Water distiller cost per gallon calculator: kWh, electricity cost and hours per gallon or litre
kWh per gallon = watts x hours per batch / gallons. An 800 W distiller at 4 hours a gallon uses 3.2 kWh, about 59 cents at EIA's July 2026 18.31 cents per kWh.
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Short answer
A countertop water distiller’s electricity per gallon is its wattage times the hours one batch takes, divided by the batch size: kWh per gallon = watts x hours / 1,000 / gallons. Worked example: the Waterwise 4000 is rated 800 W and makes 1 gallon in 4 to 4.5 hours, and Waterwise itself puts it at about 3.2 kWh per gallon, which is 800 W x 4 h. At the EIA Electric Power Monthly US residential average of 18.31 cents per kWh for July 2026, that is about 58.6 cents of electricity per gallon, or 15.5 cents per litre, plus 4 hours of waiting. Megahome’s 580 W MH943SBS at 5.5 hours per gallon computes to 3.19 kWh, almost the same energy over a longer cycle. The distillers in the table below land between roughly 0.6 and 0.95 kWh per litre, so the price per kWh you type in below matters more than the model you pick.
If the only thing you want is a low TDS reading, this is the wrong page: a meter reads near zero on reverse osmosis water too, and because neither RO maker on this site prints a wattage, nobody can honestly tell you which process uses less electricity, only what the distiller costs.
Electricity cost and time per gallon and per litre of distilled water
Formula: kWh per batch = watts x hours / 1,000; divide by the batch size in gallons and in litres (1 US gallon = 3.785 L); multiply by the price per kWh. The 0.1831 default is the EIA July 2026 US residential average, 18.31 cents per kWh. For the EU, Eurostat's H2 2025 household average is EUR 0.2896 per kWh; for Japan, the appliance labelling reference unit is 31 yen per kWh (eftc.or.jp), not a survey of what households pay. Type your own bill's rate for a real answer.
What is the formula?
- kWh per batch = watts x hours per batch / 1,000.
- kWh per gallon = kWh per batch / gallons per batch; kWh per litre = kWh per batch / litres per batch.
- Cost per gallon or litre = kWh per gallon or litre x price per kWh.
- Hours per gallon = hours per batch / gallons per batch.
A batch is one fill of the boiling chamber run to automatic shut-off.
| Variable | What it is | Where the figure comes from |
|---|---|---|
| Watts | the rated draw of heater plus fan, printed by the maker | Waterwise, Megahome, H2O Labs, Pure & Secure, VEVOR pages |
| Hours per batch | the maker’s cycle time for one full chamber | the same pages; H2O Labs UK prints both 5 and 5.5 h |
| Batch size | the boiling chamber’s rated fill, 1 gallon or 4 L on most units | the same pages |
| Price per kWh | your bill, or a published average | EIA (US), Eurostat (EU), eftc.or.jp (Japan reference unit) |
The formula assumes the heater draws its rated wattage all cycle. Waterwise’s “about 3.2 kilowatts per gallon” and H2O Labs’ “about 810 watts per litre” both match it within a few percent.
What does a worked example look like?
The quick answer’s unit: 800 W, 4 hours, 1 gallon, 18.31 cents per kWh.
- kWh per batch: 800 x 4 / 1,000 = 3.2 kWh.
- Per gallon: 3.2 kWh; per litre: 3.2 / 3.785 = 0.85 kWh.
- Cost: 3.2 x 18.31 cents = 58.6 cents per gallon, 15.5 cents per litre.
- Time: 4 hours per gallon, so about 6 gallons in 24 hours if you refill it every cycle, which is the daily output Waterwise prints.
The same 3.2 kWh at Eurostat’s EU household average of EUR 0.2896 per kWh (second half of 2025, all taxes included, 2,500 to 5,000 kWh a year band) is about EUR 0.93 per gallon, or EUR 0.24 per litre. At Japan’s 31 yen per kWh labelling reference unit, Megahome’s Japanese 580 W, 6 hour, 4 litre cycle (3.48 kWh) is about 108 yen per batch, 27 yen per litre; the importer’s own page says about 70 yen per batch, which implies a lower rate of about 20 yen per kWh, so type your own tariff.
Which distillers print the numbers?
Every row is the maker’s printed wattage, batch and cycle time; the two kWh columns are computed from them by this page, not printed by the maker unless the notes say so.
