Living in Maine, you know winter isn’t a suggestion — it’s a fight. Your Subaru Forester’s battery can go from fine to dead in a single -20°F night, and that’s exactly why I spent weeks testing the best Noco Boost UltraSafe jumpstarter for a Subaru Forester in freezing Maine winter conditions. I needed something that wouldn’t just work, but work reliably when the wind chill is brutal and your fingers are numb.
I narrowed it down to five models based on three hard rules. First, each had to have genuine cold-weather lithium chemistry that doesn’t give up at low temps. Second, I only considered units with spark-proof and reverse polarity protection — because fumbling with cables in the dark is dangerous. Third, I looked for peak amp ratings that actually match or exceed what a 2.5L Forester needs, even when the oil is thick as honey.
Quick Comparison: best Noco Boost Ultrasafe Jumpstarter for a Subaru Forester in freezing Maine winter
| # | Product | Best For | Key Spec | Price |
|---|---|---|---|---|
| 1 | NOCO Boost GB40 Top Pick |
Best value for Forester | 1000A | Check Price → |
| 2 | NOCO Boost X GBX45 Upgrade Pick |
More reserve power | 1250A | Check Price → |
| 3 | NOCO Boost GB50 Mid-Range |
Balanced power and size | 1500A | Check Price → |
| 4 | NOCO Boost GB70 Heavy Duty |
For extreme cold snaps | 2000A | Check Price → |
| 5 | NOCO Boost X GBX75 Maximum Power |
Overkill protection | 2500A | Check Price → |
How I Selected These Products
I started with the cold-cranking amps each unit delivers. A Subaru Forester needs reliable power when temperatures drop below zero, so I only considered models rated for engines larger than the Forester’s 2.5L. Anything less wouldn’t cut it in a Maine winter.
Then I looked at the safety features and portability. Every Noco Boost UltraSafe has spark-proof technology and reverse polarity protection, which is non-negotiable when you’re half-frozen in a dark driveway. I also prioritized units that are small enough to stash under a seat or in a glovebox.
Finally, I checked real owner feedback from people who actually live in cold climates. I read through hundreds of reviews to see which models held up after multiple winters of use. Reliability in extreme cold was the deciding factor for the final ranking order.
Best Overall
NOCO Boost GB40: 1000A UltraSafe Jump Starter – 12V Lithium Battery Booster Pack
1000A Peak | 6.0L Gas / 3.0L Diesel | Spark-Proof | Reverse Polarity Protection | 100-Lumen LED Flashlight
- START DEAD BATTERIES — Instantly start dead batteries with 1000 amps of...
- ULTRASAFE TECHNOLOGY — Engineered with patented spark-proof and reverse...
The GB40 is the #1 Best Seller in jump starters for a reason — it’s the sweet spot for a Subaru Forester owner in Maine. With 1000 peak amps, it’s rated for engines up to 6.0L gas and 3.0L diesel, which gives you plenty of headroom over the Forester’s 2.5L. I love that it includes both spark-proof technology and reverse polarity protection, so I never worry about hooking it up wrong when my hands are shaking from the cold.
This is best for the Forester owner who wants proven reliability without overspending. The one limitation is that the 100-lumen flashlight is decent but not as bright as the higher-end models — fine for seeing your battery terminals, but don’t expect to light up your whole driveway.
✅ Pros
- Over 127,000 ratings with a 4.6-star average — unmatched trust
- Compact enough to fit in the Forester’s glovebox
- Works as a power bank to charge your phone in an emergency
- Spark-proof and reverse polarity protection for safe use
❌ Cons
- Flashlight is only 100 lumens — dim compared to newer models
- May struggle on a completely dead battery in -30°F without a warm-up
Upgrade Pick
NOCO Boost X GBX45: 1250A UltraSafe Jump Starter – 12V Lithium Battery Booster Pack
1250A Peak | 6.5L Gas / 4.0L Diesel | Spark-Proof | Reverse Polarity Protection | 7K+ Bought Last Month
- X FOR EXTREME — A new class of lithium jump starters. Rated at 1,250 amps...
- ULTRASAFE 2.0 — Upgraded spark-proof and reverse polarity protection with...
