Cost of energy on Mars

Solar array with a Mars settlement in the background. Just one possibility out of a large spectrum of choices, from flexible film unrolled directly on the ground to high powered nuclear reactors.

The cost of energy on Mars is one of the prime parameters required to analyse martian settlement scenarios. To go beyond generalizations and actually evaluate one scenario against another, the cost of energy and the cost of transportation to and from Mars need to be known, or at least estimated to compare on a common basis.

There can be no absolute answer to this question, as the cost of energy will vary depending on the source and the level of development of the colony. If all the energy producing equipment comes from Earth, the cost will be higher than if it is produced in-situ. As the settlement grows larger, economies of scale will come into play to reduce energy costs. As automation increases, and productivity increases accordingly, the cost of energy may go down significantly. Self replication of production equipment may eventually bring down the cost of energy to very small values. This will allow the realization of projects using energy on a scale that will be, literally, cosmic.

This analysis puts production costs for energy from a nuclear reactor on Mars at about the cost of electricity on Earth (0,06 to 0,12 $/kWh), and solar at about three times the cost.

Solar energy

Design

Solar power is more than just solar panels. Due to the interruptible nature of solar, short term and long term energy storage is required to provide for all the settlement energy needs. In the present cost study, some energy is presumed stored in batteries for short term and methane/oxygen form for long term, with gensets used to produce power during dust storms. The distribution and power transformation systems are excluded, as they are presumed similar across the study. Thermal solar is also excluded, and rather considered as a potential source for specific processes, rather than distributed energy.

Solar panels

Two types of solar arrays are examined here, rigid high efficiency panels and flexible film. Although less efficient, flexible film is much lighter.

Rigid solar panels

Rigid solar panel array built on Earth should have about the following characteristics:

Solar array characteristics

Characterisitic	Value	References
Efficiency-performance	22%	This is the value of commercially available solar panels (2024).
Mass	3,5 kg/m2	This is the NASA 2018 BIG challenge target of 3 kg/m2, plus 0,2 kg/m2 for batteries and 0,3 kg/m2 for other ancillary equipment. This corresponds to about 30 We/kg.
Cost on Earth	800 $/m2	An estimate based on an average cost of 500$/m2 for conventional panels on Earth and an allocation for the rest of the required equipment.

The design is a single axis tracking array. This allows for more energy production with the same peak power characteristics. The added complexity is estimated to be a small cost compared to the transportation costs from Earth. The moving mechanism would be fitted with elements allowing for a self cleaning phase for dust removal. The panels are mounted on a single rotating and extending boom, that allows for tight packing at transportation and can be unfolded using traction from a vehicle that can also serve to transport and set down the array, eliminating the need and mass of self extension mechanisms.

Flexible solar film

Flexible solar film may be available at 100 g/m2 for 10% efficiency. Keeping the same power ratios would put batteries at 0,07 kg/m2 and ancillary equipment at 0,1 kg/m2 for a total of 0,27 kg/m2

Either solution would be transported by SpaceX Starship with other cargo and unfolded on Mars semi-autonomously. For the Cost of Transportation to Mars, we can define a range: From the cost proposed by SpaceX for their transportation system, 140 $kg to Mars to a more conservative 500$ per kg(add reference).

Solar panel cost on Mars

For rigid panels, the costs will vary between:

• 800$/m2 + 3.5 kg/m2 x 500$/kg = 2550 $/m2
• 800$/m2 + 3.5 kg/m2 x 150$/kg = 1325 $/m2 of rigid solar panel on Mars. Transportation is by far the largest part of the cost at the higher transport cost.

For flexible rolls, the costs will vary between:

• 300$/m2 + 0.27 kg/m2 x 500$/kg = 435 $/m2
• 300$/m2 + 0.27 kg/m2 x 150$/kg = 340 $/m2 of flexible solar panel on Mars. Transportation for the last case becomes as low as 5% of the cost per m2.

Solar panel energy production

The solar constant is estimated at 590 W/m2 over the whole year. Atmospheric dust losses are set at 20%. An additional surface dust factor of 10% is included. Note that such a low surface dust factor assumes that the solar panels will be regularly cleaned, ideally with automated equipment.

Under these assumptions, the solar illumination is lowered to 413 W/m2. Using solar tracking can provide peak power for about 7 hours for per day, the available energy per day is calculated as 413 W/m2 x 7h x 3600 s/h = 10 MJ.

The actual energy production with 22% efficient solar panels should be 10 MJ x 22% efficiency = 2,3 MJ per day.

