Sizes and what each one suits
Advance Appliances matches each heat pump cylinder to the baths and showers it has to serve:
| Model | Capacity | Suits | Size (diameter x height) |
|---|---|---|---|
| ECO HPL 150 | 150 litres | One bath | 580 x 1205mm |
| ECO HPL 200 | 200 litres | One bath and a shower | 580 x 1545mm |
| ECO HPL 250 | 250 litres | Two baths | 580 x 1795mm |
| ECO HPL 300 | 300 litres | Two baths and a shower | 580 x 2105mm |
| HPL 400 | 400 litres | Three baths and a shower | 580 x 2050mm |
| HPL 500 | 500 litres | Four baths and a shower | 750 x 1690mm |
For a figure based on your own household, the sizing guide asks how many people live in the property and how many showers and baths it has, then estimates the capacity you need.
Why heat pump cylinders are sized up
A heat pump usually heats the cylinder to around 50°C, lower than a gas boiler does. With cooler stored water, you need more of it to get the same amount of hot water at the tap. A 2013 laboratory study for the Department of Energy and Climate Change put it this way: "The cylinder volume needs to be larger at lower temperatures to give a satisfactory number of consecutive large DHW draw offs."
There is a limit, though. The same study notes that every cylinder loses some heat each day, so the size should be kept down to limit losses while still holding enough water for the household.
Check it fits
- Every model is 580mm across except the HPL 500, which is shorter and wider at 750mm.
- The cylinder fits a standard airing cupboard, on any floor, with no extra insulation. It must stand upright, indoors and frost free, and stay accessible for maintenance.
- Leave room for the expansion vessel and the G3 discharge pipe to the tundish, which must be visible. The installation guide sets out the pipe sizes.
- Check the mains. Advance suggests at least 1.5 bar and 20 litres a minute, and a 22mm cold supply.
Larger homes and commercial jobs
The ECO heat pump cylinders cover 150 to 300 litres for homes. The light commercial 400 and 500 litre models are listed as call or email for availability, so contact Advance on 01543 377723 before you specify one.
Weighing up a buffer store for the heating side as well? See do I need a buffer store with my heat pump.
- Advance matches cylinder size to baths and showers: 150 litres for one bath, up to 500 litres for four baths and a shower.
- Heat pumps store water cooler than boilers, so cylinders are usually sized up to give the same hot water.
- Oversizing adds standing heat loss, so size for the household rather than going as big as possible.
- Most models are 580mm across and fit a standard airing cupboard; the HPL 500 is 750mm.
- The sizing guide on the Advance site estimates a capacity from people, showers and baths.
Managing Director, Advance Appliances. 20+ Years experience