Hot Water and Power at a Market With No Outlet

Brewing coffee is mostly heating water, and many farmers markets have no electricity. I like my electric temperature-controlled kettle, and I already have a power station and a solar panel from my overlanding build. This page works out, with the arithmetic shown, whether that is enough, and what the alternatives cost.

The answer the numbers give: the battery cannot heat a market day’s water from cold, but it can easily keep already-hot water at brewing temperature. The plan that needs nobody’s permission is to carry boiling water from home in vacuum airpots and use the battery only to finish it. For the question of which kettles to buy, the answer further down is a water boiler to hold the hot water and two gooseneck kettles to pour it.

How much energy a cup takes

Heating one litre of water from 60 °F to 205 °F takes 93.7 watt-hours. (The rise is 80.6 kelvin; 4.186 kJ per kilogram per kelvin times 80.6 is 337 kJ, which is 93.7 Wh.)

A 12 oz pour-over uses about 360 g of brewing water, plus roughly 100 g to rinse the filter and warm the cup. That is 0.46 litre, or 43 Wh in the water for each cup.

What the power station can do

The power station is an EcoFlow River 3 Max Plus: 858 Wh of battery behind a 600-watt inverter. EcoFlow’s own page gives the output as “600W total (Surge 1200W, X-Boost 1200W).”

	Litres from cold	12 oz pour-overs
In theory, no losses	9.2	20
Allowing 15% loss in the inverter	7.8	17
Allowing 15% in the inverter and 15% in the kettle	6.6	14 (18 if the filter is not rinsed)

The two loss figures are assumptions; EcoFlow does not publish its inverter efficiency. On any of them, a full battery makes about fourteen to eighteen cups from cold water. That is an hour of a good market.

The kettle may not run at full speed, or at all. X-Boost lets the station drive a heating appliance rated up to 1,200 W by lowering the voltage, so the element draws about 600 W. A kettle that boils 0.9 litre in five minutes on the wall takes about ten on the station. EcoFlow’s cautions, in its own words: “X-Boost is not available to use when your EcoFlow portable power station is charging,” and “Please conduct a full test with your devices before usage.” A temperature-controlled kettle has electronics in its base, which is the case that needs testing.

What decides it is the wattage on the plate under the kettle:

Kettle rating	On this power station
600 W or less	Runs at full speed
601 to 1,200 W	Runs at about half speed under X-Boost, if its controller tolerates the lower voltage
Over 1,200 W	Will not run

For reference, a Fellow Stagg EKG is rated 1,000 to 1,200 W, the Bonavita, Brewista and Hario gooseneck kettles about 1,000 W, and the OXO adjustable kettle 1,500 W. No 600-watt temperature-controlled gooseneck kettle was found.

The test to run at home: fill the kettle with cold water, plug it into the fully charged station with nothing else connected and the solar panel unplugged, and time it to 205 °F. Note the percentage of battery used. That one test answers whether the kettle I already own will work.

Solar. The 200 W panel feeds a 220 W input. At an assumed 65% of its rating for five hours it gives about 650 Wh, which is three-quarters of a battery. Whether X-Boost works while the panel is charging the station is not stated; EcoFlow’s sentence about charging may rule it out.

The plan that works: hot water from home, topped up on the battery

A good vacuum airpot holds heat for hours. Zojirushi publishes figures for its 3.8-litre airpot: water put in at 203 °F is 174 °F after ten hours at room temperature. Fitting a cooling curve to those figures gives an estimate, not a specification:

Hours after filling at a boil	Estimated temperature
2	about 197 °F
4	about 191 °F
6	about 185 °F
8	about 179 °F

Every pump of the lever and every degree of cold morning air makes it worse, and no maker states how long its pot stays above 195 °F.

The saving is in the top-up. Raising a litre from 185 °F back to 205 °F takes 12.9 Wh, not 93.7. On the same battery and the same assumed losses, that is enough to finish about 48 litres. From 175 °F it is 32 litres.

