A gas-fired thermoelectric generator makes steady power with no moving parts, but it does so by burning fuel gas every hour of every day, and its low conversion efficiency means it burns a lot of gas for the watts it delivers. Deciding whether a TEG or a solar-plus-battery system is the right remote-power source comes down to estimating that continuous fuel burn and weighing its lifetime cost against solar's higher upfront hardware and zero fuel. This guide walks through why a TEG's efficiency is only a few percent, how to estimate its fuel-gas consumption per watt, how to turn that into a daily gas rate, and how to compare its lifetime fuel cost against solar so a designer can pick the right source for a given load.
TEG Fuel Consumption in one line: A thermoelectric generator burns fuel gas continuously because it converts heat to electricity at a low single-digit efficiency, so most of the heat its burner releases is wasted and only a small fraction becomes usable watts. To estimate its consumption you start from the load in watts, account for that low conversion efficiency to find the heat the burner must supply, and convert that heat into a fuel-gas rate using the gas heating value, giving a figure in standard cubic feet per day. Comparing that continuous fuel burn over the equipment's life against a solar-plus-battery system's higher upfront cost and zero fuel is how a designer decides which remote-power source is cheaper for a given load and site.
The single fact that governs a TEG's fuel use is its efficiency. Thermoelectric conversion turns only a small fraction of the heat passing through its modules into electricity, on the order of a few percent, with the rest rejected as waste heat. That is far lower than a mechanical engine-generator, and it is inherent to the solid-state conversion, not a defect to be tuned out. The upside the low efficiency buys is the reliability and no-moving-parts simplicity that make a TEG attractive for remote duty; the downside is that a great deal of fuel-gas energy has to go in to get a modest electrical output out.
Because the conversion is so lossy, the burner must run whenever the generator produces power, and it must supply many times more heat energy than the electrical energy it yields. If only a few percent of the heat becomes electricity, then producing a given number of watts requires burning gas worth many times that in heat, continuously, day and night, because the RTU or cathodic-protection load the TEG feeds is itself continuous. There is no idling down: the generator is either running and burning gas or off and producing nothing.
This is why fuel consumption, not capital cost, is often the dominant consideration for a TEG. The machine itself is simple and long-lived, but it eats fuel gas every hour for years, and that steady draw is the real recurring cost of owning one. Where the fuel is the operator's own low-value produced gas, the burn may be an acceptable trade for the reliability; where the gas has real value or the burn must be minimised for emissions reasons, the continuous consumption is exactly the number that pushes a designer to look hard at alternatives.
Estimating a TEG's fuel use starts from the electrical load it must carry, in watts, and works backward through the efficiency to the heat the burner must produce. Because only a small fraction of the burner's heat becomes electricity, the heat input needed is the electrical output divided by that fractional efficiency, which inflates the required heat by a large factor. A load that seems small in watts therefore corresponds to a much larger continuous heat demand at the burner, and that heat demand is what actually consumes gas. Sizing to the true continuous load, plus the battery-buffered peaks the site draws, keeps the estimate honest.
Turning the required heat into a gas rate uses the heating value of the fuel gas, the energy it releases per standard cubic foot when burned. Dividing the burner's heat demand by the gas heating value gives the gas consumed per unit time, which is then expressed per day as standard cubic feet per day for a fuel budget. A convenient way to think about it is fuel gas per watt: because the efficiency is fixed, each watt of continuous load carries a fairly predictable continuous gas draw, so multiplying the watt-load by that gas-per-watt figure gives the daily consumption directly. Manufacturers publish fuel-consumption figures for their models, and these already embed the efficiency and can be used to cross-check a hand estimate.
The reason to do this estimate carefully is that the daily gas figure is what feeds both the fuel-supply design and the cost comparison. It tells you how much gas the site must reliably deliver to the burner, which matters if the supply is limited or metered, and it is the input to the lifetime fuel cost that decides TEG-versus-solar economics. An estimate that is too optimistic about efficiency understates the gas burn and can make a TEG look cheaper than it really is, so grounding the number in the manufacturer's rated consumption for the chosen load is worth the effort.
The decision between a TEG and solar-plus-battery is a trade between ongoing fuel cost and upfront hardware cost, played out over the equipment's life. A TEG has a relatively modest capital cost and then burns fuel gas continuously for years, so its lifetime cost is dominated by that fuel. A solar-plus-battery system has a higher upfront cost - panels sized for the worst month, a battery bank with days of autonomy, and a charge controller - but essentially zero fuel cost thereafter, with battery replacement being its main recurring expense. Laying the continuous fuel burn of the TEG against the higher initial outlay of solar over the same period is the core of the comparison.
Which wins depends heavily on the site, and that is the point of doing the estimate rather than assuming. In a sunny latitude with a modest load, solar's zero fuel cost usually makes it cheaper over the life, and the array and battery need not be enormous. In a low-sun latitude, or for a load that cannot tolerate the dark, snowy stretches that force solar to be heavily oversized, the solar system's upfront cost balloons while the TEG's steady output stays the same, and the TEG's fuel burn can look like the better deal despite being continuous. The value of the fuel itself tips the balance too: cheap produced gas favours the TEG, valuable gas favours solar.
A cloud SCADA platform such as Merobix supports both the decision and the ongoing operation. Before choosing, trended data from comparable sites - solar array output through the seasons, battery state of charge across bad-weather stretches, and actual loads - grounds the sizing assumptions that the TEG-versus-solar estimate depends on, so the comparison rests on real site behaviour rather than nameplate optimism. After a source is chosen and installed, the platform verifies the estimate held: for a TEG, trending the DC bus voltage and, where instrumented, the fuel-gas supply confirms it is delivering the expected power for its expected burn, and for solar it confirms the array and battery are meeting the load through the worst month. Either way, the monitoring closes the loop between the fuel and cost estimate made on paper and how the remote-power source actually performs in the field.
Because thermoelectric conversion is inefficient, turning only a few percent of the heat passing through its modules into electricity and rejecting the rest as waste heat. To produce a given number of watts the burner must supply many times that in heat, and it must do so continuously because the load it feeds is continuous. That low efficiency, combined with round-the-clock running, is why a TEG's fuel gas consumption is its dominant operating cost rather than its capital cost.
Start from the continuous electrical load in watts, divide by the TEG's fractional conversion efficiency to find the much larger heat the burner must supply, then divide that heat by the fuel gas heating value to get a gas rate, expressed as standard cubic feet per day. Because the efficiency is fixed, each watt of load carries a fairly predictable continuous gas draw, so a gas-per-watt figure multiplied by the load gives the daily consumption directly. Manufacturers publish fuel-consumption figures for their models that embed the efficiency and can be used to check the estimate.
A TEG tends to be cheaper where solar would have to be heavily oversized, such as low-sun latitudes or loads that cannot tolerate dark, snowy stretches, because there the solar array and battery costs balloon while the TEG's steady output and fuel burn stay the same. Cheap produced gas also favours the TEG, since fuel is its main lifetime cost. In sunny latitudes with modest loads and valuable gas, solar's zero fuel cost usually wins, so the answer depends on the site's insolation, load criticality, and the value of the fuel gas.
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