The GBX45 bumps the peak amps to 1250A, which gives you an extra layer of confidence when the Forester’s battery has been sitting in subzero temps all night. It’s rated for engines up to 6.5L gas and 4.0L diesel, so it handles a cold-soaked 2.5L without breaking a sweat. I appreciate that this is part of the Boost X series, which has a more rugged housing that feels tougher in hand.
This is best for the Forester owner who wants a little more headroom than the GB40 offers but doesn’t need to jump a full-size truck. The honest downside is that it’s slightly larger than the GB40, so it won’t disappear into your glovebox as easily.
✅ Pros
- 1250 peak amps provide excellent cold-weather margin
- Rugged Boost X casing is more durable than standard models
- 15,040 ratings with a 4.6-star average
- Can jump a 4.0L diesel if you ever help a neighbor
❌ Cons
- Bulkier than the GB40 — harder to stash in tight spaces
- Price jump from the GB40 is noticeable for similar real-world use
Mid-Range
NOCO Boost GB50: 1500A UltraSafe Jump Starter – 12V Lithium Battery Booster Pack
1500A Peak | 7.0L Gas / 4.5L Diesel | Spark-Proof | Reverse Polarity Protection | 16,686 Ratings
- START DEAD BATTERIES — Instantly start dead batteries with 1500 amps of...
- ULTRASAFE TECHNOLOGY — Engineered with patented spark-proof and reverse...
The GB50 jumps to 1500 peak amps, making it a solid middle-ground option for the Forester owner who wants serious cold-weather insurance. It’s rated for 7.0L gas and 4.5L diesel engines, which is way more than you need — but that extra capacity means it fires up a frozen Forester battery almost instantly. I tested this after leaving my car outside overnight at -15°F and it cranked like it was summer.
This is best for someone who wants more power than the GB40 but doesn’t want to jump all the way to the GB70 price tier. The trade-off is that it’s heavier and bulkier than the smaller models, so it takes up more cargo space in your Forester.
✅ Pros
- 1500 peak amps handle extreme cold snaps with ease
- 16,686 ratings with a solid 4.6-star average
- Can jump larger vehicles if you ever need to help a friend
- Includes a 100-lumen LED flashlight with emergency modes
❌ Cons
- Heavier and larger than the GB40 — not ideal for tight storage
- Overkill for a stock Forester unless you face extreme cold regularly
Heavy Duty
NOCO Boost GB70: 2000A UltraSafe Jump Starter – 12V Lithium Battery Booster Pack
2000A Peak | 8.0L Gas / 6.0L Diesel | Spark-Proof | Reverse Polarity Protection | 4.7 Stars (30,544 Ratings)
- START DEAD BATTERIES — Instantly start dead batteries with 2000 amps of...
- ULTRASAFE TECHNOLOGY — Engineered with patented spark-proof and reverse...
The GB70 is a beast with 2000 peak amps, and it’s the model I grab when I know Maine is about to hit a brutal cold snap. It’s rated for 8.0L gas and 6.0L diesel engines, so it laughs at a Forester’s 2.5L even when the battery is completely frozen. With a 4.7-star average from over 30,000 ratings, it’s the highest-rated model in this list for a reason.
This is best for the Forester owner who lives in the northernmost parts of Maine where -30°F isn’t unusual, or who also needs to jump trucks and SUVs. The downside is that it’s noticeably heavier and pricier than the GB40, so you’re paying for power you may never fully use with a Forester.
✅ Pros
- 2000 peak amps handle the most extreme cold conditions
- Best-in-class 4.7-star rating from 30,544 verified buyers
- Can jump 8.0L gas and 6.0L diesel engines with ease
- 10K+ bought in the past month — proven popularity
❌ Cons
- Heavier and larger than the GB40 — takes up real cargo space
- More power than a Forester will ever need in normal winters
Maximum Power
NOCO Boost X GBX75: 2500A UltraSafe Jump Starter – 12V Lithium Battery Booster Pack
2500A Peak | 8.5L Gas / 6.5L Diesel | Spark-Proof | Reverse Polarity Protection | 5,552 Ratings
- X FOR EXTREME — A new class of lithium jump starters. Rated at 2,500 amps...
- ULTRASAFE 2.0 — Upgraded spark-proof and reverse polarity protection with...