So:

1. Fill three or four vacuum airpots at a rolling boil just before leaving.
2. At the stall, pour from an airpot into the kettle and let the kettle bring it the last ten or twenty degrees.
3. Use the first two hours’ water straight from the pot for methods that want cooler water anyway (below).

A 3.8-litre Zojirushi airpot is about $100; plain stainless-lined airpots run $28 to $80 and publish no heat figures. Four pots is 15 litres, about thirty-three cups’ worth of brewing water.

Methods that want cooler water. AeroPress’s own instructions call for 185 °F water. That is the one brewer that works straight out of a four-hour-old airpot with no top-up. Immersion and slow-drip methods, such as a French press, a Clever dripper or a phin, are generally more forgiving of water a little under 200 °F than a fast pour-over is, though that is experience and not a sourced figure.

Which kettles for the booth

I have one temperature-controlled kettle and I like it. One is not enough for a booth: a 0.9-litre kettle holds water for two 12 oz pour-overs, and while it is being refilled and reheated nothing can be brewed. The usual answer is to buy a second kettle like the first. The specifications point to a different one: a water boiler as the reservoir, and the kettles as pouring tools.

The reservoir: a water boiler and warmer

A water boiler is an insulated electric pot of four or five litres that boils water and then holds it at a set temperature, with a dispensing spout on the front. It needs no plumbing. What makes it the right tool for a market is how little power it takes to hold water that is already hot. From Zojirushi’s own manuals and product pages:

Model	Size	Heater	Average power holding 208 °F	Holds at	Price	Listed for
Zojirushi CV-JAC40 / CV-JAC50 (vacuum-insulated)	4.0 / 5.0 L	930 W	28 W / 29 W	160, 175, 195, 208 °F, or unpowered	$304.99 on Zojirushi’s shop	Household
Zojirushi CD-WHC40	4.0 L	700 W	48 W	160, 175, 195, 208 °F	$219.99 on Zojirushi’s shop	Household
Zojirushi CD-LTC50 “Commercial”	5.0 L	800 W	not listed here	175, 195, 208 °F	$192.49 at a restaurant supplier	Commercial (UL 197)

The holding figures are Zojirushi’s, for a full pot in a 73 °F room. A cool morning outdoors will take more.

What those numbers mean at a stall:

• Five hours at 208 °F costs about 140 Wh on the vacuum-insulated model and 240 Wh on the plain one. Allowing the same 15% inverter loss as above, that is roughly a fifth, or a third, of the 858 Wh battery. Heating the same four litres from cold would cost about 380 Wh once, and take half an hour on a wall socket.
• So it should arrive full of boiling water, not cold. It is then refilled through the morning from the airpots. Bringing four litres of 190 °F airpot water back up to 208 °F takes about 47 Wh.
• The heater is over the power station’s 600 W. At 700 to 930 W it falls in the X-Boost band, like the kettle, and needs the same test at home. The 700 W model is the closest to the inverter’s rating.
• The vacuum model’s unpowered mode is not a substitute for power. Zojirushi gives about 2 hours 50 minutes for a full pot to fall from boiling to 175 °F with the heater off. An airpot does much better than that. The vacuum insulation earns its price by halving the holding power, not by replacing it.
• Two of the three are household appliances. Their manuals say so in as many words. The CD-LTC50 is the one Zojirushi sells as commercial, listed to UL 197. If a licence is needed to brew at the market (the rules page), ask the health department whether it wants commercial-listed equipment before buying.

With a boiler on the table, the French press, the phin, the AeroPress and the egg coffee can be filled straight from its spout, at 208 °F or 195 °F. Only pour-over needs a kettle.

The pouring kettles

A pour-over kettle at a stall does not have to heat water. It has to hold a litre at temperature and pour it slowly. Filled from the boiler at 208 °F and set to hold 205 °F, its element hardly runs.

