Why clean filters cut your energy use

By lowering the airflow resistance - clean filters let air flow freely, so the extract fan works less hard to pull it through and draws less power; clogged filters resist the airflow, making the fan strain and use more energy. Clean filters save energy through the extract fan and how hard it works. The fan pulls the air through the whole system, working against the resistance the system offers. When the filters are clean, air flows through them freely (low resistance), so the fan moves the air with less effort - drawing less power and using less energy. When the filters are grease-clogged, the grease narrows the path, so they resist the airflow much more - and the fan has to work harder to pull the air through, drawing more power and using more energy. So clean filters keep the resistance low and the fan efficient, while clogged filters make it strain and use more. That's why keeping the filters clean cuts your energy use: it keeps the airflow path open so the fan doesn't fight against clogged filters. So clean filters let the fan work less, using less power. So they lower resistance, so the fan uses less energy. This is general guidance.

Because the grease clogging them resists the airflow, so the fan has to work harder to pull air through - and a harder-working fan draws more power; the more clogged the filters, the more the fan strains and the more energy it uses. Clogged filters make the fan use more energy because they raise the resistance the fan works against. The extract fan pulls the air through the system, and the harder it has to work (the more resistance), the more power it draws. When the filters are grease-clogged, the grease narrows the path through them, so they resist the airflow much more than clean filters - like a partial blockage the fan has to strain against. So the fan has to work harder to pull the air through the clogged filters, drawing more power and using more energy. And because filters clog fastest of all (catching the grease first), this raised resistance is common and frequent. So the dirtier the filters, the harder the fan works and the more energy it uses. This is a hidden cost of neglected filters, on top of them catching less grease. So because they resist the airflow, making the fan strain. So they raise resistance, so the fan draws more power. This is general guidance.

It's part of the wider saving from a clean system - clean filters (and clean ductwork and fan) keep the fan running efficiently on lower power; the effect adds up over time, alongside the bigger benefits of fire safety and grease control. The energy saving from clean filters is a real, worthwhile part of the wider saving from a clean extraction system. Clean filters keep the resistance low so the fan runs efficiently (drawing less power); clogged filters make it strain and draw more. Over time, running the fan efficiently rather than against clogged filters adds up on the energy bill. That said, the filters are one part of the picture: the fuller energy saving comes from a clean system throughout (clean filters, clean ductwork, a clean fan - all keeping the resistance low), as a grease-choked system anywhere makes the fan work harder (as covered in the energy-cost-of-a-clogged-fan and clean-extraction-lower-bills pages). So clean filters contribute a meaningful part of the saving, and a clean whole system delivers the full effect. And this energy saving comes alongside the bigger benefits of clean filters (fire safety, grease control) - so it's a bonus, not the main reason to clean them. So it's a real, worthwhile part of the clean-system saving. So yes, meaningfully, as part of a clean system. This is general guidance.

Yes - grease building up in the ductwork and on the fan also raises resistance and loads the fan, so a clean system throughout (not just the filters) keeps the fan efficient; the filters are just the fastest-clogging part. Yes - the ductwork and fan affect the fan's energy use as well as the filters. The fan works against the resistance of the whole system, so grease building up anywhere raises the resistance and makes the fan work harder. Grease in the ductwork narrows the airflow path (more resistance); grease on the fan itself loads and unbalances it (making it less efficient and harder-working). So a grease-choked ductwork and a fouled fan both increase the fan's power draw, just as clogged filters do. The filters are simply the fastest-clogging, most frequent point of raised resistance (they catch the grease first), which is why they're highlighted - but the fuller energy saving comes from keeping the whole system clean (filters, ductwork and fan). So don't clean only the filters for energy: a clean system throughout keeps the fan running efficiently. This is part of the wider link between a clean extraction and lower energy. So yes - the whole system's cleanliness affects the fan's energy use. So yes; clean the whole system for the full saving. This is general guidance.

Regularly, at a frequency matched to your cooking - heavy, greasy cooking clogs filters fast and needs frequent cleaning (often weekly or more); keeping them clean keeps the resistance low and the fan efficient, as well as catching grease. To keep the fan efficient (and the filters catching grease), clean the filters regularly at a frequency matched to your cooking. Heavy, greasy cooking (frying, grilling) loads and clogs the filters fast, so they need frequent cleaning - often weekly or more - to keep them from clogging and raising the resistance. Lighter cooking clogs them more slowly, so they can be cleaned less often. The principle is to clean them before they clog significantly, so the airflow path stays open and the fan runs efficiently (and the filters keep catching grease). So match the filter-cleaning frequency to how fast your cooking clogs them - frequent for heavy cooking, less often for light. Keeping the filters consistently clean keeps the resistance low, the fan efficient (saving energy), and the grease caught (protecting the duct). Your filters are designed to be cleaned regularly (in a dishwasher or by soaking), so frequent cleaning is straightforward. So clean them regularly, matched to your cooking - frequently for heavy cooking. So often enough to keep them from clogging. This is general guidance.

You'd clean them anyway for grease and fire safety - the energy saving is a bonus on top; but it's a real added benefit, so clean filters are worth it for grease control, fire safety and lower energy together. Cleaning the filters is worth it primarily for grease control and fire safety - keeping them catching grease and protecting the ductwork - which is why you should clean them regularly regardless. The energy saving is a bonus benefit on top of that: the same clean filters that catch grease also let the fan run efficiently, using less energy. So you don't clean the filters just for energy - you clean them for grease and fire safety, and the energy saving comes free with it. This is a nice alignment: the routine filter cleaning you should do anyway also saves energy, so there's no trade-off, just extra reason to keep the filters clean. So the answer is that clean filters are worth it for the combination - grease control, fire safety, and lower energy together - rather than for energy alone. So keep the filters clean for all three benefits. So it's a bonus on top of the fire-safety reason. So the energy saving comes free with the cleaning you should do anyway. This is general guidance.