Air source heat pump and solar.

Payupfront

Thanks, that's brilliant.

Netexporter

matt_drummer said:

Netexporter said:

There are a lot of variables to take into account. How well insulated and air-tight the property is, how much of the existing central heating can be re-used, etc. The installer should take you through all that, when they draw up their proposals. Once you have a firm proposal then come back and ask about anything you aren't sure about. There are plenty of knowledgeable people here who can talk you through it. 

A poorly insulated property is of little relevance to heat pumps. They are just a source of hot water.

If the property is poorly insulated then any heating source will be less efficient than it could be.

A proper heat loss survey is key and as many improvements as possible should be made to the home and the heating system.

But poor insulation does not preclude you from having a heat pump

That is true, but whilst electricity is more expensive, per delivered kWh, than oil or gas, a poorly insulated property may make the running cost unacceptably high.

What we need is a competent government that understands that insulation is the first priority. The cheapest kWh is the one you don't use.

matt_drummer

We don't know anything about your home so maybe you could tell us.

The calculations are quite simple really.

I had gas central heating and hot water and used around 13,000 kWh of gas a year.

At 90% efficiency of the gas boiler I know I need about 11,700 kWh of energy to heat our house and provide hot water.

A heat pump at 300% efficiency (SCOP) it will use 3,900 kWh of electricity.

I would hope to do better and I have just heating hot water so far, I get more like 500% to 600% efficiency.

You can do the same rough calculations.

I was lucky, all of my radiators were big enough to provide enough heat at a lower flow temperature, yours might not be.

I know that on the worst day I used 110 kWh of gas.

That means I need around 100 kWh of heat on the worst day.

At 300% efficiency I need 33kWh plus whatever my house uses, let's say 10 kWh.

So my worst day is 43 kWh

I can get most of that from my batteries charged at E7 rates and the rest comes from solar or import.

My worst case is is about £9 a day, less than I used to spend on gas and electricity.

Since April I have accumulated £1,300 of credit with my supplier and I am still building.

If I used £9 a day for four months my usage bill would be about £1,100.

Of course, not every day is the worst day.

It works, I may be a bit out one way or another but I know we won't be cold or bankrupt!

matt_drummer

Netexporter said:

That is true, but whilst electricity is more expensive, per delivered kWh, than oil or gas, a poorly insulated property may make the running cost unacceptably high.

What we need is a competent government that understands that insulation is the first priority. The cheapest kWh is the one you don't use.

I agree completely. As much insulation as possible makes any heating system efficient to operate.

But a heat pump will never be cripplingly expensive if operated correctly, even in a poorly insulated home.

I know that people install heat pumps and run them like a gas or oil boiler, it's a big mistake.

They look at the initial power draw, get horrified and turn them off.

That is not how they work.

cannugec5

We have recently, as in this month, had an ASHP installed. 

We previously had an oil boiler , that we had to replace due to a catastrophic leak. By that I mean we didn’t have a lot of time to think and discuss our options. Oil was no longer an option (tank position/ structure no longer compliant) and there is no mains gas in this area. 

So we went with ASHP and the available grant plus loan ( Scotland). The paperwork is onerous and we are still awaiting the final payment. Our installation cost in excess of £18,000. 

But, the house is certainly warm. I always have done monthly electricity meter reads, but we have not quite got there yet . Once we have we will see what our first month of ASHP  had cost. 

We did enquire about solar at the same time but the solar installer declined to quote. We are in a remote and rural area so decided not to prevaricate and just get the heating in, before the next winter is here! 

matt_drummer

cannugec5 said:

We have recently, as in this month, had an ASHP installed. 

We previously had an oil boiler , that we had to replace due to a catastrophic leak. By that I mean we didn’t have a lot of time to think and discuss our options. Oil was no longer an option (tank position/ structure no longer compliant) and there is no mains gas in this area. 

So we went with ASHP and the available grant plus loan ( Scotland). The paperwork is onerous and we are still awaiting the final payment. Our installation cost in excess of £18,000. 

But, the house is certainly warm. I always have done monthly electricity meter reads, but we have not quite got there yet . Once we have we will see what our first month of ASHP  had cost. 

We did enquire about solar at the same time but the solar installer declined to quote. We are in a remote and rural area so decided not to prevaricate and just get the heating in, before the next winter is here! 

I think you really need to get to grips with how much electricity your heat pump is using.

It sounds like you have no idea?

Your installation sounds distressed, no time to think and discuss options does not sound great.

It's only September and you are heating already?

I am not one for heating based on the date but is it that cold in Scotland?

We have discussed this in a few topics, you need to find out how to get the information from your controller about electricity consumed and heat generated.

I may be wrong but I think you may be in for a nasty shock.

Reed_Richards

Time was, when you had a heat pump installed it had to have its own dedicated electricity meter to qualify for the government subsidy.  This costs very little extra but lets you know exactly how much electricity your heat pump is using.  

markin

It can't be a small token solar system, you really have to maximise all the roof space to have any chance of covering your heating use annually, closer to a 7kwh solar system than 3.6kwh.

What is your current oil use and electric (kwh) use over the last 12 months?

matt_drummer

markin said:

It can't be a small token solar system, you really have to maximise all the roof space to have any chance of covering your heating use annually, closer to a 7kwh solar system than 3.6kwh.

What is your current oil use and electric (kwh) use over the last 12 months?

It can actually.

My 4 kW array produces 4,000 kWh a year.

Although most of that generation won't directly run the heat pump that generation has a value in consumption and export.

My heat pump consumes 3,500 kWh a year.

The solar generation has enough value to cover the costs of the imported electricity that the heat pump uses.

If you were replacing gas or oil even that small array generates enough to fund the running of the heat pump.

lohr500

matt_drummer said:

markin said:

It can't be a small token solar system, you really have to maximise all the roof space to have any chance of covering your heating use annually, closer to a 7kwh solar system than 3.6kwh.

What is your current oil use and electric (kwh) use over the last 12 months?

It can actually.

My 4 kW array produces 4,000 kWh a year.

Although most of that generation won't directly run the heat pump that generation has a value in consumption and export.

My heat pump consumes 3,500 kWh a year.

The solar generation has enough value to cover the costs of the imported electricity that the heat pump uses.

If you were replacing gas or oil even that small array generates enough to fund the running of the heat pump.

Not trying to be clever but out of interest how does your 4000kWh solar/battery setup generate £70k profit over its lifetime?