Kettle	Size	Power	Temperature control	Price
Fellow Stagg EKG (gooseneck)	0.9 L	1,000–1,200 W	To the degree; holds for up to 60 minutes	$165
Fellow Stagg EKG Pro (gooseneck)	0.9 L	1,000–1,200 W	To half a degree; hold, schedule, altitude setting	$199.95
Fellow Corvo EKG (plain spout)	0.9 L	not listed here	Temperature control; an all-purpose spout for filling a press or an AeroPress	$179.95
Bonavita 1.0 L variable-temperature gooseneck	1.0 L	1,000 W	To the degree, 140–212 °F; holds for up to 60 minutes; six presets	$89.99 (on backorder)
OXO adjustable-temperature pour-over kettle (gooseneck)	1.0 L	not listed here	104–212 °F; holds for 30 minutes	not listed here
Fellow Clyde	1.5 L	1,500 W	None: boil only	$99.95
Stovetop gooseneck, stainless	about 1 L	none	A thermometer in the lid	$22

Prices are the makers’ own and a restaurant supplier’s, read 2 October 2026. The Bonavita line is from Bonavita’s product page, which lists a “Commercial and Household UL Rating”; it is the only kettle here whose maker claims a commercial listing, and at 1,000 W it is also the lowest-powered. The OXO line is from OXO’s instruction booklet; its product page, with the wattage and price, was not loading on that date. The makers’ pages for the Brewista, Hario and Cosori kettles were not loading either, so they are not in the table; the wattages given for them earlier on this page came from retailers.

How many. Two gooseneck kettles with a hold setting: the one I own and one more. One is always full and at temperature while the other is being refilled, and two people can pour at once. A 1.5-litre boil-only kettle is the wrong second kettle. It draws 1,500 W, it has no temperature setting, and the boiler already does its job.

One more, for the days with a burner. A $22 stovetop gooseneck works on propane where a market allows it, and costs nothing to keep in the box.

What can be plugged in together

Supply	Limit	What it will run
The power station I own	600 W (X-Boost for heaters up to 1,200 W)	One heating appliance at a time, at about half speed. The boiler holding temperature, or a kettle topping up, but the two will sometimes ask for power together. This needs the home test before it is relied on.
A 1,500–1,800 W power station	1,500–1,800 W	The boiler and one kettle together, with room for a grinder.
A market outlet	1,800 W on a 15-amp circuit, and usually shared	The boiler (930 W) and one kettle (1,200 W) add up to 2,130 W if both heat at once, and two kettles to 2,400 W. Either can trip a breaker that other vendors are also using.

The way round all three is the same: nothing at the stall heats water from cold. The boiler arrives hot, the kettles are filled from it, and each element only tops up.

The order to buy in

1. Run the home test on the kettle I have and the power station, as described above. It costs nothing.
2. A water boiler. The CD-WHC40 if the 600 W power station is all there is, because its heater is the smallest. The vacuum-insulated CV-JAC if a bigger power station or an outlet is certain, because it holds temperature on half the power. The CD-LTC50 if the health department asks for commercial equipment.
3. A second gooseneck kettle with a hold setting.
4. A stovetop gooseneck, for propane days.
5. Then the second power station in the table below, which lets the boiler and a kettle run together.

A hot-water tower of the kind a café has (two to five gallons, $700 to $1,300, 1,440 to 1,850 W) is a purchase for the shop. So is a large urn-style boiler: an 8-litre one is $68 and a 19-litre one $89, but at 1,300 to 1,500 W they are for a wall socket.

Propane

A one-pound propane cylinder holds about 6,300 Wh of heat, 7.4 times the battery. On a 10,000 BTU single burner at an assumed 45% efficiency outdoors, it heats a litre in a little over four minutes and something like 27 to 34 litres per cylinder. A tank-top burner is about $60. On energy alone, propane wins easily.

The obstacle is permission. The International Fire Code’s tent chapter, as reproduced by a Michigan township fire department, says open flame is not permitted inside or within 20 feet of a tent open to the public “unless approved by the fire code official,” and that LP-gas containers “shall be located outside,” with at least 10 feet between a portable cylinder and the structure. MDARD’s temporary-food guidance says propane stoves “may require approval from the local Fire Marshall.” A single 10-by-10 canopy may fall below the size that needs a tent permit, so how much of that applies is a local question.

Propane is worth asking about at each market, and worth having for the ones that say yes. It cannot be the plan for every market.

