diff --git a/rhp/v4/rhp.go b/rhp/v4/rhp.go
index 3e454c4..05d1f16 100644
--- a/rhp/v4/rhp.go
+++ b/rhp/v4/rhp.go
@@ -582,7 +582,8 @@ func ContractCost(cs consensus.State, p HostPrices, fc types.V2FileContract, min
 
 // RenewalCost calculates the cost to the host and renter for renewing a contract.
 func RenewalCost(cs consensus.State, p HostPrices, r types.V2FileContractRenewal, minerFee types.Currency) (renter, host types.Currency) {
-	renter = r.NewContract.RenterOutput.Value.Add(p.ContractPrice).Add(minerFee).Add(cs.V2FileContractTax(r.NewContract)).Sub(r.RenterRollover)
+	contractCost := r.NewContract.HostOutput.Value.Sub(r.NewContract.TotalCollateral) // (contract price + storage cost + locked collateral) - locked collateral
+	renter = r.NewContract.RenterOutput.Value.Add(contractCost).Add(minerFee).Add(cs.V2FileContractTax(r.NewContract)).Sub(r.RenterRollover)
 	host = r.NewContract.TotalCollateral.Sub(r.HostRollover)
 	return
 }
diff --git a/rhp/v4/rhp_test.go b/rhp/v4/rhp_test.go
index ae4f0f0..295094b 100644
--- a/rhp/v4/rhp_test.go
+++ b/rhp/v4/rhp_test.go
@@ -3,6 +3,7 @@ package rhp
 import (
 	"testing"
 
+	"go.sia.tech/core/consensus"
 	"go.sia.tech/core/types"
 )
 
