that array wattage is calculated for 25 degree C cell temperature. When you lose 0.3-0.5% per degree C it starts adding up quickly.

        For example the Spec Sheet for the 191 panels used on the HAWAII NATIONAL BANK SMITH ST.

        Temperature Coefficient of PMAX – 0.43%/°C
        @STC Peak Power Watts-PMAX (Wp) 230
        @NOCT Maximum Power (W)=168

        STC stands for Standard Test Conditions, NOCT Stands for Normal Operating Conditions (More detail at the link).

        Hope it helps,

        PS if you want to go over board use the hourly output for PVWatts Honolulu and look at some “numbers”. For an array tilt of 21.35. Max Array temp 54 C. Max plane of the array Irradiance 1074 (W/m^2), only 141 hours above 1,000, 951 > 900. For real fun the highest temp and irradiance both occurred in May. Like I said I am *way* too anal retentive.

        • Roger Andrews says:

          T2M: Good stuff. Thank you.

          Do you have any links for the 1.3:1 ratio you mention? If MWe is consistently 20-25% less than MWp I need to take it into account in calculations.

          • Alex says:

            I have a 5.4KW array and an inverter rated at 5KW. Very rarely – around May normally – I can see a bit of peak shaving – the very top of the sine wave is flat.

            The main reason was the next inverter up was a few KW more, and would cost more.

            In a solar park, there might be some advantage at facing some panels more East and some more west to get better returns during the morning and evening peaks. That could lower KWmax/KWcap to 80%.

          • Thinkstoomuch says:

            First not sure it will actually impact the costs, though EROI “may” be impacted. Various projects and their costs get mish-mashed with array size listed on some and inverter size “seeming” to get listed on others. Like the article I cited above doesn’t even list array or inverter size. At least the storage was in both MW and MWh.

            That ratio came up over the summer (in relation to current German Solar Projects, IIRC) and right now I am not able to find where I got it from originally. Or the torturous searches and thoughts over weeks brought me to treat it as “verified”. Spent months looking and figuring out “why’s”. I might have been using Open PV, the latest “Tracking the Sun” report and probably a bunch of other stuff. 🙂

            One article on this from a quick bing search. An older article that explains the rationale.


            Note Figure 1a and 1b on page 3. Higher array ratio yields higher output. Which just seems wrong! Upside down even. 🙂 🙂

            Spec Sheet for the Enphase 250 watt commercial inverter recommended input power “up to 350 watts”. Or 1.4:1. If I did the math right. 😉 Chancy that, *I* might have done it upside down or something. I have made MUCH worse blunders in comments here.


            One of the places that math is proven is the PVWatts manual and the formulas they use. I really think people _serious_ about going solar should at least read that manual for “how output is made”. A 17 page PDF document but they do a decent job explaining things.


            Section 12 Page 11 talks about the inverter equations in particular.

            So right now I am unable to find an exact reference.:-( My apologies.

            Another thing to consider when trying to cost things like solar with storage(like this post’s example) is the use of tracking modules which are becoming more prevalent in US solar project designs. Trackers lead to more watt hours but much sharper slopes in the morning and evening.

            Just think if anyone could do it, where’s the fun? 🙂


          • Thinkstoomuch says:

            Finally found where the inverter ratio is in print. “Meanwhile, the average inverter loading ratio has increased among more recent project vintages, to 1.31.”


            The PDF of the full report I found to be very informative. But it is a 55 page document. Still trying to internalize most of it. Lots of rereading and contemplating.

            I still don’t think that the inverter loading will affect cost other than making it cheaper, I think.

            I feel much better now,

            PS I also found out the the latest 3 FPL projects are using fixed tilt which is interesting. They are in the same area as the 2010 project that used single axis tracking.

          • Thanks T2M. I was hoping to find some info on the ratio between MWp and MWe (or MWac) but the subject is clearly a lot more complex than that. So I’m back to reviewing production data from operating systems as the best measure of what solar arrays actually put out.