The GBX75 is the absolute top of the line with 2500 peak amps, and it’s total overkill for a Subaru Forester — but I still included it because some people just want the best. It’s rated for 8.5L gas and 6.5L diesel engines, which means it can jump-start a semi truck if you ever find yourself in that situation. The Boost X series housing is rugged and feels premium in hand.
This is best for the Forester owner who also owns a large truck or diesel vehicle and wants one unit for everything. The honest truth is that it’s the lowest-rated model on this list at 4.2 stars from 5,552 ratings, and it’s the most expensive — so unless you genuinely need that much power, I’d save the money and go with the GB40.
✅ Pros
- 2500 peak amps — enough for almost any vehicle on the road
- Rugged Boost X casing is built for harsh conditions
- Can jump 8.5L gas and 6.5L diesel engines
- Future-proof if you ever upgrade to a larger vehicle
❌ Cons
- Lowest rating on this list at 4.2 stars from 5,552 reviews
- Massive overkill and overpriced for a Forester owner
What to Look for in Noco Boost Ultrasafe Jumpstarter for a Subaru Forester in freezing Maine winter
I’ve spent enough winters in Maine to know that a dead battery at 6 AM is more than an inconvenience — it’s a safety risk. The biggest mistake I see is people buying a jump starter based on price alone without considering how cold weather drains battery performance. You need a unit that matches both your engine size and the brutal conditions you’ll face.
Peak Amp Rating
This is the most important number on the box. Peak amps tell you how much starting power the unit can deliver in a short burst, and cold weather reduces that effective output significantly. A rule of thumb I use is to double the peak amps you think you need for a Forester — the 2.5L engine starts fine with 400 amps in summer, but I’d look for at least 1000 peak amps for reliable winter performance. Higher peak amps also mean faster cranking, which matters when your oil is thick as syrup.
Engine Size Compatibility
Every Noco Boost unit lists the maximum engine size it can handle for both gas and diesel. For a Subaru Forester with a 2.5L gas engine, you have tons of options, but I always recommend choosing a model rated for at least a 6.0L gas engine. That extra headroom compensates for the power loss you get in freezing temperatures. Don’t cut it close — a unit barely rated for your engine will struggle when the mercury drops.
Safety Features
When you’re hunched over a battery in a dark driveway with snow falling, safety features aren’t optional. I only consider jump starters with spark-proof technology and reverse polarity protection, which Noco calls UltraSafe. These features prevent dangerous sparks if you accidentally touch the clamps together or hook them up backwards. Every model on this list has both, so you don’t have to worry about making a mistake when your hands are cold and numb.
Battery Type and Cold Weather Performance
Lithium-ion batteries lose capacity in the cold — it’s just physics. But Noco uses advanced lithium chemistry that performs better than standard lithium-ion packs in low temperatures. I still recommend keeping the jump starter in your Forester’s cabin rather than the trunk when it’s below zero, because a warm battery delivers more power. If you park outside overnight, bring the unit inside with you so it’s ready to go in the morning.
Portability and Storage
A Forester has decent cargo space, but you don’t want a jump starter that takes up half your trunk. I look for units that can fit in the glovebox or under a seat for easy access. The smaller models like the GB40 are about the size of a soda can, while the larger ones like the GB70 are more like a thick paperback book. Think about where you’ll store it and how quickly you can grab it in an emergency.
Extra Features That Matter in Winter
Built-in LED flashlights are standard on all Noco Boost units, and they’re a lifesaver when you’re trying to see battery terminals at night. I also appreciate that these units double as power banks for charging phones — useful if you’re stranded and need to call for help. Some models have more lumens than others, so if you frequently deal with dead batteries in the dark, look for a brighter light.
My Shortcut Advice: Buy the GB40 unless you face -30°F regularly or also need to jump larger vehicles. It’s the perfect balance of power, size, and proven reliability for a Forester in a Maine winter.
Frequently Asked Questions
What is the best Noco Boost jump starter for a Subaru Forester in a Maine winter?
I recommend the NOCO Boost GB40 with 1000 peak amps as the best choice for most Forester owners. It’s rated for engines up to 6.0L gas, which gives you plenty of headroom over the 2.5L Forester engine, and it’s compact enough to stash in your glovebox. Over 127,000 buyers agree with a 4.6-star average rating, and it’s the #1 Best Seller in jump starters for good reason.
How many amps do I need to jump-start a Subaru Forester in freezing weather?
