5th tank of gas @ 7,626 km

We filled up the Prius PHEV again on May 30, 2026, with the odometer at 7,626 km.

This is the fifth gas fill-up since we bought the car on August 9, 2025, so there’s now enough data to see a real seasonal pattern: excellent gas use in mild weather, a noticeable winter hit, and improvement again as spring arrives.

This post is a continuation of my earlier write-ups:

• Plug-In Hybrid (Toyota 2025 Prius PHEV) real-world usage
• 3rd tank of gas @ 5,001 km
• 4th tank of gas @ 5,927 km

Fill-up records so far

Fill	Date	Odometer	Litres	Cost	Price
1	Sept. 7, 2025	1,492 km	24.85 L	$37.74	—
2	Nov. 13, 2025	3,964 km	22.66 L	$32.34	$1.427/L
3	Jan. 30, 2026	5,001 km	30.55 L	$41.10	$1.345/L
4	Mar. 23, 2026	5,927 km	17.4575 L	$30.48	$1.744/L
5	May 30, 2026	7,626 km	21.068 L	$37.59	$1.784/L

One note: for fill-up 2, we did not have litres directly recorded, so I calculated it from the receipt:

$32.34 ÷ $1.427/L = 22.66 L

Totals so far

After 7,626 km:

• Total distance: 7,626 km
• Total gas purchased: 116.59 L
• Total gas spend: $179.25
• Average gas price: $1.537/L

Gas-only consumption so far:

116.59 L ÷ 7,626 km × 100 = 1.53 L/100km

So the Prius PHEV is averaging:

1.53 L/100km gas-only

That number is not the full energy picture, because the car is also using electricity. But as a gasoline-use number, it’s very low.

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Gas-only efficiency by segment

For these calculations, I’m treating the gas purchased at each fill-up as the gas used since the previous fill-up. That’s the normal way to calculate tank-to-tank fuel economy.

There is one caveat for the first segment: it depends on how full the car was when I took delivery.

Segment	Period	Distance	Gas	Gas-only efficiency
Purchase → Fill 1	Aug. 9 → Sept. 7	1,492 km	24.85 L	1.67 L/100km
Fill 1 → Fill 2	Sept. 7 → Nov. 13	2,472 km	22.66 L	0.92 L/100km
Fill 2 → Fill 3	Nov. 13 → Jan. 30	1,037 km	30.55 L	2.95 L/100km
Fill 3 → Fill 4	Jan. 30 → Mar. 23	926 km	17.46 L	1.89 L/100km
Fill 4 → Fill 5	Mar. 23 → May 30	1,699 km	21.07 L	1.24 L/100km
Overall	Aug. 9 → May 30	7,626 km	116.59 L	1.53 L/100km

The best stretch so far was the fall segment:

0.92 L/100km

The worst was the deep winter segment:

2.95 L/100km

That is still very efficient, but it is more than triple the fall result.

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The winter tax is real

The pattern is pretty clear now.

In mild weather, the Prius PHEV can do a lot of driving on electricity, with the gas engine only coming on occasionally. That’s how I got the 0.92 L/100km fall segment.

Winter changes things.

Cold weather means:

• reduced EV range
• more cabin heat demand
• more defrost use
• a colder battery
• more situations where the gas engine runs even when there is charge available

That showed up directly in the numbers. From November to January, gas consumption jumped to 2.95 L/100km.

Then, as temperatures improved, the next two segments came back down:

• Jan. 30 → Mar. 23: 1.89 L/100km
• Mar. 23 → May 30: 1.24 L/100km

So the winter penalty is real, but the car is clearly moving back toward its warmer-weather efficiency.

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Electricity cost estimate

Gas receipts only show part of the story. The Prius PHEV also uses electricity.

I do not have charger-level metering, so this is an estimate. The car is currently reporting about:

17.1 kWh/100km

At my electricity rate of:

$0.185/kWh

That works out to:

17.1 × $0.185 = $3.16/100km

Over 7,626 km, estimated electricity use is:

7,626 km × 17.1 kWh/100km ÷ 100 = 1,304.05 kWh

Estimated electricity cost:

1,304.05 kWh × $0.185/kWh = $241.25

So the electricity estimate is:

• Electricity used: 1,304.05 kWh
• Electricity cost: $241.25
• Electricity cost per 100 km: $3.16/100km

Important caveat: this is rough. Earlier estimates used a lower number (13.1 kWh/100km), but the car is currently reporting 17.1 kWh/100km, so I’m using that here. Winter was almost certainly worse than this, while warmer months may be better. Applying one number across the whole period is a simplification — the real figure likely ranges between 13.1 and 17.1 depending on the season.

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Total energy cost

Actual gas spend:

$179.25

Estimated electricity spend:

$241.25

Total estimated energy cost:

$179.25 + $241.25 = $420.50

Per 100 km:

$420.50 ÷ 7,626 km × 100 = $5.51/100km

So the all-in energy cost so far is:

$5.51 per 100 km

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Compared with my old Civic

For comparison, my old 2016 Honda Civic averaged about:

7.9 L/100km

At my average gas price so far:

$1.537/L

The Civic would cost:

7.9 L/100km × $1.537/L = $12.14/100km

Over the same 7,626 km, the Civic would use:

7,626 km × 7.9 L/100km ÷ 100 = 602.45 L

Estimated Civic fuel cost:

602.45 L × $1.537/L ≈ $926

The Prius PHEV, including estimated electricity, has cost:

$420.50

Estimated savings so far:

$926 - $420.50 ≈ $506

On a per-100-km basis:

Vehicle	Energy cost
2025 Prius PHEV	$5.51/100km
2016 Honda Civic	$12.14/100km

Savings:

$12.14 - $5.51 = $6.63/100km

That is about a:

55% reduction in energy cost

Also worth noting: the Civic would have burned about 602 L of gasoline over this distance. The Prius has purchased 116.59 L.

So even before talking about dollars, the Prius is using roughly 81% less gasoline.

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Data confidence: what’s measured vs. what’s estimated

The gas data in this post is fully deterministic — every number comes from odometer readings and gas pump receipts. The electricity data is estimated, and the savings figure depends on that estimate. The chart above breaks down exactly what’s measured versus what’s estimated, and the confidence level of each metric.

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Bottom line after five fill-ups

At 7,626 km, the Prius PHEV has used:

• 116.59 L of gas
• an estimated 1,304.05 kWh of electricity
• about $420.50 total energy cost

The headline numbers:

Gas-only consumption: 1.53 L/100km

Total energy cost: $5.51/100km

Estimated savings vs. Civic: about $506 so far

The car is not free to run, and winter definitely hurts PHEV efficiency. But even with a conservative electricity estimate, the overall cost-per-kilometre is still roughly half of what we would have spent driving the Civic.