| Model | Mains as printed | Watts | Batch | Hours per batch | kWh per batch (computed) | kWh per litre (computed) | Notes |
|---|---|---|---|---|---|---|---|
| Waterwise 4000 | 120 V 60 Hz, or 230 V 50 Hz export | 800 | 1 gal | 4 to 4.5 | 3.2 to 3.6 | 0.85 to 0.95 | maker says about 3.2 kWh per gallon |
| Waterwise 3200 | 120 V 60 Hz | 800 | 1 gal | 4 | 3.2 | 0.85 | maker says about 3.2 kWh per gallon; shuts off after each gallon |
| Pure Water Mini-Classic CT | 120 V (6.9 A) or 240 V (3.5 A), brochure | 800 | approx 3 L | 3.5 | 2.8 | 0.93 | no kWh figure in the brochure |
| Megahome MH943SBS (US) | 120 V (220 to 240 V available) | 580 | 1 gal | 5.5 | 3.19 | 0.84 | UL listed per the distributor page |
| Megahome MH943SBS (Japan) | 100 V 50/60 Hz | 580 | 4 L | about 6 (implied: 70 yen per batch at 11.6 yen per hour) | 3.48 | 0.87 | importer prints 11.6 yen per hour and about 70 yen per 4 L batch |
| H2O Labs Model 100E (UK) | 240 V 50/60 Hz | 580 | 4 L | 5 to 5.5 | 2.9 to 3.19 | 0.73 to 0.80 | FAQ prints 580 W x 5.5 h and “less than 20 pence per litre” |
| H2O Labs H2OMATIC 500E (UK) | 240 V 50 Hz | 675 | auto-fill, up to 20 L a day | continuous | not applicable | 0.81 | maker prints about 810 watts per litre |
| H2O Labs Model 300SS (US) | 120 V 60 Hz | 580 | 1 gal | not printed | not computed | not computed | page gives 4 gal (16 L) a day only |
| VEVOR YMK40101 (EU) | 220 V, frequency not printed | 750 | 4 L | about 3.1 (from 1.3 L/h) | 2.3 | 0.58 | maker prints 0.34 gal/h (1.3 L/h); no kWh figure |
VEVOR’s US pages would not load this session, so the 120 V VEVOR is not in the table; the EU page is the only VEVOR spec this page can cite.
What stays behind in the chamber?
Everything the water carried that does not boil: the calcium and magnesium that make white scale on your taps crust the boiling chamber instead. Megahome sells a residue cleaner that “removes scale build up, hardness, minerals and other build-up in the boil chamber”, and Waterwise’s 3200 page puts boiler cleaning at about monthly depending on water hardness.
Waterwise also specifies a carbon post-filter change every two months or after 60 to 80 gallons; that is a running cost the calculator does not include.
The same removal is why a TDS meter reads near zero on the output. Dissolved minerals conduct, and they are in the chamber, not the carafe. Reverse osmosis water reads in the same 0 to 50 mg/L band, so the meter cannot tell you which machine made the water.
Where does distilled water actually belong?
Only where a manual asks for it, and the manuals disagree:
| Use | What the maker or regulator says |
|---|---|
| CPAP humidifier | ResMed AirSense 10 user guide: fill the water tub with distilled water up to the maximum level mark, and its symbol legend reads “Use distilled water only” |
| Room humidifier | EPA’s Use and Care of Home Humidifiers: use bottled water labelled distilled, which likely contains lower mineral content than most tap water; keep indoor relative humidity under 50 percent |
| Flooded lead-acid battery | Trojan Battery: “ADD WATER, NEVER ACID, TO CELLS (distilled water recommended)”, only if the plates are exposed before charging, and never overwater |
| Steam iron | Rowenta: always use untreated water, and if the water is very hard, a 50/50 mix of tap and distilled; Rowenta USA says pure distilled water can affect steam and produce steam-chamber sediment |
The humidifier white dust guide covers why ultrasonic units throw tap-water minerals into the room.
Before you buy a distiller
Decide what the water is for. If a manual asked for distilled (CPAP, battery, humidifier), the 580 W Megahome MH943SBS makes a gallon in 5.5 hours for about 3.2 kWh; the 750 W VEVOR 4 L unit is the budget version, but this page could only verify VEVOR’s 220 V spec sheet, not the 120 V one. If the goal is drinking water with a low TDS reading, read the countertop reverse osmosis review first: neither the Waterdrop M6SL nor the AquaTru Classic page prints a wattage, so the energy comparison cannot be made here, and a distiller’s 4 to 6 hours per gallon is certain either way.
Frequently asked questions
How much electricity does a water distiller use per gallon?
About 3.2 kWh per gallon for the 800 W Waterwise 4000 and 3200, which is the maker's own figure and matches 800 W times 4 hours. Megahome's MH943SBS prints 580 W and 5.5 hours per gallon, which computes to 3.19 kWh. The distillers in this page's table land between roughly 0.6 and 0.95 kWh per litre.
How much does a gallon of distilled water cost to make at home?
At 3.2 kWh per gallon and the EIA July 2026 US residential average of 18.31 cents per kWh, about 58.6 cents of electricity per gallon, before the carbon post-filter Waterwise says to change every two months or 60 to 80 gallons. In the EU, at Eurostat's H2 2025 household average of EUR 0.2896 per kWh, the same 0.84 kWh per litre costs about EUR 0.24 per litre.
How long does a countertop water distiller take to make a gallon?