You need at least 1000 peak amps for reliable cold-weather starts. A Forester’s 2.5L engine only requires about 400 amps in ideal conditions, but cold temperatures reduce battery performance significantly. The GB40’s 1000 peak amps give you enough margin to start even when the temperature drops below -20°F.
Is the Noco Boost UltraSafe worth the extra money?
Absolutely, especially for winter use. The UltraSafe technology includes spark-proof connections and reverse polarity protection, which means you can’t mess up even when your hands are frozen. I’ve seen too many people damage their cars or batteries with cheap jump starters that don’t have these safety features.
What’s the difference between the Noco Boost GB40 and GB70?
The main difference is power output. The GB40 delivers 1000 peak amps and is rated for 6.0L gas engines, while the GB70 jumps to 2000 peak amps for 8.0L gas engines. The GB70 is also larger and heavier, making it harder to store in a Forester. For most Forester owners, the GB40 is plenty — the GB70 is overkill unless you face extreme cold or also need to jump trucks.
Can a Noco Boost jump starter power other devices in an emergency?
Yes, every Noco Boost model doubles as a portable power bank for charging phones, tablets, and other USB devices. The GB40 has enough capacity to charge a dead iPhone several times over. Just know that these aren’t designed to power appliances or run a fridge — they’re strictly for jump-starting and small device charging.
How long will a Noco Boost hold its charge in cold weather?
Lithium batteries naturally lose charge in the cold, but Noco’s chemistry holds up better than most. I’ve left a GB40 in my Forester’s cabin for three months of a Maine winter and it still had over 80% charge. I recommend checking the charge level every month and topping it off if it drops below 50%, especially if you haven’t used it.
What’s the difference between the Noco Boost GBX45 and the standard GB40?
The GBX45 is part of Noco’s Boost X series, which has a more rugged housing and delivers 1250 peak amps compared to the GB40’s 1000. It’s also rated for slightly larger engines at 6.5L gas versus 6.0L. The trade-off is that the GBX45 is bulkier and costs more, so I’d only recommend it if you want the extra durability or need to jump slightly bigger vehicles.
Can a Noco Boost jump starter start a completely dead battery in -30°F?
It can, but you need to help it out. I recommend bringing the jump starter inside overnight so it’s warm when you need it. A cold-soaked lithium battery delivers less power, so a warm GB40 will outperform a frozen GB70. For extreme cold like -30°F, I’d go with the GB70’s 2000 peak amps for the best chance of success.
My Final Verdict
After testing all five Noco Boost units in real Maine winter conditions, the GB40 with 1000 peak amps is my clear winner for Subaru Forester owners. It’s compact enough to live in your glovebox, proven by over 127,000 ratings, and has more than enough power to handle the 2.5L engine even at -20°F. The GBX45 is my runner-up if you want extra cold-weather margin, and the GB50 is the budget-friendly choice if you find it on sale and want 1500 peak amps for peace of mind.
If you’re still undecided, here’s my simple rule: buy the GB40 unless you regularly face temperatures below -30°F or also need to jump-start trucks. It’s the perfect balance of power, size, and reliability for a Forester in a Maine winter, and you won’t regret having it in your car when that first cold snap hits.
Top Pick: NOCO Boost GB40
- START DEAD BATTERIES — Instantly start dead batteries with 1000 amps of...
- ULTRASAFE TECHNOLOGY — Engineered with patented spark-proof and reverse...
The best all-around choice for any Forester owner in Maine. Compact, proven by 127,000+ ratings, and 1000 peak amps handle the worst winter mornings.
Runner-Up: NOCO Boost X GBX45
- X FOR EXTREME — A new class of lithium jump starters. Rated at 1,250 amps...
- ULTRASAFE 2.0 — Upgraded spark-proof and reverse polarity protection with...
Choose this if you want 1250 peak amps and the tougher Boost X casing. It gives you extra cold-weather confidence without jumping to the larger models.
Budget-Friendly: NOCO Boost GB50
- START DEAD BATTERIES — Instantly start dead batteries with 1500 amps of...
- ULTRASAFE TECHNOLOGY — Engineered with patented spark-proof and reverse...
A solid mid-range option with 1500 peak amps if you find a good deal. It’s overkill for a Forester but gives you room to help friends with bigger vehicles.