A propane tankless “camp shower” heater is not a brewing heater: the ones checked cut out at 176 °F. Its honest use at a stall is warm handwashing water.

A generator

	Output	Noise	Price
Honda EU2200i	1,800 W running	48–57 dB(A)	about $1,100–$1,200
Champion 2,500 W dual fuel	1,850 W on gasoline, 1,665 W on propane	53 dBA at 23 feet	about $400–$600

Either runs a full-power kettle. The costs are noise, exhaust, fuel and the market’s rules. East Lansing’s market bans combustion generators. Midland, which has no power at all, requires a “silent” inverter generator of 70 dB or less. Mount Pleasant decides case by case.

A bigger battery

Power station	Battery	Inverter	Weight	Price
EcoFlow River 3 Max Plus (owned)	858 Wh	600 W	about 24 lb	owned
EcoFlow Delta 3 Plus	1,024 Wh	1,800 W		$669
Jackery Explorer 1000 v2	1,070 Wh	1,500 W	24 lb	$559
Jackery Explorer 2000 Plus	2,042 Wh	3,000 W	62 lb	about $2,500

A 1,500 W inverter runs any of the kettles at full speed, and a shop grinder too. The battery is still only about a kilowatt-hour, so it does not change the arithmetic on heating from cold: about nine litres. A second station in the $560 to $670 class buys full-speed heating and a spare, and is a better first purchase than a generator.

The four options side by side

Option	Water it can heat	What it needs
Battery kettle, water from cold	6.6–7.8 litres a charge (14–18 cups)	Nothing, but it is not enough
Boiling water from home in airpots, battery top-up	15 litres carried; top-up for 32–48 litres	Three or four airpots; the kettle test passed
Propane burner and stovetop kettle	27–34 litres per 1 lb cylinder	Approval from the market and the fire official
Inverter generator and electric kettle	No practical limit	$400–$1,200, and a market that allows it

Where a market does have outlets, they cost $1 to $10 a day (Prices and Customers), and the question disappears.

How much water to bring

An estimate for a day of 60 hot cups, 40 iced drinks and 200 samples:

Use	Litres
Hot cups, with rinse water	27.6
Iced drinks (the hot half of a flash brew)	8.8
Samples at 2 oz each	12
Handwashing, 5 gallons	18.9
Wiping and utility, 2 gallons	7.6
Total	about 75 litres, or 20 gallons

That is 165 lb of water before the ice. The water has to come from an approved supply, and wastewater has to be carried away in a sealed container (the rules page).

Grinding takes almost no power

Grinding a 12 oz bag takes 6 to 8 Wh, less than a tenth of what one litre of hot water costs. The limit for a grinder is the inverter’s wattage, not the battery. That is covered on Grinders.

Sources

• EcoFlow: River 3 product page and X-Boost page; Delta 3 Plus page. Jackery product pages.
• Zojirushi SR-AG38 airpot specifications. The cooling curve is fitted to its two published points.
• Kettle wattages: Fellow’s product page; retailer listings for the others.
• Water boilers: Zojirushi product pages and instruction manuals for the CV-JAC40/50 and CD-WHC40 (heater rating, average keep-warm power, boiling and cooling times, “household” use), Zojirushi’s page for the CD-LTC50, Zojirushi’s online shop and WebstaurantStore for prices; read 2 October 2026.
• Fellow’s pages for the Stagg EKG, Corvo EKG and Clyde; WebstaurantStore for stovetop kettles, urn boilers and plumbed dispensers.
• The 15-amp circuit figure is 15 A at 120 V.
• AeroPress, “How to use.”
• Propane: trade figure of 21,548 BTU per pound; Stansport burner page.
• Fire-code text: International Fire Code chapter 31 as reproduced in a Saginaw Township Fire Department handout; MDARD temporary food establishment guidance.
• Generators: Champion’s product page; Honda figures as reported by retailers.
• Market rules: East Lansing, Midland and Mount Pleasant vendor rules.
• The 15% loss figures, the 45% burner efficiency and the 65% solar output are assumptions, stated where used.