Electricity Tariffs for ASHP owners

Octopus Go would probably be the best bet, or one of the EVv tariffs

Welcome to the forums @amyashp. I think it’s only a matter of time before Octopus introduce an ASHP tariff, but at the moment, as Batalto said, your only option is to go with a time of use tariff. 

Which ASHP have you opted for?

At the Fully Charged show a few weeks ago I was chatting to the heat pump expert on the Octopus Energy stand. He said that they are planning to release a Heat Pump specific tariff in the near future, weeks rather than month. I didn’t manage to get too many details but he said price was based on set time slots, e.g., most expensive during evening peak, so the idea would be to heat the house up ahead of this time, then set back the house temperature for a few hours to avoid the pump running. 

In practice I’m not sure how good this is as it’ll not fit with the most efficient operating practice of the heat pump to leave it running slow and steady most of the day. It’s pushing us down a route of operating the pumps less efficiently for shorter durations. But we shall see. 

Posted by: @hydros

At the Fully Charged show a few weeks ago I was chatting to the heat pump expert on the Octopus Energy stand. He said that they are planning to release a Heat Pump specific tariff in the near future, weeks rather than month. I didn’t manage to get too many details but he said price was based on set time slots, e.g., most expensive during evening peak, so the idea would be to heat the house up ahead of this time, then set back the house temperature for a few hours to avoid the pump running. 

In practice I’m not sure how good this is as it’ll not fit with the most efficient operating practice of the heat pump to leave it running slow and steady most of the day. It’s pushing us down a route of operating the pumps less efficiently for shorter durations. But we shall see. 

Hi Hydros,

I think that you will find that in most cases the opposite will be true. On the modelling that I have carried out, working the heat pump slightly harder during what is normally the warmer part of the day, even in Winter, may be offset by the improved efficiency at warmer outside air temperatures. In fact it may not be necessary to work the heat pump harder, but merely to stop it fulling back as the heat demand reduces with increased outside air temperature. Dependent upon the thermal mass of your home, it should be possible to shutdown your heat pump for several hours whilst the indoor temperature falls back to the desired level. For best operation it would be preferable to ramp the indoor temperature setting up and down in a controlled manner over several hours, like accelerating your car gradually rather than jamming your foot on the accelerator.

I know that technique actually works in practice, in that I have been using it for quite some time with our A2A ASHP, which raises the indoor temperature during daylight hours, supplied in most cases by our solar PV system, then does not need to operate again until not long before or even after midnight.

I’ve been intending to ask now for a while but why aren’t all (or at least more) electricity providers offering time of use tariffs? Is it a tech issue/limitation?

@derek-m how are you controlling the gradual ‘acceleration’ and ‘deacceleration’ of your A2A heat pump?

For us, to try and achieve this, would involve setting strict schedules on our smart thermostats. Peak times for electricity as far as I’m aware is from 1630, by which time the sun has gone down in the UK in the winter. Ramping up the heat from say 13:30 would keep most rooms warm till 19:30 if we turned off the heat pump at 16:30. 

The heat pump would then come back on at 19:30 when it’s pretty cold outside and would have to work very hard (inefficiently) to get the flow temp back to say 45C. Not ideal, but it could be cheaper than running the heat pump at crazy high tariffs. 

There’s a lot for us to contemplate and strategise before the coming winter.

@editor I was going to offer a similar observation. You need quite some thermal mass to keep the house warm through those peak hours during the winter, which many homes won’t have. I can see my house, which is reasonably well insulated, performing similar to yours. By 19:30 people are settling down in front of the TV(or with a book) and would be more likely start to feel the cold a bit more. 
Maybe it’s time to promote the trusty woollen jumper, and blanket. 50p per unit could be quite the incentive.

@editor

Hi Mars,

We have an A2A ASHP, which does not suffer from having 'fancy' controls and thermostats. Once there is sufficient solar PV generation, I simply use the hand held control to change the setpoint from 22C overnight, to 24C daytime.

For those with an A2W ASHP, it would be necessary to either schedule variations to the LWT, or the weather compensation offset, by say 1C per hour or two.

Because you operate your system using thermostats, unless you can gradually ramp up the thermostat setting then you may have difficulty controlling the heat pump response. As I think many people have discovered, heat pumps don't work that efficiently with thermostat controls.

Posted by: @hydros

@editor I was going to offer a similar observation. You need quite some thermal mass to keep the house warm through those peak hours during the winter, which many homes won’t have. I can see my house, which is reasonably well insulated, performing similar to yours. By 19:30 people are settling down in front of the TV(or with a book) and would be more likely start to feel the cold a bit more. 
Maybe it’s time to promote the trusty woollen jumper, and blanket. 50p per unit could be quite the incentive.

Hi Hydros,

My suggestion is not guaranteed to work every time, there may be odd days when the overnight temperature is greater than the daytime temperature. As you correctly point out another important factor is the thermal mass of your home. To ensure more consistency in achieving the goal of not drawing power from the grid during peak periods, then battery storage and possibly solar PV would be highly beneficial.

@hydros, I think we’re going layer up this winter and I’ll be getting the mohair socks out.  Even with our ASHP ‘ticking over’ it can chew up 2-3 kWh when temperatures in Dec or Jan are below 5C. That’s 50kWh per day. At 50p that’s simply unaffordable.