The installed power, based on the 7 hours of peak operation, should be 413 W/m2 x 22% = 91 W/m2. The same cells on Earth would have a power of about 250 W/m2. The mass ratio metric is then 250 W/m2 / 3 kg/m2 = 83 W/kg. this seems safely conservative compared to recent (2017) NASA projections

The availability of the solar panels is estimated at 95%, to account for repairs, tracking failures and other problems.

So every year a m2 of rigid solar panel would produce about 2,3 MJ x 365 x 0,95 /1000 = 0,84 GJ/m2/y.

The efficiency of flexible solar film is lower, and sun tracking is not possible, so the energy production will be much lower, at about 0,33 GJ/m2.

Short term power

Batteries will be required for bridging between day and night. As the main power loads: food, manufacturing, and fuel production, would likely be shut off during the night for a solar based settlement, the actual demand would drop to between 5 and 10% of the daily production. If a 1m2 solar array produces 2,4 MJ per day, then lithium ion batteries storing 1 MJ/kg would require between 0,12 (5%) and 0,24 (10%) kg of batteries per m2 of panel. See Flow batteries for batteries with huge energy storage abilities.

For flexible solar panels these values are divided by about three.

Backup power

Due to planet wide Martian dust storms, which can last months, there are periods when solar power may be reduced significantly, or just not be available at all. Dust storms can block unto 95% of the sun's light (tho 30 to 60% reductions are more typical). Some dust storms, have lasted for months. (See Dust Storms for more details.)

Because of dust storms, a back up system will be required and the cost of this system must be factored into the cost of solar. A 3500 KW genset on Earth masses about 10 000 kg.

As it would make sense to shut down fuel and food production during storms, the demand during a storm would drop to between 5-10% of the average demand. The mass ratio of the genset is about 350 W/kg, or 3.5 times less than the mass ratio of solar at 100 W/kg. At 10% of the peak demand, the genset would then represent about 3% of the mass of solar panels, so an allowance of 10 grams per m2 of solar panel should be added to the mass of the solar powered system. This fit's into the 300g allocation already provided.

For the first few decades of a Martian settlement, the fuel will be stored in the tanks of the cargo vehicles used to carry the settlement equipment, so no additional mass is required to account for methane and oxygen storage.

If demand during a dust storm can be lowered to 4-5%, as might be possible without fuel, manufacturing, and food production, then there will be no need for backup storage in most cases, as the solar panels will be able to supply the required energy. However, enough food must be grown and stored in advance to survive the dust storm.

Solar power overall cost

The prices below have a very broad range of uncertainty, as the cost of solar has been going down steadily, and the cost of SpaceX to Mars is pretty speculative.

Rigid solar panels

With an estimated life time of 20 years the total energy produced would be 20 x 0,83 = 16,6 GJ/m2. When divided by the cost of 2 550$ the bare cost of the energy would be 159 $/GJ. Majoring in financing, profit and uncertainties, we could expect a multiplying factor of 1.5, for a final cost estimate of 238 $/GJ for Martian solar power. In other units this is 0,23 $/MJ, or 0,86$ per kWh. This is a bit more than twice the cost of electricity on the Islands of Hawaii.

Flexible solar film

With an estimated life time of 20 years the total energy produced would be 20 x 0,26 = 6,3 GJ/m2. When divided by the cost of 230$ the bare cost of the energy would be 54 $/GJ. Majoring in financing, profit and uncertainties, we could expect a multiplying factor of 1.5, for a final cost estimate of 82 $/GJ for Martian solar power. In other units this is 0,08$/MJ, or $ per 0,29 $/kWh. This would be the minimum likely cost, with the lowest transportation cost.

So the total cost might be somewhere between 82 $/GJ to 238 $/GJ. Flexible solar film offers the bet value.

These is not necessarily the selling prices, as there might be taxes added or other costs, such as the distribution system costs. The price for energy might also be modulated; for example, the cost of night time energy, requiring the installation of energy storage systems, might be significantly higher. Or the cost of these storage systems could be factored into the base cost, if the settlement determined this was a useful policy.

Nuclear energy

Design

The MINERAL reactor is proposed for this cost estimate. Nuclear systems scale very well. As they follow a cube law, doubling any dimension creates an order of magnitude of increase in capabilities. The MINERAL reactor produces 2 MW of power for a total mass of 53 tonnes .