@@ -19,3 +20,212 @@ func TestMinRenterAllowance(t *testing.T) {
 		t.Fatalf("expected %v, got %v", expected, minAllowance)
 	}
 }
+
+func TestRenewalCost(t *testing.T) {
+	const (
+		initialProofHeight = 1000
+		initialExpiration  = initialProofHeight + ProofWindow
+
+		renewalHeight      = 150
+		extension          = 10
+		renewalProofHeight = initialProofHeight + extension
+		renewalExpiration  = renewalProofHeight + ProofWindow
+		renewalDuration    = renewalExpiration - renewalHeight
+	)
+	cs := consensus.State{}
+	prices := HostPrices{
+		ContractPrice:   types.NewCurrency64(100),
+		Collateral:      types.NewCurrency64(200),
+		StoragePrice:    types.NewCurrency64(300),
+		IngressPrice:    types.NewCurrency64(400),
+		EgressPrice:     types.NewCurrency64(500),
+		FreeSectorPrice: types.NewCurrency64(600),
+	}
+	renterKey, hostKey := types.GeneratePrivateKey().PublicKey(), types.GeneratePrivateKey().PublicKey()
+
+	type testCase struct {
+		Description string
+		Modify      func(*types.V2FileContract, *RPCRenewContractParams)
+		RenterCost  types.Currency
+		HostCost    types.Currency
+	}
+
+	cases := []testCase{
+		{
+			Description: "empty",
+			Modify:      func(*types.V2FileContract, *RPCRenewContractParams) {},
+			RenterCost:  prices.ContractPrice,
+		},
+		{
+			Description: "no storage",
+			Modify: func(rev *types.V2FileContract, p *RPCRenewContractParams) {
+				p.Allowance = rev.RenterOutput.Value.Add(types.Siacoins(20))
+				p.Collateral = rev.TotalCollateral.Add(types.Siacoins(10))
+			},
+			RenterCost: types.Siacoins(20).Add(prices.ContractPrice),
+			HostCost:   types.Siacoins(10),
+		},
+		{
+			Description: "no storage - no renter rollover",
+			Modify: func(rev *types.V2FileContract, p *RPCRenewContractParams) {
+				p.Allowance = rev.RenterOutput.Value.Add(types.Siacoins(20))
+				p.Collateral = rev.TotalCollateral.Add(types.Siacoins(10))
+				// transfer all of the renter funds to the host so the renter will need to put up the entire allowance
+				rev.HostOutput.Value, rev.RenterOutput.Value = rev.HostOutput.Value.Add(rev.RenterOutput.Value), types.ZeroCurrency
+			},
+			RenterCost: types.Siacoins(320).Add(prices.ContractPrice),
+			HostCost:   types.Siacoins(10),
+		},
+		{
+			Description: "renewed storage - no additional funds",
+			Modify: func(rev *types.V2FileContract, p *RPCRenewContractParams) {
+				// add storage
+				rev.Capacity = SectorSize
+				rev.Filesize = SectorSize
+			},
+			RenterCost: prices.ContractPrice.Add(prices.StoragePrice.Mul64(SectorSize).Mul64(extension)), // storage cost is calculated for just the extension
+			HostCost:   types.ZeroCurrency,                                                               // collateral lock up is less than rollover
+		},
+		{
+			Description: "renewed storage",
+			Modify: func(rev *types.V2FileContract, p *RPCRenewContractParams) {
+				// add storage
+				rev.Capacity = SectorSize
+				rev.Filesize = SectorSize
+
+				// adjust the renewal params
+				p.Allowance = rev.RenterOutput.Value.Add(types.Siacoins(20))
+				p.Collateral = rev.TotalCollateral.Add(types.Siacoins(10))
+			},
+			RenterCost: types.Siacoins(20).Add(prices.ContractPrice).Add(prices.StoragePrice.Mul64(SectorSize).Mul64(extension)), // storage cost is calculated for just the extension
+			HostCost:   types.Siacoins(10).Add(prices.Collateral.Mul64(SectorSize).Mul64(renewalDuration)),                       // collateral is calculated for the full duration
+		},
+		{
+			Description: "renewed storage - no renter rollover",
+			Modify: func(rev *types.V2FileContract, p *RPCRenewContractParams) {
+				// adjust the renewal params
+				p.Allowance = rev.RenterOutput.Value.Add(types.Siacoins(20))
+				p.Collateral = rev.TotalCollateral.Add(types.Siacoins(10))
+
+				// add storage
+				rev.Capacity = SectorSize
+				rev.Filesize = SectorSize
+				// transfer all the renter funds to the host so the renter will need to put up more allowance
+				rev.HostOutput.Value, rev.RenterOutput.Value = rev.HostOutput.Value.Add(rev.RenterOutput.Value), types.ZeroCurrency
+			},
+			RenterCost: types.Siacoins(320).Add(prices.ContractPrice).Add(prices.StoragePrice.Mul64(SectorSize).Mul64(extension)), // storage cost is calculated for just the extension
+			HostCost:   types.Siacoins(10).Add(prices.Collateral.Mul64(SectorSize).Mul64(renewalDuration)),                        // collateral is calculated for the full duration
+		},
+	}
+	for _, tc := range cases {
+		t.Run(tc.Description, func(t *testing.T) {
+			contract, _ := NewContract(prices, RPCFormContractParams{
+				RenterPublicKey: renterKey,
+				RenterAddress:   types.StandardAddress(renterKey),
+				Allowance:       types.Siacoins(300),
+				Collateral:      types.Siacoins(400),
+				ProofHeight:     initialProofHeight,
+			}, hostKey, types.StandardAddress(hostKey))
+
+			params := RPCRenewContractParams{
+				ProofHeight: renewalProofHeight,
+			}
+			tc.Modify(&contract, &params)
+
+			prices.TipHeight = renewalHeight
+			renewal, _ := RenewContract(contract, prices, params)
+			tax := cs.V2FileContractTax(renewal.NewContract)
+			renter, host := RenewalCost(cs, prices, renewal, types.ZeroCurrency)
+			if !renter.Equals(tc.RenterCost.Add(tax)) {
+				t.Errorf("expected renter cost %v, got %v", tc.RenterCost, renter.Sub(tax))
+			} else if !host.Equals(tc.HostCost) {
+				t.Errorf("expected host cost %v, got %v", tc.HostCost, host)
+			}
+		})
+	}
+}
+
+func TestRefreshCost(t *testing.T) {
+	const initialProofHeight = 1000
+
+	cs := consensus.State{}
+	prices := HostPrices{
+		ContractPrice:   types.NewCurrency64(100),
+		Collateral:      types.NewCurrency64(200),
+		StoragePrice:    types.NewCurrency64(300),
+		IngressPrice:    types.NewCurrency64(400),
+		EgressPrice:     types.NewCurrency64(500),
+		FreeSectorPrice: types.NewCurrency64(600),
+	}
+	renterKey, hostKey := types.GeneratePrivateKey().PublicKey(), types.GeneratePrivateKey().PublicKey()
+
+	type testCase struct {
+		Description string
+		Modify      func(*types.V2FileContract)
+	}
+
+	cases := []testCase{
+		{
+			Description: "no storage",
+			Modify:      func(rev *types.V2FileContract) {},
+		},
+		{
+			Description: "no storage - no renter rollover",
+			Modify: func(rev *types.V2FileContract) {
+				// transfer all of the renter funds to the host so the renter rolls over nothing
+				rev.HostOutput.Value, rev.RenterOutput.Value = rev.HostOutput.Value.Add(rev.RenterOutput.Value), types.ZeroCurrency
+			},
+		},
+		{
+			Description: "renewed storage",
+			Modify: func(rev *types.V2FileContract) {
+				// add storage
+				rev.Capacity = SectorSize
+				rev.Filesize = SectorSize
+			},
+		},
+		{
+			Description: "renewed storage - no renter rollover",
+			Modify: func(rev *types.V2FileContract) {
+				// add storage
+				rev.Capacity = SectorSize
+				rev.Filesize = SectorSize
+				// transfer all the renter funds to the host
+				rev.HostOutput.Value, rev.RenterOutput.Value = rev.HostOutput.Value.Add(rev.RenterOutput.Value), types.ZeroCurrency
+			},
+		},
+	}
+
+	// the actual cost to the renter and host should always be the additional allowance and collateral
+	// on top of the existing contract costs
+	additionalAllowance, additionalCollateral := types.Siacoins(20), types.Siacoins(10)
+	renterCost := additionalAllowance.Add(prices.ContractPrice)
+	hostCost := additionalCollateral
+
+	for _, tc := range cases {
+		t.Run(tc.Description, func(t *testing.T) {
+			contract, _ := NewContract(prices, RPCFormContractParams{
+				RenterPublicKey: renterKey,
+				RenterAddress:   types.StandardAddress(renterKey),
+				Allowance:       types.Siacoins(300),
+				Collateral:      types.Siacoins(400),
+				ProofHeight:     initialProofHeight,
+			}, hostKey, types.StandardAddress(hostKey))
+
+			params := RPCRefreshContractParams{
+				Allowance:  additionalAllowance,
+				Collateral: additionalCollateral,
+			}
+			tc.Modify(&contract)
+
+			refresh, _ := RefreshContract(contract, prices, params)
+			tax := cs.V2FileContractTax(refresh.NewContract)
+			renter, host := RefreshCost(cs, prices, refresh, types.ZeroCurrency)
+			if !renter.Equals(renterCost.Add(tax)) {
+				t.Errorf("expected renter cost %v, got %v", renterCost, renter.Sub(tax))
+			} else if !host.Equals(hostCost) {
+				t.Errorf("expected host cost %v, got %v", hostCost, host)
+			}
+		})
+	}
+}