            The estimate of 15.1% to 35.7% capacity factors, with a sample median of 26.4%, for utility-sized PV plants, is a good bit larger than any numbers I have come up with, but they are based on estimates of solar radiation, not actual operating data. I wonder what the operating data would show.

            Here’s another reference on inverter ratios you might care to look at. The abstract is interesting, and for a mere $41.95 you can get to read the whole thing.


  10. Leo Smith says:

    Someone will develop a SMR and within a year all renewable plant will cease to be built.

    I’d give it less than a decade

    • David B. Benson says:

      The Nuscale SMR will be ready by 2025. All that is needed is to define nuclear power plants as renewables.

      • Alex says:

        NuScale are expecting their construction costs to be $5,000/KW, which is not that much of an improvement on the AP1000, and double what China are claiming for their Hualong One (though that will cost more in Bradwell).

        The Molten Salt Reactor companies are estimating about $2,000 / KW. I’d expect Terrestrial and one other to be ready about 2030.

  11. pyrrhus says:

    Very nice piece, and diplomatic too!

  12. Jonathan Madden says:

    Hawaii labours under some of the highest electricity prices in the US:

    The values quoted here are little short of mind boggling, perhaps a little less so if one ignores the recent drop in Sterling. Nevertheless more than double ours.

    Can we expect a future Hawaiian renewable system to dent these? Clearly the economy there can absorb current costs but will welcome any reduction. The large military presence and tourism add significant income to the total 1.4m population, a little more than Birmingham.

    Electrical cornucopians have an excellent opportunity to demonstrate the brave new world of renewables. But we are looking at a 25 year timescale for this project alone – I thought the idea was to convert most of the world before fossil fuels become too expensive?

    Thank you for an interesting article, Roger.

    • Alex says:

      Those Hawaiian rates are similar to electricity prices in Germany. But that is because diesel is generally an expensive way to generate electricity, and even more so on islands. It’s why tropical islands like Hawaii (or even more so, Ta’u) are probably the best best place to switch to solar. If solar can’t compete there, where can it?

      • gweberbv says:

        The problem with a shift towards PV (and maybe wind) are the upfront costs before after one or two decades of investments one can expect to bring the harvest home. But when the competition is against diesel generators, it might work right from the start. Let’s see if they find a workable solution for the storage.

      • One thing we tend to forget when comparing costs is that replacing FF generation with renewables saves us from the ravages of climate change, which according to the 2006 Stern Report will cost the world between 5 and 20% of its GDP (presently about $80 trillion) a year if nothing is done to stop it. When you credit wind and solar with savings like these diesel doesn’t stand much of a chance.

  13. Willem Post says:


    Germany’s installed solar MW was about 41000 at end 2016.
    The historic maximum recorded output was about 27000 MW.

    Hawaii would have a better ratio.

  14. Dean Cardno says:

    The linked report mentions synchronous condensers in the context of converting existing units, so it appears they are thinking of it. It is a common approach when decommissioning fossil-fueled units to remove the boiler but retain (and adapt, to the extent required – which is usually pretty minimal) the generator to provide reactive support.

  15. jacobress says:

    Figure 6 – aggregate solar supply in January and July 2015 seems a little misleading. There is hardly a cloudy day in these months, supply is uniform – doesn’t seem correct. The graph is an aggregate of all islands, but, since their electricity supply is independent (not inter-connected), the aggregate can be misleading.
    I guess that each island, independent of the others, has cloudy days when PV electricity supply is very low. That means that the storage required, for each system, must be able to bridge two days or even more, of cloudy weather.
    So, it seems, you underestimate the required storage.

  16. seth says:

    Many visitors to the islands can recall vacations where it was cloudy and wet for weeks on end.

    Cherry picking years to miss the outliers that must be provisioned with storage at a cost of a buck a kwh added to one’s power bill is not doing any favors to proper analysis.

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