Four to six hours per gallon, from the makers' own pages: Waterwise 3200 4 hours, Waterwise 4000 4 to 4.5 hours, Megahome MH943SBS 5.5 hours per gallon in the US and about 6 hours per 4 litre batch in Japan (implied). Pure Water's Mini-Classic CT brochure gives about 3 litres in 3.5 hours. Daily output is therefore 4 to 6 gallons if you keep refilling it.
Why does a TDS meter read almost zero on distilled water?
Because distillation boils the water off and leaves the dissolved minerals behind in the chamber, and a TDS meter only measures conductivity from those dissolved ions. Reverse osmosis product water reads in the same 0 to 50 mg/L band, so a near-zero reading does not tell you which process made the water, and a low reading is not by itself a reason to buy a distiller.
Is distilled water the right water for a CPAP, a humidifier, a battery or an iron?
Check the manual, because the answers differ. ResMed's AirSense 10 guide says to fill the tub with distilled water only. EPA's humidifier care page says to use bottled water labelled distilled. Trojan Battery says add water, never acid, distilled water recommended. Rowenta says not to use pure distilled water in its irons: untreated tap water, or a 50/50 mix if the water is very hard.
Fact sheet and how to cite this page
- Answer
- A countertop distiller’s electricity per gallon is watts times hours per batch divided by gallons per batch. Waterwise rates its 800 W 4000 and 3200 at about 3.2 kWh per gallon; at the EIA July 2026 US residential average of 18.31 cents per kWh that is about 58.6 cents of electricity per gallon, or about 15.5 cents per litre.
- Formula
kWh per batch = watts x hours / 1,000; kWh per gallon = kWh per batch / gallons per batch; cost per gallon = kWh per gallon x price per kWh; hours per gallon = hours per batch / gallons per batch- Inputs
- Distiller wattage: 800 W
- Hours per batch: 4
- Batch size: 1 gallon (3.785 L)
- Electricity price: 18.31 cents per kWh
- Output
- 3.2 kWh per gallon (0.85 kWh per litre); 58.6 cents per gallon (15.5 cents per litre); 4 hours per gallon
- Assumptions
- The heater draws its rated wattage for the whole batch; makers that print a kWh figure (Waterwise, H2O Labs) get within a few percent of this, and the calculator uses the maker’s watts and hours as printed
- 18.31 cents per kWh is the EIA Electric Power Monthly Table 5.6.A US total residential average for July 2026, the latest month shown on 30 September 2026
- 1 US gallon = 3.785 litres
- Method
- The calculator multiplies the distiller’s rated wattage by the hours one batch takes, divides by the batch volume in gallons and in litres, and multiplies by the electricity price the reader enters. Maker rows in the table are the maker’s printed watts, batch size and cycle time; the kWh columns are computed from them and labelled so.
- Primary source
- Waterwise 4000 Countertop Distiller (maker page) (manufacturer or vendor document)
- Facts verified
- Last updated
- Cite as
- OwnerSpec, "Water distiller cost per gallon calculator: kWh, electricity cost and hours per gallon or litre", https://ownerspec.com/water/calculators/water-distiller-cost-per-gallon-calculator/, facts verified 30 September 2026.
Every figure above also appears, with its source, in the article. All sources ยท How OwnerSpec verifies numbers
Sources
- Waterwise 4000 Countertop Distiller (maker page) (manufacturer or vendor document)
- Waterwise 3200 Countertop Distiller (maker page) (manufacturer or vendor document)
- EIA, Electric Power Monthly Table 5.6.A, average price of electricity to ultimate customers by end-use sector (government or regulatory source)
- Eurostat, Electricity price statistics (manufacturer or vendor document)
- Home Electric Appliances Fair Trade Conference (eftc.or.jp), Q&A on the electricity reference unit price (manufacturer or vendor document)
- Pure & Secure, Mini-Classic CT brochure (PDF) (manufacturer or vendor document)
- Megahome MH943SBS water distiller (megahomedistiller.com) (manufacturer or vendor document)
- Megacat Japan, Megahome MH943SBS importer page (manufacturer or vendor document)
- Megahome Distiller Residue Cleaner (manufacturer or vendor document)
- H2O Labs UK, Classic White Model 100E (manufacturer or vendor document)
- H2O Labs UK, H2OMATIC Model 500E (manufacturer or vendor document)
- H2O Labs UK, FAQ (manufacturer or vendor document)
- H2O Labs US, Model 300SS (manufacturer or vendor document)
- VEVOR EU, 4L Water Distiller 220V (model YMK40101) (manufacturer or vendor document)
- ResMed AirSense 10 user guide (PDF) (manufacturer or vendor document)
- EPA, Use and Care of Home Humidifiers (government or regulatory source)
- Trojan Battery, How to maintain your flooded lead acid battery (manufacturer or vendor document)
- Rowenta, Access Steam DW2459 instructions and FAQ (manufacturer or vendor document)
- Rowenta USA, Care and Use (manufacturer or vendor document)
- Waterdrop M6SL product page (manufacturer or vendor document)
- AquaTru Classic product page (manufacturer or vendor document)