The unit that fits where a gas boiler used to be

Most heat pumps are designed for new construction or larger family homes. The ES M 100L is built (mainly) for something more specific: replacing a gas boiler in the space it already occupies.

That focus shapes every design choice. The size. The mounting. The DHW capacity. The outdoor unit pairings it’s designed to work with.

Gas boiler installations come with constraints. Tight utility rooms. Existing pipework. Wall mounting where the old boiler hung. Most homeowners aren’t looking for a major renovation; they want a system that fits where the old one was.

The ES M 100L is built around that brief. At 850 mm high and 65 kg, it wall-mounts where a boiler used to sit. The 100-liter DHW tank covers typical 1-2 person households comfortably, and works for households up to four when paired with the right outdoor unit.

The 100L is designed to work with the ES M8 (8 kW) and ES M12 (12 kW) outdoor units. These are the right capacities for the kinds of homes the 100L is built for — apartments, smaller houses, well-insulated retrofits.

For installations needing more heating capacity, the 15 kW outdoor unit pair with the larger ES M 250L indoor unit instead. Knowing this from the start helps you specify the right combination for the property.

Paired with an ES M8 or ES M12, the ES M 100L reaches A+++ energy efficiency.

Most homeowners aren’t comparing spec sheets. They’re asking practical questions about how the system will work in their home.

Will it fit where the boiler was?
In most cases, yes — wall-mountable, similar footprint, often a near drop-in retrofit.

Will I have enough hot water?
For 1-4 person households, yes. 100 liters with electric backup for peak demand.

What about running costs?
A+++ efficiency means lower running costs than a gas boiler — and protection against fossil fuel price volatility.

Can I see how it’s running?
Yes — a mobile app for iOS and Android gives system visibility with alerts in over 20 languages. Software updates happen automatically over the air.

Connectivity is built in, not added on. Wi-Fi and wired connections come standard. The mobile app, fleet manager, and remote diagnostics are all included — no add-ons, no subscriptions. That means you can monitor installed units, diagnose issues, and resolve many service calls without leaving the office.

Being honest about fit helps you specify the right system from the start.

That said, the ES M 100L itself works in hybrid configurations where an existing heat source remains as backup, useful for phased transitions. The 3 x 3 kW electric backup heater built into the unit also provides peak demand support and cold-weather backup.

This is one unit in the ES Energy Save residential R290 range. Other units in the series cover larger households, tankless configurations, and hybrid installations.

See the full range: ES R290 residential series →

Want the broader story? Read why we built our platform around R290 →