Characteristic	Value	References
Power	2 MW electric 5,8 MW thermal loss	Solid core, CO2 Brayton cycle power production. six 400m2 radiators.
Efficiency	25,5%
Mass of reactor	37 We/kg, 27 kg/kW

Cost of a nuclear reactor

This is the hardest metric to establish. The cost of new nuclear reactors is between 6-9 billion$ for 1100 MW on Earth. So from 6 to 9 million$ per MW. However, assigning this cost to smaller modular reactors may not be an adequate method. Using a build-up rather than top down approach yields a much lower cost, in the order of 3 million$ per MW. This puts the fabrication and development cost of a Mineral type reactor at about 6 million dollars per unit, in a scenario where these reactors are produced in many units for Earth service and lightly adapted for Mars service.

Process heat

Normally when discussing nuclear power we are interested in the amount of electricity it produces. So a plant might make 100 Megawatts (electrical) or 100 MW(e). However, a typical nuclear power plant is 40% efficient in turning heat into electricity, so that plant would produce 250 Megawatts (thermal) or 250 MW(t).

We might use some of the energy from solar cells to heat the martian base, melt ice, or heat chemicals for industrial reactions. But with a nuclear reactor, we will get heat from the reactor to warm the base, melt ice, etc. This is known as process heat. A reactor can provide process heat for industry and (if not 100% is used) use the remaining energy to produce electricity.

Nuclear power station cost on Mars

• Using 500$ per kg for transportation of 53 500 kg and six million$ for construction, the bare cost is about 32 000 000$.
• Using 140$ per kg for transportation of 53 500 kg and six million$ for construction, the bare cost is about 14 000 000$.

Nuclear energy production

The reactor, operating at 98% availability for 20 years will produce 2 000 000J x 20 x 365 x 24 x3 600 x0,98 = 1 250 000 GJ. When divided by the cost of 32 000 000$ the bare cost would be about 26 $/GJ, and 11$ per GJ for the lower transportation cost. If we have the same multiplication factor of 1,5 then the final cost would be 17 $/GJ to 39 $/GJ. This is significantly lower than the solar costs, at 82 to 238 $/GJ.

Alternative nuclear reactor designs

• Nuclear reactor designs for Mars based on the Kilopower 10 kW nuclear reactor are probably insufficient for any sizable settlement. Since their mass fraction is only 7 We/kg (143 kg/kW) rather than 37 We/kg (27 kg/kW), all other things being equal they would not be competitive with solar power.

• Future modular reactors (which are designed to be mass produced and can be shipped in a single shipping container) would be much cheaper. For example: The Chinese HTR-PM small modular reactor (a helium pebble bed reactor) started producing power in 2021, and as of 2023 is providing commercial power. It produces 211 MW(e) per reactor. (3 reactors will replace a typical Chinese coal plant.) the core diameter is 3m, its height is 11m, Helium gas output temperature is 750C, steam temperature is 567C, and steam pressure is 13.24 MaP. It is a 4th generation design, and the reactor can be refuelled while it remains online. (New pebbles are dropped in, and old pebbles are ejected one at a time.) The prototype (the HTR-10) cost $38.7M, but this included the one time costs for: building the nuclear island, R&D, and the creation of 34 unique subsystems needed for construction.. Professor Zhang Zuoyi, director of the Institute of Nuclear and New Energy Technology, has outlined the techniques to lower the costs when mass producing the reactor. This would lower the costs to $2,000 to $3,000 /kW capacity range. This means that the price of the 210 MW reactor would be from $420M to $600M, or (using the conservative figure) $2.85M / MW. (1/2 to 1/3 the estimate given above.) If paired with a Super Critical CO2 Gas Turbine (now being produced) the efficiency would increase by 10% and the mass of the turbines would be decreased ten fold.

• Molten salt reactors such as LFTR could be largely built with local materials. It is possible that the Li6 or the nickel alloys for the plumbing would be sent from Earth for early settlements. Note that several companies are developing these, and China is building a commercial reactor to be completed in 2029.

Geothermal energy

Mars has had volcanic eruptions in the last 10 million years (the present in geological terms), and there is evidence that there may be active vulcanism now. Hot rocks kilometers before the surface take hundreds of millions of years to lose their heat, so there is every reason to suspect that regions of Mars could have useful amounts of geothermal heat within drilling distance.

Geothermal energy is unsuitable for exploration bases, or early colonies, but once Mars has local industry sufficient to make pumps, drill bits, pipes, condensers, etc. Geothermal power becomes attractive. In addition to providing power, it can likely bring up hot, liquid water, a valuable commodity in its own right.

