Everyone talks about the GPU price, but a local AI rig has a running cost too. It's smaller than you fear — but if you're in Europe, it's not nothing. Here's the real math.
When people budget for local AI, they price the GPU and stop there — but a rig has a running cost too, and it's the part nobody calculates. The good news: it's smaller than you fear. The catch: if you're in Europe with high electricity prices, it's not nothing, and it changes the case for efficient hardware. A power-hungry 350W GPU running 8 hours a day costs roughly €25/month at €0.30/kWh; an efficient Mac or mini PC doing the same work costs a few dollars. Here's the real running cost of local AI, and why efficiency pays back over time.
The real numbers
Let's do the math honestly. A discrete GPU under sustained AI load draws 350–450W. Run it 8 hours a day and that's roughly 100 kWh a month. At European electricity prices around €0.30/kWh, that's about €25–30/month; at typical US rates (~$0.15/kWh), about $12–15/month. Not huge, but real — and it compounds over the years you own the card. An efficient unified-memory machine like a Mac or Strix Halo draws around 40W doing the same inference, so its running cost is a few dollars a month. That efficiency gap is why, over a machine's life, the cheaper-to-run option claws back part of its higher purchase price — a factor the GPU sticker price hides.
A 350W GPU 8 hours a day is ~€25/month in Europe — small, but it compounds over the years you own the card. · Unsplash
Running cost vs cloud rental
Here's the useful comparison. If you own a GPU, your marginal cost per hour of AI is just the electricity — pennies to a dollar depending on the card and your rates. If you rent, you pay the full hourly rate (~$0.34 for a 4090-class card). So for regular use, owning is far cheaper per hour once you've bought the card — the running cost is small next to rental. This is the other half of the rent-vs-buy math: renting has no upfront cost but a high per-hour cost; owning has a high upfront cost but a low per-hour cost. Heavy users benefit from owning; light users from renting.
Quick answers
How much electricity does a local LLM use?
A discrete GPU under sustained AI load draws 350–450W, so running it 8 hours a day uses roughly 100 kWh a month — about €25–30 at European rates or $12–15 at typical US rates. Idle draw is much lower, since GPUs sip power between generations; it's sustained work that costs. An efficient Mac or mini PC draws ~40W doing the same inference, costing just a few dollars a month. The running cost is real but modest.
Is it expensive to run AI locally?
Not really — the electricity to run a local LLM is a few dollars to ~€25–30 a month depending on your hardware and rates, which is small next to the GPU's purchase price. The bigger cost is the hardware itself. Efficient machines (Macs, mini PCs) cost far less to run than power-hungry GPUs, which matters over years and at high electricity prices. For regular use, running locally is cheaper per hour than renting once you own the card.
Does an efficient GPU or Mac save money on running costs?
Yes, over time. An efficient unified-memory machine draws ~40W versus 350–450W for a discrete GPU doing the same work, so its running cost is a fraction — a few dollars a month versus €25+ in Europe. Over the years you own the machine, that gap partly offsets a higher purchase price, especially where electricity is expensive. If you'll run AI heavily and pay high power rates, efficiency is worth paying for upfront.
The running cost of local AI is small but real — ~€25/month for a hungry GPU in Europe, a few dollars for an efficient machine. Factor it into the rent-vs-buy decision, and if power is expensive where you are, an efficient mini PC or Mac pays back over time.