Hot water brought to the surface vacuum will flash to steam, making a very efficient turbine possible.

However, the temperature of the rocks, the possibility of liquid water, the depth to drill, the cost of local materials, the value of liquid water, the cost of electricity and heat, are all not known.

Therefore, for this study, the cost of geothermal is not calculated.

Proposed cost

Compared to a cost of 20 $/GJ (0,06$/kWh) on Earth, the cost of electrical energy on Mars might be in about the same range for nuclear power. Roughly rounded to a range 20$/GJ (0,06 $/kWh) to 40$/GJ (0,12 $/kWh). The cost of thermal energy would be about one tenth of that value, with a very high availability from nuclear power, and requiring some form of thermal energy storage for solar. Much of the range is a result of the large uncertainty on transportation costs. The cost of solar power would be significantly higher, by a factor of about three. So solar might only be used in small isolated locations, or early on in the development of the settlement, until nuclear power can be provided.

Discussion

Nuclear vs solar energy is an endless source of discussion and contention. The aim of this section should be to establish a reasonable cost of energy on Mars to be able to evaluate projects, and to offer a basis of comparison with Earth. As of 2024 we find Solar is about 3x as expensive as nuclear might be. Nuclear itself would have cost similar to the mid range of Earth utility rates.

• The actual cost of solar panels in large scale installations may be significantly lower than 800$/m2
• Lower efficiencies for solar cells have significant impact. Higher efficiencies would only be impactful for low mass flexible solar cells. The mass of auxiliary systems eventually limit the potential gains for solar
• If solar panel efficiencies are higher than 30% the impact is not sufficient to offset the advantages of nuclear power.
• This article assumes that dust is cleaned off solar cells regularly (never more than 10% loss of power). An automated cleaning system is required to maintain solar cell efficiencies.
• The higher cosmic ray flux will slightly lower the lifetime of solar cells on Mars.
• The very high thermal stress on Mars may increase maintenance costs for large fields of sun tracking solar panels with automated cleaning equipment. Doing repairs outside is difficult and always somewhat dangerous, but perhaps we can assume that these are rare enough not to matter.
• For solar, in the case of a bad dust storm, industry, fuel creation and agriculture are turned off, and people live on stored food. Obviously, this is not a problem for nuclear.
• Solar power using In Situ production of components could be competitive with nuclear in certain long term cases as the transportation costs would be reduced. In particular, cheap local batteries would be very advantageous to solar. See Flow battery.
• Transportation costs may be lower or higher and represent a large fraction of the costs of the power systems.
• Based solely on surface quantities of Thorium, radioactive elements may be rarer on Mars than on Earth. This is discussed in detail in Radioactive Rarity on Mars and could make early thorium mining more difficult. However, even low grade ore will provide plenty of thorium once wide spread mining is established. Also note that thorium does not require enrichment.
• If we use CANDU reactors, they can use natural uranium, so no enrichment is needed and fuel is cheaper.
• Deuterium is 5 times more common on Mars, so heavy water should be less expensive, favoring CANDU type designs.
• The new Supercritical CO2 turbines are less massive, and improve the efficiency of power extraction. These have been created. This makes nuclear more attractive on Mars since lowering mass reduces the cost of transportation.
• If reactors can be refueled with minimum refurbishment this reduces their cost further. Note that molten salt reactors, pebble bed reactors, and other modern types can be continuously refueled.
• The NASA horizon for nuclear is 10 years, but the calculation uses 20 years, a number often used for Earth based 'nuclear batteries'.
• 20 years of operation without a major overhaul may be optimistic for nuclear. At ten years, the nuclear advantage drops significantly.
• Mars is not a significant market so creating a reactor only for Mars is unlikely, but adaptation of existing small reactors would be very cost effective.
• The development cost of a 40 kW nuclear reactor for Artemis has been floated at 1 billion$. This would make any nuclear reactor uncompetitive for decades. A examples from China make this figure very doubtful.
• The study for the Prometheus reactor cost 400 m$ and never produced a prototype. Just attributing this cost to less than a dozen early nuclear reactors would make them uneconomical. However, these and NASA costs and not commercial costs, so likely not applicable.
• Solar cost for panels keep going down, but significant advances in power/mass would be required to make solar competitive with nuclear on Mars if a reactor such as the MINERAL is developed following commercial design methods.

References

• Nuclear reactor development cost. https://spacenews.com/nasa-plans-for-lunar-fission-power-systems-face-fiscal-challenges/